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The Myth of "R" Values and How They Relate to Insulation

What does “R” value mean?

Few people in the building industry, and almost nobody outside the industry has faintest idea. And yet for almost 100 years we have based our comfort and our budget on the value of “R”.

To answer: R value measures the Resistance to the transfer of thermal energy through an object. The higher the R, the better it insulates.

So if you double the R value of the insulation in your attic, will you double your savings? Sorry.

The truth is, you will see only a 2% savings according to Fourniers law of Thermodynamics. And worse, the effectiveness of the batt or blown insulation in your attic was severely diminished the day it was installed! That’s because air movement through insulation reduces its Resistance severely.

Don’t forget, it’s in a vented attic that was designed for air flow. See Tech Talk article 1 which discusses climate. Building scientists are discovering that the number one way to reduce energy consumption is to stop air leaks in the building envelope. There is no better way to do this than seal the walls and attic areas.

There is no more effective system to do that than foam insulation.