High-Performance Envelopes: Meeting New Energy Codes with Manufactured Systems

Designing and installing high-performance building envelope projects to meet challenging new energy codes benefits from a bit of 'systems thinking'
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Sponsored by Parex USA, Inc.
C.C. Sullivan

Learning Objectives:

  1. Describe the new and more restrictive energy codes to be introduced in 2013 and how those codes and standards will affect building enclosure design.
  2. Explain typical code requirements for continuous insulation (C.I.) and the benefits of this enclosure detail for building performance and sustainability.
  3. List the types of materials used for air barriers and the general requirements of air barriers for improving building energy efficiency.
  4. Discuss other factors improving enclosure weather tightness, including moisture control and light transmission, and how those affect energy use.

Credits:

HSW
1 AIA LU/HSW
GBCI
1 GBCI CE Hour

With this year’s scheduled code updates, project teams are focused more than ever on constructing new and retrofitted building envelopes for the highest possible performance. Employing a variety of new and improved enclosure designs on the market today, it’s possible (and often relatively straightforward) to meet new energy codes, sustainability standards and even increasingly strict building codes.

Still, getting the envelope right is far from simple. Design-phase compromises, value engineering, material incompatibility and jobsite defects or craftsmanship issues can hobble a building’s performance even when all the right features seem to be in place. And in the operations phase, some buildings have displayed issues with uneven thermal protection, moisture and air infiltration that undermine the intended performance level of their overall enclosures.

Bridging the gap from effective design to proper operational functioning is difficult enough. Yet, today’s ever more restrictive codes make it even more urgent, and in some ways tougher, to pull off. To deal with these magnified challenges, project teams are increasingly turning to manufactured wall systems and pre-engineered, panelized wall products.

 New Mexico State University School of Fine Arts

IMAGE COURTESY OF PAREX USA

New Mexico State University School of Fine Arts in Las Cruces, N.M., utilizes EIFS to handle the extremes of the local climate and contribute to the building’s energy efficiency.

These industrialized technologies include metal enclosure systems such as flat-plate and lap-seam panels, composite sandwiches of metal and foam insulation, and metal-faced honeycomb and thermoplastic cores. Other insulated structural composites adhere concrete or wood panels to foam insulation, while some use polycarbonate and other clear materials combined with translucent insulation. A similar array of pre-engineered assemblies - tested as systems but built up onsite according to manufacturer specs - are variously called backup systems or universal barrier walls (UBWs). These can receive various claddings, such as rainscreens and troweled-on coatings, while maintaining a uniform substructure and barrier behind.

This robust market of varied enclosure solutions provides project teams and building owners with plenty of choices. Recently, say experts, many of the systems have been enhanced or retooled to meet the needs of more restrictive building codes and energy laws.

“There are many codes and standards on a state, regional and national level that affect both building construction and design. At this point, what has our focus are the upcoming energy code changes mandated by the Department of Energy (DOE) that will come into effect on October 18, 2013,” says Bob Dazel, AIA, LEED Green Associate, a registered architect in Ohio and marketing manager, strategic accounts for Dryvit. The October deadline will bring state energy codes for commercial buildings in line with the 2010 version of ASHRAE Standard 90.1, with many exceeding the rule.

More than a dozen states have begun using the 2009 version of the International Energy Conservation Code (IECC) or an equally stringent standard, earning them DOE grants. A few have accelerated the process, requiring adherence to the more aggressive 2012 IECC in some jurisdictions.

Code regimes will depend on who is building and where. “The IECC is used by the federal government, but states will adopt or modify the energy codes through a legislative process so that it becomes state or local law,” says Dave Evers, vice president of research and development for Butler Manufacturing and former energy committee chair for the Metal Building Manufacturers Association (MBMA). “While we do see early adopters that have already incorporated the 2012 IECC, including Massachusetts, Washington and Illinois, most are not yet even using the 2009 versions. Some states, like Missouri, do not have statewide codes, so local jurisdictions are in the lead.”

Other standards and codes will add to the challenges, including the National Fenestration Rating Council (NFRC) and the American Architectural Manufacturers Association (AAMA), says Bruce M. Keller, vice president of marketing, Kalwall. The two groups are introducing new minimum performance levels for air leakage, U-factor and solar heat-gain coefficient (SHGC) for vertical glazing assemblies.

Additionally, wall assemblies with foam plastic have to conform as noncombustible and fire-rated construction types, complying with Chapter 26 of the IBC, says Heidi Larsen, product manager, Parex USA Inc. “The building codes required that exterior walls of Types I, II, III and IV construction must be noncombustible construction,” she adds. “NFPA 285 has become the primary test to evaluate and regulate the fire performance of combustible materials used on or in exterior walls that are required to be of noncombustible construction.”

Rules for air barriers, thermal insulation and moisture protection are also seen in more codes and standards demanding stricter performance. “Air leakage causes major energy losses,” says Keith Boyer, director of design and development, CENTRIA. “The 2012 International Building Code has language originally established in the 2010 version of ASHRAE 90.1, part of which requires complete air barriers on the building enclosure. The 2012 revision has been adopted in four states already, including Maryland, so air barriers will be more prevalent in the marketplace.”

These and other new requirements for the building enclosure are also seen in green building standards, says Robert A. Zabcik, PE, LEED AP BD+C, director of research and development, NCI Group Inc. “While ASHRAE 90.1 remains the main authority on energy efficiency and their high-performance standard, ASHRAE 189.1 is finally gaining traction; today the USGBC’s LEED certifications rule the green building landscape,” he explains. “But there are other new standards and programs that are gaining popularity.” Among the most important to watch? The International Green Construction Code (IgCC) is poised to take on a significant role because of its integration into the IBC and IECC, says Zabcik, adding that the military branches and the General Services Administration (GSA) will drive the market to some degree when they choose their respective standards.

“Eventually, LEED will become the cutting-edge standard while the others will govern the jurisdictions that want green performance but don’t necessarily need to be the cutting edge,” Zabcik predicts.

Responding to Codes and Standards

In addition to LEED, new design standards are challenging old assumptions in building envelope design. “These include the International Living Building Institute’s Living Building Challenge, the AIA 2030 Challenge and the net-zero building movement; they are encouraging change also,” says Keller. “The codes and standards in force in Western Europe have always been far ahead of the U.S., and have been a driving force for us resulting in our ability to more clearly foresee what is inevitable here.”

But experts like Keller assert that ASHRAE 90.1 will remain the most important standard affecting codes, and that most authorities will refer to the IBC, IECC and IgCC, which incorporate 90.1. The later the version, the higher the expectations for performance. According to the DOE, commercial buildings designed to the 2010 version of ASHRAE 90.1 will deliver energy savings of 18.2 percent as compared to those built to the 2007 iteration.

Dazel and many others on the supply side are working to educate the industry about what these codes say and how they will affect the day-to-day for builders and architects.

“According to the DOE, buildings account for 39 percent of total energy use and 38 percent of total carbon dioxide emissions in America,” says Dazel, a frequent industry educator with more than 15 years experience in the EIFS industry. “Since the DOE is committed to reducing both of these, the new code changes coming this fall will present tighter regulations on new construction, including requiring the adoption of updated energy-related building codes across the country.”

How Manufactured Systems Meet the Need

To meet the demands for energy efficiency and high-performance green building, experts recommend that project teams consider a variety of enclosure approaches to improve the odds of beating the codes and standards. These include techniques for controlling thermal transfer, cutting thermal bridging, reducing solar heat gain and eliminating air and moisture infiltration -all of which undermine the energy performance of building walls, roofs and foundations.

“The reason pre-manufactured components are favored is that they can be tested for total R-value and for air and water resistance,” says Keller. “So the systems are known to meet the codes and certifications required as a system -not just as a material or single component.”

Many of the systems also offer exterior continuous insulation (CI) as well as airand water-resistive barriers. “These are the most effective ways to meet the new code requirements, by eliminating thermal bridging and air leakage issues often found with traditional stud framing and cavity insulation,” says Dazel.

Other products focus on ways to shield and add structure to the insulation and barrier layers. Insulated metal panels (IMPs) are one example, says Zabcik. “IMPs provide excellent structural capacity, durability, insulation performance and a continuous air barrier in an all-in-one solution,” he explains. “But don’t count out high-performance fiberglass systems either. Liner systems and filled cavity systems minimize the batt compression that has been rejected in recent codes.”

Novel techniques for proven building systems, such as EIFS, offer ways to increase overall R-value of the wall assembly, says Larsen. “The typical insulation used in EIFS is expanded polystyrene, or EPS, which provides an R-value of 3.85 per inch,” she says. “This can be installed up to six inches thick or more, a proven method to deliver superior energy conservation in a lightweight wall assembly.”

Beyond R-value alone, other techniques for improving energy performance include the use of low-emissivity (low-E) glass and coatings, as well as light-colored or reflective surfaces. “It is surprising how much of a difference roof color can make,” says Zabcik. “Fine-tuning the solar reflectance and thermal emittance with the building and site climate can shave a few additional percentage points off with no extra cost, at least for a metal roof.”

Many of these systems are designed for opaque enclosures, which are increasingly specified due to the focus on controlling a wall assembly’s solar heat gain coefficient (SHGC). Yet increased daylight and more views to the outdoors are desired by many green building standards. “Adding improved daylighting possibilities are products such as translucent structural sandwich panels, which are highly insulating and light-transmitting fenestration systems,” says Keller. (See sidebar, “School Balances Energy Efficiency and Daylighting,”)

As for the air- and moisture- barrier construction, methods such as insulated metal panels -and UBWs, also known as insulated composite backup panels, or ICBPs -offer project teams a way to ensure that the required enclosure barriers are provided using a single product or system type. These help address

 

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Originally published in Environmental Design + Construction

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