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<p class="MsoNormal">Jeffrey, <o:p></o:p></p>
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<p class="MsoNormal">I agree. We do structural analysis on every roof design and factor in the point loading at the attachment points. I had floated this idea because it came from an SE that I work with that also has a PV system. His theory is the definition
snow loads are accumulation of snow over time. And most of the time snow will slide off the panels in 3-4 days. The panels would have to be placed so the snow would completely slide off the roof. I wanted to see what others thought of this approach who have
been doing structural analysis. I appreciate your responses.<o:p></o:p></p>
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<p class="MsoNormal">Gary<o:p></o:p></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> re-wrenches-bounces@lists.re-wrenches.org [mailto:re-wrenches-bounces@lists.re-wrenches.org]
<b>On Behalf Of </b>JRQ<br>
<b>Sent:</b> Thursday, February 21, 2013 8:28 PM<br>
<b>To:</b> RE-wrenches<br>
<b>Subject:</b> Re: [RE-wrenches] Snow loads<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="color:black">Gary,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:black">The snow loads that structural engineers design to are a worst-case scenario. It is true that snow tends to slough off of PV arrays quicker than your normal roof. However, if there is a major snow event, especially
if it starts at night (this recent blizzard on the East Coast would be a good example), snow will build up on the array the same as it does everywhere else.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:black">In many cases, a PV array actually makes the engineering assumptions worst. Any snow that lands on the modules transfers down to the attachments, and point-load the structural members. The weight of the snow is
less distributed when it sits on a PV array, placing additional stress on individual members. I work in Massachusetts currently, and we often have to perform rafter upgrades to roofs that are fine otherwise for exactly this reason.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:black">If you have any snow load requirements in your area, I would highly recommend you have a structural engineer review the structure, even if a structural stamp is not required.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:black">Jeffrey Quackenbush<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><b><span style="font-size:10.0pt;font-family:"Arial","sans-serif";color:black">From:</span></b><span style="font-size:10.0pt;font-family:"Arial","sans-serif";color:black"> Bob-O Schultze <<a href="mailto:bob-o@electronconnection.com">bob-o@electronconnection.com</a>><br>
<b>To:</b> RE-wrenches <<a href="mailto:re-wrenches@lists.re-wrenches.org">re-wrenches@lists.re-wrenches.org</a>>
<br>
<b>Sent:</b> Tuesday, February 19, 2013 3:00 PM<br>
<b>Subject:</b> Re: [RE-wrenches] Snow loads</span><span style="color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="color:black">I would certainly agree with Will here. You can't make that argument as stated, it's wrong. Please don't try to make it to your AHJ, you take the chance of f-ing it up for everyone around
there. I think the best argument you can try is: aside from the usual 3-4lbs/sq/ft that the array itself ads to the roof load, snow will be very unlikely to build up on the modules to the degree that it builds up anywhere else on the roof. The freezing-rain-before-a-snow
phenomena is very real and it WILL happen sooner or later. Not often perhaps and under most conditions the snow will leave the modules before the roof. But...Gotta be real about that.<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="color:black">Bob-O Schultze<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="color:black">On Feb 19, 2013, at 11:06 AM, Will White wrote:<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black">Most structural engineers I’ve seen take a reduction for slippery surface but I think you’d be stretching things to say adding PV panels
reduces the load to zero. I have a 45 degree pitch roof and I get snow build up some times especially if we get freezing rain before the snow. </span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"> <o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black">Also if you have an asphalt shingle roof you can create an unbalanced load with snow sliding off the south side and sticking on the north
side. Most engineers take this into consideration too.<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"> <o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black">Thanks,<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black">Will<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><a name="_top"></a><u><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:#0F243E">__________________________________________________________________________________________</span></u><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:#0F243E">Will White</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:#0F243E">Regional Field Operations Manager – New England</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:#0F243E"> </span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:#0F243E">Real Goods Solar</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:#0F243E">64 Main St.</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:#0F243E">Montpelier, VT 05602</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:#0F243E">Tel: (802) 223-7804</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:#0F243E">Cell: (802) 234-3167</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:#0F243E"><a href="http://www.realgoodssolar.com/" target="_blank">www.realgoodssolar.com</a></span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"> <o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"> <o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"> <o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:black">From:</span></b><span class="yiv1875936615apple-converted-space"><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:black"> </span></span><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:black"><a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a><span class="yiv1875936615apple-converted-space"> </span>[<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org">mailto:re-wrenches-bounces@lists.re-wrenches.org</a>]<span class="yiv1875936615apple-converted-space"> </span><b>On
Behalf Of<span class="yiv1875936615apple-converted-space"> </span></b>Gary Bassett<br>
<b>Sent:</b><span class="yiv1875936615apple-converted-space"> </span>Tuesday, February 19, 2013 1:48 PM<br>
<b>To:</b><span class="yiv1875936615apple-converted-space"> </span><a href="mailto:re-wrenches@lists.re-wrenches.org" target="_blank">re-wrenches@lists.re-wrenches.org</a><br>
<b>Subject:</b><span class="yiv1875936615apple-converted-space"> </span>[RE-wrenches] Snow loads</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"> <o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="color:black">Has anyone in the snow belt areas have any luck with convincing their local building inspectors that the snow melts or slides from panels, much like a metal roof only better. Thus your
snow load would be reduced to zero where the panels have been installed.</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="color:black"> </span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="color:black">Gary</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="color:black"> </span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"> <o:p></o:p></span></p>
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