The 2014 version of the green building standard was released by the U.S. green Building Council and the Illuminating Engineering Society recently, and according to Nick St. Denis, there are significant changes afoot for windows in green buildings. The latest version, 189.1-2014, Standard for the Design of High-Performance, Green Buildings Except Low-Rise Residential Buildings has significant implications for fenestration and glass usage.
Birch Point Consulting green building expert Tom Culp explains that, “one change was in how they set the prescriptive envelope requirements, including windows. 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.”
The U-factor across all zones sets the new standard at 10% lower than the ASHRAE 90.1 value. Culp says that this will encourage the development of more efficient products such as warmth-edge sensors, fourth-space low-E coatings, argon gas fill, and high-performance framing, but that triple glazing will no longer be required.
Another change involves the solar heat gain coefficient (SHGC). The new standard factors the relationship between building orientation and daylighting in to calculations of the SHGC. Beginning with 189.1-2014, the SHGC is required to be 10% lower only on the east and west sides of the building, and it should be n lower than 0.25 overall.
The new standard has added Environmental Product Declarations (EPD) in the material requirements section, in keeping with LEED and the International Green Code’s inclusion of EPD’s. Glass and fenestration manufacturers can expect more requests for EPD’s on their products.
Onsite renewable energy requirements were strengthened in the new standard. With photovoltaics and solar panels increasingly being tied-in with the glass and fenestration of building-integrated renewable energy systems, the standard anticipates green energy requirements.
According to Culp, “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, etc.,” which means that developers “still have to purchase renewable energy credits, which still can include photovoltaics on other buildings, or off-site solar farms.”