I have a 7 year old house in Ottawa (ON). While removing an upstairs ceiling light fixture, I noticed that the electrical box was rusty to the point that I had difficulty getting the bolts that attached the fixture out. I checked fixtures in two other rooms and the same thing has happened. There is no visible water damage around the box on the drywall and no visible water damage anywhere on the ceiling. Any ideas what could be causing this? The light fixtures have a pad of fibreglass insulation to insulate the opening.
Answer:
This appears to be the result of condensation having taken place in that area. I'd want to know more about how well the rest of the attic is insulated and vapour barriered because this can be an electrcal (fire) hazard.
