Interesting problem!!!


  #1  
Old 01-03-01, 05:11 PM
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I have a ranch house that is 35 years old. I just had a new roof put on it in May 2000. I live in New England where it snows a lot in the winter, and we just had a big snowstorm. During the storm I went into my attic to put some stuff away and notice something very odd. All the nails on one side of the house that come through the plywood that hold the shingles on had snow or slush built up on them, BUT only on one side of the house. I called my roofer who has been in the biz for 17 years and he told me he never saw anything like this before. After the storm he came back with a small crew and shoveled off the roof to take a look, but everything looked perfect. His only thought was that maybe it was some kind of ventilation problem. My old roof never had a rig vent before and my new one does. Now I have the rig vent across the length of the roof plus three other vents that where there from the old roof, one spinning kind and two screened in pipe kind. The old shingles where removed before the new ones went on so there is only one layer. Does anyone have any kind of idea what could be causing this problem?
Thanks.
 
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Old 01-09-01, 08:33 AM
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This is very common. The snow or slush is actually frost which is simply a form of condensation from moisture in the air of your attic (water vapor). Once it reaches a surface which is cooler than the dew point temperature, the water vapor changes to a liquid form (water)or ice (frost). The reason the frost only appears on one side is because this side of your roof is colder than the other side. This temperature difference is most commonly caused by the roof's orientation to the sun. Email back after checking if the area NOT exhibiting frost is a sourthern, or near southern exposure.

The amount of moist air in you attic can be limited by: 1. effective attic ventilation, 2. preventing passage/leakage of warm, moist air from the home's interior into the attic with the use of a sealed vapor retarder, 3. effective air exchange and/or conditioning within the home to limit high humidity levels.
 
 

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