flat rubber roofs [RE-wrenches]

[Jeff Clearwater]

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Hey Geoff,

You should definitely consider ballasted systems 
and with that -  lower your tilt angle if it's 
negotiable.  You still get in the 90 % range of 
optimal output as low as 7-10º tilt.  Most 
commercial flat roof systems have gone down to 5º 
or even less so as to get more panels on the 
roof, lower ballast weight and simplify design. 
The little you lose in tilt is easily made up for 
in those factors.

That said,  contact Jeff Randall at DPW.  They 
have a simple ballasted rack system based on 
concrete paver blocks that can be engineered to 
any tilt and panel.  I have received quotes from 
them for ballasted systems up to 15º tilt - but 
if you go with a lower angle still you'll have 
less ballast.  That can be critical in terms of 
the weight loading capability of your roof - 
that's your first point of research - how many 
lbs/ft2 can be safely added to that roof -  (if 
you are at 5-10º, most roofs can easily handle 
the extra ballast, above that, the weight rises 
exponentially) (But in snow country you really 
need to know the safety margin you are working 
with!) - then call DP&W or any other manufacturer 
of ballasted roof systems of which there are now 
at least 5.  Contact me off list if you want my 
reviews of them.  Most are not oriented to doing 
small systems like yours.

Hope that helps,

Jeff C.
Village Powerr Design






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>I have a project with a flat rubber roof on an older townhouse style 3 story
>apt. building. shading etc wants to put our PV all in one spot... trying to
>rack 21 evergreen panels at 26 degrees... (flexible on that)  My initial
>idea is to do a conventional tilted mounting system attached to some wooden
>curbs that I would have flashed and "roofed" onto the existing roof by a
>sub.  The quotes are coming in surprisingly high ($4-5K for (6) 8' curbs).
>Is this normal? I actually do have access to the 2x12s from below - I could
>probably put in blocking and use single point standoffs - would this be a
>less expensive approach?  Maybe I should look at a ballasted approach?  I
>have thought of hefting some pre-cast concrete lintels or parking curbs up
>there and using masonry fasteners to attach to them but I certainly don't
>want to rough guess the required weight...How would YOU do it?
>
>For a brighter energy future,
>
>Geoff Greenfield
>NABCEP Certified Energy Practitioner
>
>THIRD SUN SOLAR & WIND POWER Ltd.
>340 West State Street
>Athens, OH 45701
>
>www.third-sun.com
>(740) 597-3111
>
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-- 
~~~~~~~~~~~~~
Jeff Clearwater
Village Power Design Associates
Sustainable Energy & Water Solutions for Home & Village
http://www.villagepower.com
gosolar at villagepower.com

530-470-9166
877-SOLARVillage
877-765-2784
425 Nimrod St.
Nevada City, CA 95959
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`~

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