[solarhotairpanels]

Should I decide to build new or customize my current hot air collectors I can tell you this..

The design of my return air flow chamber will be totally different next time around.

I really believe the cold air that wants to drop back into the house from the collector needs to be balanced out with and UP chamber of equal size and height.

My thinking is that cold air can't flow DOWN if it has to push the same volume amount of air UPward.

The cold air becomes 'trapped' in place.
Trapped cold air to me = NO downdraft at all unless you're heating system is forced hot air..

Homes with forced hot air heating are going to want to pull cold air out of the collector into the house anytime their fans are running so backdraft dampers installed in the hot air collectors are a necessity.

but homes with other type heating systems like forced hot water, radiators, radiant heat etc. that do not heat by movement of air are less prone to want to yank cold air out of the collector into the house.

Sure wish I didn't have forced hot air heating here.. (Grrr!)

Any future hot air collectors I build will have both Supply/Return holes at the TOP of the collector probably or designed in a way to TRAP or BALANCE the cold air in the chambers and ductwork.

Incoming air from house will connect to the back TOP of the collector and forced into traveling 'down' to the bottom of the collector then around an internal baffle or 2 prior to being sent back into the house.