Moving Hot Air versus moving cold air

[dougstove]

Hi;
About 4 winters ago I installed a system of ~25' of 4" duct to bring cold air from the lower level of my long end-split ranch house, to a stove room at the other end of the house.
I was seeking to:
-warm up the lower level
-move heat out of the large room where my stove sits, which tended to overheat.
Net result: The lower level got slightly warmer, and the stove room got cooler. But I had complicated condensation and air circulation issues elsewhere in the house.

So last fall I reversed the system, and put in a 6" duct pulling air down from near the ceiling of my stove room, and pushing it the length of the house, down to the lower level of the end split.

Net result: The downstairs is comfortably warm, my stove room stays comfortable and my air circulation issues resolved.
So: thermodynamically it makes more sense to pull cold dense air in, than to push warm light air out. But in my case, moving the warm air worked better.
cheers, Doug

 

[begreen]

True. In some cases it may make sense for pushing hot air down a story which is not it's natural path. Increasing the duct size was a good move. 4" is a small duct with a lot of friction loss over 25ft.

 

[woodgeek]

I think it was moving the heat down that required moving the hot air. Makes sense.