Tag Archives: Thermal mass

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.

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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