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.
Low-E Storm Windows
Low-E Storm Windows manufactures vinyl-frame exterior low-e storm windows. The company uses vinyl instead of aluminum for its frames because of the superior thermal performance of vinyl to aluminum: a plastic like vinyl is much less thermally conductive. Low-E Storm Windows are triple-tracked and include an insect screen panel. Research has demonstrated that low-e storm windows significantly improve the thermal performance of single-paned windows, approaching the performance of a high-performance double-glazed replacement window.
GreenSpec lists low-e, airtight exterior storm windows because they significantly improve the thermal performance of existing windows, and they also protect existing windows from the elements.
The low-e coating on the interior of the glass is exposed and consists of a hard-coat, or pyrolytic, coating with higher solar heat gain best suited for heating-dominated climates. Lower solar heat gain, low-e storm windows are also being commercialized for warmer climates.
Although most low-e storms have metal frames (baked enamel aluminum) at least one manufacturer uses a PVC frame for reduced thermal transmittance of the frame. Most exterior low-e storms are "tracked" with two (both glass sashes) or three (two glass and one insect screen) panels.
Durability is an important factor in selecting window attachments. While there isn't much available public testing data for these products, the best exterior storms typically come with a minimum product warranty of 20 years, and GreenSpec has adopted this as a minimum standard.
For additional information on low-e storm windows, see GreenSpec's partner site WindowAttachments.org.
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