I have been in my new house for about ten months and just the other day noticed a water mark on the upstairs ceiling right beside an infra red detector I had installed as part of an intruder alarm two months ago. This involved drilling a small hole through the ceiling into the attic to conect it. It is also right above the door to where the water boiler tank is housed. I got into the attic to see if there was an obvious leak but could find nothing. However, when I pulled up the fibre glass insulation over the position of the water mark there were several small dime sized pools of water present. Is this condensation??? The attic side of the ceiling is covered in a stuck-on silvery piece of film. Is this the mythical vapor barrier? I don't know what to do!! Any help would be appreciated

 

Condensation in most cases is due to air transported moisture than heat transported moisture. In other words all you have to do is seal the hole where you penetrated the ceiling. Caulking, spray foam or even tape would stop the condensation. If you want more information on this subject search the web for "air sealing" or "blower door".

 

That seems to be an awful lot of water to be present in the attic. I would keep an eye on the area to be sure that there is not a small leak in the roof that allows the water through. Tracking down the source of the water can be important. Was the insulation damp where you found the water? Is the ventilation system for the attic working properly?