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Water-source VRF Zoning 101: Combining geothermal with variable refrigerant flow

Photo © OnSite Photography

Photo © OnSite Photography

by Pamela Androff, PE, LEED AP

Variable refrigerant flow (VRF) zoning and geothermal systems are two of the most energy-efficient options for heating and cooling buildings. Now, the benefits of both systems can be combined. This article provides an overview of geothermal (or water-source) with VRF zoning technology, and its advantages compared to traditional geothermal systems, air-source VRF zoning systems, and conventional HVAC systems. Additionally, the article discusses considerations for specifying water-source VRF zoning systems and provides case studies of successful applications.

VRF zoning provides precise comfort control to buildings with multiple floors and areas by moving refrigerant through piping to the zone to be cooled or heated. Some VRF zoning systems offer highly responsive simultaneous cooling and heating, which maximizes use of heat energy that otherwise would be expelled outdoors. Regardless of the time of day, sun or shade, season, or special requirements, VRF zoning systems can deliver comfort tailored to each zone or space.

This water-source variable refrigerant fl ow (VRF) zoning systems combine the convenience of geothermal systems with the sophistication of VRF zoning systems. These are among the most effi cient and reliable cooling and heating technologies. Image courtesy Mitsubishi Electric US Cooling & Heating Division

This water-source variable refrigerant flow (VRF) zoning systems combine the convenience of geothermal systems with the sophistication of VRF zoning systems. These are among the most efficient and reliable cooling and heating technologies. Image courtesy Mitsubishi Electric US Cooling & Heating Division

A VRF zoning system was an ideal choice for Muscatine County Courthouse in Iowa because the wiring and refrigerant lines could easily retrofi t into the old chase walls without altering the existing historic structure. Photos © OnSite Photography

A VRF zoning system was an ideal choice for Muscatine County Courthouse in Iowa because the wiring and refrigerant lines could easily retrofit into the old chase walls without altering the existing historic structure. Photos © OnSite Photography

 

 

 

 

 

 

 

 

 

 

 

Geothermal technology overview
Outdoor temperatures fluctuate with the changing seasons, but underground temperatures do not change as dramatically because of the earth’s insulating properties. Geothermal systems typically consist of heat exchange equipment located indoors, and a buried system of pipes—called ‘loops’—to capitalize on constant underground temperatures to provide energy. Water in the heat exchanger circulates through loops below the surface, absorbing or expelling heat to the below-ground heat sink depending on the time of year. This function ultimately reduces the load on the compressor during the cooling and heating cycles, and results in significant energy savings.

Water-source VRF zoning systems combine a geothermal system’s benefits, with the sophistication of VRF zoning. Together, the technologies take advantage of the inverter-driven compressor coupled with a closed geothermal loop instead of air as a heat exchange medium.

Water-source VRF zoning systems have numerous benefits, including many that users have come to expect from air-source VRF zoning systems.

Flexible installation
Installation is possible in tight spaces because two-pipe designs require less space than ducted systems. Some VRF zoning systems require three- or four-pipe designs, which call for more refrigerant line runs and more brazed connections. Two-pipe designs minimize the total distance of refrigerant line and system connections, which can help reduce installation labor and eventual maintenance costs.

Relatively small water-source VRF zoning condenser units are mounted indoors and can be installed in compact utility closets with minimal access on either side of the unit. Refrigerant, water, and electrical connections are housed on the front of the unit for convenient access.

Application variety
Outdoor water-source VRF zoning units can be connected to an array of indoor unit styles to accommodate the space’s specific needs. All styles are quiet, easy to maintain, and provide optimal comfort. The configuration of the below-ground loop systems can be customized to accommodate the building’s surroundings. For example, loops can be buried under a building or a parking lot by drilling either vertical bore holes or horizontal trenches.

Low maintenance
Water-source VRF zoning systems offer easy maintenance. One VRF unit on the water loop can be serviced without taking the whole system offline. Most indoor units have washable filters that are easy to clean or replace. Condensers can be housed in floor-level utility closets for convenient access and minimal disruption to occupied spaces.

Payback period
Installing a water-source VRF zoning system may have a higher upfront cost. Over time, the system efficiency and low-maintenance expenses can offset the system’s initial cost in energy savings. The average payback period is 10 years.

Advanced controls
VRF zoning systems offer several controller types. A central controller can monitor, schedule, and control up to 50 indoor units. Multiple central controllers can be networked together with integrated centralized control software and systems can be tied to a building management system (BMS) using LonWorks and BACnet (data communication protocol for building automation and control networks).

Clean energy source
Water-source VRF zoning systems use the clean and sustainable energy stored in the earth to heat and cool buildings. This is a more environmentally responsible and efficient source of energy compared to non-renewable fossil fuels.

System efficiency
VRF zoning technology includes the use of an inverter-driven compressor in the outdoor unit that varies the motor rotation speed, allowing it to precisely meet each zone’s load requirement while reducing power consumption. Also, as mentioned, geothermal VRF zoning systems take advantage of stable ground temperatures for even greater efficiencies.

The systems always have a condenser unit in combination with an indoor air-handler unit. The condenser can be located indoors or outside, depending on the system.

Tax credits
Water-source VRF zoning systems may qualify for up to a 10 percent federal commercial tax credit for the total installed cost of the geothermal system.

An attractive wood casing covers the indoor units, seamlessly blending into the historic design.

An attractive wood casing covers the indoor units, seamlessly blending into the historic design.

When Miami University wanted to renovate its two oldest buildings and demonstrate its commitment to sustainability, the university selected water-source VRF zoning systems. The installation resulted in a 61 percent decrease in energy consumption, making the university’s two oldest buildings the most effi cient.

When Miami University wanted to renovate its two oldest buildings and demonstrate its commitment to sustainability, the university selected water-source VRF zoning systems. The installation resulted in a 61 percent decrease in energy consumption, making the university’s two oldest buildings the most efficient.

 

 

 

 

 

 

 

 

 

 

 

Water-source VRF zoning system advantages
A significant advantage of water-source VRF zoning over traditional geothermal systems is the ability of the compressor units to connect to up to 50 indoor units. Traditional geothermal systems require multiple compressors in each zone and the units must be installed in the ceiling space. With water-source VRF systems, fewer condenser units result in easier installation, less equipment, and reduced maintenance. Water-source VRF zoning system condensers are serviceable at floor level, rather than the ceiling, for improved access and minimal disruption to occupied spaces.

Another benefit of water-source VRF zoning technology over standalone geothermal systems is the potential for heat recovery. Some systems allow for simultaneous cooling and heating. In these applications, a VRF zoning system’s compressor operating power will be reduced during heat recovery periods compared to an equivalently-zoned traditional geothermal system. Water-source VRF zoning technology often exceeds the efficiency of traditional geothermal systems due to the ability to recover energy more efficiently on the refrigeration side first, compared to multiple distributed traditional geothermal systems.

Water-source VRF zoning systems contain many of the same benefits associated with their air-source counterparts, along with additional benefits. The most significant advantage over air-source systems is the heating de-rates.1 In colder climates, the expected capacity of the air-source VRF zoning equipment can be reduced due to the temperature. Sometimes the equipment must be upsized to handle the peak heating demand, but with water-source VRF zoning systems, this is not an issue. Coupling the VRF zoning units with a geothermal loop provides the benefit of higher efficiencies from milder loop temperatures. The power required by the outdoor units may be reduced by as much as 35 percent when compared to air-cooled systems.

Additionally, there are many advantages of these systems compared to unitary or boiler/chiller HVAC systems. The combination of geothermal and VRF zoning technology results in significant energy saving potential due to the milder loop temperatures requiring less work from the condensers. The water-source VRF zoning outdoor units are small, eliminating the need for large equipment rooms or above-ground space. Regarding indoor units, the refrigerant, water, and electrical connections are on the front of the unit so the condensers can be installed in relatively small utility closets with minimal access on either side of the units. VRF zoning systems also offer the benefit of inverter-driven compressors, which vary the refrigerant flow to each unit for precise and efficient control.

A two-pipe water-source VRF zoning system tied into Philadelphia’s Strawberry Mansion’s existing geothermal well fi eld and saved $50,000 up front on installation costs when compared to a four-pipe system. Photos © Tom Crane

A two-pipe water-source VRF zoning system tied into Philadelphia’s Strawberry Mansion’s existing geothermal well field and saved $50,000 up front on installation costs when compared to a four-pipe system. Photos © Tom Crane

The discreet indoor units blend with Strawberry Mansion’s historic decor while providing the climate control necessary to preserve the mansion’s collection of antiques and fi ne art.

The discreet indoor units blend with Strawberry  Mansion’s historic decor while providing the climate control necessary to preserve the mansion’s collection of  antiques and fine art.

 

 

 

 

 

 

 

 

 

 

 

 

Specifying water-source VRF zoning systems
Water-source VRF zoning systems are ideal for climates experiencing significant temperature variations throughout the year, where having the heat exchange medium located in a temperature-stable underground environment will have the most impact. Due to the combined energy efficiency of ground-source and VRF zoning technology, water-source VRF zoning systems can result in one of the most energy-efficient heating and cooling systems available.

As with all VRF zoning systems, the indoor units require minimal ductwork (if any at all), making them ideal for retrofitting older buildings and replacing old boiler/chiller systems. These systems are ideal for applications such as schools, offices, medical centers, or any building in which individual zone control is essential to occupant comfort.

There are some factors to consider when installing water-source systems. Geothermal systems require a series of wells or loops. Constructing a well field, and having the land to do so, may be cost-prohibitive in some cases, and impossible in large metropolitan cities where space is at a premium. Additionally, anytime digging into the earth is involved, care must be taken to not disturb any existing underground infrastructure. Lastly, installing a geothermal well field may be expensive up front; however, over time, these systems tend to pay back in the form of energy savings.

Muscatine County Courthouse
Iowa’s Muscatine County Courthouse is a 1907 Beaux-Arts style building listed on the National Register of Historic Places. Courthouse officials needed a replacement for a failing 30-year-old cooling and heating system that was costly in both upkeep and energy usage. They wanted a low-maintenance, high-efficiency replacement system.

Aesthetics and ease of installation were also an issue. The indoor units were loud and moldy. The large condenser unit sitting prominently on the historic building’s roof was an eyesore and needed to be replaced with a smaller unit that could be housed elsewhere. The building’s 609-mm (24-in.) thick limestone walls made the possibility of retrofitting ductwork difficult. Court sessions were conducted throughout the installation, ruling out any system requiring extensive demolition and construction.

The Muscatine County Board of Supervisors had already invested in drilling a geothermal test in anticipation of replacing the old HVAC system. The board selected a water-source VRF zoning system that would interface with the existing geothermal field. The specifying engineer and the board felt the geothermal system was especially suited for Iowa’s climate, where it is not uncommon for winter temperatures to dip below –23 C (–10 F).

A ductless, two-pipe design would save on labor and equipment cost because it required far less fittings on the refrigerant lines than a three- or four-pipe system. The ductless design also meant the installers did not have to drill through the thick limestone walls and disrupt court sessions. The compressor units could be easily transported down the stairs into the courthouse’s basement where they would be housed, rather than on the roof.

The installation proceeded smoothly and court sessions were not disrupted by the installation.

“Judges were holding court during the transition, and we could not afford to have a lot of banging, pounding, and installation of new equipment,” said Sherry Seright, county budget director.

The system also provided the desired energy-efficiency levels. Courthouse officials observed in the first summer of operation the geothermal field could handle the campus system heat transfer requirement with just 20 percent of the design flow.

Due to the installation’s success, the board decided the water-source VRF zoning systems would be the new standard for any future HVAC retrofits for Muscatine County. They currently have plans to design geothermal VRF zoning systems for two additional county-owned buildings.

Elliot and Stoddard Halls, Miami University
Miami University of Ohio, in Oxford, is the 10th oldest public university in the United States. Its two oldest buildings—Elliott and Stoddard Halls—needed a new cooling and heating system to replace the ineffective and outdated existing coal-fired steam heat system.

Selecting a new HVAC system presented two distinct challenges. The first was the need to preserve the building’s architectural integrity. Both were listed on the National Register of Historic Places and neither had existing ductwork, making a central air solution impossible. The second challenge was meeting the school’s energy-efficiency goals. The university developed a utility master plan that prioritized energy efficiency and mandated moving away from inefficient technologies like coal burning.

“Renovation of any historic building is a complex undertaking requiring a balance between the original architecture and modern building systems,” said Alec R. Carnes, PE, CEM, LEED AP, and senior principal of mechanical engineering, Heapy Engineering, designers of the system.

The design team specified a geothermal VRF zoning system for the job. “Geothermal is advantageous for our climate in Ohio, where heating and cooling loads are closely matched over the year,” said Doug Hammerle, PE, Miami’s director of energy systems. “This helps balance the well field temperature and maximize the efficiency of the system.”

Seventeen 182-m (600-ft) deep geothermal wells were placed under the sidewalks surrounding the halls. As modern footings were unknown 150 years ago, the hand-dug basements had no space for heat pumps. An easy-to-access mechanical room was built into the attic of each hall for the three heat pumps and centralized controller.

In 2011, Elliott and Stoddard switched from coal-fired steam heat to geothermal heating and cooling. Metered as one, the two halls showed an annual 61 percent decrease in energy consumption compared to 2010. The oldest buildings on campus became the most energy-efficient.

The VRF zoning systems’ ductless design also preserved the original aesthetic of the buildings. The team selected floor-mounted indoor units that could be concealed in cabinets, lending the historic look of a radiator case.

“None of this would have been possible without the two-pipe system design,” Hammerle said. “The interior would have been severely cut up with a hydronic four-pipe system.”

Strawberry Mansion, Philadelphia
Built in 1789 as a summer home, Philadelphia’s Strawberry Mansion is now a museum, but the historic building needed renovations.

One of the most pressing needs of the rehabilitation process was a new cooling and heating system to replace the existing system that dated back to the 1930s. The museum had never been centrally air-conditioned and it needed reliable climate control for the museum’s collection of antiques. With 929 m2 (10,000 sf) on four levels, 23 rooms, and masonry-bearing walls, it was a challenge to find a central cooling and heating system that would be unobtrusive and have little impact on the home. Additionally, the museum wanted to adhere to the Greenworks Philadelphia Plan—a six-year plan launched in 2009 with the goal of making Philadelphia the greenest city in America. There was a strong desire to find an inventive, green building solution to this challenge.

The mansion already had an existing 12-well geothermal field and the project team first considered a four-pipe water-based system. They soon found it was impractical to install. The 200-year-old stone walls could not accommodate many of the 609 X 203-mm (24 X 8-in.) deep chases required for the four-pipe design. In many areas, there was no space for ductwork or for pipe routes perpendicular to structural elements.

A water-source VRF zoning system was able to meet the unique needs of Strawberry Mansion. The two-pipe system and compressor units could easily fit in the old chase walls and ceiling where there was no space for ducting. The flexibility of the refrigerant lines, as opposed to ductwork and diversity of indoor unit styles, were well-suited for the design restrictions posed by the historic structure.

The design team placed the two water-source heat pumps in the basement. They are specifically engineered for closed water loop systems that would efficiently interact with Strawberry Mansion’s existing 12-well geothermal field. Designed to fit in small spaces, these units take up little room and are flexible enough to cool or heat up to 50 individual zones maximizing energy, equipment, and installation efficiency.

The system met the museum’s energy efficiency expectations and also saved the owners $50,000 upfront, compared to the original four-pipe proposal.

“Our collection has suffered from decades of no air-conditioning or humidity control,” said Beth Kowalchick, president of the all-volunteer 1926 Committee who presided over the restoration. “After a few months, I could see a noticeable difference in the appearance of our textiles, prints, antique furniture, and fine art.”

Conclusion
Technology combining variable refrigerant flow zoning and geothermal systems—two of the most energy-efficient options for heating and cooling available—can benefit projects compared to traditional geothermal systems, air-source VRF zoning systems, and conventional HVAC systems.

Notes
1 De-rates are a reduction in capacity. Lower de-rates is an advantage, meaning the system operates more efficiently. For example, if a system operates at 100 percent heating capacity at −18 C (0 F) degrees and 85 percent heating capacity at −23 C (−10 F), it has a heating de-rate of 15. Water-source VRF zoning systems tend to have lower heating de-rates than air-source systems—an advantage. (back to top)

Pamela Androff, PE, LEED AP, is product manager–commercial and product planning for Mitsubishi Electric’s U.S. Cooling and Heating Division. In 2013, she became the youngest person to serve as president of American Society of Heating, Refrigerating, and Air-conditioning Engineers’ (ASHRAE’s) Atlanta chapter. In 2014, Androff was named one of Consulting-Specifying Engineer’s “40 Under 40,” which recognizes young engineers shaping the future of the industry. Androff earned a bachelor’s degree in mechanical engineering from the University of Central Florida (Orlando), where she served as president of the American Society of Mechanical Engineers (ASME) chapter. She can be contacted by e-mail at pandroff@hvac.mea.com.

Designing for Exterior Tiles: Applications from specification to installation

Photo courtesy TEC/H.B. Fuller Construction Products

Photo courtesy TEC/H.B. Fuller Construction Products

by Tom Plaskota, CDT

Tiled walls, patios, and walkways make a powerful first impression. A well-executed exterior installation can attract customers to a business, or finish off a public space. Although worthwhile, exterior installations present potential complications requiring the examination of many factors.

The Tile Council of North America (TCNA) recommends considering various conditions of a project’s location, including:

● local climate;
● temperature fluctuations;
● humidity fluctuations; and
● freeze-thaw cycling.1

These factors must be taken into account through every step of a project—from product specification to installation. The right installation materials—effectively installed to work as one system from substrate to sealant—help outdoor tile installations withstand the elements and protect building owners from future issues.

Tile selection
For exterior installations, careful tile selection is essential. Historically, porcelain has been the most commonly recommended material for outdoor projects. However, any tile within the acceptable porosity range can be used, as long as it meets other requirements for exterior installations. Unglazed materials are often ideal for outdoor floor installations, as they normally have nonslip properties. Textured tiles can also minimize the likelihood of slipping. On walls, almost any type of tile can be used, including ceramic, glass, or stone.

Climate-specific challenges should also be considered throughout the specification process. For example, if an installation will be subject to freeze-thaw conditions, the tile should be frost-resistant. Denser materials with a porosity of less than 0.5 percent, such as porcelain, tend to have more frost resistance, while some ceramic tiles will suffer outdoors.2 ASTM C1026, Standard Test Method for Measuring the Resistance of Ceramic and Glass Tile to Freeze-Thaw Cycling, is the test standard for tile used in freeze/thaw conditions.

Sustainability goals may also influence exterior tile selection. Light-colored tiles for site hardscaping can lower a site’s heat absorption, or heat island effect. Tiles with a solar reflective index (SRI) of 29 or greater can contribute toward compliance in Leadership in Energy and Environmental Design (LEED) by complying with New Construction (NC) Sustainable Sites (SS) Credit 7.1, Heat Island Effect—Non-roof.3

The restaurant’s exterior is covered in solid porcelain tile, giving it a travertine look. It was installed with a lightweight, latex-modifi ed mortar and high-performance grout. Photo courtesy Lightshape Studios

The restaurant’s exterior is covered in solid porcelain tile, giving it a travertine look. It was installed with a lightweight, latex-modified mortar and high-performance grout. Photo courtesy Lightshape Studios

Any variation in the substrate should be corrected with an appropriate patching. Photo courtesy TEC/H.B. Fuller Construction Products

Any variation in the substrate should be corrected with an appropriate patching. Photo courtesy TEC/H.B. Fuller Construction Products

 

 

 

 

 

 

 

 

 

Substrate preparation
Whether a project involves remodeling a tiled exterior area or starting from scratch, substrate preparation is the key. Concrete is the ideal substrate for exterior floor installations, while other firm substrates, including backer board or concrete masonry units (CMUs), can be used for wall installations. When setting tile on existing concrete, any liquid membrane curing compounds must be addressed. These products can prevent proper bonding of mortar to the concrete surface, so they should be removed by mechanical cleaning and profiling methods or covered with an appropriate primer.

Laitance—a thin layer of hardened, yet weak, cement—can also affect the substrate’s bonding potential. If laitance exists, the concrete’s surface layer may appear strong and stable, but there is a risk of bond failure. Laitance can be identified by scraping the concrete with a razor knife. If the concrete scratches or powders, laitance may exist. Formal testing can then be undertaken by measuring the tensile strength of the concrete surface with specialized equipment. The remedy for a weak layer of laitance is removal, which is often done by sandblasting.

After these preliminary steps, any variation in the substrate should be corrected. An appropriate patching compound to flatten the substrate surface should be used. For tile less than 381 mm (15 in.) in size, this requirement is 6.3 mm in 3.05 m (1/4 in. in 10 ft). For tile with at least one edge over 381 mm (15 in.) in any one direction, the requirement is 3.2 mm in 3.05 m. (1/8 in. in 10 ft.). Exterior floors, decks, or patios should be sloped to allow for drainage. Concrete on grade should also have a gravel bed or other means of drainage below the slab. Drainage is particularly important for installations subject to freeze-thaw cycling, snow and ice accumulation, or where snow-melting chemicals are used, as these conditions can cause degradation over time.

Waterproofing and crack isolation membranes can alleviate the demands put on exterior tile installations. The expansions and contractions caused by the freeze-thaw cycle put mechanical stress on the substrate in exterior environments, which can cause substrate cracking.

Waterproofing and crack isolation membranes not only help isolate substrate cracks, but also prevent in-plane cracks in the substrate from telegraphing to the tile. Waterproofing and crack isolation membranes also prevent the passage of water into the substrate and can stop water from leaking into the mortar bed. They help prevent problems associated with saturation and moisture expansion and are applied to the substrate’s surface and allowed to cure before tiling begins. Crack isolation properties are particularly important in freeze/thaw environments. A membrane allowing the direct bonding of tile for an efficient installation should be specified. A water-resistive barrier (WRB), waterproof membrane, or vapor retarder membrane may be required as per local building codes.

Excessively porous substrates may prevent the formation of a strong bond. Excessive porosity in a substrate can be determined by splashing water on the concrete. If the water disappears in a matter of seconds, the substrate is porous. The application of a primer can minimize the pull of moisture from the mortar into the substrate, ensuring proper curing and bonding.

The best tile mortars for exterior installations like this mural combine bond strength with fl exibility to allow for shifts in the substrate caused by changing moisture and temperature levels. Photo courtesy Hohn & Hohn Inc.

The best tile mortars for exterior installations
like this mural combine bond strength with
flexibility to allow for shifts in the substrate caused by changing moisture and temperature levels. Photo courtesy Hohn & Hohn Inc.

Since effl orescence occurs when watersoluble minerals dissolve and migrate to the installation surface, interrupting this process with waterproof membranes and setting materials with low absorption rates can help prevent it. Photo courtesy TEC/H.B. Fuller Construction Products

Since efflorescence occurs when watersoluble minerals dissolve and migrate to the installation surface, interrupting this process with waterproof
membranes and setting materials with low absorption rates can help prevent it. Photo courtesy TEC/H.B. Fuller Construction Products

 

 

 

 

 

 

 

 

 

Mortar selection
A key element of ensuring an installation performs as expected and has a long service life is choosing the proper setting materials. It is critical to select mortars and grouts specifically engineered to safeguard against natural elements when installing in a harsh exterior environment.

The best tile mortars for exteriors combine bond strength with flexibility to allow for shifts in the substrate caused by changing moisture and temperature levels. Latex/polymer-modified thin set mortars are often best equipped for these conditions. These mortars are designed to improve adhesion, reduce water absorption, and provide greater bond strength and resistance to shock and impact. A mortar complying with American National Standards Institute (ANSI) A118.15, American National Standard Specifications for Improved Modified Dry-set Cement Mortar, would be in this category. Organic adhesives should never be used on exteriors.4

According to the National Tile Contractors Association’s (NTCA’s) Reference Manual, polymer modification is required for all exterior mortar installations unless other requirements are specified by manufacturers of other system components.5 Most current mortars have a dry form of polymer already blended in the bag, to which only water is required for mixing, but latex additives can enable unmodified thin-set mortars to meet ANSI A118.4, American National Standard Specifications for Modified Dry-set Cement Mortar. This standard denotes mortars designed for exterior conditions or for use with hard-to-bond-to substrates. The newer designation of ANSI A118.15, which indicates applications with increased bond strength requirements helps identify the best mortar types for exterior applications.

Grout selection
Grout is also an integral part of an installation’s longevity. High-performance grouts offer increased bond strengths, flexural strengths, and lower water absorption to resist frost damage.6 Some grouts are fully submersible and offer chemical-resistance—making them suitable for virtually any type of outdoor installation imaginable. Mold and mildew resistance help exterior grouts hold up to frequent moisture exposure.

In especially demanding environments, grout additives are often mixed with cement grouts, in place of water, to create stain-resistant, stronger, denser grout, that is more resistant to freeze/thaw damage and water penetration. Additives can also increase grout flexibility, providing crack resistance. Again, there are also high-performance grouts with the polymers, in the dry form, already blended in the bag, to which only water needs to be added. Products complying with ANSI A118.7, Polymer-modified Tile Grouts for Tile Installations, are recommended for exterior applications.

Tile selection can impact grout selection for exterior installations. For example, some glass tile—such as those used on pools or walls—may be easily scratched, and therefore will require unsanded grout, since sanded grout may damage delicate surfaces. Beyond that, narrow grout joints of 1.6 mm (1/16 in.) to 3.2 mm (1/8 in), which demand unsanded grout, are often preferred for stone tile installations. When scratching is not a concern, sanded grout can add stability to joints between 3.2 mm (1/8 in.) and 12 mm (1/2 in.), as its composition prevents grout shrinkage.

High-performance universal grouts—which can be used as unsanded or sanded—are available in various colors. Aesthetic goals determine the color of the grout used. Matching the grout to the tile color will visually minimize the grout joint for a more continuous design. To create a dramatic look and draw attention to individual tiles, a grout hue that contrasts with that of the tile can be specified. However, a contrasting grout color also emphasizes any irregularity in the installation.

Efflorescence, a whitish crystalline or powdery deposit on grout lines and tile surfaces, can mar even the most carefully considered exterior grout-tile combinations. On exterior installations, efflorescence is often the result of moisture below the tiled area’s surface. In some rare circumstances, prolonged exposure to rain can cause efflorescence—especially with porous grout. Careful grout selection can prevent efflorescence from affecting an installation’s appearance.

Sealers and caulks can prevent external moisture from penetrating an installation, further protecting it from external elements. When needed, a penetrating sealer can reduce moisture penetration without changing the grout’s appearance.7 These sealers are designed to completely penetrate into a porous surface without changing its appearance. They are recommended for a full range of porous tiles, stone, and grout.8

Above all, materials must work together, as a system, to combat the challenges exterior conditions present. Substrate preparation products, mortar, and grouts should all be compatible. For this reason, one should consider using a single source for all installation materials. This also makes any warranty considerations an easier process.

Setting strategies
To determine the most effective installation strategies for a particular project, TCNA recommends exterior installation sites be evaluated in advance. The team needs to determine whether the installation will be exposed to direct sunlight all day or part of the day, whether it will be exposed to harsh winds, and whether it is possible to protect the installation from the sun with a temporary shelter. Moisture can be lost to the atmosphere when the installation is conducted or allowed to cure in direct sunlight on hot, dry days. Excessive heat can prevent fresh mortar from curing properly and developing the necessary strength for long-term installation. So, on hot days, the installation should be shielded from direct sunlight by tenting. This helps keep both the materials and the installers safe and cool. If this is not possible, the installation team may have to work at night.

Cold temperatures present the opposite problem. The best temperature range for a tile installation is between 10 and 21 C (50 and 70 F) prior to install and for 48 hours after. An outdoor project should not be scheduled if there is a chance temperatures will drop below freezing.

If an exterior installation must be undertaken in extremely cold temperatures, installers must take care to keep the area’s temperature within an acceptable range by using a method such as heated tenting. Different parts of the country have different ways to deal with the environment, but all methods must observe the basic property requirements of the installation materials used.

It should also be noted cooler temperatures increase cure times. This means if temperatures drop, the installation will require extra time to cure before it is safe for foot traffic

The installation team must understand the unique coverage requirements of exterior installations. Outdoor installations require 95 percent coverage—and this requirement increases to 100 percent with natural stone. Substrate variation, bonding material, trowel selection, and troweling technique are critical factors to consider when trying to achieve proper coverage. If voids of mortar beneath the tile exceed the industry requirement, they can accumulate moisture. In freeze/thaw climates, this water can freeze and expand, causing degradation and bond failure of the thin-set.

The dot method should never be used with cement-based mortars for wall applications. With this method, the installer puts globs, or dots, of mortar on the back of the tile, rather than carefully troweling it. Although it may seem like it saves time and reduces material expenditures, the resulting voids in coverage leave tile susceptible to moisture trapping, which can cause debonding or compromise the bond.

Even the most carefully installed exterior projects may suffer from lippage—a condition occurring when tiles are not laid to a uniform level, so one edge or corner of a tile is higher than the edges or corners of an adjacent tile. Some degree of lippage is normal for exterior installations. However, lighting conditions can significantly worsen its appearance. Light shining on exterior installations at a flat angle, parallel to the surface, can accentuate normal and acceptable inconsistencies.9 Having temporary lighting that mimics the planned lighting scheme, or awareness of these overly exposed areas, help ensure the lighting and tiled installation work together.

Conclusion
Selecting and effectively using high-quality products for exterior projects requires careful consideration of various factors. No two exterior projects are exactly the same, but a comprehensive understanding of the conditions that should drive product selection will always contribute to more successful installations. Ensuring the material specification is not only rated for exterior use, but also works together as a system, pays off in the creation of a beautiful and durable installation.

Notes
1 For more, see “Environmental Classifications” in Handbook for Ceramic, Glass, and Stone Tile Installation. (back to top)
2 See David M. Gobis’s, article “Tile Decks, Patios, and Balconies” in TileLetter at www.tileletter.com/2011/10/tile-decks-patios-and-balconies. (back to top)
3 See “Green Building Standards and Green Product Selection Guide” in TCNA’s Handbook for Ceramic, Glass, and Stone Tile Installation. (back to top)
4 See “Setting Materials Selection Guide” in Handbook for Ceramic, Glass, and Stone Tile Installation. (back to top)
5 For more, see “Thin-Bed Method of Installation” in NTCA’s Reference Manual. (back to top)
6 See “Grout Selection Guide” in Handbook for Ceramic, Glass, and Stone Tile Installation. (back to top)
7 See “Grouts” in NTCA’s Reference Manual. (back to top)
8 See “Maintenance” in NTCA’s Reference Manual. (back to top)
9 See “Specific Installation Procedures” in NTCA’s Reference Manual. (back to top)

Tom Plaskota, CDT, is the technical support manager for H.B. Fuller Construction Products Inc., and is responsible for managing the field support team that develops and communicates technical information and provides technical service. He has been working with the TEC brand of surface preparation and installation systems for flooring, ceramic tile, and natural stone since 1997. Plaskota is actively involved with the National Tile Contractors Association (NTCA) and is a former industry director for the Chicago Chapter of CSI. Plaskota has more than 30 years of experience with construction methods, testing, and materials. He is certified as a Construction Documents Technologist (CDT), and holds a bachelor’s degree in civil engineering from Valparaiso University. He can be contacted by e-mail at tom.plaskota@hbfuller.com.

Investigating EIFS Performance Across Climates: Exterior insulation and finishing systems studied in long-term test

Photo courtesy EIFS Industry Members Association

Photo courtesy EIFS Industry Members Association

by Ulf Wolf

Between January of 2005 and June of 2007, the Oak Ridge National Laboratory (ORNL) undertook an extensive EIFS Industry Members Association (EIMA)-sponsored trial comparing the moisture and temperature management properties of several exterior insulation and finishing system configurations with those of other claddings in a hot and humid climate. Now, a new third phase of the study is demonstrating the assembly’s potential for other climate zones.

As part of Phase I of the initial study, researchers designed and built a test facility in Hollywood, South Carolina near Charleston—a location typical of a mixed, coastal, Zone 3 climate, as prescribed in the 2006 International Energy Conservation Code (IECC). The flexible design allowed researchers to change the wall panels with ease and to control conditions inside the building by creating two zones within the building interior.

Interior temperature and relative humidity (RH) conditions were selected based on the proposed American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) SPC 160P, Criteria for Moisture Control Design Analysis in Buildings. Building orientation and placement of the wall panels were determined based on a comprehensive study of historical weather patterns, including prevailing wind and precipitation direction.

The data were collected in two phases. In Phase I, 15 exterior cladding configurations—not only EIFS, but also stucco, brick, and cementitious paneling—were integrated into one side of the building (southeastern exposure), with the goal of having all the claddings exposed to similar weather conditions for a full weather year (15 months from January 2005 through May 2006).

In Phase II, simulated building envelope defects were introduced into some of the wall panels, which included newly constructed wall panels as well as some of the 20-month-aged wall panels from Phase I. (To simulate leaks, these defects allowed a certain amount of water to penetrate the outer envelope.) The goal was to assess the performance of cladding assemblies to water penetration, as well as the impact on the performance of wall assemblies from wall orientation on moisture infiltration, the type of water-resistive barriers (WRBs) used (e.g. sheet membranes versus liquid-applied), and different exterior cladding systems (e.g. EIFS and brick). In Phase II, wall panels were placed on both the building’s southeast and northwest sides, with data collected from May 2006 to June 2007.

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Zone 3 conclusions
The findings of these trials, as published at the time, showed EIFS was capable of controlling temperature and moisture within the wall system; it also showed these assemblies outperformed other exterior claddings during the monitored year. Phase II further established that an EIFS system, with drainage consisting of a liquid-applied water-resistive barrier coating and 100 mm (4 in.) of expanded polystyrene (EPS) insulation board, performed the best of all tested systems.

In other words, given the specific parameters of this study, the EIFS wall configurations performed better than stucco (both three- and one-coat) and brick. The EIFS wall systems with drainage maintained a consistent, acceptable level of moisture (average monthly RH below 80 percent, as defined by ASHRAE SPC 160P) within the cladding, despite varying outdoor conditions when appropriate interior vapor retarders were used. Brick and stucco tended to accumulate slightly more moisture during both Phase I and Phase II of the project and retained moisture longer than EIFS.

The trial also found EIFS with a liquid-applied, water-resistive barrier coating readily dispersed moisture introduced by the building envelope flaws installed for Phase II, unlike other claddings that retained more water. Both Phase I and II trials also confirmed vertical ribbons of adhesive provide an effective means of drainage within an EIFS-clad wall assembly.

The research showed EIFS has the ability to maintain the acceptable balance of moisture and temperature control indicative of a well-designed, properly operating, energy-efficient building without moisture problems. To quote the ORNL report summary:

EIFS-clad wall assemblies with drainage outperform other typical exterior claddings during most of the year. The results also showed that EIFS is an excellent exterior cladding choice for achieving key building performance goals in a hot and humid climate, specifically a mixed, coastal, Zone 3 climate.

These trials, however, did not necessarily answer the questions or concerns any designer, contractor, or insurer operating outside mixed, coastal, Zone 3 might have about EIFS. In other words, how does it perform in Zones 1 to 2 and 4 to 8? This is where Phase III of the ORNL trials enters the picture.

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Transient temperature at the interior surface of the wall (both Phases 1 and 2).

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Transient moisture content in plywood sheathing board (both Phases 1 and 2).

 

 

 

 

 

 

ORNL trials’ Phase III
Having compiled the full data set from Phases I and II for the mixed, coastal climate, the task remained to extrapolate these findings across all U.S. climatic regions. One way to achieve this would have been to select sites in the various climate zones and constructed additional test facilities there for live data-collection. This, however, would have been neither practical nor cost-efficient. Rather, the task fell to ORNL (more specifically, program manager Andre Desjarlais) to create a reliable, computer-simulated trial for the remaining climate zones. Desjarlais’ reports, and a recent interview with this author, has provided the overview and summary of this third phase of the EIMA-sponsored EIFS trials in this article.

Running a computer simulation of this kind requires two virtual constructs validated as behaving and performing like real-world ones. First, there are the virtual panels, which are the computerized equivalent of the real-life, constructed panels used in the Phase I and II trials. Then, there are also the virtual climate zones—the computerized equivalent of the real-life humidity levels and weather patterns of actual climate zones.

The simulation consisted of creating four virtual panels (each fully corresponding to its live counterpart), which were then placed in each of the eight different virtual climate zones. They were then virtually exposed over three simulated ‘years’ to the humidity fluctuations and weather conditions of each respective zone. At the same time, the same hygrothermal measurements of these panels, as had been monitored during the live trials, were taken:

● temperature;
● relative humidity (RH);
● heat flux; and
● moisture content.

By the end of these simulated trials, ORNL had collected performance data equivalent to four different panels in eight different locations over three years.

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The software tool
Virtual panels and climate require validated software tools to construct them. The tool used for this third phase of the trials was WUFI, which stands for Wärme und Feuchte Instationär (i.e. heat and moisture fluctuations)—a true and tested software tool long used to calculate the coupled heat and moisture transfer in building components.

This PC program allows realistic calculation of the transient coupled one-dimensional heat and moisture transport in multi-layer building components exposed to natural weather. WUFI is based on the latest findings regarding vapor diffusion and liquid transport in building materials and has been validated by detailed comparison with measurements obtained in the laboratory and on outdoor testing fields. The underlying model has been validated for more than 20 years.

WUFI, like the live study, takes into account not only thermal properties of a building component and their impact on heating losses, but also its hygric (moisture) performance since thermal and hygric behavior of a building component are closely interrelated—increased moisture content leads to heat loss, while thermal situation in turn affects moisture transport. Therefore, both have to be tracked in their mutual interdependence for an accurate result. WUFI accomplishes this.

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Virtual panels and locations
Following the guidelines summarized in ASHRAE 160-2009, Criteria for Moisture-control Design Analysis in Buildings, each simulation was undertaken for a three-year period using the design ‘cold’ year. Four wall systems were selected for study, comprising the following components:

● EIFS Panel 2 (P2): 40-mm (1 1/2-in.) flat insulation, notched trowel attachment, drainage airspace created by vertical ribbons, liquid-applied weather barrier, plywood exterior sheathing, 50 x 100-mm (2 x 4-in.) framing 400-mm (16 in.) on center (oc), with unfaced R-11 fiberglass batts and no vapor retarder, a 13-mm (1/2-in.) gypsum board, and a 10-perm paint layer;
● EIFS Panel 5 (P5): 100-mm (4-in.) flat insulation, notched trowel attachment, drainage airspace created by vertical ribbons, liquid-applied weather barrier, plywood exterior sheathing, 50 x 100-mm (2 x 4-in.) framing 400-mm (16 in.) oc, with no cavity insulation and no vapor retarder, a 13-mm (1/2-in.) gypsum board, and a 10-perm paint layer.
● EIFS Panel 11 (P11): 40-mm (1 1/2-in.) flat insulation, notched trowel attachment, drainage airspace created by vertical ribbons, a liquid-applied weather barrier, ASTM C1177 exterior gypsum board,1 18-gauge 50 x 100-mm (2 x 4-in.) steel framing 400-mm (16-in.) oc, with unfaced R-11 fiberglass batts and no vapor retarder, a 13-mm (1/2-in.) gypsum board, and a 10-perm paint layer; and
● brick Panel 14 (P14): brick façade, 25-mm (1-in.) airspace, one layer of Grade D 60-minute building paper, oriented strandboard (OSB) exterior sheathing, 50 x 100-mm (2 x 4-in.) framing 400-mm (16 in.) oc, with unfaced R-11 fiberglass batts and no vapor retarder, a 13-mm (1/2-in.) gypsum board, and a 10-perm paint layer. Airspace was considered ventilated (open top and bottom).

The eight IECC climate zones modeled in this simulation (representing cities for Climate Zones 1 through 8, respectively) were:

● Miami, Florida;
● Austin, Texas;
● Atlanta, Georgia;
● Baltimore, Maryland;
● Chicago, Illinois;
● Minneapolis, Minnesota;
● Fargo, North Dakota; and
● Fairbanks, Alaska.

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Model validation
The first step of this simulation was to validate the model itself—that is, to ensure the virtual panels behave precisely like their real counterparts, given the same hygrothermal loads. For purposes of validation, the researchers selected eight different panels from Phases I and II to emulate with computer configurations. The panels chosen for this, and their makeup, are shown in Figure 1, which is taken from the ORNL report, “Energy and Moisture Impact on EIFS Walls in the USA.” (Note: The typical interior finish for all emulated systems was 13-mm [(½-in.)] drywall, primed and painted [one coat of acrylic paint]).

The validation of these eight selected wall systems ran for the combined length of Phases I and II and was performed using the measured Natural Exposure Test facility (NET) weather station data for Charleston, South Carolina, along with the measured indoor data, and all hygrothermal material properties measured during Phases I and II of this trial.

Figure 2 illustrates the validation process. Completed, this analysis demonstrated good agreement between the WUFI hygrothermal model and the Charleston South Carolina field data, the model trends at all times following those of the Phases I and II experimental data. Consequently, the researchers could now confidently predict the heat and moisture performance of the four walls systems selected for the final simulation.

Figures 3 through 5 illustrate the type of data collected during the validation phase. EIFS Panel 2 is used as an example in this case. These figures depict both the measured and predicted (simulated) factors as follows:

● Figure 3—interior surface temperature as measured by Thermistor 17 (T17);
● Figure 4—moisture content of the plywood sheathing as measured by Moisture Content Sensor 3 (MC3); and
● Figure 5— relative humidity of the interior surface of the plywood as measured by Relative Humidity Sensor 4 (RH4).

In all instances, the predicted parameters satisfactorily agreed with the measured results.

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The simulation
Using the validated model, the researchers now performed a hygrothermal WUFI analysis following the guidelines summarized in ASHRAE 160-2009. Each simulation was undertaken for a three-year period using the design ‘cold’ year. As mentioned, the four wall systems studied were identified as P2, P5, P11, and P14.

Each wall system was evaluated with and without a vapor retarder, and with and without water penetration as specified in ASHRAE 160-2009. Traditional practice does not typically require a vapor retarder in the southern climates, but these wall systems were modeled as well for completeness.

The wall orientation provided the maximum amount of rain to emulate water penetration. Therefore, whenever rainfall was detected, one percent of the rain incident on the exterior surface of the wall system was deposited into the wall’s exterior sheathing.

The interior boundary conditions were developed as per ASHRAE 160-2009 and the initial moisture contents of all wall components were set at their equilibrium moisture content at 80 percent RH. Solar radiation and cooling due to night sky radiation were included in the analyses.

Resulting data
The volume of data generated by these simulations cannot adequately be summarized in a short article. To trim the data down into a digestible portion, the results of Climate Zone 6 (Minneapolis) will be the focus—however, it is representative of the data generated by remaining seven Climate Zones.

Figures 6 through 12 summarize the monthly average heat flux through the four wall systems, and the moisture content of their exterior sheathings in Climate Zone 6 weather conditions over a three-year period. The four pairs of graphs compare the effects of leakage (none vs. ASHRAE 160) and the inclusion of a vapor retarder (none vs. 6-mil poly).

As a lightweight wall cladding, exterior insulation and fi nishing systems (EIFS) combines insulation with various thin synthetic coatings. Photo courtesy EIFS Industry Members Association

As a lightweight wall cladding, exterior insulation and finishing systems (EIFS) combines insulation with various thin synthetic coatings. Photo courtesy EIFS Industry Members Association

It is important to note EIFS configurations P2 and P11 yield the same energy efficiency, followed by EIFS P5 and Brick P14. The addition of leaks and vapor retarders does little to modify the energy performance of these walls in this climate; the walls are hygrothermally efficient enough to prevent sufficient moisture accumulation to impact their energy efficiency.

With no leakage and no poly, all wall systems maintain exterior sheathing moisture contents well below 80 percent RH. The addition of poly has little impact on the moisture contents. Wall EIFS P5 outperforms the other wall assemblies; the low interior RH maintains the exterior sheathing to a very low level of relative humidity.

When leakage is added to the wall assemblies in this climate, their hygrothermal performance changes minimally. Both configurations do add to the moisture contents of the walls’ exterior sheathings, but they are maintained at moisture content levels at or below the 80 percent RH level.

Energy efficiency
For all climate zones, the addition of the leak did not appreciably increase the heat flux. Adding a vapor retarder on the inside of the test walls, which would retard the internal drying potential or decrease the moisture flow from the building interior, did not change the moisture contents of the walls enough to affect their energy efficiency.

The researchers found little difference in the heat flux through the four test walls in Zone 1. Moving the wall systems to colder climates, EIFS Panels 2 and 11 exhibited the best energy performance, followed by EIFS Panel 5 and Brick Panel 14. The facts the simulations are one-dimensional—and the calculations are performed in the center of the cavity—explain why one sees no effect of the metal studs in EIFS Panel 11. The differences between EIFS Panels 2 and 11 and the other two test panels increase in colder climates.

Moisture performance
For all climate zones, panels combining no leakage and no vapor retarder deliver acceptable performance. That is also true for all panels with no leakage and a poly vapor retarder. The addition of the vapor retarder increases the sheathing moisture contents for all walls in the warmer Climate Zones 1 through 4, but this addition is relatively small and on the order of two to three mass percent—in other words, not enough to compromise the durability of the wall systems. In the more northern zones, the addition of a vapor retarder is neutral; all panels behave similarly with or without the vapor retarder.

The addition of a leak substantially increases the moisture contents of all wall assemblies. In Climate Zones 1 through 4, the panels without a vapor retarder come close to the 80 percent RH threshold (levels above 80 percent for extended periods are detrimental).

When a vapor retarder is added, the moisture contents rise even further and are at levels above 80 percent RH for months each year and as systems will eventually fail. In colder Climate Zones 5 through 8, the increase in moisture content after adding a vapor retarder is less severe, and the time the sheathing is at moisture contents exceeding 80 percent RH is substantially shorter.

Conclusion
Throughout the simulation, the three exterior insulation and finishing system configurations outperformed the brick wall system for the specific measured criteria across all climate zones, with EIFS Panel 5 performing the best overall. Joseph Lstiburek, an ASHRAE fellow and a principal at Building Science Corporation, was one of the first forensic engineers to sound the alarm over moisture buildup problems within barrier EIFS in the late 1980s. At that point, he did not think highly of the assemblies. This, however, has changed over time, and today he confirms he believes EIFS to be “a phenomenal system. They addressed the fundamental flaws they had in the 1990s by adding moisture management. And now EIFS resembles the perfect wall.”2

When considering the research in this article, it is important to remember all ‘test walls’ were constructed new. A test like this will not highlight differences 20 years down the road. Further, a scientific tracking of various actual envelopes built in many climate zones as to moisture and thermal performance, as well as to insurance costs and claims, will paint a broader, fuller comparative picture amongst claddings. Finally, this study was intended to measure only the moisture and thermal performance of these wall assemblies—there are other criteria design/construction professionals and building owners will take into consideration when selecting materials for their projects.

With both the 2012 IECC and ASHRAE 90-1 now stipulating continuous insulation building envelope for new construction, the outcome of this third and final phase of the ORNL trials is very good news indeed for EIFS.

Notes
1 This is per ASTM C1177, Standard Specification for Glass Mat Gypsum Substrate for Use as Sheathing.
2 For more, see the August 2013 issue of Architect, which featured the article, “Water Under the Bridge,” by Elizabeth Evitts Dickinson. Visit www.architectmagazine.com/technology/water-under-the-bridge.aspx. (This author recently spoke with Lstiburek and confirmed his quotation still stands.)

Ulf Wolf is the senior writer at Words & Images (www.words-images.com). Since 2007, he has been a regular contributor of articles to the Association of the Wall and Ceiling Industry’s (AWCI’s) Construction Dimensions magazine. Previously, he contributed “Greener Than You Think: Exterior Organic Solvent-based coatings” to the February 2011 issue of The Construction Specifier. He can be reached via e-mail at ulfwolf@gmail.com.

Innovation with Insulating Concrete Forms

Photo courtesy Nudura Insulated Concrete Forms Ltd.

Photo courtesy Nudura Insulated Concrete Forms Ltd.

by Andy Lennox

In the construction industry, ‘innovation’ can be viewed as speed or efficiency of construction, increased durability, sustainable, new materials, systems, or processes. While innovation can also translate into safety and other aspects, it is generally spurred by economic benefit—for example, the speed of construction is a major driver, as its achievement offers cost advantages from labor, financing, and occupancy perspectives. Such is the case with insulating concrete forms (ICFs).

The ICF technology has been in the North American market for almost a half-century. It has recently made great strides over the past 25 years in the residential realm as market forces—such as lumber’s fluctuating price—have put the industry in the position of looking for other material solutions. However, over the last decade, there has been a move to use ICFs in commercial and high-rise residential applications. ASTM E2634, Standard Specification for Flat Wall Insulating Concrete Systems, describes the requirements for the manufacture of units for walls with uniform cross-sections. The respective concrete standard is American Concrete Institute (ACI) 318, Building Code Requirements for Structural Concrete.

ICFs are a permanent formwork system for reinforced concrete construction. The interlocking modular units are dry-stacked into position and filled with concrete. They can be used for almost any concrete wall—interior or exterior, below-grade or above-grade, short or tall. The concept can be seen as the marriage of two proven technologies: concrete mass sandwiched between two layers of expanded polystyrene (EPS) foam insulation.

A traditional exterior concrete wall contains six building components:

● concrete;
● reinforcement bar;
● insulation;
● air barrier;
● vapour barrier; and
● studs/strapping.

ICFs combine these six components into a single building system installed by one crew at the same time. The thermal mass effect of the concrete enhances the insulation’s energy efficiency and the forming system’s airtightness, creating an opportunity for owner/developers to realize savings through the operation of the building.

ICFs can also minimize drywalling and electrical work onsite, but care must be taken with the placing of concrete in any form. Vibration is the key to proper consolidation, specifically around windows and doors. Specially designed door and window bucks are used for ICF systems—some are proprietary and some are site-manufactured.

With innovation, there sometimes are unexpected discoveries with the use of new technology in an application. For example, innovative contractors who used the ICF system in a non-residential application found there were significant constructability advantages with the speed of construction in addition to the high-performance attributes of the ICF wall. In Canada, one Ontario builder saw a significant uptake for the construction of high-rise residential student residences. The speed of construction recognized by the owner/developers provided them with completion dates that not only saved them money, but also achieved the early occupancy they required.

This article highlights growing use of ICFs in four sectors in North America—hotels, mid-rise, schools, and tall walls—to show how the building technology significantly enhanced the speed of construction.

This insulating concrete form (ICF) tall wall bracing mechanically fastens to the concrete core in the wall and provides 2.1-m (7-ft) work and wind bays every 10.7 m (35 ft). Photo courtesy Logix Insulated Concrete Ltd.

This insulating concrete form (ICF) tall wall bracing mechanically fastens to the concrete core in the wall and provides 2.1-m (7-ft) work and wind bays every 10.7 m (35 ft). Photo courtesy Logix Insulated Concrete Ltd.

Building hotels with ICFs can allow construction to advance at a rate of one fl oor per week. Photo courtesy Nudura

Building hotels with ICFs can allow construction to advance at a rate of one floor per week. Photo courtesy Nudura

 

 

 

 

 

 

 

 

Hotels on the horizon
Hotel builders are seeing the benefits ICF construction can offer in various areas. The faster a hotel can open, the sooner its owners start generating revenue. With insulating concrete formwork, construction typically progresses much faster than traditional concrete masonry unit (CMU) block construction—this factors in ICFs being insulation, forming, and attachment surfaces all in one, whereas the block is but one component. In other words, ICFs combine formwork, structure, interior and exterior strapping, and air and vapor barriers, resulting in more efficient construction with less sub-trade congestion onsite. On average, installers are able to complete a floor a week, depending on the project size. The various manufacturers provide specialized training for the application of their proprietary system.

Another contributing factor to getting the hotels open sooner is the ability to build in differing climates. Weather can play a key role in any construction project; winter can often halt a job entirely. The versatility with ICFs offers builders the advantage of building year-round. This is because the curing process offered by the forms means concrete can be poured on the coldest days. The EPS foam containing the concrete actually serves to store the natural heat produced inside the concrete core during the hydration or curing process. Studies have proven concrete installed in this condition can be placed and maintained at temperatures as low as −20 C (−10 F), even sustained for as long as three days.1 In such conditions, the process of hydration has been proven to increase to levels as high as 27 C (80 F) within the formwork, based on a concrete core of 160 mm [6 ¼ in.] thick.

National model energy codes, such as the International Energy Conservation Code (IECC), are advancing the way in which commercial and residential exterior wall construction is approached by emphasizing the use of continuous insulation (ci) systems. As the name suggests, these assemblies provide a continuous insulation layer over an entire wall, rather than just in the wall cavities. With other traditional building systems on the market, this ci layer has to be applied, but it is an integral part of ICFs.

In addition to energy performance benefits, ICFs are non-combustible and can offer fire protection ratings of up to four hours. As an added advantage for hotels, the assemblies also provide greater sound attenuation, offering sound transmission class (STC) ratings of up to 55—the material provides a further break than traditional concrete, thanks to the addition of the insulation changing the material density. EPS, the key component of ICF products, is also resistant to mold growth, lowering long-term maintenance costs for owners compared to wood-frame hotel construction.

For this ICF-intensive condominium project, the normal percentage of insulating concrete forms was doubled by incorporating the assemblies for not only walls, but also suspended fl oors and roofs. Photos courtesy Quad-Lock Insulated Concrete Forms Ltd.

For this ICF-intensive condominium project, the normal percentage of insulating concrete forms was doubled by incorporating the assemblies for not only  walls, but also suspended floors and roofs. Photos courtesy Quad-Lock Insulated Concrete Forms Ltd.

Complex reinforcing requirements presented installation challenges overcome by an ICF design offering separate panels and ties that fi t around the rebar.

Complex reinforcing requirements presented installation challenges overcome by an ICF design offering separate panels and ties that fit around the rebar.

 

 

 

 

 

 

 

 

 

 

 

Mid-rise revolution
One great success story in mid-rise ICF construction is the La Concha Pearl condominium project in La Paz, Mexico. ICF installation on this seven-story, 33-unit luxury beachfront development took place over an eight-month period, putting the building into service far ahead of the expected norm in the region. The sales team reported the reduction in the ‘pre-construction’ sales phase, where potential customers had no real building to see, was a huge benefit in persuading would-be residents to buy. If this holds true for other projects, there may be more developers and owners actively requesting ICFs.

In this particular case, the developers, having already made a commitment to minimize the impact on the local community, undertook some re-design of the building to optimize it for ICF, minimizing wasted materials and time onsite. The design phase was also shortened because the ‘flat-wall’ ICF design meant the project engineer could confidently rely on known, published design parameters for poured-in-place concrete structures via American Concrete Institute (ACI) 318, Building Code Requirements for Structural Concrete. Though a departure from the more common masonry block building found in the region, the project engineer and local building officials were well within their comfort zone, meeting no unfamiliar challenges posed by ICFs.

The general contractor, despite starting with only a few experienced ICF hands, was able to offer great training and oversight. His efforts resulted in a doubling of average production over the course of the 240-day installation, cutting the average time-per-floor in half. Crews quickly and eagerly accepted the new technology, taking great pride in learning a new craft.

The La Concha Pearl project is ICF-intensive—the assemblies were employed for both walls and floors, more than doubling the usual amount of concrete forms found on the typical project. Only 43 per cent of the total ICF area was a wall system; the majority was used for the floors.

The general contractor reported that, once shoring was in place, his crew would lay an entire 557-m2 (6000-sf) floor in about three hours, using the ICF T-beam floor forms. Since ICF floor forms replace about half of conventional suspended floor forms, post-pour removal of only primary shoring frames and beams was easily and quickly completed. Resumption of construction on the succeeding upper floors was never delayed, as each floor was fitted with a minimal amount of re-shoring (temporary posts) to carry construction loads through to the ground-floor level.

As an additional note, the La Concha project is situated in an extreme seismic zone. This led the project engineer to an extreme reinforcing bar specification. On lower floors, a double mat of steel, pre-tied into place, was specified. The knock-down design of the ICF wall system allowed the crews to fit ICF components through the pre-tied rebar mats, row by row, without disturbing pre-positioned reinforcing.

Crews often quickly adapt to ICF technology, increasing their production rates as the project progresses.

Crews often quickly adapt to ICF technology, increasing their production rates as the project progresses.

The speed of construction offered with ICFs can mean early completion dates for owners and fi nancial benefi ts. Photos courtesy Logix Insulated Concrete Forms Ltd.

The speed of construction offered with ICFs can mean
early completion dates for owners and financial benefits.
Photos courtesy Logix Insulated Concrete Forms Ltd.

 

 

 

 

 

 

 

 

School sounds
In Pincher Creek, Alberta, a 930-m2 (10,000-sf) private school was built utilizing ICFs. The school board and designers decided on this route for a faster build as well as improved energy, long-term resiliency, and sound efficiency. The contractor was pleased, noted the recorded time spent building with ICF was about half the time of that of a typical wood build, while providing the best in insulation and sound barrier—this latter criterion was especially important given the often-powerful, noisy southern Alberta winds.

The ICF walls included the standard 1.2-m (4-ft) frost wall and 2.7-m (9-ft) walls, with 3.7-m (12-ft) walls for the gymnasium. No other form of insulation or vapour barrier was required by using the forms. The gymnasium walls provided an especially strong barrier for sporting activities with no need for plywood, which would have otherwise been required behind the gypsum in wood builds. The solidness and strength of rebar-reinforced ICF blocks was a definite factor in the choice to employ this construction methodology.

During construction and concrete pouring, use of ICF bracing made it easy to straighten walls while providing solid, safe scaffolding for construction workers. The design of the block makes it a quick and efficient to attach the upright channels for bracing utilizing simple screws. Workers have a safe platform to work from, with a built-in hand rail and no need for tie-offs that would normally be used with other construction scaffolds.

The school board was satisfied with the decision to choose ICFs in the construction of the school. In the few years since completion, there have been no complaints or issues. The fewer labor-hours in the building of the school continues to be a deciding factor for the contractor and architect as they have since used ICFs in other construction business and plans design.

Whether for retail or hospitality applications, completed ICF projects should yield sustainable, resilient, comfortable, and effi cient buildings.

Whether for retail or hospitality applications, completed ICF projects should yield sustainable, resilient, comfortable, and efficient buildings.

Photo courtesy Nudura Insulated Concrete Forms Ltd.

Photo courtesy Nudura Insulated Concrete Forms Ltd.

 

 

 

 

 

 

 

 

Greener education
Richardsville Elementary (Warren County, Kentucky) is the first net-zero ICF school in the United States. Designed by Sherman-Carter-Barnhart Architects and engineered by CMTA, this building was constructed to be a two-story, energy-efficient structure that incorporates renewable materials and insulated concrete forms for its superior building envelope.

Generating its own energy, the 6715-m2 (72,285-sf) Richardsville is the next generation of educational building standards, and a valuable tool to educate students on energy and water conservation as well as the value of recycling. The project is designed to use only 18 kBtu/sf annually—75 percent less than the nation average standard set out by American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) 90.1, Energy Standard for Buildings Except Low-rise Residential Buildings.

Richardville was a learned lesson from previous schools built with ICFs elsewhere in the Bluegrass State. During construction onsite, the Warren County School District experienced reduced time in construction schedules. With CMU-constructed schools, running electrical can add to the construction schedule. Tyically, conduit has to be placed and fished through the walls. ICF construction offered this project’s electrical contractors the ability for quick installation times and having the wiring easily accessible on the face of the wall.

Tall walls
Retail chain Cabela’s is one the world’s foremost outfitters of hunting, fishing, and outdoor gear. Looking for energy efficiency and lower long-term operating costs, its architectural firm specified insulating concrete forms for the exterior walls of a new facility in Saskatoon, Saskatchewan. As the project progressed, it became evident ICFs not only delivered high-performance tall walls, but also a faster build.

This Cabela’s store measures about 64 x 64 m (210 x 210 ft) with the exterior tall walls ranging from 8.8 to 9.5 m (29 to 31 ft) in height. The wall’s assembly included six construction steps:

● concrete core;
● steel reinforcement;
● exterior and interior insulation;
● air barrier;
● vapor barrier; and
● stud work/furring strips.

According to 2014 RS Means data, if these walls were built with CMUs and finished to the same degree, the expected labor rate to build a comparable wall assembly would be 0.217 man-hours per square foot. On this particular job, however, the ICF installation crew recorded a labor rate of 0.109 labor hours per square foot. This suggests the walls were completed using half the labor that would have been traditionally required.

Several factors contributed to this speed. For example, the exterior tall walls were designed for maximum efficiency. The 203-mm (8-in.) concrete core provided sufficient room for rebar placement and concrete consolidation. The horizontal rebar was specified at 406 mm (16 in.) on center (oc) to be consistent with the course height of the ICF system.

By specifying the vertical rebar at 20m at 406 mm oc (versus, say, 10m at 203 mm oc), less bar had to be handled and placed, resulting in lower labor costs and easier and quicker concrete consolidation. Further, the designers were mindful of the ICF block dimensions in order to minimize the time spent cutting the blocks to make them fit.

Unassembled (i.e. knockdown) ICF blocks were assembled around the pre-built rebar cages used in the pilasters every 6 m (20 ft) of tall wall. This was much faster than the alternative method of building the rebar cages around the in-situ ICFs. Rugged rebar chairs built into the webs enabled the 6-m lengths of horizontal rebar to be quickly ‘snapped into place’ by a single crew member. Additionally, slide-in end caps quickly terminated wall sections and created vertical seams for expansion control.

Contact lap splices were used in the corners to allow concrete to easily flow through the corner forms. Use of running bonding (as opposed to stack bonding) was also maximized to reduce the installation and removal of temporary form support on both sides of the tall walls. Protecting the interlock during the concrete pours also eliminated any potential delays during subsequent course placement.

Further, the tall-wall scaffolding bracing system (which can be used to brace ICF walls up to 38 m [125 ft] without additional engineering) had many additional time-saving features. For example, it quickly connected directly to the concrete core providing an improved safety factor (required by Occupational Safety and Health Administration [OSHA] standards) and the ability to quickly precision-plum the walls.

As the guardrail was attached, no tie-offs for the crew members were required. The scaffolding’s wind-bays, which also function as 2.1-m (7-ft) work-bays, were located every 10.1 m (35 ft)—this means material was easily available at high heights. With extra scaffolding onsite, sections could be erected while others were being taken down.

Conclusion
Insulating concrete form applications are only limited by the designers. Some applications may require small redesigns to handle the structural loads, but many of these formwork systems have specially designed blocks or sections to deal with any unusual details. Technological advances are also allowing the creation of larger units, which will speed up construction even more.

The recent formation of the Council of ICF Industries (CICFI) is also expected to yield additional resources for building owners and project team members interested in exploring the suitability of this material. The group represents itself as the voice of the North American ICF manufacturing industry, and will serve as the information source for all information about the forms.

Notes
1 For more, see the report, “Cold Weather Construction of ICF Walls” by John Gadja (Portland Cement Association [PCA], 2002). (back to top)

Andy Lennox is a vice president of Logix Insulated Concrete Forms Ltd. He has worked in the ICF industry for 17 years in various sales, marketing, and management capacities. Lennox is the inaugural chair of the Council of ICF Industries (CICFI). He can be contacted by e-mail at andy@logixicf.com.

Energy-efficient Design with Masonry Construction

Photo courtesy Richard Filloramo

Photo courtesy Richard Filloramo

by Richard Filloramo, B.S. Arch, A.S. CT, and Chris Bupp

Masonry materials and wall assemblies, with their inherent thermal mass characteristics, provide designers with many options to achieve efficient designs. Architects and engineers have to make new decisions to reduce their projects’ energy consumption, requiring close collaboration and coordination with building and energy codes, along with construction documents.

The most significant code changes include increased R-values for non-mass opaque walls (e.g. cold-formed metal framing), requirement options for continuous insulation (ci), a need for continuous air barriers, R-value reductions for thermal bridging, and three paths for building energy design.

The 2015 International Building Code (IBC), in Chapter 13 (“Energy Efficiency”) states buildings shall be designed in accordance with the 2015 International Energy Conservation Code (IECC). The latter code’s Chapter 5 (“Commercial Energy Efficiency”) enables designers to use either IECC or American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) 90.1-2013, Energy Standards for Buildings except Low-Rise Residential Buildings.

This article examines examples of energy design using ASHRAE 90.1-2013, Section 5 (“Building Envelope”), and also notes requirements from ASHRAE 90.1-2010 (per the 2012 IBC and IECC). Designers may select ASHRAE 90.1 over IECC Chapter 5 because it provides a more in-depth, comprehensive, and complete approach to building energy design.

First, a designer must determine the climate zone for the building location by using the ASHRAE appendix Figure B1-1 map and tables depicted in Figure 1. For example, all of Connecticut is in Climate Zone 5, while New York encompasses three Climate Zones—Table B1-1 indicates the appropriate zone for the various towns, cities, and counties.

Next, the architect will select a compliance path based on the climate zone, space conditioning category (ASHRAE 5.1.2) and class of construction from ASHRAE Section 5.2 (“Compliance Paths”), as shown in Figure 2. The building envelope must comply with Sections 5.1, 5.4, 5.7, and 5.8, along with either:

● Section 5.5 (“Prescriptive Building Design Option”), provided the fenestration area does not exceed the maximum allowed in Section 5.5.4.2 (40 percent in ASHRAE 2012); or
● Section 5.6 (“Building Envelope Trade-off Option”).

Projects may also use Energy Cost Budget Methods, Section 11, as described in ASHRAE 90.1, Section 5.2.2. This article focuses on the first option—the prescriptive path (Section 5.5)—and also discuss Section 5.4.3 (“Air Leakage and Continuous Air Barrier Requirements”).

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The prescriptive path
While larger commercial, institutional, and municipal buildings may use some form of energy modeling (Section 5.6 or Section 11), the examples shown using the prescriptive path demonstrate basic compliance with the code and assist at understanding assembly R-values for various building envelope wall systems. The prescriptive path method provides an efficient means to establish the required insulation in a wall that can be used in a final design or in a preliminary study.

ASHRAE 90.1, Section 5.5 provides building envelope design tables for all climate zones for either non-residential or residential construction. (The latter includes dwelling units, hotel/motel guest rooms, dormitories, nursing homes, patient rooms in hospitals, lodging houses, fraternity/sorority houses, hostels, prisons, and fire stations.1)

To comply with the prescriptive path for Opaque Areas (Section 5.5.3) a designer may select from one of the two following methods:

● Method A: minimum R-value insulation requirements; or
● Method B: maximum U-factor (or R-value) for the entire assembly (Figure 3).

The second method is a more efficient means to configure a masonry wall assembly.

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Building envelope basics
An essential component of wall design—masonry or otherwise—is drainage capability and ventilation air space. IBC Chapter 14 (“Exterior Walls”) requires the exterior wall envelope be designed and constructed in such a manner as to prevent the accumulation of water within the wall assembly by providing a water-resistive barrier behind the exterior veneer, and a means for draining water that enters the assembly to the exterior. While there are exceptions, this requirement is essential to successful design.

Ventilated air space is also essential to keep the wall components dry, which prevents deterioration of wall components and water infiltration. Providing a sufficient air space in accordance with industry standards has become more difficult as new energy requirements can increase insulation thickness—owners are apprehensive to allow thicker walls that will encroach on the net interior building area.

The 2015 IBC references the Masonry Standards Joint Committee (MSJC)’s Building Code Requirements for Masonry Structures (i.e. The Masonry Society [TMS] 402-13/American Concrete Institute [ACI] 530-13/American Society of Civil Engineers [ASCE] 5-13) and Specifications for Masonry Structures (TMS 602-13/ACI 530.1-13/ASCE 6-13). In Chapter 12 (“Veneers”), Sections 12.2.2.6.2, 12.2.2.7.4, 12.2.2.8.2, and 6.2.2.8 states:

A 1-in. (25.4 mm) minimum air space shall be specified.

However, this is a code minimum and not recommended. Standard construction tolerance for the veneer and backup of ± 6 mm (¼ in.) variation from plumb can leave a resulting 12-mm (½-in.) air space, which is unacceptable. Industry organizations such as the International Masonry Institute (IMI), Brick Industry Association (BIA), and National Concrete Masonry Association (NCMA) recommend a 50-mm (2-in.) minimum air space. With these new increased requirements for higher R-values and sometimes thicker insulation, a 38-mm (1 ½-in.) air space would be sufficient. If air spaces are smaller, it may be advisable to provide continuous, full-height drainage mat in the wall cavity to assist with drainage and air flow and prevent mortar bridging (Figure 4).

It should also be noted MSJC sets the maximum cavity space at 114 mm (4 ½ in.) based on prescriptive design. Cavity spaces exceeding this size are acceptable, provided engineering calculations are provided for the masonry veneer ties. Recently, newer and stronger masonry ties, anchors, and fasteners have been developed that provide sufficient strength for wider cavities.

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Understanding the prescriptive path
An example of ASHRAE Table 5.5.5 for Building Envelope requirements in Zone 5 is shown in Figure 5. A masonry mass wall (masonry veneer and concrete masonry unit [CMU] backup), non-residential, under Method B (first column), would require an assembly U-factor of U-0.090—this equals R- 11.11(R=1/U). It should be noted there was no increase in the required R-value for mass walls from the R-11.11 in 2012 IBC/IECC/ ASHRAE 2010).

The same mass wall under Method A (second column) would require continuous insulation with a minimum R-value of R-11.4. A steel-framed wall (masonry veneer and steel stud backup) under Method B requires an assembly U-factor of U-0.055—this equals R-18.18. It should be noted this is a significant increase from R-15.63 required in the 2012 IBC/IECC/ASHRAE 2010). The same stud wall under Method A would require R-13 insulation in the stud space and R-10 continuous insulation (R-13 / R-7.5 ci in 2012 IBC/IECC ASHRAE 2010).

Stud wall assemblies have much higher requirements (i.e. R-7.07) than masonry mass walls because of the benefits of thermal mass, which are now quantified in the national energy codes. Advantages of thermal mass masonry include:

● reduction of temperature swings;
● moderation of indoor temperature;
● storage of heating/cooling for later release (Figure 6);
● reduction and shift of peak heating and cooling loads to non-peak hours; and
● passive solar design.

(Designers should check National Fire Protection Association [NFPA] 285, Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Non-load-bearing Wall Assemblies Containing Combustible Components, and manufacturer’s requirements when specifying combustible insulation and/or combustible air-moisture-vapor barriers in wall systems—special detailing and letters of engineering equivalency may be required.)

Example 1−masonry cavity wall with 2-in. rigid XPS insulation
A typical 406-mm (16-in.) masonry cavity wall with a 100-mm (4-in.) masonry veneer, 70-mm (2 ¾-in.) air space, 50-mm (2-in.) rigid insulation, an air/moisture/vapor (AMV) barrier, and 200-mm (8-in.) lightweight CMU back-up is shown in Figure 7. Using prescriptive Method B, the ASHRAE table requires an assembly U-factor of U-0.090 or R-11.11 for Zone 5. The resulting R-value of 13.88 exceeds the required minimum of R-11.11 by 25 percent.

If Method A was used, the ASHRAE table requires R-11.4 ci, which, for example, would equal about 64 mm (2 ½ in.) of extruded polystyrene (XPS) insulation or by rounding up to a more common size 76 mm (3 in.). As noted, Method B is not as efficient as Method A. By using only 50-mm (2-in.) XPS (R-10) continuous insulation and the component material R-values, the cumulative assembly (R-13.88) exceeds the required minimum of R-11.11.

Example 2−masonry cavity wall with 3-in. rigid XPS insulation
A typical 406-mm (16-in.) masonry cavity wall with a 100-mm (4-in.) masonry veneer, 45-mm (1 ¾-in.) air space, 76-mm (3-in.) XPS rigid insulation, an air/moisture/vapor (AMV) barrier, and 200-mm (8-in.) lightweight CMU backup is shown in Figure 8. The wall assembly complies with both prescriptive Methods A and B, and exceeds the assembly minimum by 70 percent—this means it is suitable for ‘high-performance’ and LEED projects. The overall wall configuration remains at 406 mm, and the resulting air space is 45 mm.

Example 3−masonry veneer with 6-in. stud backup and 2-in. high-R insulation
Masonry veneer with steel-stud backup is more complex than masonry veneer with CMU backup because of higher minimum R-value requirements due to energy loss through steel studs, cavity width limitations, and dewpoint locations. The maximum cavity (distance from face of steel stud to back of brick) is 114 mm (4 ½ in.) in accordance to MSJC’s Building Code Requirements and Specifications for Masonry Structures, Chapter 12.

This is prescriptive design only and engineering calculations are common for cavities exceeding 114 mm, which require more insulation to meet energy requirements. Also, many manufacturers now make stronger masonry ties, fasteners, and anchors that can easily span wider cavities. The wall configuration in Figure 9 yields a total R-value of 16.04 (U=0.063) which is only three percent over the 2012 IBC/IECC/ASHRAE 2010 requirements, and does not meet 2015 IBC/IECC/ASHRAE 2013 R-value of R-18.18.

It is important to note this wall configuration uses ‘high-R’ (2 1/8-in.) XPS insulation (R-5.6 per inch), which is more expensive than 50-mm (2-in.) XPS (R-5 per inch). This example does not factor in any additional stud backup energy loss, which will vary with stud spacing and wall configurations.

Example 4−masonry veneer with 6-in. stud backup and 3-in. high-R insulation
Figure 10 demonstrates use of 76-mm (3-in.) ‘high-R’ XPS insulation. The cavity has been increased to 127 mm (5 in.), which will require engineered anchors. The resulting 35-mm (1 3/8-in.) air space is well below the 50-mm (2-in.) industry standard, and less than the 38-mm (1 ½-in.) acceptable air space.

One option is to add a 9.5-mm (3/8-in.) continuous drainage mat to assist at preventing mortar bridging, which can lead to efflorescence, water penetration, restricted water drainage and reduced air flow. The net air space of 25 mm (1 in.) would also meet MSJC’s code minimum. Another option would be to simply increase the overall cavity to 140 mm (5 ½ in.), which would result in a 48-mm (1 7/8-in.) air space.

The wall configuration in Figure 10 yields a total R-value of 22.82 (U=0.044), which exceeds the 2012 IBC/IECC/ASHRAE 2010 requirement of R-15.63 by 48 percent, and the 2015 IBC/IECC/ASHRAE 2013 R-value of R-18.18 by 25 percent.

Example 5−masonry veneer with 6-in. stud backup, 2-in. XPS insulation, and R-8 stud space insulation
Another option for insulating steel stud backup walls is to combine rigid cavity insulation with insulation between the studs. In this example, the 114-mm (4 ½-in.) maximum cavity is maintained the air space is an acceptable 48 mm (1 7/8 in.). Caution is advised as a dewpoint analysis is required to reduce the potential for condensation within the stud space. Generally, the maximum stud space insulation should not exceed R-8 in Climate Zone 5 conditions. Most designers avoid additional insulation in the stud space.

The wall configuration in Figure 11 yields a total R-value of 22.04 (U=0.046), which exceeds the 2012 IBC/IECC/ASHRAE 2010 requirement of R-15.63 by 41 percent, and the 2015 IBC/IECC/ASHRAE 2013 R-value of R-18.18 by 21 percent.

The dewpoint theory predicts condensation in a system at any point where the actual and dewpoint temperature lines cross. Figure 12 represents the dewpoint analysis for the ‘Example 5’ stud wall configuration. For this particular assembly, if the rigid insulation was changed to R-10 and the stud space insulation was R-13 as shown for Method A Table 5.5-6 of ASHRAE 90.1 2013, the dewpoint would fall in the stud wall space (Figure 13). This is not recommended.

It is also important to carefully review air/moisture/vapor barrier properties and location within the various wall systems for the building’s climate zone.

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Which bridge to take: Structural or thermal?
Continuous insulation is defined in ANSI/ASHRAE/IES 90.1-2013 (I-P Edition) Section 3.2 (“Insulation”) as:

Insulation that is uncompressed and continuous across all structural members without thermal bridges, other than fasteners and service openings. It is installed on the interior or exterior or is integral to any opaque surface of the building envelope. [emphasis added]

Therefore, the code does not require a reduction in R-value calculation for masonry ties, fasteners, or anchors. This is further confirmed in the ASHRAE report, “Thermal Performance of Building Envelope Details for Mid-and High-rise Buildings” (5085243.01 MH 1365-RP July 6, 2011). Brick ties are considered a clear field anomaly, and are not considered practical to take into account on an individual basis for whole building calculation (Figure 14). However, companies now manufacture various masonry ties that provide additional resistance to thermal breaks (Figure 15).

Today, masonry ties must not only effectively hold the veneer in place (especially with wider cavities), but they must also be as energy-efficient as possible while helping to create an airtight seal at the penetration point of the air barrier. New anchors are being developed with ‘thermal breaks’ built into the anchor itself to further reduce any thermal bridges, with 2D and 3D modeling showing that a properly designed thermally broken anchor can improve energy performance of a wall assembly.

‘Gasketed’ veneer anchors are critical to the success of any air barrier system, as those penetrations can not only allow potential moisture infiltration, but also be a thermal weak point that can break the continuity of the building envelope. Obviously, the study of these new anchors primarily is involved with metal stud construction where thermal bridging issues have been most prominent.

Other construction assemblies and connections require closer consideration and evaluation. Examples of these linear anomalies are shelf angles and slab edges. Typical masonry shelf angles can be suspended away from the structure by clip angles or pre-manufactured supports—this allows the rigid insulation to continue behind the shelf angle, reducing thermal loss. Of course, there are still clip angles at periodic spacing (e.g. 1220 mm [48 in.] on center [oc]) as determined by the structural engineer of record that must be considered. These fall into the classification of point anomalies as shown in Figure 16.

It is essential the architect and engineer determine which bridge to take. The structural bridge would favor the shelf angle tight to the structure to reduce the cantilevered loads and save costs. The thermal bridge would use the clip angles to reduce energy costs. How does one decide? Simply add up the costs and compare (Figure 17).

If the added structural cost to add clip angles to the relieving angles for a project is $100,000 and the owner will save $400 month in energy consumption, it will take 20 years to ‘break even.’ While this is just a hypothetical example, it is important to carefully analyze the cost benefits.

It is also important to analyze the entire building envelope, including the percentage of fenestration. If the building has a significant area of glass with R-values of R-3 to R-5, the cost to increase the R-value for a small percentage of the opaque walls at shelf angle may be unwarranted. Once again, evaluations are required.

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Conclusion
There are various masonry wall assemblies to achieve energy-efficient designs that comply with, and exceed, national energy requirements, LEED, and other high-performance standards. It is important to remember that ‘over-insulating’ opaque walls is not always cost-effective. There is a point where thicker insulation with a higher R-value just does not yield a return on investment (ROI). While buildings may consume a great deal of energy, a greater amount is used with electric lights, equipment, HVAC, and plug loads than through the loss of energy with the building envelope.

Traditional masonry walls can be designed using current technology for insulated-ventilated façades that are practical, energy-efficient, and cost-effective. These walls can also be transformed into modern, contemporary buildings.

Notes
1 The term “residential” does not apply to basic single family homes. As its name suggests, ASHRAE 90.1 provides energy standards for buildings “except low-rise residential buildings” based on the following definition: low-rise residential buildings: single family houses, multi-family structures of fewer above grade, manufactured houses (mobile homes), and manufactured houses (modular homes). Energy requirements for these buildings are indicated in the International Residential Code (IRC). (back to top)

Richard Filloramo is area director of market development and technical services for the International Masonry Institute (IMI) New England Region’s Connecticut/Rhode Island Office. He holds a bachelor’s of science in architecture from Ohio State University and an associate’s degree in construction technology from Wentworth Institute of Technology. Filloramo has more than 40 years of experience in the masonry industry, and has been involved with the design, construction, or inspection of more than 5000 projects. He served as the national IMI liaison for building codes and standards and is a member of the Masonry Standards Joint Committee (MSJC)—the code-writing body responsible for the Masonry 530 Code. Filloramo can be reached at rfilloramo@imiweb.org.

Chris Bupp is director of architectural services for Hohmann & Barnard, and has been involved in the construction industry for nearly 30 years with the building envelope as his primary area of expertise. At H&B, he works with architects, structural engineers, and building envelope consultants as an educational resource and as a national speaker and writer on the subject of masonry wall design. Bupp also serves on two committees at the Air Barrier Association of America (ABAA). He can be reached at chrisb@h-b.com.