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New Roof = Heat Loss


jurched's Avatar
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01-19-09, 05:44 AM   #1  
New Roof = Heat Loss

Well, I got the new roof on this summer and installed a whole lot of foam insulation and sheetrock so it would breathe properly and still retain heat in the walk-up attic.

Every time it snows, however, there are noticeable melt patches. This suggests spots of heat loss. But why? Two small spots appear on either end, close to the peak. But the main spot is a two yard wide streak that starts from the soil stack and runs right up to the peak.

Am I right in assuming this is an insulation weak point where the wall meets the roof, and the heat simply rises through the air space between the joists, melting snow as it goes? Should insulating that small spot at the soil stack remediate this heat loss? (I have no idea what to do about those small patches.)

J

 
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01-19-09, 07:55 AM   #2  
Insulation should have vapor retarder beneath. If batt insulation was used, the facing faces downward toward the heated area below. All gaps around perimeter, pipes, vents, chimneys, etc. should be sealed. Spray foam insulation can be used for large gaps and caulk for smaller.
Sealing the gaps will minimize the amount of warm, humid air that escapes into attic area. If you have a pull down stair or attic door, weatherstrip and insulate. A box can be built and insulated and slid off and on the pull down stair area as needed. Dryer vent, kitchen and bath vents need to be vented to outdoors and not into attic area.

Attic needs adequate insulation for your area. If you have soffit vents, make sure insulation does not cover them. It also needs adequate ventilation so warm, humid air can escape. Melting snow can cause ice dams and damage to home.

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jurched's Avatar
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01-19-09, 11:20 AM   #3  
Affirmative to all that. An ice dam has already built up below the soil stack, and icicles are hanging over the gutter because the melting snow refreezes and fills up the gutter.

As for soffit vents, those were installed after the new roof so as to allow cold outside air to flow up along the underside of the roof. That's probably where the issue lies: The insulation affixed to the underside of the roof meets the attic floor but there must be a gap of several inches where there is no insulation before the ceiling meets the wall. That must be a "heat leak" that's allowing warm air to rise up the length of the underside, thus melting the snow. Or, heat rises along the soil stack and then disperses uder the roof. How does one stop this?

J

 
Craig 845's Avatar
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01-20-09, 02:28 PM   #4  
If your attic is unheated, why did you insulate it? The only heat that would get up there is waste heat that is getting by your ceiling insulation which you don't want anyway. I keep reading in these forums about DIY'ers who want to insulate unheated spaces. Insulation only works where you have a heat or cooling source to protect. I feel that when you do things like this it's only going to cause problems down the road related to condensation setting up, etc. Insulation is meant to work across a temperature gradient.

 
jurched's Avatar
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01-21-09, 01:37 PM   #5  
I am in the process of finishing off the attic, so naturally there must be insulation surrounding future living space.

Besides, I would be experiencing a severe heat loss with the new roof owing to the open soffits and ridge vent. Before the new roof was the original roof of 1930, cedar shakes with three layers of asphalt, which provided a good insulating factor on its own.


Anyway, what's wrong with retaining excess heat in the winter? If I have proper ventilation around the roof decking, then insulation in my unheated space should slow the heat loss of the rest of the house without affecting the roof integrity, should it not?

J

 
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