Six Tips For Buying An Energy Efficient Window

by Owner on April 2, 2010

The harsh winter in the Northeast US this year rudely reminded me that I’m in the market for a new energy efficient window for my kitchen. It’s an old style split window that leaked in so much cold air that I had to use painters tape in a desperate attempt to keep out the elements at the height of our winter storm. Now that spring is here it’s time to get a new one.

Here’s what I’m looking for:

1) Energy Star label. If you’re in the US, this is a no-brainer. In order for any energy efficient window to deserve the name it must pass strict criteria developed by Energy Star, so this label is a must.

Example of Energy Star label with eligible climate zones.

2) Check your climate zone. Different parts of the country have different climates and therefore different requirements for windows. If you’re in the US, when you look at the Energy Star label there will be a map that shows you the regions for which the window is intended. The regions are Northern, North-Central, South-Central and Southern. A high quality window may be Energy Star rated for multiple or even all regions.

3) Check U-Factor and Solar Heat Gain Co-efficient (SHGC). If you see the Energy Star label then this is already done for you, since these criteria are part of the labeling requirements. U-Factor measures heat transfer, with lower values best for cold climates. SHGC measures increase in temperature inside your home as a result of solar radiation coming through the window, with low values best for hot climates. In other words, in cold climates the best windows will minimize heat escaping your house through them, and in hot climates they will minimize how much heat enters your house. Makes sense! Check the Energy Star website for specific U-Factor and SHGC values appropriate for your climate region if you live in the US.

4) Check for multiple panes. An energy efficient window will usually have multiple panes, because the air (or sometimes gas) trapped between the windows will serve as insulation.

5) Check for gas fill between panes. Argon gas and krypton gas are odorless and harmless but serve as better insulation than air. Argon gas is cheaper, but krypton gas insulates better. Blends of the two are common.

6) Look for low-emittance (Low-E) glass. If you’re in the US, the Energy Star label and its U-Factor/SHGC requirements already take care of this for you. If you’re in another country, windows with low-E glass have better energy efficiency than regular glass, so it’s something you should consider.

Finding an energy efficient window should not be difficult, as most local home improvement stores should carry them. Arming yourself with a bit of knowledge will go a long way to keeping your eco friendly home warm and saving you lots of money in energy bills.

PS: If you’re in the US, don’t forget that buying an energy efficient window makes you eligible for tax credits under President Obama’s stimulus plan until the end of 2010!

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