I have a 900 sq ft ranch w/basement home that I am remodeling. The furnace is a propane forced air and is located down stairs. I had two cold air returns upstairs and have closed one of them off. This has not seemed to have hurt the heating/furnace at all. I do not have a cold air return from the down stairs area. My question is can I leave the one cold air return closed off upstairs and should I add a cold air return downstairs?

No return air should ever be closed off because it draws air from different parts of the house. You can install a return air down stairs but it is not recommended unless you also supply combustion air for the furnace.

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Originally Posted by hvac1000

No return air should ever be closed off because it draws air from different parts of the house. You can install a return air down stairs but it is not recommended unless you also supply combustion air for the furnace.

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As I tore out a bedroom wall the returns upstairs are pretty close together. I do have a louvered door for furnace room and there is outside air (thru vent and pipe) coming into the furnace room. If it would be OK where would you install a downstairs cold air return?

You would want to try and keep it away from the furnace area to prevent the RA from interfering with the flow of air for combustion.