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condensation

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Guest User
1/3/2005
Our ribbed metal roof is only a little over a year old. It was new construction. We have overhang vents as required, ridge vent (although it appears to be pulled down to tight) and all the roof is over the same floor space. There is no underlayment under the metal roof. Metal roof is directly laying on the rafters. The puzzling part is we have no condensation problems over one side of the attic and a lot of condensation on the other half. It looks like there is an invisible barrier between the two descending sides of the roof when you go in the attic with one side wet and one side dry. Same insulation, same vapor barrier over all of roof. Any ideas? Two differents contractors have no idea why the difference. Only difference I see is the dry side faces the sunny side and the wet side gets no sun during the day but both are cold at night when the condensation occurs. Help!!
Allan Reid
Dura-Loc Roofing Systems, Inc.
1/4/2005
There could be a number of factors. Condensation happens when the inside air temperature drops across the current dew point. There could be enough residual heat in the metal roof that the temperature on the inside surface does not drop below the dew point. Also it could be on the side of the house that has the kitcen, bath, laundry etc that creates more moisture and heat which combined could be leaking into the attic on one side. Most probably you have reasonable ventilation that given a certian wind direction is moving the air up under the roof metal on one side taking the condensation out with it. Also need to look at the condition of the intake air. One side is shaded and cooler and the other would have warm siding to pull intake air from. The problem you have is that you did not provide a moisture barrier under the roof covering to isolate the attic air, which in itself limits the amount of condensation and then trap any condensation that does form and provide it with an exit at the eaves. I would suggest that you get this issue addressed, Contact the roofing manufacturer and get their recomendation.
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