Volume 25, Issue 1 - JanuaryFebruary 2011

Glass Tech

Energy Efforts
An Update on Certain 2010 Code Revisions
by Thomas D. Culp, Ph.D.

The year 2010 was very busy for energy codes and included significant changes for the future of architectural glazing. The American Society for Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) completed its 2010 version of ASHRAE 90.1, and the International Code Council (ICC) held final hearings on the 2012 International Energy Conservation Code (IECC). These revisions included numerous details and several major changes and trends related directly to architectural glass.

Daylighting Details
From a glazing perspective, we are seeing a strong, new focus on daylighting. This includes increased requirements and incentives for automatic daylighting controls, as well as significant new requirements for minimum skylight area and lighting controls in large open spaces such as big box retail, atriums and warehouses.

The focus on daylighting also helped turn back a proposal at ASHRAE that would have reduced the glazing area. Several glass industry groups and organizations had expressed concern that the proposal may actually harm energy performance. The proposal was sent back to the committee to reevaluate the technical justification, as well as reconsider other glazing requirements related to U-factor, solar heat gain coefficient (SHGC) and visible transmittance. As such, ASHRAE 90.1 continues to allow up to 40 percent window-to-wall ratio in the prescriptive compliance path, and higher levels in the performance path. The window-to-wall ratio does not include spandrel area, which is treated as wall area under the energy codes.

Likewise, the 2012 IECC also allows increased glazing area if certain criteria are met. This includes the use of simple daylighting controls and spreading the glazing around to ensure more than half the floor area is daylit.

“The 2012 IECC also allows increased glazing area if certain criteria are met. This includes the use of simple daylighting controls and spreading the glazing around to ensure more than half the floor area is daylit.”

Air Leakage
Another significant change is the focus on air leakage. Both standards include new air barrier requirements, which will require increased attention to details at the fenestration-wall interface. Also, the base air leakage requirements for fenestration have been tightened: down to 0.2 cfm/ft2 for windows (or 0.3 cfm/ft2 if specified at a higher test pressure of 6.24 psf), and 0.06 cfm/ft2 for curtainwall and storefront.

Other Glazing Details
In addition, the codes also now recognize advanced glazing technologies. Both ASHRAE 90.1 and the 2012 IECC added language to clarify and remove barriers to the use of dynamic glazing. The 2012 IECC also requires the use of on-site renewable energy (including building integrated photovoltaics), high efficiency HVAC equipment or advanced lighting systems as part of the overall design.

Finally, ASHRAE 90.1 introduced a new requirement related to glazing orientation. The standard now requires the area of south-facing glazing to be larger than the areas of west-facing and east-facing glazing.

Going Green
In addition to the base energy codes, green construction standards also took off in 2010. ASHRAE (together with the U.S. Green Building Council and the Illuminating Engineering Society) published its new standard for high-performance green buildings, ASHRAE 189.1-2010, which is already being incorporated into design requirements for all buildings owned, operated or leased by the U.S. Department of Army. The ICC followed suit, releasing the second draft of its new International Green Construction Code (IgCC). From a fenestration standpoint, these will help promote an even stronger focus on daylighting, recyclable and durable frame materials, sunshades, building integrated photovoltaics and overall energy performance.

Expect these green construction standards to continue evolving in 2011.

Dr. Thomas Culp of Wisconsin-based Birch Point Consulting is GANA’s code consultant and is engaged in the energy code process. Dr. Culp’s opinions are solely his own and not necessarily those of this magazine.


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