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.

No. The only thing it can do, by making the internal surfaces of the walls warmer, is to reduce condensation on those walls. As the amount of moisture in the air remains the same, it will find another cold surface to condense on, for example windows.

You suggest that the dampness has been increasing since you moved in, and the previous occupiers did not seem to suffer from it.

The usual cause of humidity, condensation and damp in UK homes, is the activities of occupiers adding moisture, and insufficient ventilation to remove it.

For example, it might be that someone is in the habit of draping wet washing around the home or over radiators, having baths and showers without using an extractor fan, or keeping the windows closed all day. Are any of these familiar to you?

Circulating air around your home will not remove humidity, you have to put the damp air outside.

see also
http://www.diynot.com/wiki/building:condensation_in_houses

So it would make sense that the moisture is condensing right next to the - cold - windows?

We do hang wet washing around - mainly on a clothes horse - as it wouldn't get dry outside at this time of year. However I make sure to open windows so the humidity can escape, hence using a fan to force it to circulate quicker & better. We don't have an extractor fan in the bathroom, however again the bathroom window is often open.

I suppose I'll just have to do my best and wait for summer. However I'd contemplated using packets of silica gel near the problem areas. Would this help at all?

Thanks.

no.

far too small.

the window reveals, and the internal wall adjacent to them, do not have the advantage of insulation between them and the outside surface of the wall, so will be relatively cold.

Modern houses are built with insulated cavity closers to reduce that problem.

Are you a tenant? if so speak to l'lord with regard to condensation problems you have, you need mechanical ventilation to both kitchen and bathroom, opening a window will not compensate for drying washing using the bathroom.
You should have permanent vents to both kitchen and bathroom and ideally all occupied rooms.
Ventilation is required 24/7 unless you plan on giving up breathing.

Just an update to this for anyone that comes across similar in the future; we managed to solve the problem....by sleeping in the second bedroom - which is double-glazed.

Not had to wipe the window at all since we've been in there. It's not an ideal solution, but it works.

Thanks again for the advice.