We are refinishing our basement, and are nearing competition. The walls are drywalled, and the ceiling is dropped. There will be about 500 sq ft of finished space, including a full bathroom, and about 300 sq ft of unfinished space. There are two existing vents from the supply heat / AC directly from the main duct supply, that I plan on extending down the few inches into the dropped ceiling tiles. No problem.

My question is that there are no cold air return vents pre-cut and should I add one? I can easily add one, but dont know if this is necessary in the basement. Someone told me that since all the duct is exposed (on the unfinished side and above the dropped ceiling) and the furnace is right in the middle of the basement, this would suffice in allow air circulation in the basement. I dont know if I but that argument.

If I do add one, I think I should add it at the floor level, not in the ceiling like the supply vents. This way the warm air (for heat) coming from the ceiling would be circulated to the floor for the return. Should I place it at the floor level?

3 Answers 3


I'm almost certain any occupied space is required to have a supply and return duct for HVAC.

Not quite sure if you can say it's a common plenum in the basement if the furnace is in another room.

Also - I've never seen a return in the floor. On the wall and in the ceiling. This is speaking from experience working as an HVAC controls field service engineer in my previous life. Running a return should be easy, you could get some flex ducting and run it above your t-bar ceiling.

  • I didn't mean IN the floor per se, I meant in the wall, toward the bottom of the wall (close to the floor). That way the return is opposite of the supply.
    – mohlsen
    Commented Oct 8, 2010 at 18:31
  • 1
    Gotcha - that makes sense. When you run cooling, this will work really well. Having the returns close to the floor will hopefully pull that warm air off the ceiling, so I think that would be far superior to having the supply and returns in the ceiling.
    – kkeilman
    Commented Oct 8, 2010 at 18:54
  • I just demolished my basement down to the studs and there is a cold air return in the ceiling. I'm not really keen on it and plan on installing a floor return when I do the remodel. I always felt like there just wasn't enough circulation in the basement and it always felt a bit uncomfortable.
    – user45
    Commented Oct 8, 2010 at 19:01
  • 2
    Returns in every room are not required everywhere. Here in Virginia at least, I've never lived in a house or apartment that didn't use a single large, centrally-located return vent per heat pump unit. I think it's assumed that the door sill gaps will provide a return path for air in any closed-off rooms. Commented Oct 8, 2010 at 19:35
  • Good point - I was reverting back to commercial HVAC thinking. Each occupied space must be "ventilated" which doesn't necessarily require ducting depending on the space, et al.
    – kkeilman
    Commented Oct 11, 2010 at 21:36

Yes , add at least 1 return at or near the floor ( in the wall). All the cold air in the house heads to the basement since cold air is heavier than the warm air. In some installations a central return duct and grill is installed in a central location to reduce cost,( this has become the norm) but is only to save costs. Every room should have supply and return registers. you cannot push supply air into a room with out having a way for the air to get out, ( its like a balloon). If you have a central return grill you normally need to have the bottoms of the doors shaved to allow the extra supply air to flow out. If you do not do this then the room will not receive enough air to cool or heat depending on the time of the year


Don't over think it, it's simple. Bottom open during winter, top open during summer. My top ones don't even close. If the bottom ones are open that's where the majority of the air is drawn from

Adjust Return Registers for Winter

It’s important to remember that hot air rises and cold air falls. In the winter you want the cold air to be drawn through the return registers leaving the hot air behind. By opening the lower registers and closing the top ones you keep hot air in and draw the cold air out. Since cold air is heavy it will automatically flow down to the lower register.

Adjust Return Registers for Summer

In the summer you want the cold air to remain and the hot air to be drawn out through the return registers. By closing the floor registers and opening the ceiling registers you force the hot air out while keeping the cold air in the room.

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