Tag Archives: ASHRAE 90.1

Energy-efficient Design with Masonry Construction

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”).

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.

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.

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.

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.

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.

Detailing Masonry and Frame walls with Continuous Insulation and Air Barriers

Photo courtesy Sto Corp.

by John Chamberlin, MBA

According to the U.S. Department of Energy (DOE), buildings account for 39 percent of total energy use in the United States.¹ Efforts to reduce this consumption is reflected in recent changes to building practices and codes.

For example, the DOE has mandated all states update their commercial building codes to meet or exceed American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) 90.1-2010, Energy Standard for Buildings Except Low-rise Residential Buildings, by October. Two key requirements of ASHRAE 90.1-2010 are continuous insulation (ci) and a continuous air barrier.

ASHRAE 90.1 defines continuous insulation as “insulation that is continuous across all structural members without thermal bridges other than fasteners and service openings.” Meanwhile, continuous air barriers are defined as “the combination of interconnected materials, assemblies and sealed joints and components of the building envelope that minimize air leakage into or out of the building envelope.”

With these requirements and definitions in place, compliance with ASHRAE 90.1-2010 should be easy. However, this may not be the case.

This map shows the U.S. Climate Zones based on 2009 International Energy Conservation Code (IECC). [CREDIT] Data courtesy Building Energy Codes Resource Center, Pacific Northwest National Laboratory, U.S. Department of Energy

This map shows the U.S. Climate Zones based on 2009 International Energy Conservation Code (IECC).Data courtesy Building Energy Codes Resource Center, Pacific Northwest National Laboratory, U.S. Department of Energy

Why choose continuous insulation and air barriers?
The biggest problem with many insulated buildings involves thermal bridging. These occur when poor thermal insulator materials meet, creating the path of least resistance for heat to pass through.

An easy example of thermal bridging would be studs in a building’s wall. Even though these studs typically have fiberglass batt insulation between them, the insulation does nothing to reduce the transfer of heat through the stud. Insulation materials include a nominal R-value, which is a measure of the material’s ability to retard heat flow. In theory, a wall assembly constructed with an insulating material of a certain R-value would have a minimum of that material’s R-value as an assembly. However, due to thermal bridging, the assembly’s R-value may be much lower than the R-value of the insulating material itself. This has led to the concept of an assembly’s ‘effective’ R-value versus its ‘nominal’ one.

According to studies conducted by the Oak Ridge National Laboratory (ORNL), thermal bridging in metal frame construction reduces the insulating performance of a wall assembly by 40 to 60 percent.² For example, a 152-mm (6-in.) metal stud wall assembly including R-19 fiberglass batt insulation may only have an effective R-value between R-8 and R-11. Heating systems for buildings are often designed based on the assembly’s nominal R-value, so in many cases unplanned for energy may be expended to heat a structure’s interior. This is where continuous insulation comes into play.

ASHRAE now requires minimum continuous insulation R-values for buildings based on the climate zones in which those buildings reside. The International Energy Conservation Code (IECC) has identified eight unique climate zones throughout the United States (Figure 1). These zones are determined based on the region’s average temperature, humidity level, and moisture level.

Continuous insulation on an assembly’s exterior, either by itself or in conjunction with interior insulation, is the most economical and efficient way of achieving highly effective R-values. Since ASHRAE 90.1 requires continuous insulation be exempt of thermal bridges, its nominal R-value should be much closer to the effective R-value of the assembly.

This shows a sample detail of a wall assembly featuring a fluid-applied air barrier with continuous insulation under masonry veneer on steel stud backup. Images courtesy Sto Corp.

Another major cause of energy consumption is air infiltration and exfiltration. Two of the major air pressures on buildings causing infiltration and exfiltration are wind pressure and stack pressure.

Wind pressure on buildings may have a serious effect on energy and moisture-related air leakage. Since wind pressure is not uniform across a building face, the higher up on a building, the higher the pressure is likely to be, especially as the building rises above objects that might restrict the wind’s flow. Wind pressure pressurizes a building positively on the side it is hitting, but as the wind goes around the corner of the building, it speeds up. This causes the pressure to decrease, and change from positive to negative. These changes in pressure can affect how water moves around the building, especially at corners where water may enter the wall if there is an opening at a joint in the cladding. This phenomenon is known as ‘wind wash’—its effects can be avoided as long as the air barrier is intact at the corners.

Stack pressure occurs when there is a difference in atmospheric pressure at the top and bottom of a building. This difference is the result of a variance in temperature at the top and bottom, causing varying weights of the columns of air inside the building compared to outside. In climates where the interior is heated, stack pressure may cause air infiltration at the bottom of a building and exfiltration at the top. In climates where the interior is cooled, exfiltration may occur at the bottom and infiltration at the top. Stack effect can be controlled by designing airtight vestibules, closing off openings (i.e. mechanical penetrations) between floors, and sealing vertical shafts within the building.

Air barrier systems help control air infiltration and exfiltration in buildings. These systems accomplish this by sealing joints, penetrations, and openings to create an airtight assembly. This, combined with venting and compartmentalizing, allows pressure to equalize between the interior and exterior of a structure. Without these differentials, air infiltration and exfiltration is restricted.

Air barrier systems should meet three key criteria:

They should be continuous to not allow opportunities for air leakage.
They should be structural, or in other words, permanently secured to the supporting structure. (Air barriers must be able to withstand wind pressure, stack pressure, and any pressure caused by mechanical effects, and ultimately transferred to the structure. If not a permanent part of the structure, air barriers may tear or displace under stress.)
Air barriers must be durable. (They are typically installed behind a building’s cladding and may require removal of the cladding for any type of maintenance or repair. For this purpose, a highly durable air barrier will always be preferred so maintenance can be avoided.)

Benefits of continuous insulation and air barriers
A study conducted by Morrison Hershfield, “Energy Conservation Benefits of Air Barriers,” focused on the inclusion of both continuous exterior insulation and a continuous fluid-applied air barrier. Using 3D modeling, a prototype medium three-story office building was proposed for Dallas, Seattle, and Toronto climates. Baseline case buildings were set up to meet the minimum requirements of ASHRAE 90.1-2007 for newly constructed buildings.

The installation of fluid-applied air/moisture barrier using spray equipment over sheathing.

According to the report:

Heating, cooling, lighting, and interior equipment energy consumption were modeled for each load case at 10-minute intervals and the results are summarized on a monthly usage basis in units of kilowatt hours (kWh). This data was then used to calculate energy savings over the base case, and an annual carbon equivalent was calculated based on the annual heating and cooling costs.³

The modeling determined that in terms of energy efficiency, the inclusion of a continuous air barrier actually had a greater impact than the continuous insulation. Annual energy cost savings ranged from $5000 to $19,000, compared to the baseline building which included continuous insulation by itself. Also, there was a diminishing return in energy cost savings as the R-value of the continuous insulation was increased.

The challenges with continuous insulation
The difficulty that arises with continuous insulation is ironically similar to the phenomenon that makes it necessary in the first place. The definition of continuous insulation explains it must be “continuous across all structural members without thermal bridges other than fasteners and service openings.”

In this case, ‘fasteners’ refers to materials such as nails and screws. What this definition does not account for are common details such as ties and shelf-angles in masonry construction or clips and z-grits (i.e. horizontal structural member providing lateral support to the wall panel) in non-masonry cladding assemblies.

In a recent paper prepared by RDH Building Engineering Ltd., entitled “Thermal Bridging of Masonry Veneer Claddings and Energy Code Compliance,” 3D-thermal modeling was used to determine the effects these types of details might have on the effective R-value of a wall assembly including continuous insulation. This value would change based on the actual construction assemblies and structure size. According to RDH:

metal cladding support connections occupying less than 0.5 percent and even less than 0.05 percent of the wall’s surface area can have a profound impact on effective R-values (i.e. anywhere from 10 percent to greater than 50 percent).⁴

Using masonry construction as an example, RDH goes on to explain different types of masonry ties (e.g. steel versus fiber) and various backup materials (e.g. wood stud, concrete, or steel backup) also have an impact on the degree of thermal bridging that may take place.

Continuity of the air barrier is maintained at a transition from sheathing to foundation through the use of a flexible transition membrane embedded in a fluid-applied air/moisture barrier.

Due to their low insulative value, steel masonry ties may reduce the insulation effectiveness by five to eight percent, depending on the type of steel and backup materials. Even more impactful, direct attached masonry shelf angles may reduce the effective R-value by 40 to 55 percent in conjunction with typical exterior insulation thicknesses and steel masonry ties.

Another study by Morrison Hershfield, “Thermal Performance of Building Envelope Details for Mid- and High-rise Buildings,” looked at 40 common building design envelope details and again used 3D modeling to determine the effect thermal bridging might have on the overall thermal efficiency of buildings including continuous exterior insulation.⁵

This study noted the addition of more materials with higher insulating values did not greatly improve the overall thermal performance of the wall assembly so long as these thermal bridges existed. It also points out quite clearly that even in buildings including continuous exterior insulation, all thermal bridges must be considered to determine a structure’s overall thermal efficiency.

Continuous air barrier challenges
There are numerous products that qualify as air barriers including:

building wraps;
fluid-applied barriers;
interior drywall;
sprayed polyurethane foam (SPF);
extruded polystyrene (XPS) insulation boards;
self-adhered membranes; and
polyethylene sheets.

These products help prevent air leakage. If it was possible to construct buildings out of one material, and in a vacuum, any of these would work as an air barrier.

Unfortunately, buildings are constructed out of thousands of different parts assembled together in climates with changing weather patterns, temperatures, and pressures. For an air barrier system to be continuous, it needs to be able to address joints and seams where sheathing materials meet.

Transitions between dissimilar materials must be taken into account. For example, there is the transition from the sheathing of a building to its foundation. Air barrier products should be able to bond structurally to multiple types of substrates as well as being durable enough to bridge transitions where substrates may be out of plane with one another. Movement joints are included in buildings to account for anticipated expansion and contraction. As a result, the air barrier system should also be able to accommodate expansion and contraction.

These air barrier products are also going to be subject to thermal changes that will cause additional stress on the materials during the building’s lifespan. The result is products such as kraft papers and building wraps may ultimately tear or pull away from the building. Other products like common joint tapes or self-adhered membranes may lose adhesion if not properly installed, causing discontinuity of the air barrier and potentially creating opportunities for moisture to intrude. If air barrier systems do not account for the same stresses the building will experience, then they may not only lose effectiveness, but can also actually create problems within the wall cavity that may not be detected until extensive damage has already been done.

The aging Lido Beach Towers (Long Island, NY) were retrofitted with an exterior insulation finish system (EIFS), resulting in a more than 30 percent energy saving.

The construction of an airtight building envelope greatly reduces the risk of moisture problems as a result of air leakage and condensation. However, airtight construction may be less capable of drying than air-porous construction in the case of water leakage or other unplanned circumstances that might allow water to enter the wall assembly.

Water is able to penetrate the building envelope through numerous means. For example, wind may drive rain through incidental cracks or holes in the building’s cladding, or capillary action in porous materials, cracks, or holes may draw water toward the interior. Further, water vapor may be transported by air or diffusion that can condense on cold surfaces within the building envelope.

As mentioned, there are various products that may be classified as air barriers, but not all of them can be classified as water-resistive barriers (WRBs). In fact, the International Building Code (IBC), International Residential Code (IRC), and IECC have specific requirements that must be met for these products to qualify as both an air barrier as well as a water-resistive barrier.

In the case of air barriers, an individual product will be tested according to ASTM E2178, Standard Test Method for Air Permeance of Building Materials. Further, WRBs must meet ASTM D226, Standard Specification for Asphalt-Saturated Organic Felt Used in Roofing and Waterproofing, if they are to be considered waterproof.

Common tests, such as American Association of Textile Chemists and Colorists (AATCC) 127, Water Resistance: Hydrostatic Pressure Test, measure a product’s ability to resist water penetration under adverse conditions, such as wind-driven rain, which is simulated by placing the product under hydrostatic pressure.

Traditionally, asphalt-saturated felt, kraft waterproof building paper, or building wraps have been used as the moisture protection component of wall construction. Installing these types of barriers usually involve shingle-style lapping and mechanical fastening to the sheathing with nails, screws, or staples. While these installation methods are common, because they disrupt the continuity of the air and water-resistive barrier, they actually provide opportunities for air leakage and moisture intrusion.

The best choice for an air and water-resistive barrier is one that meets a number of durability requirements and is able to resist wind and rain loads. Common criteria to look for include:

resistance to puncture, pests, and low-sustained negative pressure from building stack effect and HVAC fan effect;
ability to withstand stress from thermal and moisture movement of building materials and stress from building creep; and
resistance to mold growth and abrasion.

Fluid-applied barriers are gaining popularity in both commercial and residential construction due to their ability to form a full monolithic barrier, as well as their durability and ease of application compared to a traditional wrap or paper product. Many of these products act as both an air barrier and a water-resistive barrier.

Queen’s Landing condominium community in Kent Island, MD, was also retrofit with an energy-efficient EIFS assembly. Some of the EIFS installations included a secondary water/air management system, while some were fit with a hybrid stucco system.

Fluid-applied barriers are generally rolled or sprayed onto sheathing or concrete masonry unit (CMU) backup and fully adhere, becoming part of the structural wall. Some manufacturers use adhesion testing, such as ASTM C297, Standard Test Method for Flatwise Tensile Strength of Sandwich Constructions, to verify a full bond between the barrier and the substrate. It is often found the adhesion may actually exceed the strength of the substrate itself. However, this is not the case with paper-type products where material may tear or blow off the building, or with self-adhered membranes where a loss of adhesion may cause edge peeling or a loss of the barrier altogether.

As fluid-applied barriers are initially in liquid form, there is no lapping of materials that can create discontinuity of the barrier. Once a fluid-applied barrier is completely installed on a building’s wall, the material acts as a single monolithic barrier. Fasteners such as nails, screws, and staples are not needed to apply fluid-applied barriers, so additional holes where rain can enter are less of a concern. Also, because fluid-applied barriers may be rolled or sprayed, the possibility of installation error is greatly reduced. Proper installation of paper-type products and self-adhered membranes frequently require cutting, folding, and use of special tools and accessories. Improper installation of these barriers can be costly and time-consuming to correct; all too often, these important details may be ignored altogether.

Conclusion
Plenty of research has been done to show the advantages of continuous insulation and air barriers. The inclusion of these elements in new construction should help enhance the overall energy efficiency of buildings and allow owners to realize energy cost savings as well. For design professionals, however, the task of creating an energy-efficient building may be just as difficult. New products and new resources are being developed every day to make this task easier, but in the meantime, the key point to remember is with both continuous insulation, as well as continuous air barriers, the details must be carefully considered to realize maximum energy efficiency.

Notes
¹ For more, see U.S. Department of Energy (DOE) 2008, Buildings Energy Data Book. This resource was prepared for DOE’s Office of Energy Efficiency and Renewable Energy (EERE) by D&R International. (back to top)
²For more, see “Thermal Performance of Steel-framed Walls,” by E. Barbour, J. Godgrow, and J.E. Christian, published by the national Association of Home Builders (NAHB) Research Center in 1994. (back to top)
³ See Morrison Hershfield’s “Energy Conservation Benefits of Air Barriers–StoGuard: The Effect on Energy Conservation,” by Chris Norris. (back to top)
⁴ See G. Finch et al.’s “Thermal Bridging of Masonry Veneer Claddings and Energy Code Compliance.” The proceedings are taken from 12^th Canadian Masonry Symposium, held in Vancouver, B.C. in 2013. (back to top)
⁵ See the Morrison Hershfield report, 1365-RP, “Thermal Performance of Building Envelope Details for Mid- and High-rise Buildings.” (back to top)

John Chamberlin is product manager for StoGuard and StoEnergy Guard at Sto Corp; these divisions are focused on heat, air, and moisture management within the building envelope. Prior to this position, he served as product manager for StoCoatings and as associate product manager for StoPowerwall and StoQuik Silver. Chamberlin earned a Master’s in Business Administration at Atlanta’s Emory University and is a graduate of the University of Tennessee, with a Bachelor of Science degree in Marketing. He can be reached by e-mail at jchamberlin@stocorp.com.

Understanding Green Globes: Major advances in the building certification program

Photo © Jason Janik. Photo courtesy Green Building Initiative

by Paul Bertram, FCSI, CDT, GGP

This year, dramatic changes are happening to Green Globes to improve the building assessment and certification program’s technical rigor and usability. As the market increasingly adopts sustainable building practices, these updates will have more impact than ever before. It is important design/construction professionals understand what these programs demand and why.

The Green Building Initiative (GBI) administers the building certification program in the United States, having brought the program in from Canada in 2006. There are individual Green Globes programs for New Construction (NC)—this article’s focus—along with Continual Improvement of Existing Buildings (CIEB) and CIEB−Healthcare.

The program itself is descended from Building Research Establishment Environment Assessment Method (BREEAM), a widely used environmental assessment method that set the international standard for best practices in sustainable buildings. (North of the border, a Green Globes program for existing building certification is administered by Building Owners and Managers Association [BOMA] Canada under the name BOMA BESt [Building Environmental Standards].)

Green Globes is a web-based program that includes an onsite building assessment. The program starts with a survey to help users identify and quantify the environmental attributes of their building design or building operations. Construction documents are also submitted. A third-party assessor is assigned to review the survey and documents, and to provide feedback to the client. The feedback continues during the onsite assessment phase where the assessor verifies the information accurately reflects the building as constructed.

The new program
The total points for the environmental criterion equal 1000. Buildings need to achieve a minimum of 35 percent of potential points to be eligible for certification. Ratings of one, two, three, or four Green Globes are awarded depending on the percentage of points received.

Recently, GBI updated its Green Globes New Construction program.¹ Changes were based on an American National Standards Institute (ANSI)/GBI 01-2010, Green Building Assessment Protocol for Commercial Buildings.

Within the new construction tool, Green Globes allocates points across seven primary environmental assessment areas:

Project Management (five percent);
Site (11.5 percent);
Energy (39 percent);
Water (11 percent);
Materials & Resources (12.5 percent);
Emissions (five percent); and
Indoor Environment (16 percent).

Of the new changes, those made to the Energy and Materials & Resources areas best illustrate advances that will likely impact building sustainability professionals.

Energy category
A building’s energy performance often has the greatest environmental impact, as well as the most potential to reduce direct energy costs for the owner. In the Green Globes program, the Energy assessment area is worth up to 39 percent of the total possible points. Additionally, there is the choice of four paths for evaluating energy performance. These paths were built on established standards or measures and together address the broadest range of users, some of whom might otherwise be discouraged by cost or the difficulty of a single, prescriptive approach.

As shown in Figure 1, the four paths range from the familiar to the leading edge:

Path A: Energy Star Target Finder;
Path B: ASHRAE 90.1-2010 Appendix G;
Path C: Building Carbon Dioxide Equivalent (CO₂e) Emissions (ANSI/GBI 01-2010); and
Path D: ASHRAE Building Energy Quotient (bEQ).

Each path has specific requirements and maximum point thresholds that can be achieved. Extra points are also available to reward superior energy performance.

With regard to energy performance, there are four compliance paths available under Green Globes.

Path A: Energy Star
The Energy Star Target Finder program is structured to predict a newly designed or renovated building’s energy performance based on the U.S. Environmental Protection Agency’s (EPA’s) benchmarking methodology. The program uses the U.S. Energy Information Agency’s (EIA’s) Commercial Building Energy Consumption Survey (CBECS) data in conjunction with certain normalization factors and energy production cycle considerations (source to end user) to benchmark the proposed building’s projected (designed) energy use.

The projected energy use is derived through a design modeling and simulation process, resulting in a final design energy use intensity (EUI). This final design EUI is entered into the Target Finder online program to be benchmarked against the regional energy performance data, specific to the building occupancy type, and compared against the user’s energy performance target. When the building achieves a minimum 75 percent projected performance threshold, it is designated as “Designed to Achieve an Energy Star Label.”

The Target Finder program requires an iterative process to be effective and, in contrast to Portfolio Manager for existing buildings, the user does not submit the results to the Energy Star office to seek a building label. For building types not included under Energy Star, other Green Globes energy performance paths can be pursued.

Path B: ASHRAE Std. 90.1-2010 Appendix G
Also referred to as the ‘Performance Rating Method,’ Path B provides a method for evaluating the performance of all proposed designs (including alterations to existing buildings), as long as the design includes mechanical systems. This path uses American Society for Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) 90.1-2010, Energy Standard for Buildings Except Low-rise Residential Buildings, which is substantially improved from the 2007 version.

Per this standard, building energy models are prepared for both baseline and proposed cases. Several building components are modeled, including:

building envelope;
HVAC;
service water heating;
power;
lighting;
equipment; and
renewable energy systems.

The main purpose of creating these two models is to compare their energy costs (using utility rate structure) as opposed to their energy use or emissions. This approach is most suited to locations where peak shifting is encouraged by using thermal energy storage systems to reduce energy use during daytime peaks. The inherent limitation to this approach is it may not reduce actual energy use or emissions. Further, assumptions made about several factors affecting energy usage—such as occupancy, building operation/maintenance, weather, and changes in energy rates—will result in differences between the model and actual experience.

Path C: Building CO₂e Emissions (ANSI/GBI 01-2010)
This path measures energy performance in carbon-dioxide-equivalent emissions, offering design teams a way to quantify their reduction in ‘CO₂e’ as compared to a baseline building. After all, reducing greenhouse gas (GHG) comes not only from energy-efficient design and optimizing the building’s energy demand, but also from using low-carbon energy sources with clean/renewable energy generation.

An advantage of this energy path is the baseline building is determined by Energy Star Target Finder, so the energy modeler and design team can spend their efforts on modeling the proposed building as accurately as possible without having to also do so for a baseline building. This also prevents the tendency to model a low-performing baseline building in order to improve the performance of the proposed building by comparison.

Located in Dallas, Texas, Perot Museum of Nature and Science recently achieved a four Globes rating from the Green Building Initiative (GBI) for its sustainability practices. The six-story, 16,722-m2(180,000-sf) building boasts a 16.5-m (54-ft) escalator in a 46-m (150-ft) glass-enclosed tube-like structure that dramatically extends outside the building. Photos © Mark Knight Photography. Photos courtesy Green Building Initiative

Path C is in line with the American Institute of Architect’s (AIA) Architecture 2030 Challenge, which aims for new buildings and major renovations to be designed so, by the namesake year, they do not operate on fossil-fuel GHG-emitting energy. Both the Architecture 2030 Challenge and Path C observe similar protocols for baseline calculation. Using this approach, architects can stay focused on the priority of designing carbon neutral buildings and communities by 2030.

Path D: ASHRAE bEQ as-designed rating
ASHRAE’s new tool-based rating methodology for building energy use is the Building Energy Quotient (bEQ) program. This program relies on several standards and measures both as-designed and in-operation use. Path D employs the as-designed rating, which is based on simulated energy consumption independent of operational and occupancy variables.

The tool assigns a letter grade based on the ratio of a proposed building’s EUI to the 50^th percentile EUI of a target (baseline) building type by location. For example, a net-zero-energy building would earn an ‘A+,’ a high-performance building would earn an ‘A,’ et cetera. While the energy use and intensity of the proposed building are estimated using the ASHRAE 90.1 performance method, the baseline energy use and intensity are derived from the Energy Star Target Finder (or from the CBECS database if the building type is not eligible for Energy Star).

Materials & Resources
The selection of sustainable products is moving away from an outdated and less useful single attribute approach. With the advent of lifecycle assessment (LCA) and the availability of product certifications, design professionals have a more comprehensive view of a product’s environmental impact. They can select materials based on multiple attributes, such as appropriate application to building design and regional location and the anticipated building service life. Green Globes NC provides two paths for product selection:

Path A: Performance Path; and
Path B: Prescriptive Path.

Buildings are typically divided into two categories: Building Assembly (which includes the core and shell) and Interior Fit-Out (which includes the interior partitions, finishes, and furnishings used within the building assembly). Often, the term ‘whole building’ is used when referring to the building assembly, but this reference can be misleading because lifecycle tools that evaluate the ‘whole building’ rarely include the interior fit-out. Green Globes users have the ability to take either Path A or B to evaluate product selection for each category, providing increased flexibility as well as the opportunity for broader comparison of products being employed.

Performance Path
Green Globes promotes evaluation of buildings using a lifecycle approach wherever possible. The development of lifecycle assessment (LCA) tools and databases has made it feasible to compare LCA of various building assemblies that meet client desires and functional needs.

Ideally, it would be preferable to evaluate interior fit-outs through comparative LCA as well, which is why Green Globes includes a path to accommodate this. However, there are no tools readily available because interior fit-outs include products with multiple formulations, varying feedstocks, and often proprietary ingredients.

If a building owner or design professional wanted to pursue lifecycle analysis of comparable interior fit-outs, a third-party LCA consultant would be required. Regardless, this option is included within the Green Globes Performance Path as an acknowledgement that LCA is the future for comparing interior solutions.

Databases on chemicals and feedstocks used for proprietary products are growing and, as they do, it is anticipated they will contribute to the development of LCA tools for interior fit-outs. In the meantime, Green Globes offers a Prescriptive Path to evaluate individual products from a lifecycle and multiple attribute perspective for both interior fit-outs and building assemblies.

Prescriptive Path
Traditionally, green building rating systems, standards, and codes have used single attributes—such as recycled content, bio-based, or volatile organic compound (VOC) emissions—as a means for sustainable product selection. However, selecting a product from a single attribute perspective may not yield the most sustainable product for a given application.

A better approach—as incorporated in the Green Globes Prescriptive Path—is to use multiple attributes, evaluating all the appropriate product criteria. Green Globes accommodates three methods for performing multiple attribute evaluation of products.

The first method is use of Environmental Product Declarations (EPDs), which indicate the ingredients (feedstocks) used to manufacture a product.² There are two types of EPDs: Industry Wide EPDs, which are generic to a product type, and Product Specific Declarations, which are manufacturer specific for a family of products.

EPDs should be determined using recognized Product Category Rules (PCRs) so products are being compared to the same criteria. EPDs also require conformance to European Standard (EN) 15804, Comparable Environmental Information, or International Organization for Standardization (ISO) standards:

ISO 14040, Environmental Management−Lifecycle Assessment: Principles and Framework;
ISO 14044, Environmental Management−Lifecycle Assessment: Requirements and Guidelines;
ISO 14025, Environmental Labels and Declarations—Type III Environmental Declarations: Principles and Procedures; and
ISO 21930, Sustainability in Building Construction—Environmental Declaration of Building Products.

At minimum, EPDs should also have a cradle-to-gate scope, although cradle-to-grave—which addresses the use and disposal phases—is preferred. When evaluating EPDs, however, it is also important to consider the appropriate application of the product, including durability and building service life. For example, selecting a product with a desirable EPD that lasts only five years for a building with a service life of 25 years would not be the most sustainable choice.

Perot Museum’s Discovering Life Hall is a popular educational space. Under the Green Globes program, the facility achieved an overall rating of 85 percent. It had perfect scores for site design and enhancement measures to minimize the building’s impact, as well as for its integrated design process, integration of environmental purchasing, commissioning plan, and emergency response plan.

Another way to compare and evaluate products for specification is through third-party-certified multiple attribute standards. These standards are based on a consensus process (often ANSI-based) that includes all product stakeholders. Criteria for evaluation are agreed on and include information on feedstocks and manufacturing processes. Examples include NSF International sustainability assessment standards, Underwriters Laboratories (UL) Environment sustainability certifications, and sustainable forestry certifications.

The third method of product evaluation uses third-party-certified LCAs of products, performed by select manufacturers wanting to demonstrate the complete lifecycle of their product. This method enables a design professional to compare products based on an understanding of their environmental footprint.

Regardless of the method used, it is important durability and service life are considered when designing the building assembly and interior fit-out, ensuring specified products are both environmentally preferable and meet the application’s functional and aesthetic needs.

Process improvement
In addition to changes that increase the technical rigor of Green Globes come improvements in the process that make it more interactive and user-friendly. Green Globes users enter design data in a web-based survey that provides a projected score. A third-party Green Globes Assessor (GGA) is then assigned to verify the user’s responses and provide feedback to the project team throughout the design and construction process.

The process includes an on-site visit by the GGA at conclusion of the construction phase to verify implementation and to gather additional information used in the final report. The GBI then issues a score based on the report. Buildings achieving a score of 35 percent or greater receive a rating of one to four Green Globes, based on the percentage of total points achieved.

The updated Green Globes tool now provides suggested improvements in an optional Pre-Design review stage that help the project team make decisions early in the design process that would cost additional time and money if made later.

Conclusion
Design professionals and their clients are more savvy and informed than ever before. At the same time, the bar for building sustainability continues to rise. This year’s updates to Green Globes incorporate innovative approaches that provide building stakeholders with more support in reaching their design goals. The inclusion of both performance-based and prescriptive options also provides flexibility to accommodate sustainable construction for a wide range of building types.

Notes
¹ Visit www.thegbi.org/green-globes/revised-new-construction-program.shtml. (back to top)
²For more on EPDs, see the article, “LCAs, EPDs, and Increased Product Transparency—The Next Step to Greener Buildings,” by Julie Rapoport, PhD, PE, LEED AP, in the March 2013 issue of The Construction Specifier. (back to top)

Paul Bertram, FCSI, CDT, GGP, is a Fellow of the Construction Specifications Institute, and a past-president. He has a solid background in climate change, reporting building product environmental impacts, building-envelope energy efficiency, and net-zero strategies. Bertram represents Kingspan Insulated Panels with ASTM E60 Committee on Sustainability, ASHRAE 90.1 Envelope sub-committee, the U.S. Green Building Council (USGBC), and the National Institute of Building Science (NIBS) Building Enclosure Technology and Environment Council (BETEC). Prior to joining Kingspan, he was with the North American Insulation Manufacturers Association (NAIMA), and president of his Orlando-based graphic design firm PRB Design for 30 years. Bertram began his career in design and development at Walt Disney World. He can be contacted at paul.bertram@kingspan.com.