Thermal Efficiency

Wood in itself is a great insulator, not only against the cold but also against the heat. Wood is very slow to change it’s temperature so it cools slowly overnight and then in the heat of the day is retaining coolness. Similarly it heats during the day and provides warmth at night. Then we help it with the correct insulation material for the location climate and create sufficient “Thermal Mass” for comfortable living.

Typically, to heat a 120 M2 solid laminated log house using an 8KW wood burner would require only 6 cubic meters of wood per year to heat to a comfortable level. In France that costs around €400. Add heated towel rails and that is it. No secret just correct materials.

Theremal mass from Wiki

Theremal mass from Wiki

Thermal mass in numbers

Here are some values that give an indication of thermal mass:

Material           J/(kg·K)
================== ========
Water                  4186
Oak wood               2400
Wood fiber             2100
Concrete               2060
Pine wood              1600
Brick                  1360
Rockwook                900
Glasswool               830

Looking at the above table, you start to understand why wood and wood fiber are getting so much attention as building and insulation materials. They store solar energy like no other material (even better than concrete), and at the same time they have excellent lambda-values (meaning: high R-values), very much unlike concrete and brick.


Please check out our video below for a more in depth look at the reality of thermal efficiency between the different materials.