What is U-Factor?

U-Factor is a term you’ll hear a lot when you look at windows. It is often the first thing consumers will look at. So what exactly does it mean and what is a good or bad U-Factor?

U-Factor represents the overall heat transfer coefficient of the window. Simply put, U-Factor measures the amount of heat loss through a window.

A lower U-Factor means less heat will escape through a window and the product is better insulated. U-Factor is especially important during the winter months and can make a big difference in heating costs.

The typical range of U-Factors for windows fall between .20 (most energy efficient) and 1.20 (least energy efficient).

Here’s a look at some typical U-Factors for various windows:

• Old metal casement window 1.3
• Good quality single-pane window 1.0
• Double-pane with low-E glass .4
• Triple-pane with low-E glass .25

Next time you are in the market for replacement windows, be sure to check out the U-Factors of the different windows and choose one that will properly insulate your home.