Energy Efficiency of Log Homes

There is often confusion about the energy efficiency of log homes as compared to traditional stick-built homes.

Two Factors
There are two primary factors that determine the ability of a wall to be an effective barrier to temperature differences. One is "R-Value," which is a numerical measure of a material's resistance to heat flow over a defined thickness of that material. Second is "thermal mass," which is a measure of a material's ability to store heat and thereby delay heat flow.

Traditional Insulated Frame Walls
Conventional framed walls typically use fiberglass insulation and have an R-value of about R-13 to R-19. Fiberglass is a good, lightweight insulating material which traps air within its fibers and is therefore a poor conductor of heat. It, however, has very low mass and does not store heat.

Solid Log Walls
Log walls are dense and heavyweight, making them poorer insulators of heat than air-filled fiberglass walls. In fact, a log wall the same thickness as an insulated wall (about 6-7 inches) would only have a R-value of about R-9. However, the high density of solid wood also creates an important "mass effect." Instead of heat being conducted through a log wall, as the lower R-value might suggest, the heat is actually stored in the logs and significantly delayed in its release. This allows, for example, high outside temperatures to be effectively blocked and stored during during the hottest part of the day, and released during the cooler night. In winter, heat from the inside of your home is stored in the logs and released back during the colder night. In effect, thermal mass tends to even out large temperature changes. This interesting phenomenon is often referred to as "thermal capacitance."

What It Means
Because of thermal mass benefits, log homes, can be 2.5% - 15% more energy efficient that comparable stick-built homes, according to the National Association of Home Builders, Log Homes Council. Assuming other parts of the home, such as roof, floors, windows, and doors, are similarly insulated, log homes can cost significantly less to heat and cool. Many log homes in cold climates are heated with nothing other than a single fireplace or stove.

For More Information
Look for the report, "The Energy Performance of Log Homes" by the Log Home Council at www.loghomes.org .