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1) I plan to install a metal roof (3/4" high major rib, 9" o.c., 36" coverage panel), over existing comp shingle roof. Is it beneficial to laydown 30# felt and a reflective insulation (double bubble, foil/poly)?
2) Do you recommend any paticular reflective insulation to lay between existing comp roof, 30# felt and the new metal roof? There seems to be several available ie bubble, solarguard, foil paper.
3) Would it benefit to laydown 1x4 wood or steel hat channel on top of all this, then apply the metal panels?
4) How far apart should each screw line be?
Thanks.
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1) You definitely want an underlayment over the existing shingles and perhaps a slip sheet. Your roofing manufacturer should specify this.
2) No particular recommendation. A radiant barrier in the attic may be more effective though.
3) If you did this, you must be installing a metal panel that is approved for installation over battens. Not all are.
4) This will vary from panel to panel -- check mfr specs.
1/23/2008
Isaiah Industries, Inc.
2/6/2008