I just finished my basement and had the same issue, only removing and insulating the supplys helped. I cut in closeable supplys and returns in the basement , I keep the supplys closed in summer open in winter and return open in summer and a bit open in winter. I found a dehumidifier is needed in summer just to keep it dry and not to cold from the cool air that does filter down through the system. Many basements if fully underground only need dehumifification in summer.
I'd like to confirm something that I already suspect. I recently finished my basement where my furnace is located. I've got the furnace and A/C condensor in a small room. There are currently no air returns in the basement to the furnace. I think I need to put a cold air return in because when the A/C is running, all the cold air is congregating in the basement making it almost too cold and the upper floors are almost too warm.
You really don't have the a/c condenser inside, do you? That's the unit that gets hot when the a/c is running. It's supposed to be outdoors so it can dump its heat into the atmosphere. If the room it shares with the furnace has its door closed, that room will get hot when the a/c is running. So if you opened the door a bit, the heat from the room would spill into the basement and warm it. But this is a terrible "solution" and wouldn't add cooling to the upper floors. Move the condenser outside.
I assume that the heating system is hot air and uses the ducts as the a/c uses. What's the basement temperature like when the furnace is running? Where does the furnace get its combusion air?
How does cold air get into the basement? If through registers, why not simply close them? That would also make more cooling available to the upper floors.
Depending on the placement of a new cold return relative to the supply register, you might end up making the basement even cooler. If the two were side-by-side, the basement would get warmer (without doing anything for the upper floors), same as shutting the supply register. Putting a new return on the opposite side would make the basement still cooler.
The returns should be in the same areas as the supplies. Otherwise you will have pressure imbalances in your house. This will increase infiltration in your house and increase your heating and cooling costs. If you put a return in the same room as the furnace without having a supply there also, and the room is closed off from the rest of the house, the room will get a negative pressure. This MAY backdraft the furnace or water heater flues. You could be seriously killed! Be careful what you do, guessing without measurements could be hazardous to your health and electric and gas bills. It may also violate code.
So what are you supposed to about all the cold air that is pooling in the basement? I've got a return on each of the other two floors - warm air returns as they are in and near the ceiling. Shouldn't the basement have some kind of return? Thx
Ray - Condensor, evaporator - I can never keep them straight. I thought the piece outside was the compressor? Whatever it is, the big noisy thing with the fan that gets warm when the a/c is running is still outside. The furnace, with the blower motor is inside.
The house, along with the heat and a/c are 8 years old. I actually have no registers in the basement. The only one that was down there I "covered up" when I finished the basement as the register would have been in the ceiling of the linen closet. With no registers in the baement, the cold air is getting in the basement my "settling" down there from the upper floors. In the winter time is not that bad down there. I assume that's because I'm pumping hot air upstairs not cold so there is nothing to settle into the basement.
I think I see your error. You think that you would like to have that cold air that is pooled in the basement distributed to the top floors of your house. But I ask you where is it coming from? If it is coming from upstairs, then adding returns to the basement will just increase the flow and make your basement even colder.
Well, you can't change the laws of physics! (cold air naturally pooling in the lowest part of your house).
What you can do is control the access to your basement (shut the door or shut the vents to the basement). That should increase the conditioned air going to the rest of the house. If you have already done that, then bigger vents and returns on the upper floors and improving the insulation on the upper floors will help keep those parts of the house cooler.
you may want ot open some warm air supplies in the basment and blow some warm air into the basment but not returns
returns in the basment will lower the air pressure in the basement which along with the bad things stretch mentioned can also suck radon into your house.
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