Is this necessarily unwise when, for example, temperatures are around freezing?
I'd have thought that moisture evaporation would be very low under such conditions, with benefits in comfort and lower heat loss if ventilation was blocked. Obviously prevention is better than cure, but if underfloor insulation wasn't on this winter's list of TTD . . .
Rob
Its a very good idea.
in these times any heat leakage to below floor level can only reduce humidity as long as there isn't too much moisture leaking with it - and even if there is, it takes months of wet timberwork before rot starts, so a couple of weeks wont make much difference.
Most underfloor areas are not tanked against moisture and are designed to be well ventilated instead, to prevent timber rot. Often they have bare earth which generates a lot of moisture (or just a couple of inches of concreate poured over), and walls dropping well below the outside ground level which are [expected to be] damp most of the time. In some cases there can even be standing water under the floor when it's rained a lot and the water table rises.
I wouldn't do it without humidity monitoring, and also monitoring the moisture content of the timber down there.
In article , Andrew Gabriel writes
Funny you should say that, Scottish building regs have required underfloor areas to be sealed for over a hundred years. Older properties are tar sealed, some more recent ones I have seen have a weak conformal pour of concrete/mortar over the base.
I'd be surprised if the regs south of the border haven't adopted something similar by now as damp earth is a classic source and breeding area for fungal spores.
Which could be with a poke of the head under the floor and a good sniff.
I have carried out a partial blocking of some airbricks on a house in a very exposed location, there really wasn't the need to have a force ten under the floor to keep it dry, it was the one with the conformal mortar underfloor coat and it was fine many years later.
It's something I would definitely consider again if it felt overly draughty underneath.
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