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: General Discussion

Insulation, Ventilation and Purlins

Return to General Discussion

Return to Archive

Return to Forum

This topic has been closed by the administrator. Comments are no longer accepted.
I am looking to build a gambrel roof barn with living quarters. I have several questions about the assembly. What is the best method for constructing the building. My biggest concern is the moisture from the metal, do you apply spray foam directly to the underside of the metal, or do I need a separation between the metal and insulation? Do I need to vent the area below the insulation. Is it better to use 2x4 purlins, osb or plywood?
Guest User

9/21/2009
Share
Or copy this URL: https://www.metalroofing.com/spirit/comment/13922/find/
Applying closed cell spray foam insulation directly to the underside of the metal will eliminate consensation from forming because you are eliminating the thermal differential between the cold roof panels in the a.m. and colder months. This being said, you should fill the rafter cavities completely to the level of the ceiling in order to insulate the living space. How this is done is dependent on the construction details of the roofing/ceiling/attic, etc. Cost can be reduced by applying closed cell to the deck, which would create an air barrier, and filling the remainder of the cavity with open cell. If you're going to have attic space, then the insulation should be applied to the celings. Anymore questions? Ask away.
Aaron Scurlock
The Best in Polymer Roofing Soutions

9/24/2009
Share
Or copy this URL: https://www.metalroofing.com/spirit/comment/13923/find/
Thanks. Aaron, for your input on the insulation. One drawback to installing the metal roofing over purlins and spraying insulation on the back of the metal is that, though it may be way down the road, when the roof needs to be replaced, you will be in a situation of destroying the insulation in order to replace the roof. Personally I would put decking and underlayment down before the roof and avoid that scenario. You can insulate the bottom of the decking then. Todd Miller
Todd Miller
Isaiah Industries, Inc.

9/24/2009
Share
Or copy this URL: https://www.metalroofing.com/spirit/comment/13924/find/
  • About the MRA
    • Member Companies
    • Leadership
    • MRA News
  • For Professionals
    • Join the MRA
    • Industry Resources
    • Upcoming Events
  • Contact
  • Subscribe
©2023 Metal Roofing Alliance. All Rights Reserved. Privacy Policy Terms and Conditions