What Is the R-value of Wood?

R-value refers to the resistance a certain type of material has to heat. This is relevant to homeowners because it indicates what type of insulation is necessary for a house. When looking at wood specifically -- for instance, in a log home -- it is important to understand this value so that one can maximize the amount of energy being saved.

Wood has a low ability to insulate against heat transfer, so additional insulation is usually used in log homes

R-value Explained

The R-value of a substance is a number that indicates how much resistance that substance has to heat flowing through it. The greater the R-value, the higher the resistance that material has to heat. When talking about insulation, this means that the greater the R-value, the more ability the material has to keep a house warm in winter and cool in summer. Basically, the higher the R-value, the better the material is at stopping heat from passing through it, whether it be inside or outside the house.

Other Factors That Affect R-value

R-value can sometimes be deceiving. There are many other factors that can affect insulation. Depending on the climate of an area, energy costs change. The closer a climate gets to an extreme in heat or cold, the more necessary it becomes to use insulation with a higher R-value. In addition, the same substance with a different thickness has a different R-value. Bricks are generally 4 inches thick so it is important to look at R-value for 4-inch bricks rather than an R-value of brick in general.

R-value in Wood

Per-inch, R-value of softwood is 1.41. In hardwood, it is 0.71. Logs of around 6 inches would then have an R-value that is about 8. This value, when compared to other insulating materials, is actually pretty low; it is so low that it is below many industry standards. This means that a log home that does not use any other insulation materials would be significantly inefficient at conserving energy.

Other Properties of Wood

Although the R-value of wood is low compared to other insulators in the industry, it is not completely void of energy-saving abilities. One factor overlooked about wood as an insulator is the fact that it performs like a thermal battery. Since its mass is so large, it can store heat from the sun during the daytime and discharge this heat when it gets colder.