Below is the wall structure as concieved by the architect and thermal engineer.
This structure presents very good results in terms of insulation, heat absorbtion and diffusion. However, it poses certain challenges in two areas:
- Reaction to water penetration and humidity coming from outside through the stone wall
- Perspiration and management of humidity coming from inside the house
A stone wall is never completely waterproof. We worry that by putting rye straw directly in contact with the stone wall, we run the risk of having mold issues over time.
Based on the principle of wall perspiration, the outside layer of a wall must be 5 times more absorbant to water vapor than the inside layer of the wall. This is to ensure that water vapour will travel through the wall from the inside to the outside without condensation forming. A stone wall being more waterproof than straw and an earth & lime plaster, we worry that there could be condensation happening somewhere within the straw layer.
We are still looking for answers to the above questions before starting installing our insulation.