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Posts: 18
Reply with quote  #1 
Here in France I can't find polyiso or similar insulation capable of standing the high temperatures. I therefore wonder if it would be possible to have styrofoam on the outside of the box instead? Ie behind the plywood backing. If the collector is attached against a house wall the styrofoam could be hidden with a frame.


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Posts: 2,461
Reply with quote  #2 

Just to make sure, are you referring to what some call bead board, where the insulation is made up of foam beads pressed together? While I think you could possibly use external polystyrene, there are other options and considerations.

Ideally, you would never want a collector to get to high internally so as to break down any component inside a collector, including polystyrene. That means having enough airflow to keep the output temp below about 120˚F or lower. It begins to melt at about 165˚F, so you can see how you have very little room for error. It would likely off-gas before that but if it were externally mounted it shouldn't cause an issue.

You might also have birds, squirrels and mice nibbling at unprotected foam to use for nesting. But if attached to a wall, protection along exposed edges may be all you need.

Other options to consider are the use of insulations such as fiberglas, mineral wool, cellulose, and even chopped up denim material. All of these would obviously require the insulation to be surrounded on all sides, so essentially a box within a box for the insulation. Again, if attacked to a wall, the insulation must be protected. This also includes protection from the elements. 

And the last thought is that if the wall you are mounting the collector is insulated and smooth, maybe insulation on the back of the collector is NOT needed. If the siding is insulated and rough or you have lap siding, maybe you only need to highly seal the edges where the collector meets the siding. In this case, the back of the collector would be insulated by the insulation within the wall cavity.

I hope this helps.

Greg in Minnesota


Posts: 18
Reply with quote  #3 
Thanks gbwilson for your reply.
I was able to find some polyurethane sheets today which hopefully will be able to stand the temperatures.
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