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I work with a non-profit organization and we're trying to replace the roofs on our three buildings.
Two of them have large attics, but the third has a vaulted ceiling with exposed trusses. To preserve the interior space, we were hoping to put a second (metal) roof on top of the current asphalt shingled roof, and to create ventilation and insulation in between.
Our slope is approximately 5 over 12.
I have several questions about the best way to do this.
My general plan had been to use rigid insulation with a reflective side facing an some form of airspace creating with 1x4s or 2x4s, and installing a ridge vent at the top.
Are there any advantages to keeping the old shingles under our insulation, or should we just remove them?
Would it be possible/cost effective to use fiberglass insulation instead?
How large a gap should I leave? If the goal is simply air flow and it does not affect R-value, is a 1 inch ventilated space as effective as 2 or 3 inches?
Do I need to close off the bottom and install sofit vents, or can I just overhang the second roof past the existing roof and leave the ends open?
Thanks so much!
Or copy this URL:
https://www.metalroofing.com/spirit/comment/8932/find/
1" vented space is regarded as minimal and usually adequate. I would box in the soffits and vent them for air intake to avoid getting insects, etc. in under the panels.
I would use a rigid insulation.
There should not be a problem with leaving the old shingles in place.
Roof!
11/21/2006
Or copy this URL: https://www.metalroofing.com/spirit/comment/8932/find/Isaiah Industries, Inc.
11/23/2006
Or copy this URL: https://www.metalroofing.com/spirit/comment/8933/find/Isaiah Industries, Inc.
11/23/2006
Or copy this URL: https://www.metalroofing.com/spirit/comment/8934/find/