Andrew Krupa: Koffman Windows

‍“The R-value, or thermal resistance rating’ measures the effectiveness of a product or material in slowing down the transfer of heat. The larger the R-value, the more effective a product is at stopping the transfer of heat and the better insulated the material is. Put simply, the higher the R-value, the better the material is at insulating your home.  
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The U-value measures thermal transmittance, the rate of heat loss or gain through a structure or material. The lower the U-value, the better the material is at stopping the transfer of heat and the better insulated the material is.
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The R-value measures thermal resistance through a material, the U-value measures thermal conductivity. They are mathematically inverse of one another.”
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