Replies

1. 
   user-2310254 | Jan 22, 2021 04:29pm | #1

   Hi Merlin,

   I will give your post a bump. The clips are attached to the roof sheathing, and the rigid foam is on top of the roof sheathing. Is that correct? If you are taping the edges of the foam, can't that serve as your moisture barrier? What is the underlayment protecting?

2. 
   merlinm | Jan 22, 2021 05:28pm | #2

   Thanks for the bump, Steve.

   There will be closed cell foam against the inside of the roof sheathing. No exterior insulation on the roof. Exterior stack: roof sheathing - underlayment - air gap provided from floating clips - standing seam metal roof.

3. 
   user-2310254 | Jan 22, 2021 05:34pm | #3

   Hi Merlin,

   Maybe one of the experts will chime in with some input. In the meantime, have you considered going flash and batt on the roof insulation? You could install one or two inches and then make up the balance with air permeable. Would be cheaper and greener.

4. 
   aaronbeckworth | Jan 23, 2021 08:56am | #4

   Merlin,

   I only know of standing seam roofing installed in contact with the roof sheathing/underpayment. Can you explain what you mean by air gap? If the metal panels are not supported by the deck I’d think they’d get bent to hell if ever stepped/walked on.

   Sorry I can’t help with your actual question.

   Aaron

5. Expert Member
   Akos | Jan 23, 2021 09:10am | #5

   There is a house in my neighborhood with nothing but GAF underlayment over the front porch for the past 5 years. Still holding up.

   I'm just doing a project with HAL breathX which is another option if available.

6. 
   Jon_R | Jan 23, 2021 09:17am | #6

   IMO, more people should build roofs that meet unvented specs and can dry outward. Similar for walls.

1. 
   Malcolm_Taylor | Jan 23, 2021 11:20am | #7

   Jon,

   I agree. That's a great strategy for long-term resilience.