Tag Archives: IECC

Designing Masonry Buildings to the 2012 Energy Code: Thermal Mass Basics

A material’s thermal mass denotes its ability to store heat within a cycle of time. K-values, generally calculated on a 24-hour cycle, are important because they give general references to a material’s capabilities for storing heat. All materials may be considered for use in a thermal mass calculation, but steel, aluminum, and other metal claddings tend to cycle too quickly, while wood tends to cycle too slowly to offer desirable design values.

Masonry—such as concrete masonry unit (CMU), stone, and brick—offers a good blend of characteristics for the thermal mass design based on several values. Storing heat well, the dense material can be designed with wall thicknesses that allow for normal window and door jamb details with reasonable per-area costs to construct.

In most cases, thermal mass should be measured on a cycle representative of both a typical heating and cooling cycle or a variable daily winter cold temperature cycle. While this is done for either season with the same principals, external factors contribute to the winter wall calculations in a more direct way. Building orientation, ceiling heights, lighting, solar heating, soffits, wall finishes, number of occupants, and usage round out a general list for design.

In colder climates, thermal mass is based on the function of interior heating cycling through the core of the wall. As the evening temperatures fall and the interior begins to feel cooler, warmth that was gained and stored during the daylight hours can then reverse the heat path and move back to the interior space of the building.

Summer cycles seem a bit clearer when explained, as the heat of the day penetrates toward the core of the wall. The term ‘decrement property’ takes into account the wall’s material density (e.g. concrete mix), final façade finishes, and exposure. The decrement factor dictates the speed at which the heat can be absorbed into the building. The design should stop the absorption of the heat before it alters the interior of the building’s cooler temperature and cycles the heat to the exterior of the structure as the afternoon temperatures begin to fall.

‘R-value’ has become a term familiar to even consumers, as it is listed on every insulation package in the home improvement stores. The general thought often reduces this metric’s significance to ‘the higher the R-value, the better the product when placed in the wall.’ However, as a unit of thermal resistance, R-value is the conduction rate of heat flow through a combination of materials comprising a wall. Mass-enhanced R-value walls are a combination of thermal mass walls and use of materials that offer high resistance to heat flow. They are extremely useful in climates where the external building temperatures rise well above and fall well below the interior space daily temperatures.

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Designing Masonry Buildings to the 2012 Energy Code

All images courtesy Mortar Net Solutions

All images courtesy Mortar Net Solutions

by Steven Fechino

The 2012 International Energy Conservation Code (IECC) will bring tremendous change to the way buildings are designed, constructed, and renovated. Several of the code’s changes have already been implemented throughout the industry, with many of the currently specified systems and products meeting these new codes. However, there are also materials and assemblies that will need to evolve to remain compliant.

For instance, HVAC systems will require improvements to the mechanical systems and ductwork. Window glazing is becoming more energy-efficient to meet ever-tightening performance criteria. Further, there is this author’s focus—the insulation requirements for masonry construction have been written to higher performance levels. There are many rumors about how the changes will limit the available products with which masonry structures can be built and designed. This article will address some of those rumors by providing simple explanations of the code and some helpful insight into how the industry is dealing with the changes on a positive level.

This diagram shows the elements of a cavity wall This particular assembly includes an insect barrier and mortar-dropping-collection device.

This diagram shows the elements of a cavity wall This particular assembly includes an insect barrier and mortar-dropping-collection device.

The 2012 energy code has been adopted state by state, and jurisdiction by jurisdiction, so the changes have not been applied uniformly across the country.1 Nevertheless, the updated IECC is important to all design/construction professionals, because it is a positive step toward reducing the country’s energy consumption through the design, construction, and operation of more efficient structures. It is important to adapt to these changes as soon as possible, since all regions will likely be affected by the code sooner or later. Preparing now will make the eventual transition to the new energy standards much easier.

CMUs and continuous insulation
The prescriptive energy code for the masonry industry is based primarily on the requirement for continuous insulation (ci) within the wall envelope. This becomes an issue when one looks at the standard concrete masonry unit (CMU)—the cross-webs prevent continuous insulation within the block because they allow thermal bridging. By reducing the cross-web dimension, thermal bridging is reduced and the thermal efficiency of the unit is increased. However, this, in itself, is not the solution to code compliance. It is important to look at all the compliance criteria.

In some cases, a CMU assembly’s mass and resistance to heat transfer (i.e. R-value) are all that is necessary to meet the code, but only in warmer climates. Differing temperature conditions means various types of insulation are used in designing the many single-wythe and cavity wall systems specified across the country. Rigid insulation, foam inserts, dry loose fill, injected foam, spray-on foam, and proprietary block design round out the field of techniques for increasing R-value, with typical gains of 5 to 25.

An important factor for determining energy efficiency of a CMU wall is the envelope’s design, specifications, and the materials making up the assembly—various concrete masonry manufacturers will have similar, but ultimately different, mixes. This is one factor that can change a CMU wall’s R-value and the thermal mass performance of otherwise similar envelopes. (For more, see “Thermal Mass Basics.”)

Other factors include geographical climate history, insulation specifications (within either the CMU or the cavity), and the actual cross-section of the masonry units comprising the wall design. For assistance with this, the National Concrete Masonry Association’s (NCMA’s) TEK 6-2B, R-Values and U-Factors of Single-wythe Concrete Masonry Walls, discusses thermal performance of a CMU wall and its thermal properties based on material properties.2

This church was built with masonry cavity walls and brick veneer. An important factor for determining such a wall’s energy effi ciency is the envelope’s design, specifi cations, and the materials making up the assembly.

This church was built with masonry cavity
walls and brick veneer. An important factor
for determining such a wall’s energy efficiency
is the envelope’s design, specifications, and the materials making up the assembly.

The three paths to compliance
It is important to clear up the rumor that all masonry walls will require continuous insulation in order to meet the new standards. There are many ways a designer can achieve compliance using complete building systems to meet the new IECC requirements rather than relying solely on continuous insulation.

Right now, there are three methods available for determining code compliance, and many of the current masonry designs will show acceptable numbers in at least one of them. These methods are:

  • prescriptive compliance;
  • compliant software (also known as ‘performance method’); and
  • whole building analysis.

Prescriptive method
The prescriptive method uses a series of material or assembly requirements to meet compliance. For example, designers can employ tabulated values for mass walls that specify requirements for continuous insulation to determine compliance. This is the method most manufacturers and designers use today. Many of the products and systems on the market gain compliance through this path.

However, this prescriptive method may not be part of the next energy code in 2015, so it is important to keep an open mind to developing newer technologies and improvements to existing systems for future compliance to the code. Using the prescriptive tables is easy and straightforward, but this method also limits design flexibility and makes some masonry wall types difficult or impractical to build.

Performance method
The performance or compliant software method uses computer programs developed specifically to determine whether an assembly meets the code. There are two popular programs: the American Society of Heating, Refrigerating, and Air-conditioning Engineers’ (ASHRAE’s) EnvStd and the U.S. Department of Energy’s (DOE’s) COMcheck.3 Though the programs differ in their capabilities, they can both offer the designer thermal property constants for various masonry wall configurations. Depending on which part of the energy code the designer needs to meet, these programs can offer wall configurations that meet prevailing codes and which also comply with IECC in many cases.

COMcheck is a bit more complex to use than EnvStd, but it offers options to modify many components within the structure that can then be compiled to achieve compliance, offering the design community the ability to use the products they know how to bid, construct, and sell in energy-efficient buildings. If the designer compiles all the information about the project and compliance is not achieved, he or she can adjust various individual properties of the building envelope to meet the code requirements. This method allows more design flexibility because the designer can test how multiple building components interact to achieve compliance.

Whole building analysis
Whole building analysis is not yet widely used. However, it will likely be the prevailing method in the future because it takes into account everything about the building, and can produce accurate guidelines for the most energy-efficient sources.

This method can analyze annual total energy use rather than individual component compliance. It demonstrates when new design methods can reduce energy costs as compared to standard building methods. The whole building method not only takes into account the various wall types, but also includes entire building envelope information, plus mechanical and lighting specifications to determine compliance.

At left, a mason ‘butters’ a brick with mortar for installation in a masonry cavity wall. In the photo on the right, one can see the detail of a masonry cavity wall comprising a concrete-unit structural wall and brick veneer.

At left, a mason ‘butters’ a brick with mortar for installation in a masonry cavity wall. In the photo on the right, one can see the detail of a masonry cavity wall comprising a concrete-unit structural wall and brick veneer.

iStock_000013773064Medium

Other changes
Beyond IECC, there are a couple of other standards that have recently undergone changes of which those working with masonry design should be aware. ASTM C90-11b, Hollow Load-bearing Concrete Masonry Units, for example, allows cross-web configurations to regulate by cross-sectional area, not by web thickness. The reasons for paying close attention to this change include:

  • R-values may be increased,4 while structural characteristics and performance will not change;
  • a reduction in cost may be achieved (i.e. using less material in each block); and
  • less demand for materials to produce the units, which reduces energy costs for manufacture and transportation.

Another important change is associated with National Fire Protection Association (NFPA) 285-12, Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Non-load-bearing Wall Assemblies Containing Combustible Components. Language in the next energy code will exempt this NFPA test when:

  • material flame indexes are met to published standards (cited below); and
  • air spaces that contain insulation are kept to 25 mm (1 in.) or less.

The new language approved for inclusion in the code that permits exclusion refers to:

Envelopes where rigid or spray-applied insulation is encased by at least one inch of masonry, and there is no gap between the insulation and the masonry; or the insulation and the CMU are not separated by an air space greater than one inch, and the insulation has an index for flame rate meeting requirements of ASTM E84 [Standard Test Method for Surface Burning Characteristics of Building Materials] or [Underwriters Laboratories] UL 723 [Test for Surface Burning Characteristics of Building Materials].

Conclusion
Change is coming to the building industry, driven by a need for far more efficient energy use in the built environment. Masonry has many qualities that make it an ideal building material for energy-efficient construction, including its thermal mass, sustainability, high level of availability, and design flexibility. A combination of new building materials, a better understanding of building dynamics, and improved design software is making it possible for designers to create masonry buildings that meet the new energy codes; skilled masons will be key to making these energy-efficient buildings a reality.

Notes
1 To determine how the new IECC will affect a particular project, visit the U.S. Department of Energy (DOE) website at www.energycodes.gov. (back to top)
2 Visit www.ncma.org/etek/Pages/Manualviewer.aspx?filename=TEK%2006-02B.pdf. (back to top)
3 Visit www.ashrae.org/resources–publications/publication-updates/standard-90-1-users-manual-software-envstd-4-0 and www.energycodes.gov/comcheck, respectively. (back to top)
4 R-values may be increased because of a reduction in thermal bridging via the cross-webs and additional space for insulation. (back to top)

Steven Fechino is the engineering and construction manager for Mortar Net Solutions. He provides engineering support services and product training. Fechino has a bachelor’s of science degree in civil engineering technology and two associate degrees in civil engineering and drafting and drafting and design specializing in building construction. He can be contacted at sfechino@mortarnet.com.

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Impact of Advancements in Model Energy Codes: The Value of Energy Conservation

There are several statistics, trends, and implications related to energy consumption and conservation that can be quite eye-opening.*

Economic impact

  • annual national energy bill for buildings is more than $415 billion;
  • average household spends $1900 a year on energy;
  • improving energy efficiency by 50 percent has an annual value of $950 for the average household; and
  • during the nominal 75-year lifespan of a typical home, $950 a year in energy savings has a ‘present worth’ value of $18,500.

Resource impact

  • commercial and residential buildings account for 41 percent of U.S. energy consumption—a number higher than for industry or transportation;
  • most energy consumed in buildings is produced by fossil fuels (i.e. non-renewables like coal, oil, and natural gas), which can compete with a national security interest to conserve these resources and reduce dependency on foreign sources; and
  • if all U.S. households were to apply even a modest R-3 of continuous insulation (ci) to walls, the estimated energy savings is equivalent to 70 large oil tankers per year, the total energy produced at five large nuclear power plants per year, or removing 7 million vehicles from use (which equates to 2.5 billion gallons of gasoline not consumed each year).

Environmental impacts

  • burning of fuels to produce energy releases air pollutants including sulfur dioxide, nitrogen oxides, carbon monoxide, and particulates having consequences including smog, acid rain, respiratory disease, and many other negative human health and ecological effects;
  • energy consumption or losses from buildings generate 1.2 billion tons of carbon dioxide (a greenhouse gas [GHG]) into the atmosphere; and
  • if all U.S. households were to apply the aforementioned R-3 of ci, air pollutants could be reduced by 30 million tons per year (or 2.5 percent of the total).

* This information comes from the U.S. Energy Information Administration’s (EIA’s) 2009 annual energy review, a New York State Energy Research and Development Authority (NYSERDA) report, Comparison of Current and Future Technologies,” and a 2000 Franklin Associates paper, “Plastics Energy and Greenhouse Gas Savings Using Rigid Foam Sheathing Applied to Walls of Single Family Residential Housing in the U.S. and Canada.”

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Impact of Advancements in Model Energy Codes: What’s the effect on insulation?

Images courtesy PIMA

Images courtesy PIMA

by Jared O. Blum

In response to a national interest in, and policies for, conservation of energy, model energy codes are striving to advance the way commercial and residential building envelopes are insulated. The effect on how design professionals specify materials for thermal management will be substantial.

The International Code Council’s (ICC’s) 2012 International Energy Conservation Code (IECC) calls for a 30 percent increase in building energy savings as compared to the 2006 code. This represents the single largest efficiency increase in the history of the model energy code.

For walls, a continuous insulation (ci) system is featured as a solution in recent model energy codes because it effectively addresses these challenges. When it comes to commercial roofs, significant savings can be attained by upgrading insulation to provide an R-value meeting current code standards and practice.

Light frame and mass wall systems with continuous polyisocyanurate (polyiso) insulation for code-compliant commercial building construction.

Light frame and mass wall systems with continuous polyisocyanurate (polyiso) insulation for code-compliant commercial building construction.

Continuous insulation in walls
In American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) 90.1-2007, Energy Standard for Buildings Except Low-rise Residential Buildings, ci is defined as:

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

Of course, this insulation approach is not new—it has been commonly used for many years on various types of low-slope roofing assemblies. Since 20th century construction practices were developed during periods of ample and cheap energy, its use on both residential and commercial building walls has lagged behind its energy-saving potential. This situation is changing through the emphasis of higher-performing wall assemblies in newer model energy codes. Like any construction material, continuous insulation must be properly specified to ensure its intended performance and appropriate use.

Materials: function and versatility
As shown in Figure 1, ci can be used with various wall structural systems and cladding materials such as:

  • cement board;
  • portland cement stucco;
  • wood lap;
  • brick veneer;
  • stone; and
  • vinyl siding.

In these applications, the primary function of continuous insulation is to provide code-compliant or better energy conservation performance. Additionally, properly qualified and installed ci products can serve other important functions for exterior wall assemblies, including air barriers and water-resistive barriers (WRBs). When laminated to structural materials, ci can even provide structural functions such as wall bracing. (The designer should refer to the manufacturer’s data for code-approved capabilities.)

R-value is the measure of resistance to heat flow through a given thickness of material; the higher the R-value, the greater that resistance.

R-value is the measure of resistance to heat flow through a given thickness of material; the higher the R-value, the greater that resistance.

Various code-compliant foam plastic insulating sheathings and other types of materials are available to address ci applications on walls. The most common foam plastic insulating sheathing products are manufactured and specified in accordance with ASTM C578, Standard Specification for Rigid, Cellular Polystyrene Thermal Insulation, or ASTM C1289, Standard Specification for Faced Rigid Cellular Polyisocyanurate Thermal Insulation Board.

Material types include polyisocyanurate (polyiso) foam, expanded polystyrene (EPS), and extruded polystyrene (XPS). Each product type has different thermal properties (which affect required thickness), costs, and capabilities (Figure 2). Model building code requirements for foam plastics are found in Chapter 26 of the International Building Code (IBC).

Modern energy and building code requirements
Continuous insulation provides one of the most thermally efficient ways of complying with modern energy codes. It mitigates avoidable heat loss due to thermal bridging in walls and roofs not continuously insulated (Figure 3). Modern energy code requirements for walls feature the use of continuous insulation as shown in Figure 4.

When using continuous insulation to meet or exceed the applicable energy code, certain matters of building code compliance should also be considered.

WRBs
Many ci products can be used as a water-resistive barrier behind cladding, offering water protection and thermal performance in one product. (Design professionals should refer to manufacturer installation instructions and code-compliance data.) Alternatively, WRBs can be separately applied to walls with continuous insulation.

Continuous insulation minimizes thermal bridging and provides favorable economic and performance benefits over use of cavity insulation alone in exterior walls.

Continuous insulation minimizes thermal bridging and provides favorable economic and performance benefits over use of cavity insulation alone in exterior walls.

Wind pressure resistance
For code compliance guidance on wind pressure resistance of foam sheathing materials, one should refer to the American Chemistry Council’s (ACC’s) Foam Sheathing Committee Technical Evaluation Report (TER) 1006-01, Prescriptive Wind Pressure Performance of Foam Plastic Insulation used as Insulating Sheathing in Exterior Wall Covering Assemblies,1 along with the manufacturer’s installation instructions and design data.

It is important to verify the wind pressure resistance of other wall assembly components—including framing and siding—because testing has shown they may not be as strong as the foam sheathing material itself under wind pressure loading.

Cladding (siding) attachment
Various proprietary and standard fasteners and connection strategies can be used for attachment and support of cladding materials when installed over continuous insulation. For guidance, refer to the Foam Sheathing Committee’s Tech Matters, “Guide to Attaching Exterior Wall Coverings through Foam Sheathing to Wood or Steel Wall Framing.”

This document features solutions for direct attachment of cladding through foam sheathing and use of furring placed over and attached through foam sheathing. Both these practices minimize thermal bridging through ci due to cladding connections. Design professionals should also refer to the cladding manufacturer’s installation requirements. For example, such documentation will list minimum siding fastener size, how penetration into framing should be maintained, and whether longer fasteners are required.

For this table, wall R-values are shown as cavity insulation alone or as XX + X where the first number is the cavity insulation R-value and the second is for continuous insulation. (Continuous insulation R-values are shown in red.) The commercial Wall R-values are based on all commercial building use groups, except R (residential) which may require additional continuous insulation depending on climate zone.

For this table, wall R-values are shown as cavity insulation alone or as XX + X where the first number is the cavity insulation R-value and the second is for continuous insulation. (Continuous insulation R-values are shown in red.) The commercial Wall R-values are based on all commercial building use groups, except R (residential) which may require additional continuous insulation depending on climate zone.

Fire performance
Foam plastics are held to a comprehensive set of fire performance requirements that include various types of tests and criteria to address flame spread, smoke development, and ignition protection. By far the most significant code requirement that applies to walls with continuous insulation (foam plastics) is the 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. This flame spread test uses full-scale, multi-story wall assemblies.2 In general, compliance with NFPA 285 is not required for buildings meeting limitations for Type V construction or one- and two-family dwelling construction.

Moisture vapor retarders
It is important to ensure ci is specified together with moisture vapor retarders in such a way that moisture vapor is properly managed. Recent building code improvements (i.e. 2009 IBC Section 1405.3, Vapor Retarders) ensure adequate R-value is provided in different climates to prevent condensation by keeping walls warm (i.e. above dewpoint) and to ensure vapor retarders are used in a manner that promotes seasonal drying capability.

Energy codes and the roof
One of the best and simplest ways to achieve a high degree of energy efficiency is by increasing the levels of insulation on the roof. In fact, for long-term energy savings, the commercial roofing market provides a significant multiplier effect to accelerate energy efficiency efforts. For every new roof installed on a building, approximately three additional ones are installed on existing buildings to replace older, less energy-efficient assemblies.

More than 370 million m2 (4 billion sf) of flat roofs are retrofit annually, with untold other existing roofs waiting for their turn.3 If all these commercial roofs were upgraded to meet the requirements of the 2012 IECC, energy savings would be significant.

Published by Polyisocyanurate Insulation Manufacturers Association (PIMA) and the Center for Environmental Innovation in Roofing, Roof and Wall Thermal Design Guide provides information regarding the prescriptive thermal value tables in the 2012 IECC and the references to these tables in the 2012 International Green Construction Code (IgCC). The guide translates this information into simple and straightforward roof and wall R-value tables covering the most common forms of commercial opaque roof and wall construction.

For example, R-values for the 2012 IgCC and IECC for “roofs with insulation entirely above deck” are determined by reducing the overall roof assembly U-factor by 10 percent, and converting the assembly U-factor to the corresponding insulation R-value. Resultant R-values in the table (Figure 5) are rounded to the nearest 0.5 R-value.

In 2013, both ICC and ASHRAE adopted language making it clear once and for all the R-value required for new building construction also applies where “the sheathing or insulation is exposed” during reroofing. For attics and other roofs, the rated R-value of insulation “is for insulation installed both inside and outside the roof or entirely inside the roof cavity.” This information can be found in Figure 6.4

R-values for roofs with insulation entirely above deck, as set out by the building codes.

R-values for roofs with insulation entirely above deck, as set out by the building codes.

R-values for insulation installed inside and outside the roof, or entirely inside the roof cavity.

R-values for insulation installed inside and outside the roof, or entirely inside the roof cavity.

Construction detailing
It is important to provide workable and complete construction details for walls and roofs with ci to ensure a constructible and functional assembly relating to many of the topics discussed in this article. Construction details to consider include:

  • envelope component attachments;
  • integration of flashing and WRB;
  • integration of furring (if used) around wall penetrations and flashing;
  • attachment of cladding to wall framing through ci or to furring;
  • details for cladding attachments through ci at inside and outside corners; and
  • installation detailing per NFPA 285 tested assembly when required. Some useful detailing resources or concepts can found from various sources. Proprietary cladding systems may also include details for accommodation of continuous insulation.

The advancement of model energy codes represents another step forward in ensuring a reduction in energy consumption, which in turn helps stabilize or even decrease utility costs.

Whether for new construction or energy-efficient retrofits, new ways of thinking about insulation are leading to improved products, refined assemblies, and better outcomes. Photo © BigStockPhoto/Gina Sanders

Whether for new construction or energy-efficient retrofits, new ways of thinking about insulation are leading to improved products, refined assemblies, and better outcomes. Photo © BigStockPhoto/Gina Sanders

Notes
1 The group’s membership includes numerous foam sheathing manufacturers, along with the ACC’s Center for the Polyurethanes Industry (CPI), EPS Molders Association (EPSMA), Extruded Polystyrene Foam Association (XPSA), and Polyisocyanurate Insulation Manufacturers Association (PIMA). For more information, visit www.foamsheathing.org. (back to top)
2 For more information, refer to the Foam Sheathing Committee’s Tech Matters, “NFPA 285 Tested Assemblies Using Foam Sheathing,” and the specified manufacturer’s fire test data. (back to top)
3 This comes from a 2012 report, “Twenty-five Years of Polyiso: The Energy and Environmental Contribution of the Polyiso Insulation Industry 1987−2011” prepared by Tegnos Research for PIMA. (back to top)
4 Additional details on these wall and roof types, as well as others, can be found in the Roof and Wall Thermal Design Guide. Visit c.ymcdn.com/sites/www.polyiso.org/resource/resmgr/latest_news/icodesguide2012_snglpgs.pdf. (back to top)

Jared O. Blum is the president of the Polyisocyanurate Insulation Manufacturers Association (PIMA), the Washington-based North American trade association representing manufacturers of polyiso foam insulation. He can be reached via e-mail at joblum@pima.org.

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