What is an R-value? Text

R-value is a measure of how effectively insulation, windows or another building material resists heat flow. Generally, the higher the R-value, the greater the product's insulating power.

You'll run into R-value when you buy windows or insulating products for your attic.

Windows
When you are blasting cool air in the summer, your windows might be letting a lot of it escape to the outdoors.
 
Most U.S. homes still have single-pane windows that let the sun's hot rays in during the summertime, making air conditioners work overtime. They have an R -value as low at R-1.

Rosie recommends a double-pane window with a high-performance coating, which can have an R-value of up to R-5. Choose a window with a low-emissivity (low-E) or spectrally selective coating, will prevent the heat from penetrating the glass in the summertime.

R-value is a measure of how much heat can get through the window in an hour. Windows with a high R-value allow less heat to enter your home. The greater the R-value, the greater your energy savings will be.

When shopping for windows, look for the Energy Star label, which means the window meets strict energy-efficiency standards. If you are building a new home, installing energy-efficient windows might save you money buy allowing you to purchase a smaller heater or air conditioning unit. 

Insulation
R-value is a measure of how effectively insulation resists heat flow.

While it's true that the greater the R-value, the greater the product’s insulating power, a product with an R-value that's too high can reach a point of diminishing returns--and actually make your attic hotter.

In Arizona, the recommended R-value for attic insulation is R-38. So if you install insulation to achieve R-60, that's overkill.

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