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GOM

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Posts: 72
Reply with quote  #1 
I'm really partial to drainpipe collectors, I guess because they're so elegantly simple and work really well even though not to the efficiency of the screen units.  Anyway, here's my question:

I paint my drainpipes with high temp, black paint when installing them in their box. Would I gain any advantage by lining the box with high reflective insulator sheets? Would reflective inner surfaces bounce more solar energy back to the pipes rather than being absorbed by a dark lining?  I realize some radiation would be reflected back out through the glazing so what's the trade off if any?  

Appreciate the members views on this and especially info from anyone who's tried reflective insulation with DP collectors.

Thanks, GOM 

KevinH

Registered:
Posts: 557
Reply with quote  #2 
Here are my opinions for a tube-type collector like the downspout:
- Use the maximum number of tubes that will fit in the collector width.  Some people think that gaps are a benefit, but since the tubes are what is heating the air I want as many as I can fit.
- Use the thinner aluminum downspouts if you have a choice between two grades.
- With no (or very little) spacing between the tubes, only paint the top black.  The bottom, if painted black, will radiate more heat out toward the insulated back than a lighter color.  You want the tubes to heat the air, not radiate heat toward the insulation.
- With no (or very little) spacing between the tubes, leave the shiny foil on the polyiso below the tubes unpainted.  No sun is hitting it, so no need to paint it black.  With downspouts I would probably use the white ones or try to get the paint off the back.
- For the small area on the sides above the tubes, it probably doesn't matter much if they are black or left shiny (mine are black, mainly because I spray painted the tubes in the finished box).
- For a rectangular downspout (like 2x3 inch) have the 3 inch side toward the sun (minimize the amount on area not hit by the sun).
- Put the tubes in parallel with a plenum at each end (no snaking back and forth through a single tube).

Kevin H
MN
 
GOM

Registered:
Posts: 72
Reply with quote  #3 
KevenH,  Thanks very, very much for your informative response!  GOM 
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