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

Metal Roof Ventilation

Return to Ventilation

Return to Archive

Return to Forum

This topic has been closed by the administrator. Comments are no longer accepted.
We are trying to decide on the correct approach for our new cathedral roof that we are designing. We want very high R-values in this home, and thus don't want to be limited by the standard approach: leave a 1" gap in the joist cavity and ventilate it. Instead, we had planned to fill the cavity, and even add a layer of rigid on top of the sheathing - as highly advised by many places I've read on the web. Problem is, no one explains how to ventilate with this situation. The sheathing is generally what you want to ventilate, if I understand correctly - but now it is sandwiched. Seems silly to vent between the insulation as it just negates the top layer. If Do we ventilate above the rigid, using strapping like I've read about here? Does this do much good? I thought the goal was to dry out the sheathing that is likely to get wet from vapor condensation. Hmmm... Any advice or alternate approaches would be very much appreciated.
Guest User

7/31/2009
Share
Or copy this URL: https://www.metalroofing.com/spirit/comment/13655/find/
I would suggest a vapor barrier behind your ceilings to prevent moisture migration into the roof assembly. Still, I would say that building codes call for a minimum 1/2" vented airspace in your roof assembly and I would encourage you to do so. You could vent on top of the sheathing with a cross grid of vertical and horizontal battens followed by roofing. Todd Miller
Todd Miller
Isaiah Industries, Inc.

8/1/2009
Share
Or copy this URL: https://www.metalroofing.com/spirit/comment/13656/find/
Thanks Todd, We will certainly put a vapor barrier behind the ceiling. Do you mean to vent with battens: - on top of the sheathing, and under the rigid insulation (does this negate the insulative effect?) - on top of the rigid insulation (& water barrier), and under metal roof
Guest User

8/3/2009
Share
Or copy this URL: https://www.metalroofing.com/spirit/comment/13657/find/
I would do this venting on top of the insulation. Todd Miller
Todd Miller
Isaiah Industries, Inc.

8/7/2009
Share
Or copy this URL: https://www.metalroofing.com/spirit/comment/13658/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