PV Integrated Roofing [RE-wrenches]

[Jim Hartley]

Doug Pratt wrote:
> Wrenches,
> 
>   The recent discussions about roof mounting, and the various and many
> problems with hanging PV materials up there has me thinking about that
> long-time dream of incorporating the PV material into the roofing.
> 
>   Uni-Solar introduced shingles and metal roofing a few years ago, and
> in spite of strong consumer interest...has flopped big time with them.
> They had a number of problems (like not having a fire rating!), were
> poorly represented, etc.  Uni-Solar is working on a second generation of
> roof-integrated PV materials now.  My friend (and architect for the new
> house I'm building) Steve Heckeroth has just been appointed Uni-Solar's
> V.P. in charge of roof-integrated PV.  He'd love to hear feedback from
> the wrenches out there, and I'd be happy to pass all email on to him.

Okay, this is interesting.  I'm not that familiar with their roofing 
product material myself.  This came on the scene after I took my five 
year sabbatical from PV.  That was in '94 when they had just the various 
module products.  

Two things about it, though, concern me beyond whatever code problems 
they ran into.  Don't get me wrong, I like the idea.  But the efficiency 
and long term stability concern me.  That is somewhat offset by the fact 
that the ENTIRE roof surface area could be utilized.  That's a lot of 
area to work with.  Secondly, many traditional homes don't have a solar 
optimized pitch to begin with, again adversely impacting the possible 
annual solar gain.  I can add another thing too - the huge snow buildup 
during winter in northern latitudes.  But this too has an offset factor 
when I think about it, that being what must be a much slicker surface 
than shingles. This characteristic would probably permit much greater 
shedding of snow loads owing to reduced friction.

My thinking is, as you intimate, that this material might be ideal for 
new construction if and when it is sensibly and reliably integrated.  
Coupled to this is the fact that new construction permits the inclusion 
of other features which can work hand in hand with something like the 
product UniSolar has.  To wit, intentional inclusion of more logical 
wiring practices and any number of energy conserving devices such as 
state of the art low power lighting products, etc., that won't 
overburden the PV component.

Existing structures are a bit more problematic.  On the other hand, code 
compliance where renovations are concerned sometimes tends to be a 
little more waffling and, hence, forgiving.  That may be because so many 
people do renovations on their own and/or on the sly and the code people 
are not aware of what might be happening.  With this stuff, being also a 
roofing material by definition, you have to have it approved for use and 
then, most likely, done by people well versed in the manner of its 
proper installation.  Who would that be?  Solar folk or roofing folk?  
Bear in my mind that the authorities will be watching with the greatest 
curiosity.
> 
>   If you could have any kind of electricity-generating waterproof roof
> covering, what would it be, how would it install, etc?  Uni-Solar is
> willing to start with a blank sheet of drafting paper on this.  Of
> course we do need to work with the existing basic Uni-Solar amorphous
> material.

Understood.  Okay, how about a sizeable membrane ala roofing paper you 
can just unroll laterally so that where joints occur you have a flap 
overlapping the next section downhill.  At the joint they could be 
"pasted" together or bonded somehow to one another.  You'd still need to 
keep the whole thing stuck in place somehow [to the roof decking] so is 
doesn't want to buckle up or get sucked up during a 
some negative pressure episode.  Further, whatever edge seal you have 
must be foolproof waterproof.  On roofs, water can go uphill by 
capillary action in the most quixotic fashion sometimes in the 
relentless quest to find holes into the interior.  I think, too, some 
form of waterproof underlayment would be essential.  These products, 
fortunately, exist now.  One of the more confounding problems about this 
whole technique would be how do YOU stay up there on top of this stuff 
as it goes down?  You would end up walking on it.  Is that something a 
person could do and do so without slip sliding all over the place?

How you treat the various roof protrusions [plumbing stacks, chimneys, 
etc.], I don't know exactly.  Maybe they produce "filler kits" to use in 
such situations that aren't photovoltaicly active components.  The big 
question really has to do with how long this material of theirs will 
last before degrading appreciably.  Once spent to some degree, what 
happens then?  Would it be easy to remove and redo?  And at what cost.  
How many years of use are we talking here?  10, 15, 20 years?  
> 
>   And least anyone think that working at Real Goods has made me rich
> enough to hire architects and build a custom house...HA! 

We know this to be so. We checked out your financials as a condition of 
inclusion here. :-)

 Not a chance!
> This is the work of my son-in-law, the Silicon Valley zillionare, who
> decided that Mom and Dad needed better housing (bless his silicon-coated
> heart).

Hmmm.  I have two sons who are denizens of Silicon Valley.  Maybe I 
should pass my cup their way, you think.  I could see myself in 
something more opulent.  Thanks for the tip, Doug.


Jim Hartley
http://www.homestead-specialties.com
Business Email: JamesHartley at homestead-specialties.com
Direct Email: grail at inil.com

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