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About R-Value and U-Value

What is R-Value?


R-value, is the term to measure resistance to heat flow, has become a “buzz phrase” among the home improvement industry. So suddenly it seems as though anything that even remotely qualifies as an insulating material has an R-value attached to it. The higher the R-value the better the product and everyone is yelling, “My product has a higher R-value than your product”. This makes it hard for the average consumer to know what is a good product or if it’s what they are looking for.


Honestly, up to a point R-value does provide a valid measurement of a materials ability to insulate. But that is all it is a measure of the insulation quotient of a material.


R-value does not measure the ability of a material to stop air infiltration.

 And air infiltration is frequently the largest source of heat loss in a home.


To put it bluntly, if a material cannot prevent or substantially reduce air infiltration, its R-value is misleading at best, and meaningless at worse.


What is U-Value?


U-value, also known as the coefficient of heat transmission, is a measure of the rate that non-solar heat loss or gain through a material or assembly. U-values gauge how well a material allows heat to pass through. The lower the U-value, the greater a product's resistance to heat flow and the better its insulating value. It describes how well a building element conducts heat and measures the rate of heat transfer through a building element over a given area, under standardized conditions.

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