Installing solar panels over rigid foam insulation
blueskye
| Posted in Green Building Techniques on
We are about to break ground on a pretty good house in Virginia (Zone 4). The attic will be included in the conditioned area for upstairs bedrooms, so we will be building an unvented roof. Roof insulation is planned as Roxul ComfortBatts inside and ~R20 in two layers of rigid foam outside, topped with OSB (Hunter nailbase panels).
All that sounded great until I considered putting solar panels on the roof. Fastening to the roof trusses through 3″-4″ of foam seems like a hit-or-miss proposition.
Do any of you clever folks out there have advice? Thanks in advance!
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Replies
Esther,
What are you using as a finished roof? There are panel mounts that clip to some profiles of metal roofing.
Malcolm - Sorry, I should have remembered to say.
The plan is for architectural shingles; metal is apparently a multiple of the cost around here.
Call any solar installer who can tell you what you need to do. You might need to modify the roof sheathing in some way.
Thanks, Stephen - I was hoping to go into such a call a little better informed.
Esther,
I try to keep up with the different hardware options for roof-mounted PV racks -- but I feel that it's really hard to keep up with changes in the industry. These days, hardware manufacturers keep coming up with many new methods for attaching rails and racks to roofs. Some require fastening to rafters; others require fastening to sheathing; for low-slope roofs, some are ballasted.
In short, there are lots of new options, and the available hardware is evolving rapidly. I agree with Stephen that you should ask your installer about this issue.
Esther,
OK, after a little more Googling, I found a product you might want to consider: EcoFasten Solar Eco-44R-NDD.
"The Eco-44R-NDD is the perfect solution when installing solar roof mounts on Structurally Insulated Panels (SIPs). The base plate of the Eco-44R-NDD system requires 8 fasteners, allowing the system to be installed directly to the roof deck without engaging a rafter. ECO-44R-NDD can be used on new or existing (retrofit) roofs."
Thank you, Martin!
I am always impressed with your range of knowledge and your patiently shared advice for all. Keep up the great work!