You have already been given quite a long list of things to do and check but as a window/fascia fitter I just wanted to add a couple of points.
While someones up on a ladder checking your guttering get them to push a few tiles up and check the felt. Old felt tends to shrink at the edge and can let water into the cavity's from above. Fitting some felt support tray should be fairly cheap and easy if this is the case.
While you are doing some plastering around the window try to get some expanding foam around the frame. Cold air from the cavity could be making the edges of the window and plaster cold attracting condensation and mold.
For the misted up units with lead design it would be most economical to have them repaired. Don't fall for the company's that come to your house drill a hole in them and clean them as this wont last long. They need to go to a factory and be stripped down, Cleaned and remade with new spacer bars and sealant. For any non leaded units its best to have new ones made.
Do you have wall cavity insulation and is your loft insulation upto modern specs ie 300mm deep? This would help to reduce cold ceilings and walls.
While someones up on a ladder checking your guttering get them to push a few tiles up and check the felt. Old felt tends to shrink at the edge and can let water into the cavity's from above. Fitting some felt support tray should be fairly cheap and easy if this is the case.
While you are doing some plastering around the window try to get some expanding foam around the frame. Cold air from the cavity could be making the edges of the window and plaster cold attracting condensation and mold.
For the misted up units with lead design it would be most economical to have them repaired. Don't fall for the company's that come to your house drill a hole in them and clean them as this wont last long. They need to go to a factory and be stripped down, Cleaned and remade with new spacer bars and sealant. For any non leaded units its best to have new ones made.
Do you have wall cavity insulation and is your loft insulation upto modern specs ie 300mm deep? This would help to reduce cold ceilings and walls.
