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I am having a metal (galvalume) roof installed over our existing layer of shingles. The house has a steep pitch creating a high sloped ceiling in our attic. We use our attic as another room and as an office, so it is heated. We live in the Upper Peninsula of Michigan only a couple miles from Lake Superior. We decided to go with metal to prevent ice dams (our gutters are all nearly ripped off from ice) and slough off snow. My concern is how hot it might get in the attic. I'm not sure about the existing venting - I believe there is a soffit vent. The previous owner had tried to finish the ceiling and put up a lot of insulation and covered it with wall-board. Our valleys are leaking, prompting us to choose a metal roof. Will we be stifling hot in the summer? What can we do to keep the temperature down? Thanks for your informative Web site.
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Proper ventilation requires intake and exhaust. Often, soffit vents are the intake, with air then circulating beneath the roof decking and exhausting through ridge vent.
Oftentimes, when finishing an attic, homeowners will pack in solid insulation, eliminating the possibility of ventilation.
The big problem with this is not so much heat (though that can be an issue too) but moisture control. We generate moisture inside our homes in various ways -- cooking, bathing, houseplants, etc. That moisture, if not allowed to escape in some fashion, can end up condensing when it hits the cool skin of the home and then that condensation can result in wood rot, mold, etc.
Sometimes this situation first shows itself after we do other things to update or weatherize our homes such as add siding, tight windows, etc. Once these things are added, the home no longer breathes through the walls and that moisture cannot escape so it migrates to the attic where, if not vented out, it will condense and cause problems.
This is not a metal roof issue -- this situation can occur regardless of the roof covering.
I am concerned that your home could be "set up" for this type of problem to occur down the road.
It may be wise to now, when you're re-roofing, address some ways to add the airspace and ventilation if it does not exist already. You may need to get a structural engineer involved to help analyze how this can safely be done.
As for heat -- yes, heat can be trapped by lack of ventilation as well. However, metal roofing is not "hot" roofing. In fact, generally, it has attributes which keep it pretty cool. By going to a light color or a product which utilizes new heat reflective pigments in the paint coating, you can also enhance the "coolness" of your metal roof.
If you like, call me sometime. 1-800-543-8938 ext 201 Todd Miller
11/16/2004
11/16/2004