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.

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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.


Jean Asta

Jean Asta has been a freelance writer for domestic and international clients since 2005. She also acts as a training consultant to businesses and nonprofit organizations in the southeast United States. Asta holds a Master of Public Administration with a concentration in nonprofit management and a Bachelor of Arts in English literature, both from the University of Georgia.