Q&A / 

Cold Air Return

DEAR TIM: We live in a Cape Cod style house that was built in the early 1960's. The problem is that in the summer the basement is cold, the main floor is comfortable, and the upstairs is hot. In the winter the reverse is true. The basement is hot, main floor comfortable, and the upstairs is cold. Every supply vent is open on the upstairs, and closed in the basement. There is no cold air return from the upstairs, so from what I've read, that seems to be my problem. I would like to know where to install return ducts. I understand what you said about them being near the ceiling to bring the hot air back down in the summer time. But in the winter, would that not also return the hot air needed to heat the room. Should there be two sets, one for summer near the ceiling, and one in winter, near the floor to get rid of the cold air? Tim Schoell, Omaha, NE

DEAR TIM: Ideally you want to have cold air return registers in every room. These should be located at the top of the wall on an interior wall. The supply registers should always be on an exterior wall preferably under a window or near a door.

You don't need two sets of cold air return vents. The reason is simple. The supply vents should be in the floor and the cold air return grilles are high on wall. If you could see the air come out of the floor registers, you'd see it be pulled across and up through the room. Because your body is in this path way, you get the benefit of either hot air or cold air being drawn across your skin providing you comfort.

If you can't easily install a true cold air duct back to the furnace from each room, you can sometimes fake it. You can install a cold air return register above the door from each room that connects to the hallway. The air flows through these openings from each room. The air flows across the ceiling in the hallway towards a larger cold air return that does extend to the basement furnace.

You do this and I guarantee you that the second floor is going to be much more comfortable year round.


13 Responses to Cold Air Return

  1. i am wondering the cold air return vent down stairs is pulling so hard that the vent is starting to howl but the up stairs cold return is pulling nothing we did the tissuie thing is there anything or linning on the inside of the duct work that could cause it to plug up the duct

  2. I recently purchased a new half duplex and have found the main room return air vent is not connected directly to the return ducting, it just goes into the floor joist. There is slab heating in the basement and the bedroom was cold with the door closed so a return vent was installed to improve circulation and again it was not connected to the duct, just a hole cut in the ceiling into the joists.
    Is a there a building code standard that I can refer to request the builder to correct.

    • I have no idea because the code can be modified by towns and cities. Most are lax about the exact practices of ducting. You CAN USE joist spaces as return air ducts. I've done it for years with great success. The bottoms of the joists are covered with interlocking pieces of sheet metal.

  3. You may need to just adjust the dampers on the returns going to the furnace. The description of your returns that attach to the ceiling joists is called panning which is a fast way to run a return if done correctly. The biggest problem with panning is that the contractors don't seal then correctly all the time and air may be leaking out. I have a cape cod and it's hot in the summer. I pushed more air into the 2 rooms upstairs by dedicating a supply directly to the plenum of the furnace and added returns and did the same to the return side of the plenum. It is now comfortable all year round. In the winter it gets too hot so I adjust the dampers down to almost closed and summer fully open

  4. Tim
    On this subject, I have seen houses with cold air returns high and low on same stud space. They have dampers on them so you can use the high return for heat and low for A/C I presume. I have only installed high returns on inside walls in my construction.
    Do you have any info on these types of installs

  5. I am not an HVAC guy but the logic in this post makes NO sense. Heat rises, Hence a return near the ceiling makes sense in the summer. In the winter, a return near the floor will pull all the cold air off the floor allowing the hot air to fill the room. Tim's initial assumption is spot on. High return in the Summer, Low return in the winter. Always a low return on your bottom most floor and always a high return on your upper most floor.

    NOTE FROM TIM CARTER: Mike, What is your plan / mechanism to make the returns magically reverse themselves as the seasons change?

  6. Please advise. I have a two story house with a finished basement. On the first floor is a cathedral ceiling. The thermostat is also on the first floor. In winter we set the heat at 71 and with that the first floor is chilly but the upstairs where we sleep is 76, actually too warm. In the summer with the ac on the first floor is set at 74, and it seems chilly, the upstairs is 78, again too hot. How do I solve this problem. This is a new house, six years old.

    • Roger,

      Simple. Hot air rises. Your thermostat is telling you the temperature of the air exactly WHERE IT IS, not 16 feet up in the air.

      If the cathedral area is connected by a balcony or ??? to the second floor, no wonder it's so hot up there.

      You need a smart programmable thermostat that has a sensor upstairs as well as downstairs.

  7. Upsizing my HVAC return ducts to the plenum. Does the crimped end have to face the opposite direction of air flow? Have two 14" ducts meeting at the plenum using a 16x14x14 WYE, but one crimped end faces the wrong direction. Maybe I should use a TEE instead? Or, have each duct go directly into the plenum?

  8. I am going to purchase a house that has a finished basement. Somehow, it was finished without a cold air return vent. How hard and expensive is it to install one and do I need to have it done professionally or can it be something I can do?

  9. I have a ranch style home in northern Georgia. I have two cold air returns connected to each other with a "jumper". They are not connected to the air handler/furnace at all. The nearest cold air returns that are connected to the air handler is at the opposite end of the house. The actual air flow to this area of the house is low. Should this "jumper" be connected to the air handler to improve air flow to these rooms? The registers are in the ceiling in a bedroom and an alcove leading to the main hallway.

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