It's a fact that your house leaks most of its heat through its windows. Poor seals on cheap windows allow drafts to intrude which lead you to turn the heating higher. It's also true that common or garden glass is not a particularly good insulator. Ok, you probably know a lot of this already but the problem is you balk at the price of energy-efficient windows, right? What you have to bear in mind is that the right windows can reduce your house's energy usage by up to 25 per cent.

The United States' Federal Government thinks so, and is offering homeowners a tax credit of ten percent of energy-saving windows' purchase price (up to $500 per year). This is a tax credit, not a deduction. So, if you purchase and install a $1000 patio door that is "Energy Star" rated or has a Manufacturer's Certification Statement, you can reduce your tax bill for the year by $100, and your patio door's effective cost is only $900. This tax credit is known as the "Existing Home Tax Credit for Fenestration", and is good for windows installed between December 31, 2005 and January 1, 2008.

There's an organization that has come up with a rating system to work out the energy efficiency of windows. It is the National Fenestration Rating Council or NFRC. Its' rating systems are the U-Factor which determines how good your windows are at retaining the heat in your home (the lower this rating, the better) and the Solar Heat Gain Coefficient which measures how the windows help to keep the house cool (again, the lower the rating the better). If you want to qualify for the Federal Government tax credit you need to install products that have been rated by this organization. You'll need to submit a copy of your receipt as proof of purchase along with the product's NFRC sticker.

What should you look for in a window, besides an Energy Star rating? The market supplies many choices, but here are some guidelines.

The majority of windows that have an energy-efficient insulating function will be double- or even triple-glazed. Between the glass panes will often be an inert, insulating gas like argon or krypton.

Next, window manufacturers can achieve lower U-Ratings by glazing the glass to various degrees with a special film or a reflective metallic coating. Some glazing even reduces transmission of damaging ultra-violet rays. In addition to insulating your house, this kind of glazing can protect your furniture and drapes from deteriorating due to UV exposure. If installing a West window, try to get glass with the lowest Solar Heat Gain Coefficient possible --- rooms with West exposure are notorious for overheating in the afternoon, and this type of window will help.

Finally, good windows have a tight seal that you should be able to feel when you open and close them in the showroom. Try it out. Repeatedly. Compare the cheap windows to the more expensive ones. With practice, you should be able to tell a well-sealed window from a badly sealed one. Only the seal on your refrigerator door should be better.

Look at your heating and cooling bills, and take off ten percent. Price out your windows, and take ten percent off the price of the energy-efficient ones. Now, can you afford not replace your drafty old non-insulating windows?