Wind-Loading and Tilted panels on roofs [RE-wrenches]

[Joel Davidson]

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Use PVWATTS to see the cost versus benefits of stand-off mount versus custom 
tilt-rack mount. PV is still too expensive to waste, but squeezing every 
possible watt-hour is not always necessary.
----- Original Message ----- 
From: "Doug Pratt" <dmpratt at sbcglobal.net>
To: <RE-wrenches at topica.com>
Sent: Saturday, February 19, 2005 8:26 AM
Subject: RE: Wind-Loading and Tilted panels on roofs [RE-wrenches]


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Justine, trying to make modules face south on an east or west facing roof
always ends up looking like hell, takes forever to install (measure and cut
each leg custom), and presents a huge potential sail. I cringe every time I
see this done.
According to data from Sandia Labs, a flush-mounted array on a 4:12 pitch
roof facing east or west will deliver 88% of the best possible year-round
performance of a south-facing roof. You only take a 12% hit. Throw up a
couple extra modules...that you could afford now that you aren't trying to
erect that kattywompus monstrosity...and you've got it covered.
Cheers,
Doug Pratt


-----Original Message-----
From: Justine Sanchez [mailto:solarsisterj at yahoo.com]
Sent: Friday, February 18, 2005 1:14 PM
To: RE-wrenches at topica.com
Subject: Wind-Loading and Tilted panels on roofs [RE-wrenches]


Hi folks,

Justine from SEI here...we have a question regarding wind loading on roof
mounted  panels at a tilt. We have seen some structural damage to a local
home here with panels mounted at a tilt and are wondering if anyone else has
had this experience. On a new project we need to mount some modules to a
roof that has an East/West orientation (ie the ridge line runs N-S)....so
that to face our modules south we would have to mount them on either the
east or west roof space tilted to the south. Unfortunately this is the only
good solar access on the property...but we have concerns about the
wind-loading.

Any comments?

Thanks!
-Justine Sanchez
Solar Energy International

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