Energy Efficiency

Most R-19 Walls Are Not R-19 Making Homes More Energy Efficient

When the buyer of a new home talks to the builder about insulation, he or she learns that resisting the flow of heat is measured in "R-Value' – the higher the R-Value, the harder it is for heat to get through. Here's what they don't learn: Most "R-19 walls" are not R-19.

Only the wall cavities are R-19. The other 25 percent of the wall is the wood framing. This is the case because wood is a poor insulator. In a home that is insulated only in the cavities between the studs, the wood framing creates "thermal bridges" – places where heat can pass through more easily. Even when non-insulated sheathing, like plywood or OSB, is nailed onto the outside of the wall, the R-value through the framing is less than half the value through the cavity. So it's not surprising a lot of heat passes through the framing.

This is why many builders are now turning to insulated sheathing, such as STYROFOAM, extruded polystyrene insulation, to make homes more energy efficient.