Roofing/Ice dam problem

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Question
Hello: I live in a region with -30C winter weather,and a good deal of snow.My home is a story and a half,built in the early 50s.I had a new roof put on about 7 years ago,and it incorporates an anti-ice dam membrane covering the complete roof surface.
Due to the ice dams,I have resorted to using a roof rake over the last few winters to remove snow from areas that are leaking heat.Insulation upgrades are not possible in my situation,as there are sealed roof areas,especially in the steeply sloping front of the house,which would be very expensive to open and re-insulate.The back of the house has a shallow sloping roof,and the main attic cavity ends about 6' before reaching the outside wall-I did have this strip of roof opened and filled with foam,but heat still escapes through this area,resulting in large ice dams at the roof edge.One spring the ice was so thick it pulled the gutter off the back of the house!
My reason for writing is to ask if it would be feasible to place a false roof about 6" above the entire original roof.My reasoning is that escaping heat from the old roof would guarantee adequate air flow,and keep ice dams from forming.Has this been done before to your knowledge?
Thanks!

Answer
Michael,

The structure appears to have been design as what is typical, the eave locations being a cold roof design (no insulated and eave venting to the outside environment. The heat loss would typically be the culprit that is forming the icing issue as it facilitates melting of snow and when water freezes it forms ice. It would makes the most sense your icing issue is a function of heat loss into these regions of the roof. Solutions to the icing issue, in my opinion, is a function of remediation of the heat loss or consider heat tape in the icing areas to implement constant "melting" of the ice/snow.

If I am understanding what you are proposing, erect an elevated roof that would still have heat loss flowing between the two, this is unlikely to aid in the icing issues as the roof is still a warm roof area, which promoting melting of snow and build-up of ice as it refreezes.

Your challenge is remediating heat loss is areas likely designed as cold roof areas. The other potential option is to have the whole roof as a warm roof, this will not prevent icing but have a more uniform condition that may allow more even melting and limit ice build-up. The better or easier option you may consider first is to utilizing heat tape in the trouble areas to create melting of ice build-up, especially in the gutter regions.

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Steven C. Wadding RRC,RRO,CDT

Expertise

General questions in regards to most roof types and situations. As the Technical Services Manager for Polyglass USA, Inc. this would not be a forum to address any issues directly related to a product my employer manufacturers.

Experience

I have been active in the roofing and waterproofing industries for more than 30 years with extensive experience from product installation, product development and consulting. I have been active in the Construction Specifications Institute and Roof Consultants Institute for approximately 20 years. I am a member of ASTM and am a voting member of various subcommittees. I have many years of consulting experience in the fields of Roofing, Waterproofing and Exterior Building Envelope disciplines.

Organizations
Roof Consultants Institute Construction Specifications Institute ASTM

Publications
Division 7 Technical Binders for Malarkey Roofing Products and Polyglass USA, Inc. CSI Phoenix Chapter Cactus Comments

Education/Credentials
Registered Roof Consultant - Roof Consultants Institute Registered Roof Observer - Roof Consultants Institute Certifified Document Technologist - Construction Specifications Institute Spray Fireproofing Special Inspector - International Code Council

Awards and Honors
Registered Roof Consultant - Roof Consultants Institute Registered Roof Observer - Roof Consultants Institute Certifified Document Technologist - Construction Specifications Institute Spray Fireproofing Special Inspector - International Code Council

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