Join the MRA | Member Login
Find a Professional
  • Why Metal Roofing?
    • About MRA
    • Benefits of Metal Roofing
    • Compare Roofing Materials
    • Homeowner Testimonials
    • Inspiring Metal Roofing Projects
  • Homeowner Resources
    • Metal Roofing Buyers Guide
    • Resilient Housing Guide
    • Metal Roof Sustainability Guide
    • Above All Else You Need a New Roof eBook
    • MRA News
    • Member Provided Resources
    • 3rd Party Articles
    • Frequently Asked Questions
    • Preparing for Hurricane Season
  • Gallery
  • Visualizer
  • Ask The Experts
    • Energy Efficiency
    • Existing Metal Roof Questions
    • Installation
    • Is A Metal Roof Right For My House
    • Metal Roofing Benefits
    • Product Selection
    • Other
    • Archive
  • Find a Professional
Join the MRA Member Login
Sign Up Log In Add New Topic

TOPIC: Ventilation

Low sloped roof ventilation

Return to Ventilation

Return to Archive

Return to Forum

This topic has been closed by the administrator. Comments are no longer accepted.
Hi, redoing roof on a low sloped simple gable roof(3/12)with on-the-ridge chimney. Considering using metal roof with insulation on the outside directly over tongue and groove deck. My dilema is the type on venting I require. I want to vent the air space between the rigid board insulation and the metal which will be spaced by strapping. The roof on one side of the house has open rafters/tongue and groove catheral ceiling. The other half has an attic space.(not vented - this is how it was built 35 yrs ago.) Since it snows alot in this area and the snow accumilation on the roof is at times 2-3 feet high, I suppose a ridge type vent like Cor-A-Vent, for example, would not work under these conditions? What would you recommend?
pat man

2/5/2007
Share
Or copy this URL: https://www.metalroofing.com/spirit/comment/9203/find/
The building code calls for venting both vaulted ceilings and attics. Vaulted ceilings require a minimum of 1" vented air space between the roof covering and insulation. I would install an air barrier over the existing deck, then ridgid insulation (butted ticht and taped, then an underlayment, then strap the roof vertically over the rafters and then horizontally to accept the new metal roof. For the attic side it requires 1 sf of free air for every 150sf of ceiling space with 50% provided at the ridge. A vented ridge detail will provide venting for both the vaulted and attic bu you will need to cut the ridge open on the attic side and provide eave or soffit intake air. Ask the manufacturer to recommend ridge venting accessories. Hope this helps.
Allan Reid
Dura-Loc Roofing Systems, Inc.

2/6/2007
Share
Or copy this URL: https://www.metalroofing.com/spirit/comment/9204/find/
You mentionned that I should install an air barrier first over the existing roof. Question: should I be using a vapour barrier instead?Like a plastic sheet since it ends up on the warm side? But rigid insulation is already considered as a vapour barrier.(unless I use Cladmate which is not a vapour barrier created for cold climates. The underlayment , should I use roofing paper OR sheathing paper since sheathing paper has a better permeability rate than roofing paper. Its all too confusing, the details , at least...thxPat
pat man

3/3/2007
Share
Or copy this URL: https://www.metalroofing.com/spirit/comment/9205/find/
Just wanted to add one idea as a cost saving measure. Since one half of roof has an attic space and already has insulation, would it be feasible to add rigid insulation to the other side of the roof only ?( the cathedral part of the roof) Then strap the whole roof to receive the metal. What do you think? thx Pat
pat man

3/4/2007
Share
Or copy this URL: https://www.metalroofing.com/spirit/comment/9206/find/
  • About the MRA
    • Member Companies
    • Leadership
    • MRA News
  • For Professionals
    • Join the MRA
    • Industry Resources
    • Upcoming Events
  • Contact
  • Subscribe
©2018 Metal Roofing Alliance. All Rights Reserved. Privacy Policy Terms and Conditions