It measures the process of the amount of heat transfer from the outside to the inside of the house. For example, in California Title 24, it states a window can be more than .27 for efficiency. So, your windows have to be .27 or below that measure rating. The U-Value is that .27 or higher. Otherwise, you can't get a permit if it’s lower. In short, it has to do with the energy efficiency.

That’s the opposite of U-Value. If U-Value determines how much heat is going through your house, the R-Value determines how much heat is being absorbed in your window. The better glass you have, the more R-Value you have. In other words, if your window glass is hot, that’s not a good R-Value, which means that the window has no Low-E or Argon Gas. You want your window glass to stay cool even when it’s hot.

It’s a special program run by the EPA and the U.S. Department of Energy. In a nutshell, it’s a program that certifies that certain products are energy efficient. In our case, all of our Anlin windows are Energy Star-approved and certified eco-friendly by both state and federal titles. Energy Star also provides information on a product’s energy consumption and how you’re helping the environment.