Before specifying efficient heating and cooling equipment, it’s important to do what we can to reduce heating and cooling loads. Insulation is one of the key products to consider here, but because there are so many insulation products on the market, we look for additional benefits. Examples include cellulose insulation with recycled content, mineral wool insulation with no flame retardants, and fiberglass insulation with no formaldehyde binders. Other products in this area are high-performance windows and glazings, products that contribute to building airtight envelopes, products that reduce thermal bridging, and window-retrofit products.
With products in this area under constant development, we are always refining our approach. For example, as we have learned about insulation products with hazardous flame retardants and blowing agents that have high global warming potential, we have removed those products from GreenSpec, pending manufacturing changes. We encourage building professionals to pressure manufacturers for those changes through specification language and purchasing decisions.
Gorell High-Performance Vinyl Windows
Gorell was founded as a manufacturer of vinyl windows in 1994. The company offers a number of energy-conserving glazing options for replacement and new-construction applications; many meet the GreenSpec criteria for vinyl windows. All Gorell windows feature heavy-duty construction with four-point fusion welding and the PPG Intercept spacer system. Gorell's best-performing glass is Ultra Master III, a triple-glazed unit with two low-e coatings and krypton gas-fill. The highest-performance Gorell products in the NFRC Certified Products Directory have unit U-factors as low as 0.18. More than 92% of Gorell's product line qualifies for the Energy Star label.
Plastic windows come in both ABS and vinyl (PVC). A selling point for these windows is that they are low-maintenance. ABS does not contain chlorine and so, unlike PVC, ABS has no risk of dioxin generation during an accidental fire or incineration at the end of the product's life.
Energy performance is GreenSpec’s primary green consideration for windows, and new developments in window technology enable today's products to far outperform those of a few decades ago. Among the improvements are multiple glazing layers, low-conductivity gas fills, better seals on insulated glazing units, heat-reflective (low-emissivity) coatings, advanced weather-stripping, and new frame systems.
Low-emissivity coatings which allow short-wavelength solar radiation (sunlight) to pass through but reflect long-wavelength radiation (heat) back into the conditioned space are now standard options from all major window manufacturers. Further improvement in energy performance is achieved with triple-glazing and multiple low-e coatings; sometimes an additional glazing layer is provided as a suspended polyester film.
While vinyl products are listed here, there are some performance concerns specifically with regard to expansion and contraction. Plastic windows listed by GreenSpec must achieve an NFRC-certified unit U-factor of 0.20 or lower, or be Passivhaus certified.
To qualify for GreenSpec, windows with the listed U-value must not only be available, but actively marketed.
LEED Credits
EAc1: Optimize Energy Performance
EAp2: Minimum Energy Performance
EQc8.1: Daylight and Views—Daylight 75% of Spaces
EQc8.2: Daylight and Views—Views for 90% of Spaces
IEQc2.4: Daylight and Views
IEQc8.1: Daylight and Views—Daylight
IEQc8.2: Daylight and Views—Views
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