mobile home ceiling vapor barriers

[wjt]

My MH is about 23years old.It's roof construction consists of: curved metal roof with 1/8"plywood under, then poly vapour barrier then 6" fiberglass then another vapor barrier. Trusses are open web. We have recently had leaks and after opening up the ceiling we found wet insulation which we removed. We noted water globules on underside of upper vapour barrier but no evidence of wood rot except at the point of water leak into the room. WE have had the roof seams permanently waterproofed and wonder if: 1. the upper vapor barrier is causing problems of condensation; 2. should we install a grill in the ceiling to promote air circulation (We have a roof vent installed) .Any other advice bearing in mind we are pensioners and can not afford costly renovations. Thank you.

[trmimo]

If you have had a roof vent installed that is probably your culprit. This house ws designed with a sealed roof cavity. The idea was that if no fresh air at all gets in to the attic you won't have condensation. Once you introduce some fresh air into this type of attic you have to introduce enough and exhaust enough to let the moisture out. You do not want a vent between the attic and the living space. This will make the problem much worse. If you are in a cold climate, winter air is cold and dry and the air in the house is warm and damp. It is when the 2 come together that you get condensation because the warm air cools and the moisture drops out. You need more vents to the outside to let air in and then back out again. Air flow is a problem with this type of roof, so you might want to consider a couple whirlybirds (wind turbine vents) or a power vent in order to force air flow.