Insulation over asphalt shingles under metal roof

Guest User
10/30/2004
On a low-pitch home which has an existing asphalt shingle roof and is to be replaced by a new metal roof what is the best method to insure the roof is properly insulated? The home is only 5 years old but is hot in summer and cold in winter.
Allan Reid
Dura-Loc Roofing Systems, Inc.
3/28/2005
One needs to determine if it is an attic or vauted ceiling structure. If it is an attic, then adding insulation under the roof covering does little good. If it is vaulted, then it ius an ideal time to upgrade the insulation. You need to determine the compsition of your roof assembly. The code calls for an R40 insulation plus ventilation over it. In a vaulted ceiling case, this should be a minimum on 1" in the US and 1.5" in Canada. The most practical way is to add ridgid insulation either in sheets or foamed in place which is the best. Choose a product that mounts on strapping and can provide the vertical air flow and don't forget to put down a quality underlayment.
Guest User
4/22/2005
Hi, Allan. Your answer seems to be addressing exactly my problem. We have a low sloping roof (about 3:12) with 10 year old asphalt shingles (only one layer). Exposed ceiling and beam cathedral ceilings underneath with very little insulation. To add to the problem of ice daming, we have 3 foot eaves! I was thinking that I needed to increase the pitch when I put on a new metal roof, but maybe all I have to do is add rigid insulation between the shingles and the new roof. How do I make sure that there is adequate ventilation on top of the insulation? Also, how does the gable end of the house get finished off? Thanks for your help!
Allan Reid
Dura-Loc Roofing Systems, Inc.
4/25/2005
Choose a product and contact the manufacturer aqnd get their advice on how to comply with the building code. Our main systems as example install on 2x2 strapping, so we recommend that the roof be strapped vertically over the existing rafters and fastened to them. In the case of adding insulation, the ridgid (high density)insulation can be installed first and then the vertical strapping. We recommend that deck screws be used for fastening and don't forget the underlay.
Guest User
6/25/2005
The owners of our cabin had the same issue. When buying the cabin (with vaulted ceiling over 2/3), the bank insisted they put on a new roof. They had someone install a metal roof (not standing seam) on top of one layer of asphalt shingles. THIS DID NOT WORK OUT. We bought the cabin 2 years later and are now trying to get the sellers to pay for a new roof. Had three contractors look at it and was advised that the metal roof type used was never intended for use over residential structures; has problems with flashing and should not be used when slopes are minimal. We have had water instrusion frm the stove pipe exit through roof (no flashing), around the skylights (inadequate flashing), and where the main roof joins the less-sloping roof that proceeds over the porch. Leaks and lack of venitlation, ice jamming and melting, and regular old rain water have been problems. We have mold and mildew inside and a useless roof and associated anxiety over what to do. I'm not a roofer - but CAVEAT EMPTOR - let the buyers beware!!
Todd Miller
Classic Products, Inc.
6/25/2005
I will be responding to you via direct email
Guest User
9/16/2010
I am building a timber roof to put on asphalt shingles on top of it and want to expose the rafter inside the building is there a way i can use an insulation on top of the timber then put on the asphalt shingles and if there is what kind of insulation can i use thanks
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9/17/2010
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