You have decided to take advantage of tax rebates by replacing windows with energy-efficient ones to reduce your heating and cooling bills at the same time. That's a good decision, because thirty percent of a typical home's energy costs are lost through the windows. But it is just the beginning. There are lots of things you need to know about windows before you can put your plan into action.

What to Look For in Replacement Windows

You should have a general idea about heat transfer and the principles that reduce it. For instance, energy-efficient windows consist of multiple panes of glass--two, three, or sometimes four--with an inert gas between them. This inert gas acts as an insulator, much the way a thermos bottle works. Window frames made of wood, fiberglass, vinyl, or vinyl-covered wood provide better insulation than metal frames. The type of window is also a factor. A horizontal slider, for example, does not perform as well as a swinging-sash design. The basic criteria for how well a window insulates is its U-value; the lower the U-value, the better. In addition, low-E coatings (a thin metal film) help to lower the U-value and reduce solar heat gain in the summer. Bronze or green window tints also lower the SC (shading coefficient), which further reduces solar heat gain.

Replacement Windows You Can Trust

There are any number of window manufacturers who make an excellent product, and a few who don't. But, armed with knowledge of how energy-efficient windows work and some of the terms, you are better prepared to choose a superior product. But before purchasing new windows, check with reliable sources (Better Business Bureau, Consumer Reports, trusted friends and co-workers). And do the math to determine your return on investment, figuring in tax incentives and reduced energy bills.