Most efficient roof choice
What would you choose? I’m in southwest Florida and need a new roof. I originally wanted foam board over sheathing, and a standing seam metal roof, but can’t find roofers willing to do it. It seems most do standing seam direct to underlayment. Currently the house is shingle over sheathing and vented attic from soffit and exit at ridge.
Option 1: Standing seam Galvalume direct to sheathing, or willing to put rfoil single bubble insulation underneath. Without the air gap the reflective part will be void, but would this block some conductive/convective heat?
Option 2: Stone coated steel panels on battens with the associated air gap.
Option 3: Keep searching for another roofer to install vented airspace between metal and sheathing.
Thank you!
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Replies
Rybuffet,
If you have a vented attic, that is where you can take measures to keep heat out of the house, by increasing ventilation, or the levels on insulation on the floor. The priority for the roofing should be to keep water out, and stay in place in high winds.
With that in mind, installing it directly to the sheathing makes the most sense. It is easier to detail, has backing for fasteners wherever you want them, and can have a more aggressive fastener schedule in high wind areas.
I would also skip the bubble insulation. Metal roofs reflect a lot of their heat, and the bubble underlay gets compressed at fasteners, creating dimples in the panels that can either collect water, or if left too loose allow leaks.
Good points and thanks! I am definitely going to work on attic insulation as well.
Given the expense of the roof and need to replace it due to the hurricane, I wanted to make sure I maximize what I can do for the topside, as long as cost is reasonable.
I really appreciate all the advice here!
Rybuffett,
The two things that do a lot towards making a snap-lock metal roof more wind resistant are increasing the number of fasteners, and hemming the bottom of the panels over the drip-edge at the eaves: https://www.youtube.com/watch?v=Nv3lerxWLH8
Metal roofs usually use specialized fasteners that are sized for attaching directly to wood underneath. That's probably why roofers are reluctant to put anything between the roof and the sheathing.
Makes sense. It seems that few or none do it in my area, unlike other places like Texas. Maybe because of wind rating or some other issue. Probably best to let them stick with what they know and get a better install.