[Greenbuilding] Al Pex for Solar Heating System

[Keith Winston]

I am still deeply unconvinced Dawn Solar and analogous systems are worth 
doing. The SRCC numbers associated with it are beyond pitiful: 
essentially worthless. And it's not a cheap install in most 
circumstances. I don't see how you easily keep tubes from getting 
punctured on your roofing install, or reroofing. But the bottom line in 
my mind are the SRCC numbers. There is one report, done I think in 
Canada, that suggested it wasn't completely worthless, but it didn't 
seem like a stirring recommendation either -- I can't find it now. This 
is sometimes called Building Integrated Solar Thermal, Roof Integrated 
Solar Thermal, or Roof Integrated Solar Absorbers. Ah, here's the link:

http://www.builditsolar.com/Experimental/RISAPaper_SolarForum2001.pdf

They claimed it as 8% efficient for heating domestic hot water in 
Florida. I'm sorry, but that's like feeding fish in a barrel 
(PETA-approved analogy): you can leave a jug of water out on your back 
deck in Florida and get better performance. The whole point here is how 
quickly performance degrades in cold or windy weather.

Keith



Peter Caradonna wrote:
> Sacie,
>
> Take a look at Dawn Solar in New Hampshire.  They use pex in a combined heat
> and power system for roof applications.  The system uses pex in a track
> system overlaid with metal roofing and thin film solar panels between the
> raised seams of the metal roof.
>
> Peter
>
> -----Original Message-----
> From: greenbuilding-bounces at listserv.repp.org
> [mailto:greenbuilding-bounces at listserv.repp.org] On Behalf Of Sacie
> Lambertson
> Sent: Wednesday, January 02, 2008 11:55 PM
> To: Greenbuilding
> Subject: [Greenbuilding] Al Pex for Solar Heating System
>
> When we built our house we plumbed it for a back-up solar water heating
> system.  Unfortunately this was before I learned that PEX could not be
> used.  Now I'm ready to complete the job (our propane bills have gone from
> $350/yr to $750/yr) but I'm told that AL PEX should NOT be used either, that
> it can't take the extreme heat of the glycol coming out of the solar panel.
> I would appreciate hearing some opinions and best advice on this.  Copper is
> the only recommended carrier this knowledgeable source told me (though he
> had heard of using copper for the first six feet, with an alternative after
> that, but didn't think this a good idea either).  I really don't want to use
> copper if I can help it.
>
> A follow up question: what is the best insulator for the copper/alternative
> line which will have to be buried for 20 ft before it enters the house?  Yes
> I know that copper must be contained if it is going to be buried in the
> ground.
> Thanks
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