Solid Wood Walls are able to store and release large amounts of moisture. A house with thick walls and negative CO2 emissions can have 100 cubic metres of timber. This timber would weigh approximately 40 tonnes, and so if the walls absorb 400 litres of moisture, the moisture content of the wood only increases by 1%.

The breathable walls stabilise indoor air humidity to a healthy 40-60% and there is no chance of moisture condensing within walls, or on windows.

Solid wood walls dry out slowly over summer giving a cooling effect, and absorb moisture slowly over winter giving a warming effect. The latent heat of the moisture movement adds considerably to the thermal mass effect of the solid wood walls.