The R-Vaue Insulation Myth

A common misperception (and one apparently endorsed by many government agencies that intend to promote energy efficiency) is that the energy effectiveness of a wall depends almost solely on the R value of the insulation in that wall. Definitely not true. Think of how a wall is constructed. Lumber, windows, sheathing, house wrap, drywall. Each stick of lumber not only conducts heat or cold from the outside, but makes that much less room for insulation. What about windows? The more windows, especially those that don’t have the benefit of direct sunlight, the less energy efficient the wall system.  If you want to consider the overall efficiency of a wall, don’t just consider the R-value of the insulation. Consider how the entire wall system is constructed. For instance, for the Zero Net Energy home we constructed in Breckenridge, we reduced the amount of lumber in the exterior walls so that we could increase the amount of insulation. We did this by using engineered lumber from Boise Cascade. This allowed us to place the vertical framing studs farther apart, increasing the amount of insulation in the wall. We used blown in rigid (blue)  foam insulation which filled every potential air gap. Air infiltration in fiberglass insulated walls dramatically decreases a wall’s energy efficiency.  And then we wrapped the entire house in rigid foam board insulation, increasing the R-value  and further eliminating air infiltration. Windows on the north and north western sides of the home were reduced in favor of more window area on the southern areas of the home. Exterior wall systems properly engineered are an order of magnitude more energy efficient than conventionally constructed walls with higher R-value insulation, thereby putting the R-value Insulation Myth to rest.