Planning Roof for Future Solar Panels
idahobuild
| Posted in Energy Efficiency and Durability on
Hey all,
Should I specify CDX on my plan set for the portion of the roof that may later support solar panels. The area would be about 650 sq. ft. (about 21 sheets). The plans drafted up thus far only ref. being code compliant. I assume that the framers will use 7/16″ OSB, but should I both change the spec. for the solar side of the roof to 7/16″ CDX and specify for the remainder that 7/16″ OSB be used?
Thanks.
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It's more a question of, do you really want to penetrate 100's of screws into a roof to mount the panels?
You didn't mention what your roofing material is, but I assume asphalt shingles.
I'd suggest looking into doing a standing seam metal roof, because there are clips that can mount the future solar panels to the seams. Thus no penetrations, and the roof will last much longer so taking off the panels to fix leaks or re-roof is not an issue.
I'm biased though, I personally hate asphalt shingles in general. Even without solar panels.
Jamie
I'm with Jamie on this. Your roof line looks not too bad for standing seam.
For solar I would run a conduit from your panel to a roof AC/DC junction box (ie Soladeck or Jaybox).
Also spec a panel that is either PV ready (that is dedicated PV busbars) or a 200A panel with 400A busbars to get around the 120% limit.
In either case, I would go for CDX for a roof, simply holds up better in the long run.
I am considering a standing seam roof, but the cost is crazy expensive. I have a couple of friends that installed standing seams themselves, but their roofs were simple, single plane.
Even though our roofline is fairly streamlines, with the hips and valleys I'm not sure it is something that I want to DIY. Though I am now considering metal-shingle roofing -- installs similar to asphalt but supposedly more rugged. With metal-shingles I'd likely specify CDX; since there would be more fasteners. And I'd also use a ice/snow shield under the whole roof.
The solar panel mounts are placed over and lag bolted to the roof framing members. The have flashing that slides under comp shingles. Since it is new construction the trusses should be designed for the weight of the solar panels. The roof sheathing does not support the panels.
user ...358,
Unless he goes with a standing seam roof and rib-clips. Then the type and thickness of the sheathing begins to matter, as it determines the holding power of the concealed fasteners on the metal roof panels.
Solar PV systems can add up to 5 pounds per square foot to the dead load of a roof, so the roof framing should be designed with additional 10 pounds per square foot to the roof's dead load. If you are in high wind, you may need even more.
I've used both, CDX and OSB, structurally it's no difference.
I've added a note to the list for the Engineer's review to check loads with PV. Thanks Armando.
I always thought it was pretty hokey the way they just drill holes in an existing roof to put the standoffs on. Maybe squirt some silicone in the hole. So one thing to consider is putting a layer of ice and water shield on the whole roof. Another thing to consider is running conduit up to the roof so you don't have ugly wires.
Have you picked out a solar installer? Best thing would be to ask them.
In my case the solar install would be about $45K before tax credits. The cost of a standing seam roof over asphalt is what....double?
On my panels, the bases had a butyl foot and they were able to go right through 5/8 zip. There were not hundreds of screws put through the roof for the 16 panels I had installed. Only a few dozen. It is definitely worth installing a soladeck roof mounted junction box with conduit down to the electrical panel or utility room, wherever you anticipate an inverter being placed.
The solar panels do add weight to the roof, but snow does not stick to them very easily, especially on a steeper roof.