R-Value Calculator

What are the R-Value and U-Value?

The R-value is a measurement of the effectiveness of a fenestration product in resisting heat flow. A higher R-value indicates that the fenestration produce is more effective at preventing heat transfer. 

The U-value is also used to measure a fenestration product's insulating characteristics, meaning that it will tell you how well the product will hold in heated of cooled air. U-values generally range from 0.1 (very little heat loss) to 1.0 (high heat loss), so the lower the value, the better the insulating performance.


Why do they matter?

Fenestration products with a high R-value and/or a low U-value will provide better thermal performance and increase the overall energy efficiency of the building. By more effectively mitigating heat transfer, these products reduce the amount of energy required for heating and cooling by minimizing heat loss during cold periods and blocking out unwanted heat during hot periods. By controlling the interior temperature of a space these products increase thermal comfort without increasing energy demand, meaning that energy consumption (along with the utility bill!) goes down. 


About the Calculator

This calculator simplifies area-weighted R-value or U-value calculations. Inputs for R-value or U-value are imperial units only. 

Use it to find combined thermal resistance, based on the effect of multiple assemblies.

For more information, please contact us.