New member, potentially stupid north-facing roof question

[pleppik]

The rafters are 16ft. What if the panels are mounted lower than the ridge? Would this reduce winter exposure too much?

You should be able to get a solar installer to do a site survey and calculate exactly how much production you will lose from shading by the roof, nearly trees, etc. An experienced installer may also be able to offer some alternative ideas for placement of the solar panels.

[nok32]

Excellent, I love it when I am told what I want to hear.

But, really, I am glad to know the possibility exists and google doesn't know it all. Thanks. I wonder though if anyone has some example photos of this type of install.

[J.P.M.]

The short answer to your question is no, provided the wind loading and other structural calcs are done correctly. Those calculations, while different for every application, are fairly straightforward. A good solar vendor knows this and will not be intimidated by some design work that may need to be farmed out, done and sealed by a P.E.

I did my own calcs/design for a water cooled thermal collector back in the day, had the design reviewed and checked by another P.E. and sealed it myself. That was a pretty non standard design and as I recall probably took 2-3 hrs. Id guess things are a bit more standardized these days for PV.

A bigger cost may well be due to any modifications necessary to the support structure that may need beefing up from the added external load combinations. South facing, tilted arrays on north facing roofs can be a very viable way to use those surfaces.

[nok32]

The rafters are 16ft. What if the panels are mounted lower than the ridge? Would this reduce winter exposure too much? They would also have a windbreak created by another adjacent roof structure to the east. Could the underside of the module frame be covered, such that wind could not get underneath the arrays?

The basic reasoning for doing this is that all the south-facing roof is glazed. I am miles away from anyone who would care about code blah blah, so that is not a concern, unless it is related to safety, structural integrity or some other valid reason besides "the neighbors".

[pleppik]

Hi, I was googling trying to figure this out and couldn't find the answer.. maybe it is a dumb idea, at the very least, I know it is "not recommended", but as to the "why".. I dunno:

Is there any problem with mounting PV modules on the north-facing section of a ridge roof and tilting them up to point at the proper south-facing angle? Let's say the roof has a 12:12 pitch (45deg). I am not concerned about aesthetics or aesthetic-based code considerations. Please only point out any valid structural and performance issues. The one consideration I can see is high winds near the ridge peak. That is valid.. is that the main concern? Maybe there is still some practical way to work it.. some kind of wind shroud? I am curious to see any links or photos to successful installs of this sort. Thanks!

I guess my question is, why would you want to do this? I'm seeing a lot of expense and complexity, and little to no benefit.

Wind is likely to be the main concern, since what you're describing is pretty much a giant sail on the roof of your house. Personally, I would want a structural engineer to review any such scheme, to make sure it's not going to rip the entire roof off the house in a windstorm.

Also, depending on where you live, many municipalities have height limits in their zoning codes. If the panels extend above the ridgeline of your house you may need to get a variance (or at least check to make sure it's allowed).

[nok32]

Hi, I was googling trying to figure this out and couldn't find the answer.. maybe it is a dumb idea, at the very least, I know it is "not recommended", but as to the "why".. I dunno:

Is there any problem with mounting PV modules on the north-facing section of a ridge roof and tilting them up to point at the proper south-facing angle? Let's say the roof has a 12:12 pitch (45deg). I am not concerned about aesthetics or aesthetic-based code considerations. Please only point out any valid structural and performance issues. The one consideration I can see is high winds near the ridge peak. That is valid.. is that the main concern? Maybe there is still some practical way to work it.. some kind of wind shroud? I am curious to see any links or photos to successful installs of this sort. Thanks!