Windows are a critical component in sustainable building design. Most energy flows in and out of a building through its windows, but with intelligent design and technological innovation they can be used to provide heating, cooling and lighting for a better indoor environment. Here is what to look for…
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Wood frames are very energy efficient, and are available in FSC wood, but can also be expensive and need to be sealed or painted regularly to protect them from water damage. Fiberglass frames are low maintenance and energy-efficient but can also be expensive. Aluminum frames are inexpensive but conduct heat easily and are therefore less energy efficient than other options.
Creates an insulated air space between the two pieces of glass, resulting in better thermal performance. Insulated glass also reduces condensation while keeping the heat in during the winter, and heat out during the summer.
Low-E Glass is coated with a virtually invisible layer of silver that reflects radiant solar energy while permitting visible light to pass through the glass. Low-E Glass can either have a low Solar Heat Gain Coefficient (the best choice in climates dominated by cooling) or a high SHGC ( the best choice in climates dominated by heating or for south facing windows in climates with a mix of cooling and heating requirements).
Added inside an insulated panel with Low-E Glass, Argon gas is an invisible, insulating blanket that replaces most of the air during the manufacturing process. With Low-E reflecting heat away, Argon gas buffers thermal transfer to enhance the performance of the whole glass panel.
Doors that are considered to have sustainable qualities must be especially good at creating a seal between the outside and inside, and a large part of energy conservation is about reducing heat (or cold) exchange with the outdoors. A good exterior door will fit tightly and use the best available weather-stripping technology. The most energy-efficient doors are made of fiberglass or wood-clad steel, or painted steel, filled with a core of polyurethane foam.
One aspect to sustainability is the material that the door is comprised of. Material that is locally sourced, rapidly renewable or comes from a managed forest tends to have some long lasting green qualities.
Here are a few materials to choose from:
There is an abundance of styles and textures to choose from. Fiberglass can come either flush, paneled, smooth or textured. Masonite is a large manufacturer of fiberglass doors. The good thing about fiberglass is that it is very energy efficient but is still a lightweight product that allows for great thermal efficiency. It can also be recycled through a two-step process.
When looking for a wood door, there are two things to look for. First, is the type of wood – is it a local wood, is it locally milled and is the forest it comes from managed? Two of the big third-party certification groups are FSC (Forest Stewardship Council) and SFI (Sustainable Forestry Initiative), both verify that a forest is being properly managed. The second aspect to look for is whether it is formaldehyde-free, meaning there is no added urea-formaldehyde in the wood. Wood has naturally occurring formaldehyde, but in some cases, it is added to the adhesive used in wood products. AAW Inc is a manufacturer of wood doors that is striving for sustainability from bamboo doors, water-based stains, low e glass, and FSC certified Mahogany.
Most steel has significant recycled content as a standard in the manufacturing process. Steel is durable and strong. Durability is something that is important to sustainable design; durability and good quality equal a longer life cycle, which means less waste from discarding a product and less energy into making a new product. To ensure a full life cycle with a high traffic door, install either a kickplate or storm door to prevent potential denting.
Certifications and Ratings
Look for the National Fenestration Ratings Council (NFRC) label on the window or patio door. This label shows the U-Value, Solar Heat Gain, and visible light transmittance values.
R- and U-Values
R-Value is a term that measures the insulation properties of a material like insulation, but the energy efficiency of windows is measured by ‘U-Values’. The higher the R-Value, the greater its insulating ability, but for U-Value, the lower the number the better that product’s insulating efficiency. To find a U-Value, divide the number ‘1’ by the R-Value. For example, an R-Value of ‘4’ is equal to a U-Value of .25.