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Re: Attic Solar heat recovery

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Posted by nicksanspam on July 18, 2005, 10:56 am

Argo Industries #1560 fin-tube has 5.2 Btu/h-F-ft of 140 F water to 65 F air
thermal conductance. An 8' piece with 2" fins on 3/4" copper costs $5.67.
You might circulate a little water through it at night to prevent freezing
and add a gutter or dew-point controller for condensation. Is this stuff
like refrigerant copper tubing, with a thin wall with limited lifetime in
an open system?


Posted by David L. Jones on July 18, 2005, 11:19 pm

What temperature does your attic get to?

I put temperature dataloggers in my roof space last winter and found it
wasn't really worthwhile extracting heat from there.

Dave :)

Posted by nicksanspam on July 19, 2005, 12:55 am

If you need a new south roof, you might replace it with Dynaglas
transparent corrugated polycarbonate, as I did. It costs about
$/ft^2, goes on quickly, and comes in 4' wide x N' sheets with
a 10-year guarantee against loss of light transmission and an
estimated 20-year mechanical lifetime.


Posted by David L. Jones on July 19, 2005, 1:48 am
 nicksanspam@ece.villanova.edu wrote:

Don't think I'll be replacing my Terracotta roof tiles with clear
Polycarb sheeting any time soon :->
I'd have the weirdest looking house in the suburbs!

Dave :)

Posted by News on July 19, 2005, 12:25 pm
What about in the summer?  A finned copper pipe in the apex, with insulation
just above it, will preheat water fed to your cylinder or on-demand heater.
Maybe worth it.  I have a south facing grey tiled roof and the temperatures
in summer can get to 55C in there. Even when its just above freezing and the
sun shines it can get to 20C up there.  Two lines of finned tube running
down the apex, with a U bend at one end must make a financial difference
when pre-heating DHW.  I haven't done any figures yet, but gut feeling, if
DIYed, tells me in my case it might be worth it.

I was thinking of four to eight lines, of 12mm, or less, plastic pipe, as
this is unlikely to burst if any freezing up there.  Plastic has less
conductivity than copper, but if a 3/4" pipe is split to many smaller pipes,
giving a large surface area, the heat capture will rise and may be

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