About Energy Efficient Windows
Windows serve a number of important roles in a house: bringing natural light into a space, providing passive solar heating, blocking the escape of heat in the winter, slowing the entry of unwanted heat in the summer, and providing views to the outdoors.
| Window Coatings |
Window Glazing |
Window Frames |
Window Coatings
A transparent or translucent material (glass or plastic) that may be applied to directly to the glass surface or to thin sheets of plastic film that are suspended in the air cavity between the interior and exterior glazing layers that determine how easily heat can move through the window—or the U-factor. Coatings can be used on windows, skylights, or greenhouses.
What Makes It A Green Product
- Coatings are used to admit light and/or to reduce heat transfer.
- On the south, we want the winter sun to be able to enter the house so use a coating that transmits the most sunlight.
- On the west and east, more summer sun enters windows so a coating that transmits less sunlight.
- Low-emissivity (LOW-E) coating prevents heat loss in winter months and has a metallicized look.
Window Glazing
CSI Division: 088000 | Residential Category: Window Glazing
Windows can be purchased with single, double, or triple panes. The temperature on the outside of the glass will be almost the same as on the inside due to heat conduction through the glazing or glass. Double and triple pane windows have two or more layers of glazing separated by layers of air or inert gasses such as argon or krypton.
What Makes It A Green Product
- These layers of gas greatly increase the insulation value of double and triple pane windows. They provide a more comfortable environment and lower heating and cooling costs
Negative Environmental Considerations
- Single pane windows have one piece of glass or plastic and provide almost no protection from heat transfer and should be avoided.
The materials used in the construction of window frames affect the overall insulation capability of the window and the quality of their installation determines how much air leakage occurs through them. Wood and vinyl frame windows are the most popular; other windows are framed with aluminum.
What Makes It A Green Product
- Wood should come from properly managed forests or be certified by a third-party organization. Certified wood is widely available.
- Recovered and Salvaged wood is widely available and should be used provided all appropriate documentation is presented.
- To reduce the negative environmental impact of using vinyl windows (see below) be sure the windows are made from waste or recycled vinyl instead of virgin material.
- Aluminum windows can and should have high-recycled content.
Negative Environmental Considerations
- Wood window frames may come from old-growth Douglas fir. Therefore you should verify that they come from sources that are certified by third-party organizations for sustainability or from a reliable salvaged or recovered sources.
- Frames made from vinyl (polyvinyl chloride or PVC) can contribute to significant pollution from manufacture and disposal so the product’s life-cycle should be considered.
- Standard aluminum window frames transmit the most heat. This heat transmission will raise utility costs and lower comfort levels of the occupants of the building. To reduce heat transmission, use aluminum frames with thermal breaks.
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