flat rubber roofs [RE-wrenches]

[Randy Sadewic]

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Wrenches,
I will add one more vendor to the list.  UniRac makes a ballasted
system.  The tilt for this system can be as high as 30 degrees, but of
course requires tons of ballast.  I used 20 degrees for a particular job
in 90mph wind area and ended up with about 25 lbs/sq foot including the
racks and modules (over the required ballast). UniRac provided the
formula to determine the ballast.  

The cost of this system including the ballast material and labor to get
that on the roof ended up at about 2x the cost per watt of a normal
non-ballasted system we buy.  The finished product looked very nice.  I
can send pics off line.

Interestingly, I had my 35 year old flat roof home reviewed by a
structural engineer and it is rated for 30lbs per sqft of dead load
which surprised me.  

Randy

Randy Sadewic
randy at positiveenergysolar.com
Positive Energy, Inc.
3225A Richards Lane
Santa Fe, NM  87507
Phone 505 424-1112
Fax     505 424-1113

Enjoy the Sun!


-----Original Message-----
From: Jeff Clearwater [mailto:clrwater at earthlink.net] 
Sent: Wednesday, February 15, 2006 2:43 PM
To: RE-wrenches at topica.com
Subject: RE: flat rubber roofs [RE-wrenches]

Geoff,

YES - what Brad Said!

You can get most 5º systems down to 5 lbs/ft2 or 
even less.   but as Brad says YOU GOTTA CHECK OUT 
IF THE ROOF WILL EVEN HOLD THAT AND SNOW!  No 
more Poland pigeon repeats please.  The roof we 
did in northern MA had 20-25 lbs/ft2 safety built 
in so no problem but we confirmed first with the 
building's original engineer.  Most commercial 
roofs are built to handle air conditioners etc. 
but some are not.

Jeff C.




>
>Geoff,
>
>You really should have an engineer look at the structure. I remember
>quoting a US post office job and when the engineer looked at it, he
said
>the building did not meet code as is, and said he would not be
surprised
>if it would collapse in the next really heavy snow (I haven't heard
that
>it has yet, but maybe no heavy snow there... yet). He would not OK
>putting ANYthing on the roof. And this was a govt. building.  So I
don't
>think you can assume any roof is strong enough without taking a look.
>Residential roofs are standard enough that you can probably judge it,
>but maybe not commercial roofs.
>
>Brad
>AEE
>
>
>geoff at third-sun.com wrote:
>>
>>  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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