# Insulating a Wooden House

The general idea about wooden houses is that they are very well insulated, and a lot better insulated than brick houses. Is this correct? A short explanation. #### Lambda, R-, U- and k-values

In order to calculate the thermal insulation of a wooden house we have to go back to high school. In Science class we had to deal with Ohm, Volt and Ampère. Thermal insulation works just the same only Volt is now Kelvin, Ohm is now R-value, The energy we lose via a wooden wall can be calculated with a U-value. The principles are all the same. To calculate the U-value of a double wooden wall of two times 14 centimeters pine with 9 centimeters mineral wool in between, we do the following: mineral wool has a lambda-value of 0,043 pine has a lambda-value of 0,17 So for the double wall we calculate as follows:

• outside wall, 14 cm. pine, R = 0,14/0,17 = 0,82
• inside wall, 14 cm. pine, R = 0,14/0,17 = 0,82
• mineral wool, 9 cm., R = 0,09/0,043 = 2,09
• total R-value: (0,82+0,82+2,09) = 3,74 m²K/W.

The U-value is 1/3,74 W/m²K, that is 0,27 W/m²K. That is a very good value. In most European countries municipalities will require 0,4 W/m²K for outside walls and with a traditional brick wall such values have become impossible. The U-value can easily be improved by adding mineral wool. If we increase the 9 centimeters to 14 centimeters, then the resulting R-value would be 4,90 m²K/W and the U-value would be 0,20 W/m²K. Instead of mineral wool we could use glass wool, we would then come to R = 5,85 m²K/W and U = 0,17 W/m²K.