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Posts: 185
Reply with quote  #1 
I'm going to be building 2 new collectors this fall and am interested in hearing what other builders have used for the frame of their collectors. 

For my last build of a 44 sq ft collector, I used 1" x 6" redwood planking for my frame. I went that deep because I was using some roofing insulation I had that was over 3 inches thick. The redwood has been incredibly durable. Looks like new in it's 4th year. It was easy to build with.  Not the most professional/industrial look. 

My coming build will be placed on the roof and I'd like it to look more like electrical solar panels. I'll use twinwall polycarbonate for the glazing. I'm planning on using just 2" thick insulation on the back this time. 

Please chime in with the materials you've used. I'd like to hear about:
1)Ease of build
4)Performance (insulating qualities)
6)Anything else you think I should consider

Thanks in advance for your expertise.


Denver, CO

Double screen hot air collector


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Posts: 2,385
Reply with quote  #2 

If my collector(s) were permanently installed against the side of the house, my outlook on build materials would be very different. As it is, my collectors have to be moved in and out of their winter position seasonally. This means they also have to be stored outside.

Being mobile, my collectors must be durable, yet light. This is NOT what you get with a collector made with wood. Wood is heavy, and can have durability issues with weathering and rough handling during seasonal moving. Wood expands and contracts a great deal, which can make proper selling difficult. I tried to improve upon wood construction by using galvanized steel stud track for the sides and a thin wood panel for the back. For those that don't know, stud track is basically a metal stud replacement. Granted, it was a thinner build, and looks great. But stud track has the issue of limited ways to mount items inside the collector. So I had to add wood reinforcements along the sides and ends. This led to rust where the wood met the metal. This was likely due to condensation inside the panel. 

I have been looking at composite wood for a collector, but it is very heavy and pricy. I also looked at HDPE, which is the same material your trash bin at the curb is made from. But it is pricey, and can not be glued without GREAT expense. This makes it difficult to properly seal as no glues or sealants such as silicone stick to it. So for my next collector I will be making the frame out of hollow square aluminum tubing. The back and sides will be aluminum sheets or flashing. My friend Krautman built his 2nd ZP this way and it looks great!


But the best thing is that the collector will be very light and never need paint. A 4x16 unit should weigh less than 100#. Oh, and it will be mounted on wheels for easy seasonal positioning. Wood is the cheapest and easiest and to work with. The cost of the aluminum tubing and sheeting should be roughly double that of a wood framed collector. But I should never have to repair, paint, or maintain again, so it is worth the extra cost. Because if I have to rebuild every few years, my heat savings could quickly be diminished.

Frankly, if my collectors were mounted to the side of the house, I wouldn't even have a back to the collector. And I could likely build it out of wood and never have a problem.

Greg in MN

Posts: 6
Reply with quote  #3 
I've just finished my first build (Build thread coming), and looked at several options.... Won't go into details, but long story short, for insulating qualities, ease of build, and bang for the buck, I went wood. I had aluminum scrap laying around that works have worked well, but found the cost to insulate it was equal to the cost of the lumber, and for my first build I figured it was a smart move to use something simi-disposable.

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Reply with quote  #4 
One might consider cellular PVC "lumber". It's about double the price of wood but doesn't require painting and can be glued with ordinary PVC cement. So far l've seen it in 1/2" sheet and standard size "boards". It's lighter than wood, won't rot and takes screws fairly well. It's not as rigid as wood and would likely require insulation. I'm still experimenting with it and have NOT built a collector of it (yet).  I did however put a small piece in a pot of boiling water.  It did not melt but did soften to where it could be deformed.


Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay

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Posts: 541
Reply with quote  #5 
I like cedar for the frame and poplar for inside support. It's easy to attach to and adds more insulation to the collector. Cedar is suppose to be resistant to rotting. Poplar is suppose to off gas less than other wood.

I also like the metal track for looks and weight but they are flimsy. If I used them again I may go to the six inch dept. You usually have to buy them in qualities of 10 though.

Bert K.


Posts: 48
Reply with quote  #6 
Before I started my panel project I special ordered heavier 20 Ga. galvanized stud tracks from ClarkDietrich building systems (6" wide with 1-1/2" Leg, 20 Ga. galvanized Structural Track) to allow the direct driving of self tapping screws anywhere into the collector frame with worry about stripping out screws. This avoids all the fuss about adding threaded nuts and other clips to avoid screws from stripping out.

see clarkdietrich.com    This is the same company that supplies Menards and their web site is difficult to use.
I used a local foundation building supply company found on the ClarkDietrich web site to order my stud-tracks.
part # 600T150-33(33ksi,CP60) Un-punched,  33mils (20 Ga)
coating: CP60 per ASTM C955  (galvanized)
10' lengths weight about 10# each.  3 pieces per collector.  6 pieces cost about $70. plus #8-1/2" wafer head tek screws, $6.

Here is an early picture of (2) 4'x 9' ZPDP collectors that swing under the eve during summer months. The 20ga. x6" stud tracks allows self tapping screws to be used anywhere on the frame.  It has 2" insulation with 4" of air travel space the full length (hence the Double Pass). It can easily shoot up to 200+ deg. F. on a sunny day if the fan is not on which can cause a multitude of problems. 


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