These readings are for a cavity wall with no insulation. The external vent is blocked with insulation, cavity RH is continually monitored and varies from 70% - 80%.
Indoor temp 18C Cavity temp: 2-3C Outdoor temp: within a few degrees of zero each way
Why?
NT
Despite the blocking of the external vent, could it be that there is a draught in the cavity, constantly introducing new air? I don't think cavities are ever properly sealed. Often the top of the cavity is open, under the tiles.
Bill
I think it proves that the wall above is cavity construction, which was uncertain, and that the top is open. That means a practical insulation opportunity.
NT
Go round all your upstairs sockets, unbolt the socket and hold your face close to it. Do you feel any cold drafts ?.
Air-leakage through a cavity can be extreme and all your heat end up in the loft.
It has to be cavity all the way up, and has to be open at the top. What else would account for the readings?
If brush strips can be got into the right places, which would be a major challenge, then at least its CWIable. They would need to travel horizontally from a removed air vent, there's no other access. I don't know how to do that.
NT
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