This is for a house in Portugal, where most houses have no insulation. I want to insulate the house (it is quite cold in the winter). The plan is to lay down some isolation material on the floor of the attic. The attic is completely isolated from the rest of the house. The only way to get to it is from the roof. The floor is very thick concrete (80 cm of concrete).
The range of insulation product is fairly limited, because very few people isolate their house in Portugal. I basically have the following choices:
- glass wool
- rock wool
- synthetic material consisting of several layers of aluminium, polyester and polyethylene
Glass wool is out because rock wool appears superior in all respects. Rock wool is great because it is fire retardant, but I worry that it might cause allergies to people living in the house (I am not worried about the allergy during installation, only for the people using the house). The synthetic material seems great, but it is very flammable. Insulation quality is not a criterion because it is comparable.
So I basically have to decide on allergy versus fire retardant properties.
Given the very thick slab of concrete, is it reasonable to not worry about the flammable properties of the synthetic product? Maybe I can consider that the concrete will be protection enough? (it is a country where fires are common, due to high temperatures).
For allergies with rock wool, can anyone speak to that risk? Does the fact that the attic is completely closed from the rest of the house, with no window prevent the risk of allergy?