A u-factor is a measurement of the efficiency of a window or door. When considering a window purchase, it should be a key deciding point when choosing your windows.
Some people may think a window is just a window. That’s like saying a coat is a coat. While it’s technically true, you wouldn’t want to walk out into a Wisconsin blizzard with the same sort of coat you might wear while walking your dog in Florida. It’s the same thing with windows, but unlike a coat, you can’t tell just from looking at them how efficient or not efficient they are.
That’s where u-factors come in. A u-factor is a number assigned to a window by the independent National Fenestration Ratings Council. Also known as the NFRC, these ratings will tell you how efficient the window you purchased is. A word of caution. Some manufacturers and even some authorized dealers will stretch the truth when it comes to marketing their products with u-factors. What you need to find out is what the u-factor is on the windows you are looking at. It won’t do you much good to be told that a company has a great u-factor when you later find out that the testing was done on a 12-inch by 12-inch picture window and you are basing your entire purchase decision on the u-factor of a window that you’re not even putting in your house.
The federal stimulus package which covers windows and doors purchased and installed through 2010, allows you to receive back 30% of the cost of your new windows up to $1500 as a tax credit as long as they meet two simple requirements. First, they must have a u-factor no higher than .30 and an SHGC (Solar Heat Gain Coefficient) of no more than .30
When your windows are installed, you should look for the factory-applied stickers on the glass of your windows. These stickers will feature the NFRC u-factors. Keep those stickers as they will act as proof for the government that the windows you purchased qualify for the federal stimulus tax credit.