Black metal roof — bad idea?
My better half loves the look of black standing seam metal roofing.
I am concerned with the heat gain, both into the living space and its effect on any sealants (roof penetrations, edge trim pieces). I’m not sure if spray foam is effected by these kinds of temperatures, but its going to be hot up there in the baking August sun. Obviously it doesn’t get much hotter than black. I suppose in the winter we will welcome the heat.
We are in zone 5b (central Oregon — very sunny and temps in the 90’s for weeks).
The roof will have synthetic underlayment, as well as snow and ice barrier. Then 3/4″ plywood, under which will be 3.5″ of closed cell spray foam, and then the remainder of the 11 7/8″ I-beam will be filled with blown-in-blanket fiberglass insulation. (R-49 total, with very good air sealing). The roof will be unvented.
Should I push for a more ‘modest’ color? (charcoal, bronze were both options).
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Replies
Black means extreme heat means maybe the paint wears out and flakes off in fewer decades than it would have. Might pay off to make sure it's a decent metal underneath (Galvalume) to protect against corrosion, or it might be dry enough in your area that this isn't important.
Normal peel and stick membranes don't seem to like this kind of temperature. Apparently Grace sells a high temperature version of ice & water shield. https://gcpat.com/en/solutions/products/grace-ice-water-shield-roofing-underlayment/grace-ice-water-shield-ht-us-version
Also check the specs on the synthetic underlayment, which will be at effectively the same temp.
Consider raising it off the roof decking on vertical battens to get some airflow underneath and give a thermal break. Understand that you're building a bit of a noise resonator if you choose this. I would like to experiment with something to damp the sound; For a 24" seam metal roof, perhaps something like 2x4 battens 12" OC (got to get the midway point between seams to damp) with 3.5" strips of Rockwool Comfortbatt stapled to them? Something very compressible, but heat resistant.
Note: Metal roofs with surfaces which are perfectly flat at one temperature involve some "oil-canning" at a very different temperature; Make sure she is alright with that, and if you don't like the look, examine striated panels, which are creased beforehand to give some flex to them, to see whether those are visually acceptable. Probably the noise damping is going to introduce its own visual impact, and I don't know how prominent it would be.
Ryan,
When building our house, I really wanted a light-grey or white standing seam metal roof. My wife wanted a black standing seam metal roof. So, we compromised and went with the black one.
A hot sun definitely has an effect on it. As soon as the sun rises the roof begins to pop and hiss like an electric cooktop. We can't hear anything inside the house- this is only audible outside the house. I doubt its causing any real damage but I might be a bit reluctant to have this black metal roof in an arid, sunny region like eastern Oregon.
Consider putting your house design into sketch-up to play with the roof color. I still think a light grey or white roof would have looked and performed better on our house. Every summer, I look for possible roof damage from the excess heat so that I can give my wife a hard time about it. Alas, the damn thing is holding up just fine. :-)
"I really wanted a light-grey or white standing seam metal roof. My wife wanted a black standing seam metal roof. So, we compromised and went with the black one."
Nice compromise :)
I installed a Black standing seam on my roof but have a cold roof system over the top of the SIPs panels. The coating from ABC Roofing is reflective by Energy Star Standards or so they say. I installed Rhino U20 directly underneath the Metal this past fall. No problems so far. Still have yet to see how it is in warm temps in ZOne 5 Upstate NY.