Insulation
Insulation is a must-have in any home, and a valuable investment to save energy - and the planet.
Even Buildingbiologists can argue about the best insulation. They all insulate well, but which is the healthiest for people? Which is the most sustainable for the environment?
Available types are
Spray foam
Reflective metal foil
Fibreglass batts
Rockwool batts
Polyester batts
Wool (from sheep, yes…) batts
Rigid boards, made from polystyrene, polyurethane, or phenolic foam, often with foil facing outwards, also available made with wood fibre.
Loose-fill, blown in, often consisting of fibreglass, rockwool, or cellulose.
The voices are overwhelming and everyone tells you their product is the best for you. - In Buildingbiology, we have criteria, that help us deccide.
Is the insulation breathing, or does it force condensation to occur inside the wall?
Is the insulation Mae with sustainably sourced materials?
Is the insulation natural or inert, not out-gassing any harmful chemicals or microscopic dusts.
Without going into a lengthy discussion, I’ll jump right to the conclusion, - even though your architect or builder will have to perform the calculations of where the dew point is.
Spray foam, if open cell, is allowing vapour and air to penetrate, so the wall can breathe and stays dry. However, the chemicals used to inflate the foam are still being investigated. - Do your research, check the data sheets!
Reflective foil provides the perfect surface for condensation, and I have seen rotten timber frames, myself.
Fibreglass batts can release fine dust that is hazardous during installation, and when disturbed. The modern binders are not toxic or emitting formaldehyde, anymore.
Rockwool is less bio persistent than fibreglass. However, it is irritating and especially so during installation or when disturbed. (Respirator, gloves, sleeves needed)
Polyester is also used for bedding and for clothes. It is an ‘endless’ fibre (no dust) that is inert and does not emit anything. Tradies often don’t like it, because it is more difficult to cut and fit, but from a health point of view, it is a preferred choice.
Woollen batts are sometimes combined with polyester and treated with borax, but in any case a natural and well performing, renewable insulation material. It can take up water, and house vermin. Make sure to purchase from a proven and well established supplier.,
The rigid boards are made from different types of foam. This is a topic in itself, as outgassing (isocyanates, flame retardants, VOCs) and fire danger are dominant issues. - If the boards have aluminium backing, they certainly seal the home and stop any air or vapour exchange with the outside, thus creating potential for mould growth.
Loose-fill insulation can be natural, using cellulose fibres (recycled paper) protected with borax, against insect infestation, and also as a fire retardant. However, it is relatively heavy, and it compresses over time. It can also soak up humidity, which reduces its insulation properties. I’ve also heard that vermin love it to build their nests in.
In conclusion, this article is just a trigger to motivate you to do your own research. If your priority is sustainability, cellulose fluff is the best option, and if you want functionality and longevity, choose fibreglass. However, there may be situation with certain wall constructions that would make rigid boards the best choice.
It is always a good idea to get a building designer to model the dew point in your wall. A concrete wall would be entirely different to a brick veneer, or an earth wall, or a log home.
