contents
volume 73 . number 1 . january 2020
16
Concrete and Sustainability
Over the past few years, 
there has been considerable discussion on concrete construction and its impact 
on global warming. The authors argue concrete is, in fact, a relatively low-impact material, not only due to its durability, long service life, and recyclability, but also because of increasing investments in more sustainable manufacturing technologies.
Michael Stanzel 
and Natalee Sembrick

Ceiling Panels 
with a High NRC
Standards now require high-performance sound absorption overhead in many building types. Understanding the acoustic requirements within the building standards and translating those correctly into
a project’s written specification is only the first step. One should also understand other potential impacts on the building design to ensure the facility sounds good overall when completed.
Gary Madaras, PhD

Wood Ceilings 
and Acoustics
Wood ceilings can not only provide inviting, eye-catching aesthetics, but also effective acoustical control, making them a versatile and functional design element. However, the panels must be perforated and backed with a sound-absorbent liner or fleece to obtain the required acoustic benefit.
Sean D. Browne

Renovation of Senior Living Facilities
The senior living design renaissance goes far beyond rethinking the residential 
unit itself. It is important for developments as a whole to nurture community building 
and echo and connect to existing urban fabrics. Traditionally left-out amenities such as spas, restaurants, gyms, walking trails, and theaters are now 
a benchmark for success.
Rockland Berg, AIA, NCARB

Natural Stone Creates Iconic Public Spaces
Today’s megalopolis must provide its citizens with not only basics such as housing and transportation, but also with attractive public places for leisure time and city identification. For thousands of years, natural stone has provided one of the best materials for creating iconic spaces in cities because of its many benefits.
Jason Kron
42
On the Cover
The 427-m (1400-ft) tall condominium in Manhattan features cast-in-place concrete made with white Portland cement.
See article on page 16.
Photo © Nathan Cox
50
26
34
Departments

8 CSI NEWS & Notes

9 TO BE SPECIFIC
Choosing the Trades
Ken Lambert, CSI, CSL

10 SPEC MATTERS
Changing the Language
of Concrete
Chris Bennett, CSI, and Keith Robinson, RSW, FCSC, FCSI

58 FAILURES
Five Common Failures 
in Curtain Wall Installation
Doug Dietrich, AIA, CSI, CDT
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News &  Notes
CSI Community on ‘Planting Construction Career Seeds’
In this issue’s edition of “To Be Specific,” Ken Lambert, CSI, CSL, president of the New Hampshire Chapter of CSI, discusses how and why the association should encourage more young people to consider a career in the trades. A version of the blog was also published at www.csiresources.org, and discussed in the CSI Connect Community Forum. Here is one of the suggestions:
“We need to start ‘planting construction career seeds’ at an earlier age than just high school. If parents see their children developing interest in working with their hands, and not being able to afford four years of college tuition debt, they may develop a lot more interest in encouraging their children to pursue a trades career.
“While no careers are recession-proof, buildings need to be built, and they will always need the trades. Today’s tradesperson is working with the latest tools and technology, they are able to work in safe conditions, and at the end of the day they are proud to say, ‘I built that building!’”	Showcase Your CSI Appreciation—New Shop is Now Open!
The CSI store is officially open for business at www.csiresources.org. You now have access to branded apparel, drinkware, gift sets, and more. Whether you are shopping for yourself, 
or your chapter, many products are available for bulk purchases, or in a quantity of one. All items in the store are also customizable.
The store is open 24-7, and will be adding new items throughout the year, including pins, bookmarks, notebooks, and pop-up event banners. If you would like the store to offer a specific product, just reach out to marketing@csinet.org with your suggestion.	Support Education through 
the CSI Foundation
Start the New Year off right by helping create new opportunities in the construction industry by joining your fellow members in supporting the 
CSI Foundation. Your gifts help fund educational programs, workforce development initiatives, scholarships, and much more. Find out more about the foundation, and the impact of your contributions at www.csiresources.org/institute/foundation.	Write for The Construction Specifier to Grow Your Brand
CSI members—and all construction industry professionals—are invited to submit content to The Construction Specifier, to share their expertise, insight, and role as a thought leader in the construction industry.
As regular contributor Michael Chusid, RA, FCSI, CCS, notes, “Every member of the institute is an authority on something worth sharing with others. Some are world-class experts on construction technology, others have unique insight into industry practices, and everyone has case studies about how they handled the special challenges on their projects. I believe we can make the magazine a more lively and essential part of our organization by encouraging members to write for the publication.”
The Construction Specifier is always in search of insightful, timely information that will make the magazine an even greater resource for everyone. Regular departments include technical features, case studies, and columns. For more information on how you can contribute to the magazine, contact the editor Nithya Caleb at ncaleb@constructionspecifier.com.	to be specific
Industry Needs to Steer Teens Toward the Trades

Photo © BigStockPhoto.com
Ken Lambert, CSI, CSL, has worked in the construction industry for more than 20 years as a sales engineer, licensed construction supervisor, and writer/presenter. He is also the president of the New Hampshire chapter of CSI. Lambert can be reached at klambert@red-thread.com.
It was a quick and good-natured comment from a neighbor of mine, but it still struck me. We were talking about applying for college financial aid and all that entails, and I made a comment like, “Well, this is going to be a real pain with the twins, if or when, they decide to go to college.”
The person interjected, “Oh, not ‘if’ – WHEN they both go to college.” This is the basic attitude of nearly every adult I know; it is the default position and that is a problem.
If parents or other adults are demeaning or being condescending toward a teen who wants to go into the building trades in lieu of the four-year college route, that young person can easily forgo their chief interest, and instead try to struggle through four or six more years of schooling for no great reason.
I did go to college, and received my bachelor’s degree. I also have been in the construction field since (or before) my college graduation. That said, I do see both sides. Being in college, or even graduating with a bachelor’s degree, does not make one intelligent.
One of the smartest people I have met in my life did not have a bachelor’s degree, but was a firefighter in addition to running a general contracting/carpentry business. By the time he retired, he had accumulated more wealth than probably 80 or 90 percent of the general population, all with just an associate’s degree.
The point, of course, is we continuously, as representatives of the architecture, engineering, and construction (AEC) community, must encourage and promote teens and young adults to learn about and seek out careers in the building trades. Part of that is just stating to the general public there is absolutely nothing wrong with being a carpenter, plumber, welder, etc. Society and the general economy needs people to fill these roles, perhaps more so than several of the degree programs now being offered by many public and private colleges.
There are many positives to working in the trades. For one, generally you would be eliminating significant student loan debt; this alone is causing years of problems for millennials. Another fringe benefit is the basic physical activity required in some of these construction roles.
The advantage of working in construction 
is you get to see something that you actually helped create and build. There is something relevant and meaningful about that. When one adds all these benefits to job security and strong earning potential, it would be foolish for many to not consider a career
in the AEC industry.	

Note
1 This article is adapted from a blog by this author that first appeared on the CSI website.
spec matters
Polished Concrete: Not Just Shiny
Photo © Chris Bennett
Chris Bennett, CSI, is the owner of Bennett Build, 
a network of construction professionals and researchers dedicated to helping organizations understand and solve concrete and flooring problems. He can be reached via e-mail at chris@bennettbuild.us
Keith Robinson, RSW, FCSC, FCSI, is an associate at Dialog in Edmonton, Alberta. Robinson also instructs courses for the University of Alberta, acts as an advisor to several construction groups, and sits on many standards review committees for ASTM and the National 
Fire Protection Association (NFPA). He can be reached at krobinson@dialogdesign.ca.
Designers specify polished concrete floors because they are durable and easy to maintain. They also reduce material use because existing slabs, or purpose-made slabs, can be employed to create a final floor finish. Additionally, polished concrete has a broad aesthetic range. Color can be selected through the use of pigments, dyes, acid stains, or even sand and aggregate choice. Aggregates can be exposed to different levels. Special aggregates such as marble chips and colored glass could also be added. The reflective characteristics of a polished concrete floor can be expressed from low-sheen matte to high-gloss, mirror-like reflective finishes. It is also straightforward to specify slip resistance using quantifiable coefficient of friction (COF) values and testing procedures. Unfortunately, many of the benchmarks used to specify and build polished concrete floors focus on aesthetics alone, leaving durability, sustainability, and COF unanswered.
Polished concrete’s popularity has increased in the last 15 years. Despite this growing demand, the industry has not been able to standardize the language to describe durable, safe, and attractive concrete floors. During polished concrete’s infancy, specifiers, designers, and owners turned to contractor terms like grit to help them establish a baseline without fully appreciating the variety of solutions this word represents, and opened themselves up to undefinable benchmarks.

Use of contractor terms
Grit describes the abrasive size of industrial diamonds in the matrix of grinding and polishing pads used to polish concrete. It helps craftspersons select tooling choice for the refinement steps they are working on, and navigate the execution of a polished concrete floor. However, it does not communicate the design outcome by using a qualitative approach. Though grit sizes are fairly universal, abrasive grains can vary from metal chaff to industrial diamond and other materials. There can be pure mixtures of abrasive grains of only one size or the matrix of the polishing puck (often called a diamond tool) can contain variable dimensions to create an average size. The size and shape of the polishing puck also affects outcomes on the floor, delivering different scratch patterns and refinement levels. As concrete varies in hardness, so do the diamond polishing pucks. An individual manufacturer can produce a variety of abrasive tools within a specific grit category. In other words, a company could offer multiple types of abrasive tools varying in size, shape, and matrix material (all with different scratch patterns), and yet designate them with an identical grit number. Unless one is truly skilled in the trade and understands the thousands of differences that the word grit could represent, the specifier is in unfamiliar territory that will quickly land him/her in a means and methods quagmire.
There are other problems with using the word grit that may not be readily considered. Grit also describes the size of abrasive grains on janitorial buffing and burnishing pads, opening up even more variables to this word. These types of pads can be used with topical solutions that can become shiny through burnishing. Instead of a polished concrete floor, a client can unknowingly be handed a coated shiny doppelgänger lacking durability and quantifiable COF. Further, some styles of epoxy resin coatings are sold in solid form as diamond tools containing abrasive grains. These, therefore, carry a grit designation (i.e. 400, 800, etc.) However, what actually happens with these types of products is that they are super-heated under the weight of commercial grinders. The high-speed revolutions of the grinding cause the epoxy to melt and become smeared across the concrete and leave the floors with a shiny coat through resin transfer.

Defining polished concrete
Specifiers are not the only ones affected in this seemingly confusing world of attempting to quantify polished concrete. In attempts to gain flooring market share, many coating companies joined trade organizations and relevant committees to lobby for the expansion of the definition of polished concrete to include all materials that could make a floor shiny. As an example, the current definition of polished concrete, according to the Concrete Polishing Council (CPC) and the American Society of Concrete Contractors (ASCC) is, “Polished concrete is the act of changing a concrete floor surface, with or without aggregate exposure, to achieve a specified level of gloss using one of the listed classifications—bonded abrasive polished concrete, burnished polished concrete, or hybrid polished concrete.”
It is not that they have ruled out polished concrete created through refinement of the material itself, but they have also included liquid-applied coatings and classified it all as “polished concrete.” As the character Inigo Montoya famously said in William Goldman’s the Princess Bride, “You keep using that word. I do not think it means what you think it means.”
The preferred method to quantify polished concrete from CPC and other groups is again limited to gloss and reflectivity—this misses the qualitative attributes necessary to provide full performance criteria relating to the floor’s use. As an example, groups will use reflectivity as 
a benchmark via distinctness of image (DOI) gloss. DOI is an aspect of gloss characterized by the sharpness of images of objects produced by reflection at 
a surface, per ASTM E284, Standard Terminology of Appearance. This is helpful to describe the aesthetic appearance, and has been used in the automobile coating industry to define reflective car coat quality for some time—hence, the attempts to use similar benchmarks for polished concrete.
The devices used to carry out these tasks are called gloss meters, with the degrees of radiant light measured in lumens (lm). These tools are useful for various applications and are accurate for reporting the amount of gloss reflected (or light quality) off the floor, but they do not remotely begin to tell how the light is reflected. Was the concrete properly refined, meaning is the finished surface durable, sustainable, and enjoying some measure of COF? Or did a resinous coating product from Division 09 get installed, and will not be discovered as an apparent substitution until the floor fails?
Over the past decade, building professionals have been working hard to create testing methodologies that are easy, repeatable, and speak to physically making concrete slabs tough as well as shiny and beautiful. Bruce Nicholson, one of the earliest polishing contractors in North America, along with the late Harry Gressette, were some of the first, skilled tradespersons to begin measuring the floor itself and not just reflected light. Along with craft persons like Chris Swanson and pioneering architectural firms like DIALOG, Laith Sayigh’s DFA, Johnson McAdams Group, Gensler, SRG Partnership, and Thrailkill Associates, empirical research at the University of Alberta, Alberta, Canada, and the University of Akron, Ohio, and training events around North America began to prove through millions of square feet benchmarks for polished concrete can be quantified by readings taken from the concrete micro-surface texture with simple stylus devices (e.g. profilometers), while mechanically processing a floor to achieve a surface with high physical durability and chemical and stain resistance within an aesthetic framework. However, despite the evidence supporting using quantifiable and qualitative methods like measuring micro-surface texture there is yet to be an accepted standard for project team members to clearly communicate definitions and check polished concrete benchmarks.
The Concrete Sawing and Drilling Association (CSDA) published the first standard known as ST 115, Measuring Concrete Micro Surface Texture, to measure concrete surfaces and their surface texture value to evaluate how the concrete itself (versus mere reflected light) influenced the finishing process with regards to gloss, friction, and sustainability. It was an amazing success when compared to previous standards from the Concrete Polishing Association (CPAA) and similar groups where gloss considerations were used for benchmarks. However, due to ST 115’s attempt to create a micro-surface texture grade scale that equaled an approximate ‘grit scale,’ this well-intentioned standard was unable to achieve a clear path on a methodology to achieve consistent roughness average (Ra) readings and measure accordingly.
The National Center for Education and Research on Corrosion and Materials Performance (NCERCAMP) at the University of Akron continues the study of polished concrete, abrasion resistance, COF, and even the installation and maintenance of carbon footprint for this floor finish. In April 2020, it will host the third annual National Concrete and Corrosion Symposium in partnership with Kent State University, Ohio, as well as other schools and organizations to further research. Additionally, the National Concrete and Corrosion Symposium Research Fund has been created to allow owners, architects, academia, constructors, and manufacturer team members to participate and help develop a standard and installation curriculum that can be utilized to define quantifiably, not only what is to be achieved as a condition of the construction documents, but also how to do so with the goal of aiding design professionals reach net-zero emissions in their projects.

Conclusion
Liquid-applied ‘doping-agents’ and ‘finishing enhancers’ that are used to manage the grinding and polishing process suffer from the same contractor-derived meanings as grits. They are helpful for describing the process, but not for illustrating the qualitative slab properties, such as stain resistance, water repellency, or COF, a design professional wants to achieve. Each of these properties could require different liquid-applied products or grit profiles. Specifications describing ‘sealers’ or ‘densifiers,’
in general terms, cannot fully provide the required performance values to explain the required degree of stain resistance. A performance requirement must describe what stains the finish is required to resist, be that orange juice, ketchup, and mustard, wine and beer, or animal byproducts, as all of these may require a different doping-agent or combination of sealers and densifiers to achieve the expected performance.
Simply stating constructor terms has done a disservice to the industry as a whole by trying to market various doping-agents into niche categories. Very few people are able to determine the difference between the sealers and physically refined polished floors. Stating the use of the different doping-agents without mentioning the performance expectations can lead the contractor to propose substitutions. Only few specifiers can determine potential differences, and only after floor performance is affected.
The lack of standardized terminology results in bids, including fully refined, ground, and polished concrete floors as well as surface-applied sealers or coatings. Using contractor terminology to build a means and methods specification always backfires, and the nature of the language leaves the design firm and owner at risk for poor outcomes.
Specifications with micro-surface benchmarks measured in microinches (μin) or micrometers (μm) as a means to describe surface profile and COF combined with distinctiveness of image to confirm the aesthetic appearance can successfully describe performance criteria without relying on application of resinous coatings or topical sealers.	Many of the benchmarks used to specify and build polished concrete floors focus on aesthetics alone, leaving durability, sustainability, and COF unanswered.
A profilometer is used to take floor measurements. Micro-surface benchmarks are measured in microinches (μin) or micrometers (μm). Polished concrete does not rely on application of a resinous coating or topical sealers to achieve performance benchmarks.
Image © Chris Bennett, Bill DuBois, John Guill, and Keith Robinson
A graphic identifying the aspects of coefficient of friction (COF) on polished concrete floors. The more design professionals know about the refinement of floors the more one can understand about ways to achieve and maintain high-traction COF.
Image © A New Concrete Glossary, created by Mike Smith and Kathryn Marek
To achieve the aesthetic and refinement requirements of this large aggregate concrete floor, the specification required a 0.4 μm (16 μin) in roughness average in addition to gloss requirements.
Image © Concrete Intelligence Agency
‘Shiny’ does not equate to polished concrete. Many Division 09 finishes mimic a polished finish without providing the strength, safety, and sustainability of an actual refined concrete floor.
Photos courtesy XRQ Corp
Cement and Concrete, 
Still Outperforming 
in the Sustainability Era
by Michael Stanzel and Natalee Sembrick
Photo © Carole & Roy Timm Photography

Sustainable design in construction is motivating designers and builders to 
re-evaluate the materials, methods, 
and metrics used in creating greener communities. Sustainable structures must balance the environmental footprint, service life, social aspects, and economic factors. As modern society shifts to a circular, carbon-neutral built environment, concrete continues to deliver ‘best-in-class’ performance as a building material.

One of the most important challenges facing the world today is meeting the habitation and food needs of a growing world population, while mitigating climate change. With the construction, operation, and decommissioning of structures and infrastructure accounting for approximately 40 percent of all man-made greenhouse gas (GHG) emissions, it is self-evident construction practices need to change and buildings must become low-carbon and more resilient to the changing climate.1
Over the past few years, there has been considerable discussion about concrete construction and its impact on global warming. Concrete is the most widely used manufactured material in the world. Each year, more than 20 billion tonnes of concrete are produced globally.2 The environmental impact of concrete is due primarily to its widespread utilization as a building material. Concrete is, in the authors’ opinions, a relatively low-impact material, not only due to its durability, long service life, and recyclability, but also because of increasing investments in sustainable manufacturing technologies. It is locally available, and a good material for most applications, such as building foundations and structural or architectural elements, dams and bridges, schools and hospitals, pipe and water treatment facilities, residential homes, curb and sidewalk, pavement, etc.

Importance of life-cycle assessment
To build greener communities, a growing number of designers are relying on life-cycle assessments (LCAs) to measure the environmental impacts of construction projects at all stages, from raw material extraction and processing, transportation, and installation to use in service, and, if necessary, disposal.
“Emission Omissions: Carbon accounting gaps in the built environment,” a landmark study by the International Institute for Sustainable Development (IISD) argues LCA is the best approach to measure carbon emissions in buildings, but that more data, transparency, and robust standards are needed (Figure 1).3 All sources of carbon must be considered to ensure a big picture approach in prioritizing material and energy efficiencies and long service life in designs.
The study identified the omissions of emissions related to concrete, wood, and steel building products. It also identified forestry products as the material with the greatest carbon accounting uncertainties, with up to 72 percent of carbon emissions unaccounted for in current LCAs (Figure 2, page 18). When these emissions are included, concrete’s carbon footprint could be up to six percent less intensive than that of wood products, giving designers and policy-makers reason for pause when making decisions about building materials.
P. Purnell, a professor at the University of Leeds, United Kingdom, argues many of the analyses on the embodied carbon of structures are simplistic and do not take into account the utility of each material and the structural purpose of the element.4 Purnell recommends defining a ‘functional unit’ that allows comparisons of like with like. As an example, a column designed to resist a particular compressive load at a specific height should evaluate the mass of carbon dioxide (CO2) per unit load capacity per unit height. For many structural member dimensions, reinforced concrete provides a competitive carbon footprint compared to other materials.
Studies from the Massachusetts Institute of Technology (MIT) demonstrate the passive energy efficiency of concrete’s thermal mass combined with smart design and the long service life of these structures results in the lowest annual operating costs and global warming potential (GWP).5 In some cases, particularly with insulated concrete forms (ICFs), the total life cycle GWP can be as much as eight percent lower than alternative designs and materials and could potentially be less than 14 percent with the increased use of low-carbon cementitious products.

A sustainable solution
Continued global growth and the trend toward urbanization means building material solutions must be abundant, affordable, and easily adapted to meet future needs. Concrete is a sustainable solution striking a strong balance between the social, environmental, and economic aspects of the communities’ infrastructure needs (Figure 3, page 20).

Strength
Concrete offers good compressive strength for the cost and weight of materials, where other structural characteristics can be enhanced through reinforcing materials. While the compressive strength of conventional concrete is typically less than 50 MPa (7 ksi), high performance concrete mix designs used in high-rise construction can have compressive strengths of up to around 100 MPa (14 ksi), and ultra-high performance concrete (UHPC) can have compressive strengths of more than 180 MPa (26 ksi). By carrying loads more efficiently, the quantity of materials and overall costs for a structure can be reduced. Similarly, lower strength and lower density concrete made with lightweight aggregates produced from recycled materials can help reduce the dead load of buildings.

Versatility
Concrete is flexible, robust, and workable. Mix designs can be adapted to optimize performance and concrete can be placed in a variety of conditions by various methods while offering reliable and predictable performance. Due to its initial plastic state and workability, concrete is able to fill any shape or form to create elegant straight lines or complex geometries, offering a plenitude of architectural and structural options to both the designer and owner.

Raw materials
The materials used for concrete construction are locally sourced, and readily available and mined from the earth’s crust, resulting in low-impact resource extraction and transportation. Aggregate, which comprises the largest proportion of material in concrete, requires little processing and is naturally occurring and locally available. Also, mineral extraction is tightly regulated, and sites can be restored in order to deliver a biodiversity gain to the surrounding environment.6

Durability and resilience
Concrete is durable and able to provide a long service life 
in a variety of natural climates and environments, resisting weathering action, chemical attack, moisture, and abrasion while maintaining its engineering properties. Additionally, reinforced concrete offers resistance to natural disasters and a changing climate. Concrete is sometimes used in areas where it is exposed to substances that can cause deterioration. In such situations, high-durability mix designs that employ a low water-to-cement materials ratio and a high quantity of supplementary cementitious materials (SCMs) can be enhanced by application of protective coatings or membranes.7 However, consideration must be given to the Living Building Challenge’s Red List.

Energy efficiency and healthy living environment
Concrete offers advantages to energy performance such as reduced heating and cooling costs through its excellent thermal mass, with a high heat capacity for storage (around 1000 J/kgoK) and moderate thermal conductivity (around 0.5 to 3 W/moK). Additionally, concrete can result in mitigation of the urban heat-island effect, and increased lighting efficiency due to an albedo reflectance of around 0.35 and solar reflective index greater than the threshold value of 29 required for hardscape in most green building standards and rating systems.8 It also offers improvements in air quality due to negligible levels of volatile organic compounds (VOCs) and elimination of uncontrolled through-wall infiltration, which can be enhanced through the use of photocatalytic cements that remove and decompose contaminants from the air. Concrete also offers effective sound attenuation, with concrete masonry units (CMUs) offering sound transmission classes (STCs) from 40 to over 60 depending on thickness, density, and design.9

Adaptability
The use of concrete not only reduces maintenance and operational costs of buildings over their service life, with up to 10 percent lower annual operating GWP than alternative designs, but also provides the option to repurpose, reuse, or recycle structures and the materials at the end-of-life, decommissioning stage.10

Absorption of CO2
Just like trees, concrete naturally absorbs CO2 from the atmosphere. Science shows concrete absorbs the equivalent of up to 25 percent of the emissions generated in creating it over its lifespan.11

Low-carbon innovation
Innovations in the cement sector ranging from lower carbon cements and low-carbon fuels and materials from the waste stream to investment in carbon capture utilization and storage technologies are putting concrete on a path toward carbon neutrality. These effects could even transform the material from a significant emitter of carbon into a carbon sink.

Environmental impact of concrete
The primary environmental concerns regarding concrete are related to its CO2 footprint and the amount of energy required for manufacturing. These impacts are predominantly associated with concrete’s active ingredient, cement. Concrete is formed when cement is mixed with water, which binds the aggregate into a strong, cohesive structure. Cement production is energy- and CO2-intensive, but the product itself accounts for only 10 to 15 percent of the volume of a concrete mix. The other ingredients in concrete consist of aggregates, taking up 60 to 75 percent of the volume, and water, which accounts for around 15 percent of the volume (Figure 4).
Cement is manufactured by heating a mixture of ground limestone and other minerals containing silica, alumina, and iron up to around 1450 C (2642 F) in a rotary kiln. At this temperature, the oxides of these minerals chemically transform into calcium silicate, calcium aluminate, and calcium aluminoferrite crystals. This intermediate product, called clinker, is then cooled and finely ground with gypsum (added for set-time control), limestone, and specialized grinding aids, which improve mill energy consumption and performance to produce cement (Figure 5, page 22). Those calcium silicates chemically react with the mixing water in concrete, through a process called hydration, to form an extended network of bonds. These bonds bring the aggregates together and give concrete its characteristic strength and durability.
On average in the United States, 1 tonne of cement results in a global warming potential (GWP) of approximately 1040 kg CO2-eq.12 Approximately 1/3 of this is from the energy and heat requirements for manufacture, and 2/3 is from the calcination of calcium carbonate into calcium oxide and CO2.13

How is the industry addressing sustainability?
The CO2 impact of concrete construction is due to the sheer volume required to keep up with global needs.
While the cement and concrete industry has long been committed to providing responsible and sustainable high-performance options, there has been a stronger focus on enhancing concrete’s inherent sustainability in recent years.

Cement
Cement producers have made significant strides in operational efficiency and heat recovery, plant modernization, and recycling of industrial byproducts as raw material sources. The cement industry is investing in many innovative technologies, products, and research projects on its journey towards carbon neutral concrete before 2050. Finding ways to reduce both the energy needs and reliance on fossil fuels is a top priority for cement companies and they have been making measurable progress since the early Seventies (more than a 40 percent).14
On top of this, manufacturers are offering lower carbon products. Portland-limestone cements are specially formulated to provide performance equivalent to traditional Portland varieties, but with a portion of the limestone diverted past the pyro-processing stages and incorporated directly into the product. This avoids around 10 percent of the CO2 emissions from calcination and combustion.
SCMs, such as ground slag, are recycled materials that react with relatively inert byproducts of the hydration reaction (mainly calcium hydroxide) to form compounds that densify the cementitious matrix and enhance later age strength and permeability. SCMs are added to concrete as part of the total cementitious system, and judicious use is desirable not only for the technical advantages, but also environmental benefits. In Canada, it is common to see 25 percent replacement or more of the cement in concrete with these materials—this corresponds to a comparable reduction in manufacturing energy consumption and GHG emissions, as captured in environmental product declarations (EPDs). Due to these benefits, the industry is trying to increase SCM utilization and investigate new sources of potential materials.
The substitution of traditional fossil fuels with lower carbon alternatives derived from non-recyclable waste, including single-use plastics and waste biomass, has the potential to reduce the industry’s carbon emissions by 20 to 30 percent across Canada.
Finally, breakthrough carbon capture, utilization, and storage (CCUS) technologies could yield, when scaled, carbon-neutral or even carbon-negative cement and concrete.

Admixtures
Admixtures are small quantities of various nanomaterials or chemicals added to concrete to improve both performance and efficiency. They can provide air entrainment, control setting characteristics, and improve the workability and constructability of fresh concrete. For hardened concrete, they can increase compressive strengths, reduce shrinkage, and help lower permeability. Admixture producers are evolving their technology to enhance concrete’s durability and longevity, while reducing the need for higher quantities of environmentally intensive and costly materials within a particular mix.

Concrete
Concrete producers develop and optimize mix designs to balance the performance requirements of a project while minimizing the environmental impact, resource use, and waste. Several concrete associations in Canada and internationally have developed eco-certification programs for their members. The industry has also been diligent with developing independently verified regional EPDs for various mix designs to communicate transparent and comparable information about the life-cycle impact of products.
The academic research community is at the leading edge of testing and developing new materials and innovative technologies. This involves working with the standards community to identify requirements for material properties and use, developing appropriate test methods to measure performance, and ensuring the fitness of these products. This includes CCUS-related innovations, such as replacing virgin aggregate with alternatives manufactured from captured carbon as well as various methods for injecting carbon directly into the concrete mix as it sets.

Ensuring sustainable concrete
Sustainable concrete meets the performance requirements of the owner, designer, contractors, and the material supplier while minimizing energy consumption, GHG emissions, virgin material extraction, and waste generation. It will also take advantage of local and recycled materials and have high durability and a long service life. Specifications for concrete should not restrict the concrete mixtures being supplied to the jobsite from being more sustainable.
During a project, several parties will be involved in the production and construction process. The custody of the concrete will change hands several times, with each party having the ability to affect the material’s final performance. Problems can arise when conflicts exist between the specification and performance requirements. Fundamentally, these issues arise due to unfamiliarity with the most current and appropriate standards and lack of knowledge regarding local materials, communication, and planning.
The options for specifying concrete are prescriptive and performance-based specifications or a combination of the two.
With prescriptive specifications, the owner stipulates material types, sources, quantities, air content, slump, and construction processes, while the contractor plans construction methods around those parameters. The concrete supplier then verifies the concrete complies with those criteria. The specifier assumes responsibility for concrete performance.
Under the performance option, the owner specifies the structural and durability requirements and other performance criteria. The contractor is responsible for procuring concrete and working with the material supplier who will establish mix proportions to meet the plastic and hardened requirements. With performance-based requirements, the concrete supplier assumes responsibility for material as delivered. The contractor is responsible for the concrete as placed. This option provides an advantage as the involved parties are free to use their expertise to innovate and ensure the most efficient, economical, and sustainable product is finally used.
There are a number of obstacles to achieving sustainable construction, but the two most significant and easily managed issues are:
• 
removing barriers in specifications and opening them up to allow more sustainable options; and
• 
avoiding poor construction practices onsite.

Sustainable specifications
It is important to ensure sufficient time is allowed for project bidding so material suppliers and contractors can discuss requirements, evaluate options, develop and test mix designs, and conduct any necessary prequalification testing and optimization.
Prescribing mixture proportions or specific materials should be avoided as restrictions on material types or source often result in the use of unfamiliar products, greater overdesign (i.e. material inefficiency), potential material incompatibilities, and increased transportation distances.
Outlining the details of construction methods should also be avoided as this falls within the contractor’s realm of expertise and experience. Slump specifications, in particular, are best addressed by the designer, supplier, and contractor discussing construction requirements and working together.
It is also important to not insist on faster construction schedules than required unless there is a tangible and measurable benefit to the project. Sometimes, the more sustainable option may be using a concrete with slower strength development.
Restrictions on reasonable changes to concrete mixture proportions should also be avoided as slight adjustments throughout a project might be necessary to maintain performance as material and environmental conditions change over time.
Planning and communication are keys to success. It is important to discuss concrete performance requirements with the producer and contractor to allow them to optimize mix designs. It is advisable to ask them how they can contribute to the project’s sustainability as they can often see the whole picture related to material efficiency and can come up with solutions providing a win for all the involved parties.

Best practices onsite
Onsite testing should be carried out by a competent agency following proper ASTM testing procedures. False negatives in test results lead to greater overdesign and material waste. It is important test results are shared with all parties in a timely fashion to allow control and optimization of concrete mixes for performance and sustainability.
Improper scheduling and estimates or insufficient labor and resources on the project can lead to delays onsite and excess waste generation, while undersized loads increase vehicular emissions. It is critical the site is adequately prepared, access and traffic plans are in place, and designated staging and washout areas are established to avoid delays and potential safety impacts or site damage.
Concrete must be properly protected and cured to reach its potential. Curing is necessary for the hydration reaction between the cement and water to continue. A lack of curing significantly reduces the durability and service life of concrete. Additionally, pouring during extreme weather conditions without proper precaution can result in delays and increased energy consumption to maintain favorable concrete conditions and risk of failure of an element.
It is important to follow the American Concrete Institute (ACI) specifications and guidelines to ensure the proper design is followed, reinforcement is properly spaced, jointing is timely, and excessive water addition beyond the design parameters is avoided.
Pre-placement and routine update meetings, site-specific plans, risk assessments, and procedures for document control and inspection and verification practices must be established to ensure all parties contributing to a project are on the same page.

The final word
Sustainable design in construction is motivating designers and builders to re-evaluate the materials, methods, and metrics used in constructing greener communities. A focus on the material’s performance allows each of the parties involved to bring their knowledge, expertise, and innovation to the table. Concrete offers a robust, reliable, and sustainable solution in many applications as it consumes minimal materials and energy, and when designed and placed correctly, is very durable.	

Notes
1 Consult the “2018 Global Status Report: Towards a zero-emission, efficient, and resilient buildings and construction sector” by the Global Alliance for Buildings and Construction at globalabc.org/uploads/media/default/0001/01/3e7d4e8830bfce23d44b7b69350b2f8719cd77de.pdf.
2 Refer to “the Cement Sustainability Initiative: Recycling Concrete Executive Summary,” by the World Business Council for Sustainable Development at www.wbcsd.org/contentwbc/download/2410/29973.
3 To access the study, visit www.iisd.org/library/emission-omissions.
4 For more information, read the paper “the carbon footprint of reinforced concrete. Advances in Cement Research Purnell,” by P. Purnell at eprints.whiterose.ac.uk/78456/1/adcr25-0362.pdf.
5 Read the 2011 research report “Methods, Impacts, and Opportunities in Concrete Building Life Cycle,” by the Massachusetts Institute of Technology (MIT) Concrete Sustainability Hub at rediscoverconcrete.com/assets/files/MIT-Buildings-LCA-Report.pdf.
6 Visit en.wikipedia.org/wiki/Crust_(geology) and 
www.quarrylifeaward.ca/what-quarry-life-award.
7 Refer to the “Effects of Substances on Concrete and Guide to Protective Treatments” by Beatrix Kerkhoff.
8 Visit www.cement.org/docs/default-source/sustainabilty2/hwu_sustainablecement_adv15-digital-(002).pdf?sfvrsn=
2&sfvrsn=2.
9 For more information, visit www.ncma-br.org/pdfs/5/TEK%2013-01C.pdf.
10 See Note 5.
11 Read “the Role of Cement in the 2050 Low Carbon Economy” at cembureau.eu/media/1500/cembureau_2050roadmap_lowcarboneconomy_2013-09-01.pdf.
12 Details at www.cement.org/docs/default-source/sustainabilty2/pca-portland-cement-epd-062716.pdf?sfvrsn=2.
13 Visit ghgprotocol.org/sites/default/files/co2_CSI_Cement_Protocol-V2.0_0.pdf.
14 For more information, read “U.S. and Canadian Labor-Energy Input Survey 2012.”
A typical cement production facility.
Image courtesy Lehigh Hanson
Figure 1
The range and average contribution of life-cycle stage emissions to overall total building emissions, as per “Emission Omissions: Carbon accounting gaps in the built environment,” by the International Institute for Sustainable Development (IISD).
Images courtesy International Institute for Sustainable Development
Figure 2
According to the IISD study, when combined factors, such as primary-to-new-growth-forest-conversion, forest regeneration rates, and soil carbon loss, are accounted for, the cradle-to-grave embodied emissions for a wood building could be six percent greater than for a concrete structure of the same height and area.
Figure 3
Benefits of concrete construction and how it helps projects  attain their sustainability goals.
Images courtesy Lehigh Hanson
Figure 4
Typical concrete composition by volume.
Figure 5
A microscopic image of a clinker shows the various mineral phases (blue equals alite and brown is belite).
Ensuring sustainable construction requires planning and teamwork with clear expectations and responsibilities.
Additional Information
Authors
Michael Stanzel is the tech sales representative for GCP Applied Technologies for cement additives in Canada. Stanzel holds a bachelor’s degree in chemical engineering from Queen’s University, with more than 18 years of experience in both cement and concrete quality and operations. He is a member on the Canadian Standards Association (CSA) A3000, Cementitious Materials Compendium, and an associate member on CSA A23.1, Concrete materials and methods of concrete construction. Stanzel can be reached at michael.stanzel@gcpat.com.
Natalee Sembrick is a marketing specialist at Lehigh Hanson in Irving, Texas. She holds a bachelor’s degree in marketing from the University of Arkansas, with a minor in supply chain management. Sembrick can be reached at natalee.sembrick@lehighhanson.com.

Key Takeaways
Over the past few years, there has been considerable discussion about concrete construction and its impact on global warming. Concrete is, in fact, a relatively low-impact material, not only due to its durability, long service life, and recyclability, but also because of increasing investments in more sustainable manufacturing technologies. It is locally available, and a good building material for most applications. Continued global growth and the trend toward urbanization mean building material solutions should be abundant, affordable, and easily adapted into use. Concrete is a sustainable solution striking 
a strong balance between the social, environmental, and economic aspects of the communities’ infrastructure needs.

MasterFormat No.
03 00 00–Concrete

UniFormat No.
A–Substructure
B–Shell

Key Words
Division 03
Concrete
Sustainability
Specifying Ceiling Panels
with a High NRC

by Gary Madaras, PhD
Photo © Robert Pepple, Images courtesy Rockfon
Standards now require high-performance sound absorption overhead inside many building types. Understanding the acoustic requirements within the building standards and translating those correctly into a project’s written specification is only the first step. One should also understand other potential impacts on the building design to ensure the occupied building sounds good overall when completed.

Section 11.5.4. of the new American National Standards Institute/Green Building Initiative (ANSI/GBI 01-2019), Green Globes Assessment Protocol for Commercial Buildings, contains sound absorption requirements for various rooms in office buildings, schools, and healthcare facilities. There are two compliance paths: one being minimum ceiling noise reduction coefficient (NRC) and the other is maximum reverberation time (RT). Patient care areas in healthcare facilities and resident care areas in senior living facilities are required to have ceilings with a minimum NRC of 0.90, or if a portion of the absorption is provided on the walls and floor, a maximum RT of 0.50 seconds. In this example, writing the project specification is straightforward. The specified ceiling panel should have an NRC of no less than 0.90. This ensures compliance with this section of the standard.
There can be, however, other potential impacts on the building design and compliance with other sections of the standard. Section 11.5.1.2 requires the minimum sound transmission class (STC) rating of the floor/ceiling assembly to be 50. The design and specification of the floor slab, floor finishes, underlayments, and high NRC ceiling system must comply with the STC-50 requirement. Meeting the absorption requirement in 11.5.4 does not stand alone. It is related to meeting the floor-to-floor, airborne, noise isolation requirement as well, and one should not compromise the other. As project specifications are amended to comply with the high NRC requirements, there are other building design impacts that should be considered.

Review of acoustic ceiling panel
Modular acoustic ceilings comprise of a metal suspension grid—ceiling panels made from a porous and fibrous material, such as stone wool, fiberglass, or mineral fiber—and various building systems elements, such as light fixtures, air terminals, sprinklers, and speakers.
The ceiling panels are made of lightweight materials that are typically less than 5 kg/m2 (1 psf) and are fibrous and porous to permit the airborne sound energy to enter the panels and dissipate due to conversion to heat energy. This process decreases noise and reverberation, making speech more intelligible in enclosed rooms like classrooms and creating privacy, comfort, and freedom from distractions in large open spaces. In most everyday spaces, such as schools, healthcare facilities, offices, and restaurants, the higher the amount of sound absorption, the better.
A ceiling panel’s ability to absorb sound is indicated by NRC, an acoustics metric that averages the measured absorption coefficients at the 250, 500, 1000, and 2000 hertz (Hz) octave bands. NRC can be categorized as high-performance when is it 0.90 or higher. Many of the standards, guidelines, and rating systems require a minimum ceiling absorption of NRC 0.90. If the absorption is not provided by a contiguous acoustic ceiling, the alternatives should offer an equivalent amount of sound absorption.
 
Sound absorption in the standards, guidelines, and rating systems
ANSI/GBI 01-2019 requires minimum ceiling absorption of NRC 0.90 in open offices, patient and eldercare areas, medication safety zones in healthcare facilities, and exam and treatment rooms in medical office buildings. The General Services Administration (GSA) PBS-P100, Facilities Standards for The Public Buildings Service, requires ceilings over open offices areas to be NRC 0.90 or higher for 100 percent of the space.1 According to Sound Matters: How to achieve acoustic comfort in the contemporary office, a related GSA document, published in December 2011:

Open workspaces require acoustical treatment on a significant portion of the surfaces in the space to absorb noise from people and equipment. The more absorptive the material added to the open space and the higher the acoustical performance rating of the material, the more acoustically comfortable the environment will be. Two surfaces are key contributors to absorption: high quality acoustic ceiling material is typically the most significant contributor to sound absorption. Similarly, walls may be treated with acoustic material, either applied to a surface or integral with the wall finish.

The WELL Building Standard requires the ceiling over an open office space is NRC 0.90 or higher for the entire surface area exclusive of light fixtures and air devices.2 Complying with this criterion improves the functioning of the cardiovascular, endocrine, and nervous systems of the building’s occupants.
Section 5.3 of ANSI/Acoustical Society of America (ASA) S12.60, Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools, requires core learning spaces to be designed in a way their RTs can be readily adapted to achieve RTs not greater than 0.30 seconds. To achieve this level of performance, the ceiling of an average-sized classroom needs to be a minimum of NRC 0.90, possibly even higher, and some wall or floor absorption is required as well.

Why NRC 0.90?
While it is known good acoustic design requires high-performing sound absorption of NRC 0.90 or higher, the question of ‘why’ might still linger in the minds of some architects and specifiers. An abbreviated answer to this question is because exhaustive and conclusive research has shown the benefits of it.
In the early 2000s, the National Research Council Canada (NRCC) methodically isolated and tested a set of a dozen physical features of open offices relative to speech privacy.3 Those features included ceiling absorption and height, screen wall absorption and height, light fixtures, workstation size, furnishings, etc. Some studies used mockups of actual cubicles in open spaces. Other studies used sophisticated acoustical analysis software based on the image sources technique. These studies used the acoustic metric sound absorption average (SAA), which is very similar to NRC.
Of the design features studied, it was found ceiling absorption, screen wall height, and workstation plan size have the largest effects on speech privacy. The most significant noise paths are those that reflect sound from the ceiling and diffract sound over the separating screen wall. However, only a limited range of these parameters will lead to acceptable speech privacy.
The ceiling is a critical element. There are no obstacles to prevent sound from reaching the ceiling and being reflected down to other areas. The absorptive properties of the ceiling can have a large effect, but speech privacy values are only substantially reduced for highly absorbing ceiling tiles. For a wide range of medium- and low-absorption ceiling tiles (NRC 0.50 to 0.80), acceptable speech privacy is unachievable and not influenced much by the ceiling absorption because too much sound is still reflected off these low-performing panels (Figure 1).
The main conclusion about ceiling absorption, after years of intense investigation, is a minimum ceiling absorption for achieving acceptable speech privacy is an NRC/SAA of 0.90. In practice, it would be better to have an even more absorptive ceiling than this to compensate for any limitations or absence of the other important design parameters.

Seeing the NRC 0.90 difference
The foundational studies conducted by NRCC 20 years ago have been corroborated more recently by research conducted by an acoustic ceiling manufacturer and presented at InterNoise 2018, an exposition on noise control engineering.4
A sound intensity probe was used to scan an acoustic ceiling system with panels of different absorption performance levels of NRC 0.60 to 0.95 while loud, broadband noise was played in the space under it. A high-definition camera and analysis software tracked the location of the probe and the sound intensity levels it measured. These location-specific sound intensity data were then processed into color sound maps, which were overlaid onto the digital image of the ceiling (Figure 2, page 30).
Yellow and red colors in Figure 2 indicate loud noise reflecting off the acoustic ceiling while blue indicates noise being absorbed by the acoustic ceiling. Red areas are mostly caused by noise reflecting off the hard, painted metal—plaque-style—air diffuser, and light fixtures. Note the open return air grille on the right side of the images (blue) acts as an effective sound absorber because the noise passes through the opening into the plenum and is not reflected. The base question is, at what NRC rating does an acoustic ceiling stop behaving like a reflector (red and yellow) and behave more like an effective absorber (blue)? Based on the series of images in Figure 2, the answer is NRC 0.90.
The perception of what constitutes high-performance sound absorption has slipped over time. Some have come to believe NRCs as low as 0.70 to 0.75 are acceptable, but as the sound intensity scans in Figure 2 show, at that level of performance, the ceiling is still acting more as a noise reflector than absorber. Fortunately, building standards, guidelines, and rating systems are now reinforcing what science has shown for decades.

Improved well-being
In 2003, a multiorganizational study conducted by academic institutions in the United States and Sweden inside a Swedish hospital investigated the effect high-performance, sound-absorptive ceiling panels had on the quality of care and physiological state of patients in an intensive coronary care unit (ICCU).5 The study was conducted in an actual hospital ICCU under clinical conditions and involved 94 coronary patients.
During the 20-week baseline condition, the ceiling was hard and sound-reflective. Patient physiology (heart rate and variability, blood pressure, pulse, etc.) and acoustic conditions (RT) were recorded. At the end of the baseline condition, the ceilings in the ICCU were changed to high-performing, Class A, acoustic ceiling panels. Class A in Europe is equivalent to NRC 0.90 in the United States.
Patient physiology and acoustic conditions were then monitored for another 22-week period. The study showed the effects of the high-performing, acoustic ceiling panels decreased patient heart pulse amplitude and their rehospitalization rate. In other words, the high-performance ceiling panels reduced stress in the patients’ bodies and cardiovascular systems, while they were in the hospital, resulting in fewer of them being readmitted after three months due to complications or reoccurrence.
In 2010, researchers from the Department of Psychology at the University of Kaiserslautern in Germany studied the effect of RT and noise on speech perception and listening comprehension in child and adult students.6 Acoustics conditions in a real classroom, before and after an acoustic renovation, were measured and then simulated in the laboratory of the university’s Hearing Research Center.
The acoustically unfavorable condition, representing surfaces with low sound absorption performance, had an RT of 1.10 seconds. The acoustically favorable room, representing surfaces with high-performing sound absorption, had an RT of 0.47 seconds (as mentioned, ANSI/ASA S12.60 recommends classrooms be adaptable to an RT of 0.30 seconds). More than 350 first-graders and third-graders, and adults were tested under both acoustic conditions. The results showed with the high-performance sound absorption present, speech recognition improved significantly in all test subject groups. As an example, with the high-performance absorption in place, first graders sitting in the third row recognized 22 percent more words than when the acoustic conditions were unfavorable. Similarly, adults recognized 18 percent more words under the favorable acoustic conditions.

Ceiling alternatives
While the standards often state the absorption requirements as ceiling NRC, it does not necessarily mean every space must have a standard, contiguous, modular, acoustic ceiling. That approach does not always agree with the preferred architectural style or aesthetic of the room or building. Other sound absorptive systems are permitted if they provide at least the same amount of absorption as an acoustic ceiling of NRC 0.90.
An equal amount of absorption can be achieved with a variety of acoustic metal or wood ceilings—suspended, horizontally oriented, clouds, or islands—or vertically oriented baffles. The first step is to determine how much absorption a ceiling with NRC 0.90 would have provided.
A sabin is the unit of sound absorption. Sound-absorptive elements that hang free in space, such as acoustic islands and baffles, have their performance specified in sabins rather than NRC. There are both metric and imperial sabins—it is important to distinguish between the two when reviewing product information.

Metric 
For every square meter of floorspace, NRC 0.90 ceiling provides 0.9 metric sabins of absorption. Another way to look at it is to multiply the total area of the floor in square meters by 0.9 metric sabins per square meter to get the total number of metric sabins required inside the room by any absorption system.

Example
A 100-m2 (1076-sf) classroom should have 90 metric sabins of absorption over it (100 m2 x NRC 0.90 = 90 metric sabins). If a baffle provides 1 metric sabin of absorption each, then 90 baffles would be needed over the classroom.

Imperial
For every square foot of floorspace, an NRC 0.90 ceiling provides 0.9 imperial sabins of absorption. Therefore, multiply the area of the floor in square feet by 0.9 sabins per square foot to get the total number of imperial sabins required inside the room by any absorption system.

Example
A 1000-sf (93-m2) classroom should have 900 imperial sabins of absorption over it (1000 sf x NRC 0.90 = 900 imperial sabins). If a baffle provides 10 imperial sabins of absorption each, then 90 baffles would be needed.

Conclusion
Building standards, guidelines, and rating systems are now requiring high-performance acoustic absorption overhead with a minimum NRC of 0.90. This requirement is based on both quantitative research and studies showing the positive impact on occupant well-being in offices, schools, and healthcare facilities. Specifiers should remember complying with the high NRC requirement may impact other acoustical requirements, such as minimum airborne sound isolation between vertically oriented rooms. Other sound-absorptive systems, such as acoustic islands and baffles, can be used in lieu of ceilings if they provide equivalent absorption.	

Notes
1 Referenced from Table 3.1 on page 101 of the 2018 version of the General Services Administration (GSA) PBS-P100, Facilities Standards for The Public Buildings Service. This rating is for when sound masking is not used in the space.
2 Details can be found in the Comfort section 80 on page 130 of version 1 of the WELL Building Standard. While version 2 pilot has been released, it is still to undergo a public review process, and as such, is not yet finalized. 
3 Read the National Research Council Canada (NRCC) reports on “Acoustic Design Guide for Open Offices,” “Measurements of Sound Propagation between Mock-up Workstations,” “Acoustical Design of Conventional Open Plan Offices,” “A Renewed Look at Open Office Acoustical Design,” and “Acoustical Design for Open-plan Offices” for more information.  
4 Consult Look, Do You See the Noise Leaking Through that Ceiling? by Gary S. Madaras, for InterNoise exposition 2018.
5 See Influence of Intensive Coronary Care Acoustics on the Quality of Care and Physiological State of Patients by Inger Hagerman et al from the International Journal of Cardiology in 2005.
6 Read Effects of Noise and Reverberation on Speech Perception and Listening Comprehension of Children and Adults in a Classroom-Like Setting by Maria Klatte, Thomas Lachmann, and Markus Meis in Noise & Health, 2010.
Building standards and guidelines require good acoustics and are evolving with more stringent requirements. Many now require the use of high noise reduction coefficient (NRC) ceiling panels.
Photo © Joe Ciarlante
Modular acoustic ceilings comprise a metal suspension grid, ceiling panels, and various building system elements, such as light fixtures, air terminals, sprinklers, and speakers. Even when the ceiling panels offer high sound absorption, these components may result in unwanted sound transfer.
Figure 1
In this figure, speech privacy (vertical axis) improves with lower speech intelligibility index (SII) values. Once ceiling sound absorption average 
(SAA)/NRC is 0.90 and higher, acceptable speech privacy can be achieved in open offices (gray box in lower right). Each incremental increase in SAA/NRC above 0.90 results in an appreciable improvement to speech privacy.
In modular ceiling systems, panels are made of lightweight materials such as stone wool, fiberglass, or mineral fiber that are fibrous and porous to permit the airborne sound energy to enter the panels and dissipate due to conversion to heat energy. This process decreases noise and reverberation, making speech more intelligible in enclosed rooms and creating privacy, comfort, and freedom from distractions in large open spaces.
Figure 2
Ceiling panels with NRC ratings varying from 0.60 to 0.95 reflect different levels of noise (red and yellow) when they are below NRC 0.90, but absorb most noise (blue) at NRC 0.90 and above. The color scale represents wideband noise in decibels (dB). 
The WELL Building Standard requires that the ceiling over an open office space is NRC 0.90 or higher for the entire surface area exclusive of light fixtures and air devices. This improves the functioning of the cardiovascular, endocrine, and nervous systems of the building’s occupants.
High-performance acoustic ceiling systems with a minimum NRC of 0.90 show a positive impact on occupant well-being in offices, schools, and healthcare facilities.
Additional Information
Author
Gary Madaras, PhD, is an acoustics specialist at Rockfon. He helps designers and specifiers learn the optimized acoustics design approach and apply it correctly to their projects. He is a member of the Acoustical Society of America (ASA), the Canadian Acoustical Association (CAA), and the Institute of Noise Control Engineering (INCE). He authors technical articles and speaks publicly on the topic of optimizing acoustic experiences. Madaras can be reached at gary.madaras@rockfon.com.

Key Takeaways
Building standards, guidelines, and rating systems now require high-performance acoustic absorption overhead with a minimum noise reduction coefficient (NRC) of 0.90. This is based research showing the positive impact on occupant well-being in offices, schools, and healthcare facilities. However, specifiers should remember that complying with the high NRC requirement may impact other acoustical requirements. Other sound-absorptive systems, such as acoustic islands and baffles, can be used in lieu of ceilings if they provide equivalent absorption.

MasterFormat No.
09 51 00−Acoustical Ceilings

UniFormat No. 
C10−Interior Construction

Key Words
Division 09
Acoustics
ANSI
Ceilings
Noise reduction coefficient 
Sound absorption
Sound transmission class
Wood Ceilings Combine Beauty with Performance 
by Sean D. Browne
All photos courtesy Armstrong Ceiling Solutions
Wood ceilings can not only provide inviting, eye-catching aesthetics, but also effective acoustical control, making them a versatile and functional design element. To obtain the acoustic benefits, the panels must be perforated and backed with a sound-absorbing material.

Designed to impart warmth to a space, wood ceilings continue to grow in popularity. One reason for that is they offer shorter lead times and lower costs than custom millwork. Another is their ability to create a rich, natural, custom look using only standard panels. Third, today’s wood ceiling systems are offered in a wider variety of sizes, shapes, and forms than ever before.
By combining beauty with performance, wood ceilings are especially well-suited for use in applications ranging from retail, healthcare, hospitality, office environments, and higher education to lobbies, entryways, and conference rooms. Long popular in European commercial design, this traditional material can impart a visual impact that makes it a focal point in signature spaces.
Wood is also gaining increased usage in ‘free-floating’ acoustical clouds and canopies, especially in exposed structure applications. In both cases, the cloud or canopy must be perforated and/or backed to obtain acoustical benefits.

Variety of choices
Wood ceilings are made with either real wood veneers or solid wood. Due to all the variations in color, grain, and texture, there are scores of finishes to choose from. In the case of veneers, white oak, light cherry, and dark cherry are the most popular. Custom veneers are also available. The most common solid wood is poplar.  
When it comes to sizes, shapes, and forms, the myriad of choices include the following.

Tegular
These are square or rectangular panels in which the face of 
the panel is lower than the face of the grid. Panel sizes usually range from 610 x 610 mm (24 x 24 in.) to 1219 x 2434 mm (48 x 96 in.). Tegular wood panels are also offered in triangles, trapezoids, and parallelograms as part of a new ceiling system that gives architects the ability to mix and match different panel shapes, sizes, colors, and textures.  

Linear 
This is offered in either planks, panels, or channeled in veneered wood or solid wood. Plank widths are much narrower than panel widths.  

Concealed  
The suspension system is completely hidden for a monolithic visual. Panels are installed on suspension system with hooks. 

Grille
This type is growing increasingly popular as design trends embrace the linear look. 
It provides wide choice of slat widths, heights, spacing, and number of slats per panel. 

Case study 
Baptist Health South Florida wanted the design of its new Miami Cancer Institute in Miami, Florida, to reflect the warm Mediterranean style of the other healthcare facilities it operates. 
“The client wanted to create a friendly, hospitality-type feel such as you would find in a fine spa or hotel,” said Barbara Kubasti, principal at ZGF Architects.
Inspired by the connections to nature found in the surrounding landscape, the design team selected natural materials for the interior of the center, creating 
a comforting environment for patients and families.
Reinforcing the connection to nature, the lobbies and corridors feature wood linear veneered ceiling panels in a cherry finish. Each of the custom panels comprise three different widths of wood planks with a narrow reveal between each one, creating a linear visual aligning directionally with the corridors. 
“We wanted the warm feel of wood and because the wood ceilings are linear in fashion, they accommodate the continuance of the long corridors that form the circulation spine of the building,” explains Kubasti. “The panels are backed with a factory-attached acoustical fleece to help control noise in the areas where they are installed.”
The eye-catching wood linear veneered ceiling panels provide patients and families with a quieting connection to nature that helps in the healing process, while also serving as a wayfinding tool which helps with navigation around the building.

Acoustic performance
In the past, specifiers often had to make a trade-off between sight and sound, between aesthetics and acoustics, when it came to wood ceilings. Today, that is no longer the case as there is a broad range of options affecting acoustical performance.
To obtain the acoustic benefits of a wood ceiling, the panel must be backed with a material to absorb sound. Perforations in the panel increase the absorption of sound striking the surface. 
The number, size, and shape of the perforations and the percent of open area all affect the acoustical absorption of the ceiling panel. Perforations vary in size and pattern depending on aesthetic appeal. For years, only limited perforation choices were available. Now, perforations are offered in a myriad of shapes including custom ones. Circles and ovals are the most popular.  
Today, it is also possible to have microperforated panels in which the perforation openings are so small, they are virtually invisible. The result is the look of solid wood but with the ability to absorb most of the sound striking it.  
The perforation pattern also affects the acoustical absorption of the ceiling and can impart a compelling visual effect. The most common standard patterns include horizontal and vertical rows, slots, and diagonals. Custom patterns are available as well.

Backloading the panel 
The sound-absorbent material behind the perforations is usually in the form of a black acoustical fleece, encapsulated fiberglass, or a mineral fiber infill panel. The thickness and density of the material will affect its acoustical properties. In typical applications, the absorbent material is placed on top of the wood panel with an air gap between it and the deck above. 
Today, it is possible to obtain the acoustic benefits of both sound absorption and sound blocking in a wood ceiling at the same time. To do so, it is recommended to back the perforated wood panel with a mineral fiber infill panel that has a noise reduction coefficient (NRC) of 0.60 or higher and a ceiling attenuation class (CAC) of 35 or higher in the same panel.
The NRC rating indicates the sound absorbing performance of a material. A ceiling panel with an NRC of 0.60 means it will absorb 60 percent of the sound striking it. The higher the NRC, the more the material prevents noise from bouncing around the room, reduces noise levels and reverberation time, and enhances speech intelligibility.
The CAC measures how well a material blocks sound from traveling from one space to another. The higher the CAC, the more the material reduces noise from adjacent spaces, ensures speech privacy, and provides quiet for concentration and focus. Panels with a CAC of 35 or greater represent high performance and are well-suited for spaces where speech privacy is a key consideration.

Case study
The administration building at Lyric Opera of Kansas City, Missouri, houses the regional opera company’s offices. When designing the space, architect Richard Hu of HJM Architects wanted to include a material that would add warmth to the building’s two-story lobby and open reception area on the second floor.
“The building has a very industrial aesthetic,” explained Hu. “Everything is exposed. We needed a warm material to offset all those cold, hard surfaces.” 
The design team also needed to control acoustics. “The lobby is all concrete and glass, so it can get pretty noisy,” said Hu.
To accomplish both goals, the design team selected acoustical clouds comprised of concealed wood ceiling panels. Five acoustical clouds consisting of dark cherry wood veneer ceiling panels were suspended in a sloped, ribbon-like pattern above the space. Each cloud consists of a single row of standard panels with coordinated trim and a narrow reveal between each one. 
In addition to adding warmth, the wood veneer panels also improved acoustics in the lobby and reception area. The panels are perforated in an oval, straight-slotted pattern and backed with a fiberglass infill for acoustical control.
The design team was pleased with the result, noting the ceiling design complemented other linear elements in the building. 
“We were trying to do something dynamic that drove people directionally to the upper lobby,” says Hu. “The ceiling design not only provides subtle wayfinding, but also a nice, rich look—almost like a tapestry.”

Accessibility 
As building services equipment overhead becomes increasingly complex, ease of access to the plenum becomes more of a priority. Routine cleaning and servicing of ductwork, air diffusers, plumbing, fire protection, and the like require easy accessibility. The installation, maintenance, and updating of today’s generation of cable and lighting technology and wireless access points adds even more demand for access.
To achieve an accessible wood ceiling, tegular assemblies with ‘hook-on’ installation are the easiest to install and provide full downward accessibility for safe, efficient removal of panels. More complex wood ceilings, including custom flat, curved, and radial, can also be designed for access.

Case study
Owners of the Gulf Canada Square Food Court in Calgary, Alberta, decided it was time for an update and commissioned Stantec to refresh the space with a design that would work with the existing seating configuration.
To attain that goal, the existing drywall ceiling had to be replaced with a more dynamic one. 
“We needed to find a solution that would be visually exciting and be easily removed to service the equipment in the plenum,” said Craig Ainsworth, lead architect.
The solution was a custom wood access ceiling system that radiates out in a sunburst design.
“The space lent itself to an oval shape so we just played off that shape and the placement of the existing structural columns to develop this large wood ceiling with lines radiating out from the center,” said Ainsworth.
The 316-m2 (3400-sf) ceiling consists of 234 wood panels in a dark cherry finish that gradually get smaller as they approach the center. With a consistent reveal between each of the panels, the design team was also able to take advantage of the acoustical properties of the new ceiling. 
“Since sound could penetrate up into the plenum, we were able to take advantage of the acoustic treatment on the back of the panels,” Ainsworth explains.
The panels are suspended from a grid system that was painted black to obscure the equipment 
in the plenum. 
“Everything behind the ceiling disappears so the wood panels become the dominant plane of the ceiling,” said Ainsworth.

Installation and humidity
The most important part of a wood ceiling installation is making sure the panels are acclimated to the space. All wood panels are hygroscopic, meaning they respond to changes in humidity levels. Consequently, the HVAC system must be in place and in operation before installation.  For best results, it is important to follow the manufacturer’s recommended guidelines for temperature and humidity levels. The temperature range with normal HVAC in operation is usually 10 to 30 C (50 to 86 F) with a relative humidity of 25 to 55 percent. The wood panels should also be stored in the conditioned space at least 72 hours before installation.
Wood ceiling panels are heavier than traditional acoustical ceiling tiles. As a result, they need to be installed in a heavy duty suspension system instead of a standard system. When creating a reflective ceiling plan, it is important to try to limit cut panels as the exposed edges have to be stained to match the panel.
In the past, installing light fixtures in wood ceiling systems was a challenge, especially in terms of integration. Today, as a result of ceiling manufacturers partnering with lighting manufacturers, pre-engineered lighting integration options are now offered. Specially designed low-profile, light-emitting diode (LED) linear luminaires are available that are the exact length of a ceiling manufacturer’s panels, resulting in a flush, sleek visual. The fixtures are attached to the suspension system using a special connection clip, eliminating the need to independently suspend them from the deck.
Seismic performance 
The seismic performance of wood ceilings is primarily determined by the installation of the suspension system. The purpose of installation requirements for suspended wood ceilings where seismic performance is a factor is to provide a system strong enough to resist lateral forces imposed upon it without failing and to prevent border panels from falling from the ceiling plane.
Any panel weighing 1 kg (2.5 lb) per square foot or more (which is most wood) must also be installed per the additional installation requirements of Seismic Design Category D, E, and F.  Some jurisdictions, including the California Building Code (CBC), require wood or other hard or heavy panels to be positively attached to the suspension system.

Sustainable spaces 
Environmentally, many of today’s wood ceilings are certified as products representing responsible production and consumption practices from the forest to the consumer. The major environmental certifications for wood ceilings are as follows. 

Forest Stewardship Council 
Forest Stewardship Council (FSC) certifies that wood products come from responsibly managed forests through a verified chain of custody. 

Rainforest Alliance
Rainforest Alliance certifies wood products are sourced from forests managed to protect endangered species, areas with high conservation value, workers, and communities.  

US Department of Agriculture BioPreferred 
This certifies bio-based products from plants and other renewable sources. 
Additionally, environmental product declarations (EPDs) are standardized, internationally recognized, independently verified, comprehensive descriptions of a product’s full environmental impact. Natural substrate and veneer materials can also make significant contributions to Leadership in Energy and Environmental Design (LEED) credits.

Assistance available
The increasing popularity of wood ceiling systems for sound control has resulted in the need for much more collaboration between specifier and ceiling manufacturer, especially in the case of custom installations. To meet this need, a number of ceiling manufacturers now offer a consultative design service that provides project management for the ceiling system, from concept to completion. It consists of specialists with expertise in both architecture and engineering whose sole mission is to partner with architects and designers in the implementation of signature ceilings.  

Warm acoustical element 
Wood is often one of the most elegant and warm architectural element in a space. As a result, its use in acoustical ceilings is perceived as upscale and stylish, even when used with a standard suspension system and ordinary light fixtures. Since ceilings can also reduce noise levels and help create a calmer interior environment makes the specification of wood ceilings a viable choice, whether it is a new construction project or the renovation of an aging space.	Wood ceiling panels are offered in triangles, trapezoids, and parallelograms as part of a new ceiling system that gives architects the ability to mix and match different panel shapes, sizes, colors, and textures.
Wood is gaining use in ‘free-floating’ acoustical clouds, especially in exposed structure applications. Wood clouds must be perforated and backed to obtain acoustical benefits.
Linear wood veneered ceiling panels at the Miami Cancer Institute, Florida, impart a quiet connection to nature while serving as a wayfinding tool. The panels are backed with an acoustical fleece to control noise.
Acoustical clouds consisting of concealed wood veneer ceiling panels are suspended in a sloped, ribbon-like pattern at the Lyric Opera of Kansas City, Missouri. The panels are perforated in an oval, straight-slotted pattern and backed with a fiberglass infill for acoustical control.
Wood ceilings can provide eye-catching aesthetics along with effective acoustical performance, making them a versatile and functional design element. They can also become a focal point in signature spaces.
Linear wood ceiling panels control acoustics and heighten the visual of the theater at the College Football Hall of Fame in Atlanta, Georgia. Perforated and acoustically backed, the panels are installed in folded planes that go across the ceiling and down the walls.
Wood grille ceilings are growing increasingly popular as design trends embrace the linear look. A wide choice of slat widths, heights, spacing, 
and number of slats per panel are offered.
Additional Information
Author
Sean D. Browne is senior principal scientist for Armstrong Ceiling & Wall Solutions in Lancaster, Pennsylvania, where he leads the Armstrong acoustics program. A member of the Acoustical Society of America (ASA) and ASTM International, Browne has engineering degrees from Florida State University and the University of Miami, and has been published in the journals of the International Symposium on Room Acoustics (ISRA) and Acoustical Society of America (ASA). He can be reached at sdbrowne@armstrongceilings.com.

Key Takeaways
Wood ceilings can provide inviting, eye-catching aesthetics, and also effective acoustical control, making them a versatile and functional design element. To obtain the acoustic benefits, the panels must be perforated and backed with a sound-absorbing material. Wood ceilings offer shorter lead times and lower costs than custom millwork. They are also able to create a rich, natural, and custom look using only standard panels. Today’s wood ceiling systems are offered in a wider variety of sizes, shapes, and forms than ever before. By combining beauty with performance, wood ceilings are well-suited for use in applications ranging from retail, healthcare, hospitality, office environments, and higher education to lobbies, entryways, and conference rooms.

MasterFormat No.
06 00 00–Wood, Plastics, and Composites
09 51 00–Acoustical Ceilings

UniFormat No. 
C10–Interior Construction

Key Words
Divisions 06, 09
Acoustics
Ceiling attenuation class
Noise control
Noise reduction coefficient 
Sound absorption
Wood ceilings
Wood veneers
Better Designs for 
Quality Senior Living
A renaissance in senior communities design drives renovation

by Rockland Berg, AIA, NCARB
Photos © Will van Overbeek. Photos courtesy three
Perhaps no other commercial design market is evolving faster than senior living. What started as a targeted push in the 1990s toward scaling down and decentralizing developments for the elderly—creating models less institutional in aesthetics for aging residents with challenges in health, cognition, mobility, and sensory abilities—has, in recent years, exploded into a full-on typology reboot.

The senior living design renaissance goes far beyond rethinking the residential unit itself. It is important for developments as a whole to nurture community building and echo and connect to existing urban fabrics. While traditionally, amenities such as spas, restaurants, gyms, walking trails, and theaters were left out of senior developments, access to them is now a benchmark for success.
A national gathering of experts at the 2018 Environments for Aging conference in Salt Lake City, Utah, revealed another driver of this trend toward more amenities in the senior and residential care typologies—more owner-operators are trying to attract multiple generations to their communities. While the greatest generation (i.e. those born from 1910 to 1924) still requires options, owners are gearing up to meet the needs of baby boomers.
With this in mind, what are the best ways, in architectural terms, to foster generational coexistence? One trend is the growing implementation of universal design principles in building independent living residences, thereby creating spaces that are homely, while flexible enough to allow occupants to age in one place.
Savvy owner-operators are taking it a step further by integrating hospitality concepts and typologies—as in hotels, resorts, restaurants, and lounges—into the architectural partí or starting point for senior residential care design. Adapting proven hospitality models to senior consumer preferences and carefully tweaking them to incorporate effective housing and healthcare elements has emerged as a successful strategy for many new senior developments. Concepts drafted from hospitality include resident-facing architecture that creates a ‘choreography of discovery,’ as well as discreet but effective back-of house efficiencies, the multipurposing of entertainment and food venues, and an emphasis throughout the property on promoting a sense of well-being.
These novel approaches require a close look at both the codes and standards for senior care as well as key trends in caregiving. The findings have led to opportunities in renovating existing facilities to meet today’s expectations and benchmarks.

Privacy and personalization
Residential care settings have emerged as an essential and common life choice for older adults and people with health challenges and disabilities. Delivering long-term care and life support in a community of neighbors, caregivers, and friends, senior living facilities offer an alternative to in-home services. For those who do not need the intensive level of care (and high costs) offered by nursing homes, but are uncomfortable residing on their own (or with relatives), these community-based living alternatives—typically identified as independent living, assisted living, and memory care—are popular and successful. There are close to 25,000 residential care settings with almost one million dwellers, according to the U.S. Department of Health and Human Services.
Beginning in the early 1990s, the increasing popularity of assisted living stemmed in large part from their mission to allow residents a high degree of privacy. Seniors would seek private rooms and bathrooms, small apartments, and even single-occupancy units with tiny kitchens. Over time, many states adopted new rules requiring private rooms and apartments, though this is not a universal standard.
The minimum requirements for assisted-living facilities (ALFs) in Oregon, for example, call for “individual apartments with a lockable door, private bathroom, and kitchenette facilities conforming to relevant state and federal building codes as well as the Americans with Disabilities Act and Fair Housing Act.”
Shared units in that state, as in many others, are a function of resident choice. For bathrooms, the baseline elements include a toilet, sink, and a roll-in, curb-less shower. Kitchen areas should be equipped with a sink, refrigerator, a removable cooking appliance, counter space, and storage. That is the starting point.
With this in mind, many senior care developments are increasing their offerings of private and personalized living units—as part of their campaigns to make timely, cost-effective improvements based on scale and market conditions. Single-occupancy rooms and private apartments for assisted-living residents earn a premium rental rate while costing less to build in terms of per-unit cost, making them the most profitable and leading developers to refer to them as ‘high-revenue product.’ These revenue additions help the financing of desired amenities and infrastructure, which, in turn, boost resident and employee satisfaction, happiness, and pride. The upgrades satisfy needs to serve the growing demand for today’s aspirational senior lifestyles and future generation appetites. In this way, they improve market competitiveness for existing senior care communities, while leveraging costs across 
a larger business platform.

Planning to renovate
Leading developers and operators in senior care start the renovation process by building a proactive, optimistic consensus with resident community leadership with an eye toward adding ‘high-revenue products’ to support the long-term sustainable value of the area. Before drawing up the architectural concept and project requirements, the owner group establishes a business plan supported by expert partners in the process, including marketing, operations, finance, development, design, and construction. This multidisciplinary leadership team works the plan through consultant expertise with go/no-go steps engaging resident and staff input and communication at key milestones.
A number of the resulting building strategies focus on differentiating senior facility operators in their increasingly competitive markets. Elegant, amenity-rich environments for many residential care communities are designed with a material palette reflecting the importance of connections to art and the outdoors and nature, or biophilia, for engendering a relaxing, healthful atmosphere. For this reason, architects are integrating their designs with nature, utilizing natural materials such as exposed wood and stone finishes in many renovation and addition works. These enhanced community experiences also inspire more visits from family members and friends, who leave the premises, reassured their loved ones are enjoying a high-quality living experience.
One common expansion strategy involves adding an additional wing of independent-living apartments, and perhaps cottage duplexes or ‘big houses,’ to meet market demand. Often the added units are larger than their predecessors, with great-room floor plans, island kitchens, spa baths, media/exercise dens, and walk-in closets. The added units typically feature universal and sustainable design principles in their layouts and specifications. Since land is often scarce in these master-planned communities, below-grade garages offering premium parking and storage can be an attractive, but expensive, amenity.
Another dimension of renovating and expanding 
a senior care community is the opportunity to overlay new ideas in how environments support aging bodies and brains. Today’s medical understanding of dementia and memory impairment, for example, has led to new support models for care delivery, which address both the causes and effects of these health changes. Insights into the stresses exacerbating dementia, for example, can optimize spatial and material designs for care delivery and memory-support wings or pavilions.
These findings optimize architectural and interior design choices, not just care provision. Programming of the memory-care renovations, for example, often follows a pod-based design grouping of 10 to 16 residents in secure, partitioned zones with ample views of nature and the outdoors. Rather than connected by corridors, all shared spaces are open to each other to result in simple circulation pathways ideal for dementia patients.

Access and egress
How residents enter and exit communities and how they experience the indoors and outdoors are central to an enriching, enjoyable living experience. Looking again at minimum requirements, entries today have detailed flooring transitions and materials allowing for ease of movement on foot, with a walker, and by wheelchair. Automatic doors with motion sensors and easily operable, lever-style hardware, where needed, are baseline specifications for public and common areas. Each residential unit should also provide universal access and function.
In most states, the use of the International Building Code (IBC) mandates that for residences up to a certain height, “All units must have an escape window that opens directly onto a public street or alley, yard, or exit court.” Security and life safety are foremost in planning for additions and expansions.
Security is essential to successful communities and often run counter to the desired lifestyle experience or hospitality-inspired amenities. Unobtrusive perimeter detection, access control systems, and closed-circuit monitoring are among the typical approaches to protect residents and caregivers, while conferring a sense of freedom and openness. Along those lines, comfortable access to proximate amenities and shared community spaces is appreciated by residents, who benefit from minimized grade changes and adjacencies that reduce walking.
For specialized memory-care settings, many owner-operators prefer designs maximizing the availability of windows and outdoor views. With this in mind, those wings or pods are planned without double-loaded corridors, allowing more windows and presenting residents with enhanced visual connections to the outdoors, trees, and gardens. On the other hand, studies show when dementia patients see views of exit paths or destinations they may try to leave 
the premises—called elopement in the caregiver’s parlance—so it helps to obscure exit doors, gates, and parking lots. Additionally, lighting systems and solar shading materials can be employed for the clinical purpose of reducing instances of sundown syndrome, or sundowning, which the Mayo Clinic (an academic medical center in Rochester, Minnesota) describes as a “state of confusion occurring in the late afternoon and spanning into the night [including] anxiety, aggression, or ignoring directions.” Low lighting levels and increased shadows contribute to the effects.

Diverse offerings
Another element of renovating existing senior communities highlights the need to achieve balance throughout the campuses or complexes. For example, constructing additions and improvements that add real contemporary value to the community may also necessitate a campaign of strategic improvements and upgrades to bring the rest of the community up to date. Additionally, some owner-operators add high-revenue product where possible to not only increase income, but also to support the needed improvements and additions.
Related to that idea, when adding new residences to a community, it is appropriate to consider a strategy to upgrade the existing units to create consistency of brand and avoid an ‘us versus them’ environment. This needs to be a thoughtfully conceived plan that can occur even before the primary project begins construction, signaling goodwill and conviction to the future posture of the community.
Many of the senior living and care communities operating today were conceived in the 1950s, 1960s, and 1970s. Several of them have undergone modernizations—typically the periodic refreshing of product and retrofits of building systems—that are likely to be structurally and operationally outdated. Many are inefficient and inappropriate for today’s residents and their families.
Even communities built during the 2006 recession, now over 10 years old, suffered from the insecurities of the season, with many unable to realize their full vision during the fragile market conditions. Many of those owner-operators are now reassessing today’s market opportunities, drafting plans to bolster revenue strength and resident vitality, while addressing the larger amenity and healthcare needs of their communities. This regrouping also offers a chance to rebrand and re-message to the coming wave of baby boomers, who are considering simplifying and refocusing their lifestyle aspirations.
This requires resisting the convenience of following a formula, but instead to consider a true hospitality model to retain and attract lifestyle-seeking residents. While the focus of this dialogue is through the eyes of an experienced architect, the big moves before any design discussions should consider the neighborhood’s appetite for change and growth, the surrounding communities and their demand for additional supply, and the pragmatic diagramming for sound business success and risk mitigation.
With the addition of revenue-generating units to the overall community income stream, consideration can be given to underwriting the renovation of worn-out common spaces or older and more institutional healthcare environments. This opportunity responds directly to the demand (“what are you going to do for me?”) of existing residents, while they endure the turbulence of a construction project in their midst. Ultimately, the improved amenities and up-scaled healthcare solutions are a welcome enhancement to the residence of choice.
Opportunities to contemporize finishes and modernize appliances and fixtures, while attending to the installation of universal design elements at showers, sinks, and doorways are all low-hanging fruits, but require strategic planning and logistical forethought to gain resident satisfaction. Infrastructure improvements attending to low water pressure, insufficient Wi-Fi capacity, or poor air quality can be considered during this season of rebirth.
Lighting, for example, is vital to crafting the right mood. In living units, floor plans are more open, often with taller ceilings, extra daylight, and generous windows connecting residents to the outdoors. Color, texture, and acoustics enhance the senior’s world of diminishing capacities, weaving positive and stimulating experiences. Material and daylighting can help seniors with recognition, wayfinding, wellness, and safety.
Subordinate projects can include the adding and diversifying of dining options, expanding entertainment venues, and enhancing wellness components. These integrated improvements are driven by the personal compulsion of existing building occupants and community leadership.
Any rebranding or renovation effort should begin with the recognition and commitment to ‘change for the better,’ while recognizing the risks involved. Defining plan and communicating the vision are paramount to shareholder buy-in. Working the plan and incorporating checks and balances with contingency alternatives has proven to lead to successful and sustainable outcomes.

Process and pragmatism
Residential care projects are complicated right from the beginning, requiring full-time attention to move the growing demand of decision-making forward in a pragmatic and linear process. The decision input is intentionally diverse and specialized to craft a design and final product that is tailored to the prospective resident’s lifestyle expectations.
Despite all the process planning and stewardship, expert leadership will also recognize the need to modify the ongoing process to adjust for changing parameters brought on through external forces such as market demand and construction costs. Unlike acute-care settings, where the goal is for patients to recover and leave the facility as soon as possible, residential settings including ALFs, skilled-nursing facilities (SNFs), and continuing-care retirement communities (CCRCs), the design must speak to and allow for the highest-quality care possible over the longest time needed. Senior residents may need different kinds of care, but all of them seek real comforts, enriching experiences, supportive communities, and a real sense of empowerment and independence.
These desires reinforce the trend toward more hospitality-focused designs. Places designed for hospitality have a reputation for transcending generational differences, and that holds true even when developing housing for seniors. The thinking behind this strategy is people come back to places that feel grand, comfortable, and unique, has a pleasant ambience, and provides a good experience. This is why many successful senior living settings present a series of ‘wow’ moments within each project informing and connecting the residential and service spaces.
Using the luxury-hotel-as-housing model makes senior residents feel more positive and engaged, and also attracts younger consumers to the developments—
a win, win.	Adding, diversifying, and upgrading food service options are common components of effective renovation projects in senior living facilities and residential care communities.
For the repositioning of the 1960-era campus Pinnacle at Eden Hill, New Braunfels, Texas, the architects at three capitalized on the park-like setting above two rivers.
Woodlands at Furman

Woodlands at Furman, a single-site community in Greenville, South Carolina, is currently going through an expansion with high-end hospitality flair. Conceived to introduce a new 1208-m2 (13,000-sf) ‘community village’ space with a fitness center, salon, swimming pool, and multipurpose room, the project scope also includes 40 new independent living apartments, as well as renovations to dining and bar amenities and employee breakroom venues. Gary Koerner, AIA, met with groups of residents and staff during planning to discuss their concerns about the proposed changes, and to ensure the project team meets their needs and circumvents major disruptions for those living and working onsite during construction.
“The tricky part is the sweeping renovation of the dining area,” says Mary Lou Merkt, CEO of Woodlands at Furman. “To meet demand the project has to double our dining capacity.”
The project’s architectural team is coordinating with interior designers and dining consultants to reconfigure the existing floor plan, while expanding the dining area footprint, modernizing the kitchens, and introducing an ‘action station’ with a brick oven, Mongolian grill, and other to-order services. Meanwhile, the exterior of the new community village and the new residence wings will harmonize with the existing architecture, and all interventions will emphasize maximizing penetration of daylight and views of the natural surroundings.
The design team visits the site monthly for ongoing staff and resident meetings. The intent of continued engagement is to maintain a dialogue connecting the construction to anticipated improvements, making those who will be inconvenienced feel invested in the project’s success.	Adapting proven hospitality models, such as emphasizing wellness and ‘discovery’ in resident-facing architecture, can be a successful strategy for senior community repositioning.
The Pinnacle at Eden Hill renovation project introduced hospitality concepts to enhance the residential experience while making the community more appealing and competitive in the marketplace.
Presbyterian Village North

The design concept for Presbyterian Village North (North Dallas, Texas) will implement a cohesive aesthetic across the property’s many structures, while reconfiguring and updating the core common areas and amenities.
Image courtesy three
This 40-year-old, 20-ha (50-acre), park-like senior community in North Dallas, Texas, has received several updates and expansions by multiple architects since it opened, resulting in an incongruent mix of architectural styles. For the current planned expansion and reimagining, the project team is working on a design concept that will reunify the property’s many structures aesthetically, while reconfiguring and updating the core common areas and amenities, and adding a new independent living building that will replace a number of outdated residential units.
To unify the campus architecturally, the design concept will demolish smaller residences now considered obsolete and replace them with a major state-of-the-art residential addition connected to a newly renovated 2787-m2 (30,000-sf) commons building at the core of the community. The reconfiguration of the drive approach and building entrance is elementary to the master plan of improvements. Ironically, implementing this brand vision will require partial demolition of an entrance tower feature originally designed 20 years ago, as part of a previous expansion. The improvements will unify the overall aesthetic and improve wayfinding significantly, so the loss of the tower feature was considered objectively and without sentimentality by the architects.
“The goal is a well-thought-out experience and environment to support the residents’ lifestyle,” says CEO Tim Mallad, “with an aesthetic that provides a subtle ‘wow’ factor, a place that is livable and also feels good to live in.”
To support this goal, the architects focused on interventions that will deliver the desired experience within the requirements for high-performance operational efficiencies. The design will draw residents and visitors through sequences that unfold ever-widening vistas, making the most of the natural beauty of the trees and water course on campus—features retirees who are considering the greater Dallas Metroplex are drawn to.
“We worked closely with the architects on the ‘character profile’ we wanted for our residents. The planning and design process were fully engaged and we, the client, were encouraged to be creative,” adds Mallad.	The Pinnacle project updated the overall aesthetic, including both landscape and architecture, to promote a sense of wellness among residents and visitors.
Additional Information
Author
Rockland Berg, AIA, is founding partner of three, an architecture practice headquartered in Dallas, Texas. Involved in senior living architecture for more than two decades, Berg is well-known throughout the market and speaks frequently on developing trends, including on NBC Nightly News. He can be reached at berg@threearch.com.

Key Takeaways
Traditionally, amenities such as spas, restaurants, gyms, walking trails, and theaters were not included in senior developments, but access to them is now a benchmark for success, as more facility owner-operators are trying to attract multiple generations to their communities. To foster generational coexistence, project teams are increasingly implementing universal design principles in building independent living residences. Savvy developers are also integrating hospitality concepts and typologies—as in hotels, resorts, restaurants, and lounges—into the architectural partí. Thus, adapting proven hospitality models to senior consumer preferences and tweaking them to incorporate effective housing and healthcare elements has emerged as a successful strategy for senior developments.
MasterFormat No.
06 00 00–Wood, Plastics, and Composites
08 10 00–Doors and Frames
08 50 00–Windows
08 70 00–Hardware
09 75 00–Stone Facing
12 20 00–Window Treatments
25 50 00–Integrated Automation Facility Controls

UniFormat No.
B20–Exterior Vertical Enclosures
C1030–Interior Doors
C20–Interior Finishes
C2030–Flooring
D20–Plumbing
D7010.10–Access Control
G2050.30–Recreational Areas

Key Words
Divisions 06, 08, 09, 12, 25
Access control systems
Automatic doors
Flooring
Senior living facilities
Solar shading
Universal design
Natural Stone 
Creates Iconic Public Spaces
by Jason Kron
Photo © Nelson Byrd Woltz

Worldwide, cities are growing. Today’s megalopolis’ must not only provide its citizens with basics such as housing and transportation, but also with attractive public places for leisure time and city identification. Outdoor spaces transcending function and offering beauty and serenity in the bustling city landscape often become iconic. For thousands of years, natural stone has provided one of the best materials for creating outdoor spaces in cities.

Stone meets sustainability goals
For gathering places such as parks with fountains, memorial sites, and urban plazas, natural stone offers numerous benefits. It is a timeless, classic building material offering beautiful aesthetics and modern applications. Natural stone has one of the lowest embodied carbon levels among building materials.
Further, owners and designers can now specify sustainably certified natural stone options. Natural stone quarriers and fabricators with the “Certified Genuine Stone” label comply with the American National Standards Institute/National Stone Council (ANSI/NSC) 373, Sustainable Production of Natural Dimension Stone. The third-party verified ANSI/NSC 373 defines environmental, ecological, socially responsible, and human-health metrics for extracting and manufacturing natural dimension stone.
Projects seeking green building certifications can choose certified natural stone to achieve their design goals. ANSI/NSC 373 aligns with materials and resource credits for U.S. Green Building Council’s (USGBC’s) Leadership in Energy and Environmental Design (LEED) v4 and the materials petal of International Living Future Institute’s (ILFI’s) Living Building Challenge (LBC).

Standing the test of time
Capable of withstanding the elements of weather and human interaction, natural stone performs well in urban hardscapes. A low-maintenance natural stone requiring minimal upkeep (e.g. granite) is a suitable material for public memorials. The Martin Luther King, Jr. National Memorial in Washington, D.C., Victory Memorial Drive in Minneapolis, and the East Tennessee Veterans Memorial in Knoxville, Tennessee, are beautiful civic tributes constructed with granite.
Structures built with natural stone more than 50 years ago remain standing today as a testament to the material’s resilience. One noteworthy example is the Air Force Academy Cadet Area in Colorado Springs (Denver), which was completed in 1958 and covers about a fifth of a square mile in the heart of the academy’s campus. It features concrete retaining walls finished with gray granite slabs.
As is noted in the National Historic Landmark Nomination, the retaining walls “accentuate the height of the plateau...[and] rather than blend the retaining walls into the colors of the earth, SOM [the project architect] chose to create an almost temple-like appearance. Architectural Forum declared that the architects ‘shaped the slopes as powerfully as the Babylonians, the Incas, and the Greeks once did.’”1
A similarly enduring icon is the “Word of Life” mural on the Hesburgh Library at the University of Notre Dame, Indiana. Completed in 1964, the mural is composed of approximately 6700 individual pieces of granite, in more than 140 colors. An article in the university’s journal, the Notre Dame News, emphasizes the durability of the granite and quotes Rev. Theodore M. Hesburgh, CSC, president emeritus of Notre Dame as saying, “The climate here is abominable at times and no one could say that it would last. The amazing thing is that it has lasted this long, and it has kept the richness of its color.”2
The Franklin Delano Roosevelt Memorial on the National Mall in Washington, D.C., is another important symbol of civic pride featuring granite. For this project, sourcing American stone was a particularly important requirement. The memorial consists of 4-m (12-ft) high walls of rugged, split granite appearing as though they have just emerged from the quarry. The walls encompass four outdoor ‘rooms,’ signifying the four terms of Roosevelt’s presidency. Dedication of the memorial in 1997 marked the culmination of a 20-year effort.
In addition to providing a long-lasting building material, natural stone helps project teams create interesting frameworks for open and enticing spaces. With natural stone, design teams can:
• create a sense of place;
• provide a tactile experience for the public; and
• express the cultural and natural environment.

Sense of place
The Denver Union Station is the nucleus of the city’s multi-modal transportation system, including commuter trains, light rails, and buses. Originally constructed in 1881, the landmark was recently renovated and reopened to the public in 2014. Surrounding the exterior of the project is a series 
of public spaces designed to connect the site and create gathering areas and event locations for denizens of Denver.
To create a sense of place, the project design team incorporated popup fountains where children splash and play in summer months. The fountain is computer-programmed to create numerous effects, and uplighting adds nighttime beauty. In winter, the inactive fountain leaves an unhindered hardscape area.
While sunshine, restaurants, and moveable chairs and tables characterize the south plaza, the quieter north plaza features raised perennial beds, abundant shade, and granite benches for seating.
Granite was a primary building material for the plaza, selected not only for its beauty, but also for its surface hardness and durability. According to the owner, the team achieved its goal of making the union station the most attractive public space in Denver.

Front door to the city
In many cities, natural stone can transform unused or underutilized spaces into vibrant public areas. Such was the case with the Dilworth Park project in Philadelphia, a revitalization of the city’s aging center square, formerly known as Dilworth Plaza. The design team transformed an inaccessible, multilevel plaza into a vibrant, open civic space. Situated above Philadelphia’s main transportation hub, the park also serves as a gateway to the city’s public transit.
Dilworth Park’s new design is a fusion of modern and historic, and granite plays a key role. According to the design team, granite was selected for its ability to provide a contemporary look while complementing the historic surroundings. Further, the design team noted the importance of using stone for projects because of its low embodied energy.
Stone was a suitable choice for the new plaza’s surface, but designers were challenged with determining the best way to channel stormwater. The stonework had to maintain sufficient tolerance to achieve the required drainage characteristics. Exceptional fabrication with computer numerical control (CNC) technology achieved the precisely shaped stones meeting the specifications needed for drainage (See “CNC Technology Brings New Era of Stone Fabrication,” page 54).
CNC technology also allows producers to create shapes and designs in stone that were not possible even a few years ago. For example, curved stone walls can be more precisely cut, aligned, and joined together. Electronic files provide cutting details allowing even for the construction of sculpture and other art installations. Not only does the level of accuracy available when using CNC permit greater freedom of design, but also the ability to control the design concept from development through fabrication results in better project outcomes and quality control. The marriage of cutting-edge technology with the traditional material of stone allows for new paths of creativity, while the resulting designs maintain a time-honored, classic feel.

Cultural and natural environment
In St. Louis, Missouri, Citygarden provides an excellent example of urban revitalization as new generations develop an appreciation for downtown living and amenities. Designed to provide a vibrant and serene urban oasis, and funded by the Gateway Foundation, Citygarden sits at the heart of the Gateway Mall just a few blocks west of the famous Gateway Arch and Mississippi River. The redesign developed Citygarden from a two-square-block space that was underused for decades and often sat idle as an open lawn.
The foundation and City of St. Louis wanted the garden to embody a timeless quality evoking the city’s history and spirit. The selection of natural stone for this project was instrumental in obtaining that quality. The foundation wanted to ensure the park would not be dated and would remain durable for decades to come. As such, the selection of granite, limestone, and bluestone provided the durability to withstand harsh environmental elements and heavy use, while also creating a dramatic and aesthetically pleasing visual effect. The foundation liked the use of limestone native to the area for sustainability purposes and its ability to help knit the garden to its regional geology. The granite color selections complement the glass pavilion café in the northeast quadrant of the garden. Totally, the project encompasses 3345 m2 (36,000 sf) of granite in paved areas.
Citygarden is structured as three precincts delineated by two walls. The northern precinct represents the high upland ground and the river bluffs. The middle represents the low ground or floodplain. The southern band represents the cultivated river terraces. While all the territories are interrelated and interconnected, each precinct possesses distinct characteristics. The first wall, granite-capped and offering seating, snakes through the park’s southern portion. The arcing second wall measures 168 m (550 ft) long and is constructed of Missouri limestone.
While providing park space, Citygarden also serves as a sculpture garden including 24 modern and contemporary works. Other features include a massive ‘spray plaza’ and a split-level pool whose two parts are joined by a waterfall. The project has won the Urban Land Institute Amanda Burden Urban Open Space Award. The award is designed “to recognize an outstanding example of a well-used public open space that has spurred regeneration and the transformation of the surrounding community.”
During the opening ceremony for the park, Mayor Francis Slay said, “With one stroke, Citygarden has made downtown so much more attractive as a place to do business, and as a place to live, too.”

Durability and performance
The city of Cincinnati, Ohio, has used stone so abundantly in its public spaces and city landmarks that a paper highlighting this use of stone was published in celebration of Earth Science Week 2000.3 The paper, formatted as a walking tour celebrating stone as a natural resource, highlighted the extensive use of granite, including in the city center’s Fountain Square where Bavarian igneous rock composes the fountain itself. Both polished and unpolished granite elements  are used for paving, benches, stairs, railings, and a performance stage.
More recent developments in Cincinnati have continued to rely on stone as a durable, aesthetic building material. A transformation of the city’s riverfront began in 2008 when a piece of once-dormant land was envisioned to become the region’s new gateway. The project was a response to redevelopment of a 1960 interstate expressway that had consumed a huge swath of riverfront acreage and severed access between the city’s downtown and riverfront.
Construction on the riverfront started with the 18-ha (45-acre) Smale Riverfront Park and adjacent 7-ha (18-acre) development known as the Banks. The park design accommodated the area’s inevitable flooding as well as provided durability in the face of aggressive winter de-icing. Designers selected materials that would minimize ongoing maintenance and also provide a long-term cost advantage, with initial incrementally higher prices being offset by lower repair costs later. Granite was chosen for a grand stairway and bicycle ramp not only because of its resistance to salt and flood damage, but also for its color and texture that would enhance the park’s visual appeal.

Conclusion
The creation of a public space is an important task leaving a lasting imprint on a city’s legacy. Perhaps, the noted landscape architect Carol R. Johnson sums it up best: “A great event is not made out of any of these details: it is just a layer of enrichment in a whole experience.”	

Notes
1 For more information, visit npgallery.nps.gov/NRHP/GetAsset/b41bd68a-28e8-4c87-a096-d5b9621d6640.
2 Read the article at news.nd.edu/news/touchdown-jesus-turns-40.
3 Access the paper at geosurvey.ohiodnr.gov/portals/geosurvey/PDFs/Tours_Walking_Driving/cinctour.pdf.
Constructed with 4645-m2 (50,000-sf) of granite, the Martin Luther King, Jr. National Memorial in Washington, D.C., is capable of withstanding the elements of weather and constant human interaction.
Photos courtesy Coldspring
The Air Force Academy Cadet Area in Colorado Springs, Denver, was completed in 1958 and features concrete retaining walls finished with gray granite slabs.
The Franklin Delano Roosevelt Memorial in Washington, D.C., consists of 4-m (12-ft) high walls of rugged, split granite that appear as though they have just emerged from the quarry.
Completed in 1964, the iconic “Word of Life” mural on the Hesburgh Library at the University of Notre Dame, Indiana, is composed of approximately 6700 individual pieces of granite, in more than 140 colors.
CNC Technology Brings New Era 
of Stone Fabrication
Computer numerical control (CNC) technology has made its mark on stone design and fabrication, providing numerous benefits to those who take advantage of its capabilities. With computers controlling the machines, stone fabricators produce intricate, inspiring creations with exact precision once thought impossible or too costly to achieve. As a result, architects and designers are expanding their creative limits and experiencing many benefits including:
• increased freedom of design;
• control of the design concept from development through fabrication;
• quality control; and
• accuracy of stone shaping and the final fit and finish.
Despite CNC’s benefits, many design professionals hold misperceptions about the process. Chief among the misconceptions is CNC is only used for granite slabs. It is often difficult to imagine a computer-controlled machine handling a large block of stone and producing the result of 
a finely trained sculptor with a chisel in hand. Quite the opposite, CNC machines can accept both slabs and cubic stones of all sizes with ease, depending on the type of machine type.
Another misperception is the CNC process is not budget friendly. Although CNC technology is advanced, it is not cost-prohibitive. Historically, large profiled stone components and cubic free-form shapes were labor intensive to produce. Today’s designs, in most cases, begin as a digital project in one of the many computer-aided design (CAD) or digital design tool software packages. Using this ‘master model’ format, the fabricator realizes lower costs since much of the drafting work required for the old manual method is eliminated. Further, CNC achieves a very fine tolerance, reducing the need for multiple or follow-up processes. Fabrication and lead time are reduced, and custom designs are easier on the budget.	A granite stairway and bicycle ramp at the Banks park in Cincinnati, Ohio, provides resistance to salt and flood damage as well as a color and texture that enhance the space’s visual appeal.
Photo © Patrick McCue Photography
Additional Information
Author
Since 1999, Jason Kron has specialized in the natural stone industry. In his current role as director of sales at Coldspring, Kron works with the architectural and design communities to meet their natural stone needs and with cemeteries for product and development needs. He can be reached via e-mail at jkron@coldspringusa.com.

Key Takeaways
Worldwide, cities are growing. Today’s megalopolis must provide its citizens not only with basics such as housing and transportation, but also with attractive public places for leisure time and city identification. For thousands of years, natural stone has provided one of the best materials for creating iconic spaces in cities because of its many benefits. For gathering places such as parks with fountains, memorial sites, and plazas, natural stone is 
a suitable material.

MasterFormat No.
04 40 00–Stone Assemblies

UniFormat No.
G2030–Pedestrian Plazas and Walkways
G2080–Landscaping

Key Words
Division 04
ANSI/NSC 373
Landscape architecture
Natural Stone
Urban hardscapes
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failures
Five Common Failures in Curtain Wall Installation
Although the means and methods are the responsibility of the general contractor and subcontracted trades, it is wise to conduct a deeper dive into the installation ‘nuts and bolts’ to better understand possible areas for creative collaboration resulting in a cohesive building envelope.

Focus areas
Curtain wall installation requirements, means, methods, and materials continue to evolve, yet many of the basics remain the same. Most curtain walls have similar installations, but differ on size, location, alignment, and anchorage of components. Here are some of the critical areas to focus on for a successful curtain wall installation.
1. F
ailure to correctly size or properly position weep holes in the curtain wall pressure plates and covers are all too common. The drainage path and the size, type, location, and frequency of weep holes vary by manufacturer. Some systems are weeped via holes in the bottom of the covers and others at the ends through the joint between the horizontal at vertical cover intersection. For example, if the weep is located too high, it will trap water in the glazing pocket causing the bottom of the insulated glass unit (IGU) to sit in water, and likely, voiding warranty. Weeping strategy must be clearly identified in installation instructions and shop drawings according to the manufacturers’ requirements.
2. 
Failure to prepare additional pressure plate fastener holes can occur when an installing contractor needs to modify material in the field. Additional fastener holes should be prepared at the ends of the pressure plate to provide adequate pressure. The types of pressure plates and their required compression can be unique to each manufacturer, but fastener holes typically are within 50 mm (2 in.) of the vertical member. In simple terms, it is advisable to ensure the correct screws are put in at the proper place with the appropriate torque.
3. 
Failure to seal around the front of shear blocks, and along the front edges of horizontal sections can lead to air and water infiltration. When it comes to sealant, more is not better. Too much sealant can plug weeps and mask leaks making troubleshooting very difficult.
4. 
Failure to install or properly seal the water dams or zone dams can lead to serious damage. Water dams are a critical component in typical curtain wall systems. They are installed at the horizontal to vertical frame intersections to keep the water compartmentalized at each lite.
	The water dams at structural glazed verticals 
	
also should be sealed on their horizontal tongues. Additionally, sealant should be applied to the water dam’s frame prior to installing the vertical pressure plate. If a water or zone dam is accidentally left out or improperly sealed, water will drain down to next lite and can flood the system.
5. 
Failure to seal other key connections can result in the curtain wall system’s poor performance and water damage to critical areas. Sealant must be applied to the horizontal gasket abutting the vertical gasket. It also needs to be between the horizontal pressure plate and the vertical cover. Finally, it is recommended to ensure sealant is applied around the base of the vertical mullion running to the building substrate at an entrance.
To avoid these common failures, it is best 
to review each curtain wall manufacturer’s guidelines. Additional best practices include specifying performance mockups are tested prior to installation and field testing occurs early in the built phase. Some specifications will also indicate the work must be done by experienced and certified installing contractors. Helping prevent these key points of failure will further ensure the curtain wall meets the required performance.	More is not better when it comes to sealant as too much of the material can plug weeps and mask leaks, thus making troubleshooting very difficult.
Doug Dietrich, AIA, CSI, CDT, is an architectural representative with Tubelite Inc. He is an architect with more than 30 years of experience helping building teams achieve energy efficiency, structural compliance, condensation resistance, and blast hazard and hurricane mitigation. Doug can be reached at ddietrich@tubeliteinc.com.
The opinions expressed in Failures is based on the author’s experience and does not necessarily reflect that of The Construction Specifier or CSI.