Knowing the Difference between R-Value and U-Value for your South Shore Remodel

By Terrance F Quinn.

Remodeling can be daunting, as remodelers we know that. Many materials in your home your windows, doors, siding etc. have lots of little parts that make up the whole. And when you are selecting products you need to know a lot of things to make an informed decision that is best for your home and your wallet. There is a lot of terminology in remodeling that can be confusing. Two terms you should know the difference about to save yourself time and money at R-Value and U-Value.

Two pieces of information you should know about the windows you are looking at are the U and R Values because these are the most important differences used to evaluate products. The difference is that U-values are used to evaluate windows and R-values are used to evaluate the insulation in walls and ceilings.

U-values
U-values (the overall heat transfer coefficient) are used to figure the amount of heat that is transferred through a window by conduction, radiation, or convection. THE LOWER THE U-VALUE THE BETTER.

The nationally recognized rating method for windows is for the whole window not just the glass. The whole window will be higher than the center of the glass only, so be sure to check if the rating is for the whole window.

High performance glass, such as double or triple pains can have u-values as low as 0.15

Low-E (low thermal emissivity) windows have a special coating that limits the transfer of heat through the window. Low-E coatings have about the same insulating value as an additional pane of glass, so double glazed windows with low-E insulates about as well as triple-glazed clear windows.

BUT, the most important part of a window installation is not the window but how it is installed. Replacement Windows not properly installed are just a waste of money and in some cases can be less energy efficient than your old window.

R-values
R-values is a measure of the thermal resistance to the flow of energy. A high R-value is a higher resistance to energy loss. THE HIGHER THE R-VALUE THE BETTER.

A piece of foam insulation board has an R-value of 5. This means that it takes five hours to increase the temperature on the other side of the material by one degree.

Air is an excellent insulator and has an R-value of approximately one per one inch of air gap thickness. This is important when sizing window spacers between the panes of glass

Manufacturer R-values apply only to PROPERLY installed insulation. Squashing two layers of batting into the thickness intended for one layer will increase but not double the R-value.

High R-values can be achieved by replacing air with argon gas when practical such as between sealed double-glazed windows.

To sum it up. Low U-value, High R-value and proper installation by competent home improvement companies are the way to save money in this economy. If you have more or specific questions, comments or concerns about this information please give us a call. The difference in U & R values of different products will affect the costs so make sure you are using this information when making comparisons.