Hugo Morvan wrote:What heating do you have? Wood stove? Central Heating? Radiators in every room?
If it's really drafty, you can't heat the place up properly. Humid air comes in all the time. If you can't heat up properly, you can't evaporate all the water from the walls and condensation into the air. Which is what you want to do and then open the windows and get all that high humidity air out when it's low humidity outside (sunny cold day , unfortunately unlikely in UK). But there must be days where there is less humidity in the air.
Which is totally contradictory to what people think, You open the window, a lot of hot air leaves the building, cool air comes in. But they say that it takes less energy to heat that air, because you don't have to heat all that water which is in the air after.
Or was it mornings you have to vent? I've heard that early mornings the outside air contains usually less humidity. It cools in the night, cool air can contain less humidity so then it falls out everywhere. There was a rule like that. But that you can find out.
Insulating the attic and in between floors (blow this papery insulation in)might make it easier to get the place heated up properly.
When i renovated my place i had done a lot of concrete and rendering of walls which caused humidity, This helped then.
Also there where no gutters at the time, so water just ran onto the wall. Drainage pipes dug under the flooring, concreting it up with a plastic vapor barrier underneath. I am running a pipe from the gutter from the front of the house under the floor to the lower back end of the house into a reservoir. All things that helped. No condensation here. Got one wood stove, that's it.. There is some draft, which i likeold barn redone, but nothing exaggerated.
But i can see you can't do these things short term. Maybe you could get everybody to come to one floor or two floors? Make it more compact for this winter. And then the heat bill won't be so high.
Next summer might be another scorcher, open windows all the time and vent,vent,vent.
Do you live on a hill? Could be that you could divert the flow of water with drainage pipes and store it in a pond or something away from the house.
People throw out crazy good windows and windowsills, double glazing even, check your local window builder/ installer. He/she will know, if you come with maximum measurements ( can always fill a bit up) he/she might have them soon. Here they're happy if you pick them up for a bottle of something. Drill a few holes put in plugs et voila.People make their own improvised greenhouses with them.