WHAT IS THE U-FACTOR? HOW TO SELECT?
The U-factor, or thermal transmittance, of a window or door, is the main factor determining how well your home stays warm in the winter and cool in the summer and it's not just about windows and doors. The U-factor also refers to the ratio of heat flow through glass, meaning that factors such as framing, glazing, sealants, etc., will all affect the U-factor of your window or door. So here's what you need to know about thermal transmittance, so you can make smart purchasing decisions to keep your home comfortable year-round.