The limits of “U value”

An insulating material’s ability to reduce conductive heat flow is determined by its U value.

But this only concerns heat that is transferred through it. Far more energy is lost to air leakage, which can potentially account for around 40% of a structure’s energy loss.

In addition, U value only does so much to prevent even conductive heat flow. Beyond a certain point, improving insulation U value makes very little difference, if any. Above a certain thickness of insulation material the heat flow reduction due to conduction reaches a plateau. In fact, the cost of improving U value alone can actually far outweigh the energy savings that result, meaning it will take much longer to break even.

And even regarding conductive heat flow, U value has its limits. Beyond a certain point, improving the U value of an insulation system will see very little real difference, if any. Once insulation material reaches above a certain thickness, reduction of heat flow due to conduction plateaus. A system that relies solely on improving the U value can actually cost far more money than any resulting savings on energy bills, delaying a return on investment.

This means that you can see the best results from a solution that combines both improved U values, and an effective air barrier.

Our AirTight spray foam system provides both these features in a single product.

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