Foam Insulation

R-Value was created in a controlled environment to determine a material's ability to resist heat loss. The test that was used to determine this number was done in an environment with zero wind and zero moisture. There are no real-life buildings that are privy to such standards. There are always elemental factors that influence buildings. Thus, relying solely on R-value to determine the insulative abilities of a material is absurd. No one would buy a property if the only information they had was the final cost. They would want to know the location, the size of the house, the conditions of the house, etc.

The test certainly favored fiber insulators, such as  fiberglass, rock wool, and cellulose. They showed (again, in a zero wind/moisture scenario) they were the most effective insulators. But what happens to these materials when we introduce moisture? Fiber materials often include a double vapor barrier. This sounds nice but the reality is that small amounts of moisture will get trapped between the fibers and will accumulate over time. It only takes a couple years to have fiber insulation full of water and need to be completely redone. Small amounts of moisture can reduce R-value by 50% or more.

Now add in air flow and convection currents that exist within fiber insulation. They move vast amounts of air, carrying heat from the underside of the fibers to the top, where it escapes. If you seal it off, it will generally also seal in water vapor, which contributes to the rotting of a structure. The presence of water vapor decreases R-value and so does it's solution-ventilation. The use of ventilation to avoid trapped water vapor is the emergence of moving air, which also negatively affects R-Value.

Fiberglass is often used for most furnace filters because it allows for air flow. Why then, is it also used for insulation? The R-value seems to supports it's use but if you wrap a building in it, you are still allowing for air flow. The average home with all its doors and windows closed still has enough air leaks combined to equal an open door. Resistance to heat permeation has more to do with seal than it does the actual insulation. The only insulation that truly creates a seal and does not lock in moisture is spray polyurethane foam (SPF).

R-value may have been created with the intention to determine the best insulation technique but unfortunately the whole concept failed to consider the impact that realistic environmental factors would have on the effectiveness on a building's insulation. Look at the bigger picture and you will see that R-value is really nothing more than a myth.