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samantha.77 01-05-2011 12:20 PM

cold air return vents in the basement
Hello I have a very tricky question that was hoping some of you all have experience in.

I am wondering if it is a good idea to have a cold air return vent in the basement. I have asked a lot of people this question and I get a different answer all the time, no one really knows if it's a good idea or bad.

Can some one with experience in this area help me out.

I am wondering if to install a cold air vent in the basement rec-room.


Jackofall1 01-05-2011 12:28 PM

The answer is yes you should, the amount of return should be equivelant to the amount of supply or as closely matched as you can get without going out and buying expensive measuring equipment.

But this topic will be debated fiercely in this forum and until the cows come home.

Good luck

samantha.77 01-05-2011 12:45 PM

Thank you Jackofall1 for your reply,

"But this topic will be debated fiercely in this forum and until the cows come home"

I know what you mean by debatable, I have asked this question before and I get different answers all the time. The best one so far was to install one with a damper and if it causes problems just close off the damper. Others say don't ever put one will effect pressure, not to sure what that means but has to do with negative and positive pressure, down draft, but not sure.

Jackofall1 01-05-2011 12:52 PM

In the heat of debate I have advised of the same process, add 1 with a damper, if any undue problems happen you can always close the damper.

But by adding RA you will better circulate the air in the space you are heating/cooling. As far as pressure differentials, if there is no RA then the room becomes pressurized, minutely, but pressurized. With the addition of an RA it will mitigate this pressure and offer what is know as a balanced condition.

samantha.77 01-07-2011 10:32 AM

O.k here is an update concerning the cold air return in the basement. I had a HVAC company come to my house and told me the following, taught I would share with you all and maybe get some input on the situation.

He said DO NOT put any returns in the basement, it is acceptable to open up some supply registry to get some warm air blowing into the basement use a fan to circulate the air but no returns. His response was that he use to put returns in the basement and it works to balance out the pressures but soon realized it did not work the same for every house due to their basement layout and in some cased it lowered the air pressure in the basement causing things such as back draft, increased humidity in the home, excess condensation which all seems to go away when the return was closed off.

His advise was to be on the safe side and just open up some warm air registry to blow air down and use fans to circulate the air instead of installing a cold air return, he also advised that it is better to have a slightly positive pressure in the basement than a negative pressure.

Another thing he mentioned that I would like to discussed was that the only way I can have a cold air return in the basement was if I put a 5" dia insulated flex duct from the outside (fresh air intake) and bring it into the basement and loop it up like a "U" this way fresh air is introduced, will balance out the pressures and the cold air return can circulate fresh air through out the house. He also advise do not put the flex duct directly into the cold air return because he has seen frost developed in the inside of walls and he showed me some pictures as well it is never a good idea to have -30 deg C temp passing over your furnace the best was was to do the "U" loop thing and let the cold air return pick it up.

I don't know if that all makes sense just taught I would mention it and get some feedback.

Jackofall1 01-07-2011 10:51 AM

Hello again, the contractor you contacted is a non-supporter of RA in the basement and as mentioned last week, you will those that agree and those that don't.

The flex duct he is referring to is to bring combustion air into the area of the furnace, something that is installed with all new furnaces, but was never considered in the days of yore.

As far as creating all the other problems by installing RA, I don't buy it, like I said last time, install one with a damper, I am sure there would be positive results, but in the unlikelyhood there was negative results, one could always close the damper.


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