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Converting vented roof to non-vented Post New Topic | Post Reply
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Raymond Brooks
Posted: Jun 28, 2007 12:35 PM
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Converting vented roof to non-vented
I have a customer with traditional vented roof and an attic w/AC unit and duct work in it. We are going to spray the cap and gable ends, and introduce an AC feed and return to condition the attic. The question is there is about 15' of north side roofline from soffit vent to the access in the attic that will still have fiberglass filter in it. Is a problem being created by closing off the top of the rafter vent system? If so, does it make sense to foam the soffits to prevent convective looping? I understand just enough of this stuff to confuse myself. Your input is greatly appreciated.
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mason
Posted: Jun 28, 2007 01:07 PM
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The fiberglass insulation requires venting to prevent condensation. Either spray the foam completely and seal off the soffits or isolate that area and vent it. Also, when you condition the attic, be sure to put a thermal barrier (not an ignition barrier) over the foam. |
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Scott Snyder
Posted: Jun 30, 2007 02:44 PM
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Ref. the thermal barrier in the conditioned attic space - if only the air handler and ductwork are installed in the attic, must there still be a thermal barrier installed? If attic space is vented with foam between ceiling joists and air handler in attic, must a thermal barrier be installed on top of ceiling joists? |
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mason
Posted: Jul 02, 2007 02:00 PM
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As I read the initial question, they were going to to condition the attic space with air from the inhabited areas of the building, In that case the codes require it to have the same thermal barrier as the inhabited areas. If they don't pipe the air in from below, an ignition barrier could be used. |
