At the moment enquiries are being made to find out how the roof is isolated and whether or not this is included in the package. The isolation of the walls is not included in the package and therefore enquiries regarding an ecological/green alternative are being made.
An alternative isolation material is either hemp or flax, both of which are entirely natural products and are readily available. When these materials are compared with steel wool or glass fibre, both score well. The isolation value is expressed in W/m.K and the lower the rate, the better. Of course various types and quality are available. If for example, one looks at Rockwool, they have not only various densities, but also various hard and/or soft and extra fire-proof types.
Just a few values for comparison (the lower the figure, the better the value):
|Material||Warmth conduction coefficient|
|glass fibre |
The next step is to find out where this is produced/manufactured and so far my most favoured material is hemp. The maximum thermal resistance for a newly built house must be 3,0 or higher.
How is this calculated?
Thermal resistance (R-value) = thickness of the material (per metre) divided by the warmth conduction coefficient.
The wall of the building consists of:
- A beam on the outside, 95 mm thick
- A gap of 150 mm
- A beam on the inside of 95 mm thick
The gap is filled with the isolation material - hemp - giving us the following calculation:
Isolation value of the beams = 0,19 (total thickness) / 0,14 (Thermal conduction coefficient of pine)
Isolation value of the beams = 1,357 (R- value of the pine beams)
Buildings with bricks on the inside and outside give a value of 0,2 ? almost no isolation value, while a wooden building gives an isolation value of 1,357.
The isolation value of 130mm of hemp = 0,13 (total thickness) / 0,040 (thermal isolation coefficient)
The isolation value of hemp = 3,25 (R-value hemp gap filling) Total R-value = wood + isolation (hemp) = 4,607
This is way above the required value of 3.