New Green Building Code Revises Glass, Fenestration Requirements

December 23rd, 2014 by Editor

ASHRAE, ANSI, the U.S. Green Building Council and the Illuminating Engineering Society recently released the 2014 version of the green building standard. The new version, Standard 189.1-2014, “Standard for the Design of High-Performance, Green Buildings Except Low-Rise Residential Buildings,” has implications for the glass and fenestration industries.

“One change was in how they set the prescriptive envelope requirements, including windows,” says Tom Culp of Birch Point Consulting. “Rather than develop the traditional tables of criteria for each zone and each product type, ASHRAE 189.1 now just sets its requirements as a set percentage better than ASHRAE 90.1.”

In the new standard, the U-factor is set 10 percent lower than the ASHRAE 90.1 value in all zones, which Culp says will encourage more efficient products–including higher-performance framing, warm-edge spacers, argon gas fill and fourth-surface low-E coatings–but without requiring triple glazing.For the solar heat gain coefficient (SHGC), the standard considers how SHGC ties into building orientation and daylighting, so it’s 10 percent lower only on the west and east sides of the building, and no lower than 0.25.

For the solar heat gain coefficient (SHGC), the standard considers how SHGC ties into building orientation and daylighting, so it’s 10 percent lower only on the west and east sides of the building, and no lower than 0.25.

Another alteration to the standard is the addition of Environmental Product Declarations (EPD) in the material requirements section, similar to LEED and the new International Green Construction Code’s inclusion of EPDs. Culp says that as the standard is adopted, manufacturers in the glass and fenestration industries will start to see more requests for EPDs on their products.The new standard also strengthens requirements for onsite renewable energy, which often comes in the form of rooftop solar panels or building-integrated photovoltaics—which ties to the glass and glazing industry.

The new standard also strengthens requirements for onsite renewable energy, which often comes in the form of rooftop solar panels or building-integrated photovoltaics—which ties to the glass and glazing industry.

“An onsite-renewable system that provides between six to 10 kBtu per square foot of roof area is required, unless the building does not receive a minimum amount of solar incidence due to shading, building location” or other factors, says Culp. “In that case, they still have to purchase renewable energy credits, which still can include photovoltaics on other buildings, or offsite solar farms.”Additionally, one of the biggest aspects of the standard is what didn’t change–the window-to-wall ratio.

Additionally, one of the biggest aspects of the standard is what didn’t change–the window-to-wall ratio.

“As reported last January, the proposal that would have reduced the glazing area allowed under the prescriptive path by 25 percent was defeated,” says Culp. “This was a huge issue, and the entire industry joined together along with daylighting and other building science experts to show how the proposal was actually counter to high-performance building design, daylighting and occupant well-being. The committee agreed, and withdrew the proposal.”

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