I live in a very well insulated house and have never suffered with condensation so badly. You could swim on my window sills of a morning. I used this spray in all Windows as the vile black spongy mould was rampant and making my breathing funny. Sprayed and left for 40 mins, a little longer than suggested and rinsed off with soapy water. The mould rolled off the Windows and has not returned in the three weeks since applied. Usually in seven days with bleach the mould is back. So far so good. The smell wasn't that bad and just needs airing sufficiently. WARNING: when spraying the frames of the Windows don't be a pillock like me and spray it when there is a light wind outside. You get huge blowback from the outside draft. It honestly felt like someone had set fire to my eyes for about five seconds. After the three pints of tears flowed from my sore eyes they felt fine. Oh yes, I also managed to bleach a section of my left eyebrow white, which is noticeable but I now have very clean Windows and sills!