The Dilemma of Windows

Windows are a classic example of a "good news/bad news" dilemma of energy conservation, and as a result, are often the source of much confusion and many questions.

On the positive side the natural light provided by windows helps not only in the enjoyment of the space, but also saves energy due to the decreased need for artificial lighting and can be a source of passive solar heating in the winter.

However, while the passive solar characteristic that is a benefit in the winter, is a detriment in the summer as it can result in increased air conditioning requirements. Furthermore, the insulation value of window itself is generally so low they can be a major source of heat loss.

There is also the dilemma about the need to replace old windows. Drafts around old windows are one of the most common sources of energy loss in a house. While new windows are better insulated, the cost of replacing windows is a major expense, not to mention the potential waste caused if the old windows are simply sent to landfill rather then to a recycling centre.

For existing windows, here are two simple things you can do to increase their energy efficiency:

Draft proofing

Check all your windows for drafts by holding a feather or source of smoke [incense] around the seam of the window to identify air movement. To seal the drafts pick up some draft proofing tape or plastic window covering from your local hardware store. This is an inexpensive, easy solution that will not only save money, but improve the comfort of your home.

Use window coverings

Blinds and drapes are a great way to save energy! In the winter open them during the day to take advantage of the natural light and passive solar heat. Close them at night to add another insulation layer.

If you are considering getting new windows, look carefully at all the different window material options. Factor in not only the insulation value of the frame in particular, but also the durability. Window frames that are not durable are likely to become a source of drafts, decreasing the return on your investment.

When incorporating windows into new construction, factor into the design the location for windows.

South-facing windows are most advantageous for daylighting and for moderating seasonal temperatures. They allow most winter sunlight into the home but little direct sun during the summer, especially when properly shaded.

North-facing windows are also advantageous for daylighting. They admit relatively even, natural light, producing little glare and almost no unwanted summer heat gain.

Although east- and west-facing windows provide good daylight penetration in the morning and evening, respectively, they should be limited. They may cause glare, admit a lot of heat during the summer when it is usually not wanted, and contribute little to solar heating during the winter.

For more information on windows check out these sites:

US Dept of Energy Efficiency and Renewable Energy

Eco Building Options

Canadian Mortgage and Housing Corporation