State and local governments have had building codes in place for hundreds of years to protect public health, safety and general welfare. A more recent addition to building codes are energy codes which can cover walls, floors, ceiling insulation, windows, air leakage and duct leakage. The standards for energy code compliance vary from state to state and from municipality to municipality. Compliance is the responsibility of those constructing the home. In most cases, log cabin energy code compliance is expected just as in traditionally built homes.
The Energy Code, R-Value and Log Cabins
R-Value is one of the measurements used to determine energy efficiency. R-value is the capacity of an insulating material to resist heat flow. The higher the R-value, the greater the insulating power. According to the US Department of Energy, the R-value for wood ranges between 1.41 per inch (2.54 cm) for most softwoods and 0.71 for most hardwoods. Ignoring the benefits of the thermal mass, a 6-inch (15.24 cm) softwood log wall has a clear-wall (a wall without windows or doors) R-value of just over 8.
Compared to a conventional wood stud wall (3½ inches (8.89 cm) of insulation, sheathing, and wallboard, for a total of about R-14) the log wall is apparently a far inferior insulation system. Based only on this, log walls do not satisfy most building code energy standards. However, to what extent a log building interacts with its surroundings depends greatly on the climate. Because of the log’s heat storage capability, its large mass may result in better overall energy efficiency in some climates than in others.
Logs act like “thermal batteries” and can, under the right circumstances, store heat during the day and gradually release it at night. This generally increases the apparent R-value of a log by 0.1 per inch of thickness in mild, sunny climates that have a substantial temperature swing from day to night. Such climates generally exist in the Earth’s temperate zones between the 15th and 40th parallels.
Because log homes don’t have conventional wood-stud walls and insulation, they often don’t satisfy building code energy standards that require prescribed insulation R-values. However, several states — including Pennsylvania, Maine, and South Carolina — have exempted log-walled homes from normal energy compliance regulations. Others, such as Washington, have approved “prescriptive packages” for various sizes of logs, but these may or may not make sense in terms of energy efficiency.
Log Cabin Insulation Kits
When log walls do not meet code on their own, other measures can be considered. This is especially
necessary in cold climates. Conestoga has optional insulation kits for walls, floors and ceilings. With an insulation kit, there is no reason a log cabin shouldn’t be just as comfortable in Alaska as it is in Alabama.