Wood is a natural insulator

Energy efficiency is critically important as we seek to better use the planet’s finite resources. As more homes move towards a net zero goal, meaning the amount of energy used is roughly equal to renewable energy created by the home, more attention is being paid to the building systems, design and appliances that best support energy efficiency.

Softwood lumber as a structural material is cost-effective, versatile, easy to build with and familiar to builders and contractors. This makes it ideal to create the enclosure for an energy efficient home.

Because of wood’s higher R-Value, an insulated wood framed home will be more energy efficient than a similarly insulated home built with steel framing. Wood’s thermal insulating properties promote energy efficient walls.* This means homes use less energy for cooling in the summer and heating in the winter.

According to the U.S. Forest Service’s Forest Products Lab, four important thermal properties of wood are thermal conductivity, heat capacity, thermal diffusivity, and coefficient of thermal expansion. Thermal conductivity is the rate of heat flow through a material. The thermal conductivity of common structural woods is much less than the conductivity of metals. Heat capacity is a material’s ability to retain heat energy. Wood has more than double the heat capacity of aluminum or concrete, of equal weight. This means that wood can absorb more heat before its temperature rises.

Thermal diffusivity is a measure of how quickly a material can absorb heat from its surroundings. Because of the low thermal conductivity and moderate density and heat capacity of wood, the thermal diffusivity of wood is much lower than that of other structural materials, such as metal, brick, and stone.

The coefficient of thermal expansion describes how the size of an object changes with a change in temperature. Wood’s coefficient of thermal expansion is less than half that of steel or concrete.

*“Among structural building materials, wood has by far the lowest heat conductivity. As a result, it is typically easier to meet certain insulation targets (e.g., effective R-value, or U-factor) with wood-based wall systems when following current construction practices.”

Resources:

Building Science Corporation: Thermal Control in Buildings

Department of Energy: High-R Walls