R-Value and U-Value Explained December 12, 2014 There’s actually a lot of misunderstanding when it comes to R-value and U-value for replacement windows. In order to explain what these values mean, it’s important to first understand the basic premise of your home. Every home is essentially a shell. You might never have thought about it in that way before, but it is. That shell protects you, your family, and your possessions from the elements outside. Those elements could be the sun, rain, wind, and hot or cold air. If you didn’t have that ‘shell,’ you would be exposed to all of it and that would make life much tougher for you and your family. It wouldn’t do your furniture, computers, or anything else much good, either. This shell is made up of walls, insulation, windows, and doors. All of that is a barrier against the outside world. Anyone who has any experience with home improvement projects might have come across R-value with regard to insulation. Windows are also given an R-value. The R-Value An R-value is basically a rating that determines the insulating quality of the material. A higher R-value means the material will protect against heat loss more effectively, thus saving you money on heating expenses during the winter. So, for example, a window with an R-value of 4 would be more effective at protecting against the cold air outside than one with a R-value of 2. The U-Value Some windows will also (or instead) have a U-value. This is actually an inverse number of the R-value. It basically provides the same type of information as the R-value, just in a different method, or calculation. A U-value is actually an inverse of the R-value. So, for example, a window that might have an R-value of 4 would have a U-value of ¼. A window with an R-value of 2 would have a U-value of ½. The lower the U-value, the more energy efficient it will be. The higher the R-value, the more energy efficient it will be. This should make it easier for you to find the ideal windows for your family.