TOPIC: Energy Efficiency
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I have a storage attic, some 25 * 48 feet, currently roofed in tile and unvented. It gets insanely hot, probably in part because there are no vents.
Is metal a good choice for a re-roof?
What is the best way to moderate the attic temperature?
Foam between the rafters, foam above the deck? Fiberglass below?
Spacers below the metal -- and if so how are sparks kept out?
What design keeps weight down, yet also temperature down?
Is there a good published guide to this topic?
In this case:
2 story stucco home, climate Zone 3C marine, San Francisco Area, Fire Zone, Class A roof required California WUI code , solar to be added. The long side of the roof faces south. 2 dimensional x 5.5 inch rafters with minimal structural purlins and some rafter sag. High hazard earthquake zone.
www.airvent.com is a good source of information on attic ventilation. What is on the floor of the attic? Insulation? Vapor barrier? Can you add ventilation to the attic including intake and exhaust vents? Another thought would be a radiant barrier attached to the bottom side of the rafters, and perhaps ventilation on top of that?
Does a radiant barrier help under a metal roof? I thought a metal roof was a radiant barrier?
Attic floor has nothing but lathe and plaster.
350 nfa of venting could be added a ridge, with 400 nfa of dormer vents in the field of the metal panels down low.
Attic venting seems controversial: https://www.greenbuildingadvisor.com/article/all-about-attic-venting
Many metal roofs have reflective pigment in their coatings, or shiny back sides, to help act as a radiant barrier. In some cases though an additional radiant barrier inside the attic, especially with ventilation between that and the roof deck can be a good idea. Yes, there are other options as well including closed cell foam and creating a conditioned space. It is all a matter of talking through what offers the benefits you want at the price you desire. Give me a call at 1-800-543-8938 ext 201 if you'd like to discuss your exact needs further.
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