Cold air coming from cold air return

anthony_15

The second furnace downstairs is not connected to the cold air returns in question, there is also no vent on the outside of the house.

anthony_15

cold air coming from cold air return

I recently bought a house that was built in the 1950's. The second floor was added after the house was built, and the house has two furnaces because they did not want to but in additional duct work. In the upstairs, when the furnace turns on it sucks cold air through the cold air return in the floor (it uses the floor joice), when the furnace shuts off cold air comes up through the cold air return. Is there any way to stop this? it is making the furnace go on alot more.

Big Ed

Wind Chill Factor

When the air is being sucked down the return it feel cold on the skin..

Cold air falls warm air rises.

Guy_6

Hmmm

Perhaps it is an effect of the other furnace. It may be pulling from that return. Try each furnace independantly and see if it makes a difference.

Ed_26

cold air

Possibly the return air has a make-up air connected to it?
(that is a duct from the outside)that provides fresh air to the building for exhaust & combustion, & protects the building from negative pressure. The cold air coming in may mean that your house needs fresh air.

John H.

Cold air

If in fact air is coming back up the return. blow out a mathc and look at the smoke. It is eather being blown up from a fresh air sorce that is unseen. You say the joists are being used maby they dident block off the runs from the outside walls or other wall stacks causing a draft. I would try and look down the run or use a light and mirror.

or the upstairs is under a neg pressure. check to see if a attic fan is stuck on.