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When internally insulating a wall, should I batten the walls and fix insulation to the battens?
Unfortunately this was the method prescribed by even the BRE (Building Research Establishment who advise on Building Regulations) up until a few years ago but it has since been found to encourage mould growth and timber decay.
Warm air from within the building often leaks into this cavity and condenses on the surface of the masonry. This moisture often creates perfect conditions for mould growth and also for rot in the timber battens or any other timbers seated in the walls such as floor joists. Once the mould begins to grow, it releases spores into the cavity which can migrate into the building and cause respiratory problems in the occupants. This applies to all types of insulation, including wood fibre and other breathable insulations.
If you absolutely have to use a timber frame to hold the insulation then the cavity between it and the wall must be ventilated by air from outside. This will require air bricks to be fitted at regular intervals along the top and bottom of the wall being insulated to ensure air flow.
In short, any insulation that you fix to the interior of a wall should be in direct contact with the masonry, with any voids filled by a levelling or adhesive plaster.
We offer dynamic heat and moisture modelling as well as condensation risk analyses.
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