40+ years of experience from the solar pool industry shows that shingle roof attachments without flashing with proper sealant and methods can be very successful. Typical pool heating systems involve 50+ attachments done without flashing. BUT, that experience is primarily based on two things that differ from the PV industry. First, the hardware for solar pool heat is designed specifically for this installation method. More importantly, the expansion and contraction issue does not really exist in the same sense. Solar pool heaters and straps that hold them down are inherently flexible to an extent, and the panels "float" under the tie-downs.
Aluminum rails are rigid, and I can see expansion and contraction over long rail sections having a much greater degree of impact on an L-foot or standoff, especially given the leverage available with a taller attachment. This same issue exists with rail-less systems because the modules are rigid and presumably have a different coefficient of expansion than the roof. On the other hand, I don't think there is enough study and evidence to say definitively that a flashing-less PV system is necessarily detrimental to all shingle roofs, and most I have seen have been trouble-free going as long as 15 years. Where I have seen problems is where L-feet are tightened too much or too little, or were installed at angles that dug into the shingle with the sharp edge of the aluminum. I can see how a wider base would be smart for a manufacturer trying to get away without flashing. With all that said, my conclusion and vote is why risk it? Flash it. I find it to be a solid competitive advantage over those that don't anyway. The race to the bottom for the cheapest and least labor intensive installation method is not necessarily good for the industry. Jason Szumlanski On Thu, Aug 6, 2015 at 12:47 PM, Daniel Young <dyo...@dovetailsolar.com> wrote: > Writing the subject above, it seems like I’ve heard this question on the > wrench list before, but I could not find it in my old email archives. Feel > free to pint me back to the old discussion if it’s there. > > > > I’ve been using a flashing based roof attachment for 8+yrs now (quick > mount or similar). Now we are looking at Rail-less systems (quick rack is > a good example). There is also a non-flashed rail-less racking from > roof-tech http://roof-tech.us/ . I’ve always been of the opinion that > simply crushing some sealant/gasket onto an asphalt shingle work fine at > first (the test data from roof-tech is impressive), but would be an issue > 10+yrs down the road (thermal expansion movement, freeze/thaw, etc). I can > make a good waterproof seal at first by just slathering some butyl/silicone > to an L-foot and cranking it down on the shingles, but that practice really > disappeared 8+yrs ago. > > > > Maybe consider this a Poll: (to flash, or not to flash) > > > > With Regards, > > > > Daniel Young, > > NABCEP Certified PV Installation ProfessionalTM: Cert #031508-90 >
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