Window Shopping: Energy-Efficient, Eco-Friendly Windows and Frames

Pick the most energy-efficient and environmentally friendly windows and frames.

| March/April 2010

  • Marvin's Ultimate Double Hung low-E, argon-filled window features a Forest Stewardship Council-certified mahogany frame.
    Photo Courtesy Marvin Windows
  • Weather Shield EnduraShield windows surpass Energy Star's updated 2010 window requirements.
    Photo Courtesy Weather Shield Windows & Doors

Windows are an essential element in your home’s livability. They are its eyes, ears and even nose, letting in light, sound and scent. At the same time, windows can draw in and hold warmth, welcome a natural breeze or banish a frigid wind. Good-quality, energy-efficient windows are a must.

Glass guidelines

The most important aspect of any window is the glass, a relatively environmentally harmless material made from sand. You can opt for single, double or triple layers of glass and choose between different types of insulation and tinting, or glazing. “Double-pane is pretty much the standard,” says Nils Petermann, spokesperson for the Efficient Windows Collaborative in Washington, D.C. “To further improve performance, go to triple-pane,” he says. Simply put, double-pane windows double insulation, and triple-pane windows triple it.

The more glass, the more expensive the window, but you can gain insulation without additional glass. That’s where glazing comes in.


Manufacturers enhance window insulation by injecting air or inert gas between the panes. Energy Star windows typically use krypton or argon gas. Because argon needs more space to do its job, triple-pane windows are generally insulated with krypton. Both gasses are nontoxic, but neither is cheap.

“The added cost for the argon itself is probably no more than $10 per typical window,” Petermann says. “But overall, the cost for any gas fill may be higher because special care is required for a manufacturer to fill the glass with argon and seal the unit well so that the gas doesn’t escape.” The biggest expense for an argon-filled window is often the labor required to produce it. However, rising krypton prices—due to limited supply—make the gas the most expensive element of a krypton-filled window.

The second part of the glaze is the tint, or low-emissivity (low-E) coating, an undetectable layer of silver oxide. Low-E coatings block sun to reduce the ultraviolet light that is harmful to people, furniture and art. The coating also helps insulate. “Low-E coating is as powerful as adding another pane of glass,” Petermann says. “So, a window with a double pane is twice as good as a window with single pane, but a double-pane window with low-E is three times as good. A triple-pane with low-E is four times as good. If you add in krypton, three panes and low-E, the window is five times as good as a single pane for energy efficiency.”

Frame facts

Window frames are built out of four materials: wood, metal, vinyl and fiberglass, plus composites.

Wood frames are the most environmentally friendly option. Look for frames made from locally harvested, certifiably sustainable sources. Some small companies make frames from reclaimed wood. Any wood frame must be well-manufactured to avoid mold problems and sealed properly to protect it from moisture.

Fiberglass—glass-reinforced plastic—frames win high marks for longevity, strength and insulation. They are less energy-intensive to make than other traditional materials such as vinyl. On the downside, they’re not easily recyclable. Fiberglass frames have been common in commercial buildings but are becoming more popular with homeowners as a vinyl alternative.

Composite frames are made of a blend of materials such as wood, vinyl and metal. The frames’ energy-efficiency, eco-friendliness, cost and other attributes vary depending on the manufacturer and composition.  

Metal and vinyl frames are at the bottom of the list. Metal—aluminum or steel—is cheap and readily recyclable but offers little insulation and frequently invites condensation. Vinyl is also inexpensive and has good insulating properties, but it is a known carcinogen that is bad for people and the environment. “In terms of environmental impact, vinyl is worse than metal, but the windows work better,” says Natalie Freidberg, a Los Angeles-based sustainable building consultant. “It’s always the tradeoff: Are you going to choose the best material for Mother Earth or choose the best thing for energy efficiency—considering increased efficiency also benefits Mother Earth?”

Window covering basics

Window coverings can address a number of issues, including privacy, insulation, light control and aesthetics. Consider shades made from sustainably harvested, rapidly renewable sources such as bamboo shoots and various water plants.

Fabrics made from sustainable plants such as hemp and organic cotton are another good option. They are more expensive than traditional fabrics but do not have the pesticides found in cotton, and prices are coming down. Some eco-friendly options also provide insulation. EarthShade’s Hemp Insuliners offer an R-value (a measure of insulating properties) of R-4.5.

Blinds and shutters have recently become available in Forest Stewardship Council-certified woods and bamboo. They are good for light control and privacy, but they are not very insulating.



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