I had double glazed windows installed last summer and have been having excessive condensation in my 5 x 2.5ft cloakroom this winter. Even the lampshade has been soaking it up! The cistern and cold water tap are fed off the rising main, the cloakroom is on the corner of the house under a flat roof, with two walls cavity-filled; the third wall abuts on to the porch and doesn't have a cavity. There's a small radiator.
I've checked various sites and have noted several ideas for reducing condensation on the cistern, though none seem that effective. Would some sort of air brick or ventilation grill put in the porch wall (for ease of fitting) help?
I retained the old wooden front door and original single-glazed porch window (6 x 2.5ft). The latter is next to the cloakroom and also gets soaked with condensation. I'm going to have the door and window replaced with PVCu items this year. I wonder whether to wait to see if this will reduce the problem in the cloakroom.