Hometech Windows and Doors Inc Top Windows and Door Specifications from Hometech | Page 6

U-RATING
While we’re still on energy rating, it is important to note a specification that you will come across when
buying windows for your home – the U-Rating or U-Factor. These terms refer to the rate at which heat
passes through a window (window, in this case, refers to pass-through windows such as sliding doors as
well). Glass that is Energy Star certified should have a low U-rating. However, if you come across a product
that doesn’t have an Energy Star label, you need to understand how the U-Factor affects the energy
efficiency and thermal performance of the window.
A high U-Rating means that the glass lets heat out easily, and it is not energy efficient or thermal efficient.
For example, one with a rating of .40 is not energy efficient. Similarly, a rating of .28 would be better than
.35. The recommended rating for Energy Star certified glass is a U-Factor of .30. Therefore, as you go
shopping, don’t invest in windows that have a U-Rating of more than .30.