Question:

Hi, I live here in PEI and am looking for some guidance in insulating and roofing my home. My rancher made in 1966 has a 12:2 low slope pitch with asphalt shingles and inside it has a cathederal ceiling. This cathederal ceiling has the roof rafters exposed (inside) and in between these rafters (24 inch centres) there is r12 fiberglass and then drywall overtop. (you can see the lower 8 inches of the rafter when you look at the ceiling) My problems are: here is no vapour barrier, minimal insulation (r12) and also no ventilation air gap between the insulation and roof. Therefore my roof shingles are curling and on hot summer days I sometimes get condensation inside the house on the high pt of the rafters. Ice dams are an issue in the winter. I recognize that minimal insulation and no roof ventilation are my 2 problems here. This summer I plan to install a low-slope friendly steel roof. Under this roof, I plan to create a 3/4-1" air gap with the appropriate soffits|ridge vents to promote ventilation under the steel roof. Secondly, I would like to add extra white foam insulation (breathable kind)right on top of my old roof. (Between the old roof and the new air gap and steel roof) I do not plan on removing the 1 layer of old shingles. Basically I will nail the insulation to the old roof then 1x4s vertically then 1x4s horizontally then attach the steel roof. My questions are: 1. Will adding 1-2" of white foam insulation make a difference? 2. Is this a good solution to my insulation and ventilation issues? I would like to keep the the existing look of the cathederal ceiling intact. Any suggests would be appreciated. Sorry for the long-winded reply. Thank You! Aivars Berzins Thanks for your help

Answer:

Hello, 1) I do not recommend a metal roof on a low slope <4/12 2) White bead board "insulation" has no R value 3) The old roof must be removed as it will continue to deteriorate and rot the substrate. In the Ottawa area there are many folks with the same problem you have. What we have done in the past is, remove the existing layer of shingles and underlay, remove the wood decking and save for reinstallation, remove the batt insulation and discard. Now cut phenolic rigid foam insulation to fit snuggly between the rafters (2 layers of 2" - approximately R 30 - 40), add a 2"x 2" to the top of each rafter and reinstall the sheathing. This will give you good insulation value and some ventilation space. Now you must install the roof in low slope fasion (ie: ice and water shield on the complete roof, shingles and ridge vent from gable end to gable end. This will solve everything but the vapour barrier, this must always be installed on the warm side of the insulation (ie: remove the drywall???) Sorry for all of the bad news!! Keep me posted! Matt Churchill CP Roofing & Sheet Metal of Ottawa Ltd. 613-821-4455

Answered By: Ormand & Matt Churchill

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