Morning all. I moved into a flat in December and was informed that it'd recently had cavity wall insulation put in (maybe a fortnight before I moved in). Most of the windows are single glazed, so at the minute I'm having to wipe/dry them every day, as well as soak up the water that's sat on the frames. I noticed a couple of weeks ago that there were darker patches on the wall at the bottom of each side of the (single-glazed) bedroom window. I didn't think much of it, except the patches are now a couple of inches 'higher' than they used to be, and mould is starting to grow on them. There's a radiator beneath the window - along with foil-covered cardboard stuck to the wall to reflect the heat. Around this the paint is also dark, so presumably there's damp in there as well. There's also mould starting to grow just under the window sill. Presumably the previous tenants didn't have a problem with damp/mould as the walls were a uniform colour when we moved in. I'm wiping and drying the windows nearly every day, opening the windows to get some circulation in and also pointing a fan at them to force circulation. So my question is, can cavity wall insulation cause damp problems with single-glazed windows? If so, what can be done, and if not - what can I do anyway, to stop this? Thanks.