Layer 2 (in between) doesn't, and extends an inch or two beyond the holes on either side. Paint the lot with blackboard paint on the inside.
Separate layers 1 and 2, or 2 and 3, or both, by maybe 1/2 inch and you have all you need.
My darkroom has an open grille on an outside door (layer 1, exposed to full sun at times in the courtyard -- it's the old wine cellar) and an impeller fan on the inner layer (layer 3). Layer 2 is thin plywood.
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