Solar-standing seam flat roof combo?

David Roodman
3/2/2010
Hello. I am working through the process of putting solar panels on my roof. It is surprisingly complicated because solar is in no small part a roofing job. My house has a 25'x40' footprint, a flat roof sloping 1:12 in the long direction (from front to back), and false mansard facades on the front (high, short) side and along one of the long sides. (You can look at the Google map at http://j.mp/cCPvDN.) My house was built 7 years after the great snow storm of 1922 that caused a theater to collapse here in Washington, DC, killing 98 people. So the roof seems to have been built tough: there are 3 purlins supporting the roof, every ~9 feet, each made of two 2x12's sistered together. I have shied away from having the panels installed by bolting them to the rafters because of all the penetrations. Several contractors proposed laying I-beams across the house along the short dimension and mounting on those. This seems inelegant and expensive to me, and also would involve puncturing the facade along the long wall. Another issue: I have bitumen roof now and repairing or replacing it could require removing the panels and reinstalling them: not cheap. So the clever idea arose: put in a standing seam steal roof and clamp the panels to the seams, laying them flat to minimize wind load. The roof would be part of the solar panel structure, as with thin film installations, so it well might be eligible for the federal solar tax credit too. But it would produce 2-3 times as much power as thin film. Presto! Long-lasting roof, no penetrations, elegant design, high power output, nice tax credit. Or too good to be true? I actually signed a contract to have this installed, and now the contractor is worried that the roof is too flat for standing seam and is offering to cancel the contract. Any advice or wisdom would be greatly appreciated! Thank you.
Info @windowsonwashington.net
An informed customer is our best customer.
3/2/2010
Mechanically seamed roofs are usually acceptable for low slope applications. You should be fine.
Guest User
3/2/2010
Thank you, Windows on Washington. A more precise question: how to I find manufacturers in my area who will warrant a steel standing-seam metal roof for a 1:12 slope?
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