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Old 08-20-2013, 04:19 PM   #16
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Return Air in the basement


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If your appliances are getting their combustion air from the basement, the air won't get stale.

Move the return to the upstairs.
But the utility room is not wide open, getting combustion air should not mean that I have fresh air in the basement, right?

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Old 08-20-2013, 04:22 PM   #17
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Return Air in the basement


Is the utility room open to the rest of the basement in any way?
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Old 08-20-2013, 08:57 PM   #18
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Return Air in the basement


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Is the utility room open to the rest of the basement in any way?
Yes, open to the rest of basement through a door. But if I put the return air in the basement outside the utility room. It is advised to keep this door closed.
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Old 08-20-2013, 09:03 PM   #19
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Return Air in the basement


Yes. And to install a combustion air intake from the outside into the utility room.
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Old 08-21-2013, 03:00 PM   #20
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Return Air in the basement


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Yes. And to install a combustion air intake from the outside into the utility room.
Then if I do not have a return in the basement, the basement will not have any ventilation since the fresh combustion air that is taken in stays in the closed the utility room.
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Old 08-21-2013, 03:40 PM   #21
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Return Air in the basement


After you seal the utility room from the rest of the basement. A small supply at the utility room end, and an equally small return at the opposite end is ok.

Doubt you will really need it though. Air from the basement will want to rise to the first floor. And will do so through any small hole it can find.

Plus your supply duct work probably has some leakage to the basement. I would run the return to the first floor, and see how the basement does for a month. Only add a supply and return if it really needs it. It doesn't take much to heat a basement.
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Old 08-23-2013, 10:22 AM   #22
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Return Air in the basement


Hi all, I urgently need suggestion on how to ventilate the staircase area to the basement because the contractor will start working on Monday. After talking to many HVAC contractors, I decide to have 3 12*6 inch returns spreading out on the first floor. I will keep 1 small return in the basement. All four of the returns will go through a filtration system.

There are 2 vents down at the basement. I hope that the 2 vents and 1 small return will keep the basement ventilated.


My biggest concern now is how to ventilate the staircase. Currently, the air flows down to the return in the basement through the bottom of the door. After I move the return upstairs, there will be no air flow in the staircase. Please see the picture. It already smells musty in the staircase if I turnoff AC because Humidity rises to the top of the staircase and stays there. I guess it will become worse after I move the return upstairs. Anyone has suggestion to solve this problem? I want to keep the door closed because I have a 15-month old at home.

Thank you!
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Return Air in the basement-staircase.jpg  

Last edited by kgkg; 08-23-2013 at 10:25 AM.
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Old 08-23-2013, 10:49 AM   #23
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Return Air in the basement


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Hi all, I urgently need suggestion on how to ventilate the staircase area to the basement because the contractor will start working on Monday. After talking to many HVAC contractors, I decide to have 3 12*6 inch returns spreading out on the first floor. I will keep 1 small return in the basement. All four of the returns will go through a filtration system.

There are 2 vents down at the basement. I hope that the 2 vents and 1 small return will keep the basement ventilated.


My biggest concern now is how to ventilate the staircase. Currently, the air flows down to the return in the basement through the bottom of the door. After I move the return upstairs, there will be no air flow in the staircase. Please see the picture. It already smells musty in the staircase if I turnoff AC because Humidity rises to the top of the staircase and stays there. I guess it will become worse after I move the return upstairs. Anyone has suggestion to solve this problem? I want to keep the door closed because I have a 15-month old at home.

Thank you!
Trying to add something to the stairwell is overkill. If your AC is off, having a return or supply in that area wouldn't do anything. When your system is on, there will still be air circulation up the stairs and under the door.

My basement isn't finished but I run a dehumidifier all the time. When my AC is off, the top of the stairs does smell a bit stale. However, the stale air quickly dissipates once the door is opened.

As a side note, have you measured the humidity levels in your basement?
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Old 08-23-2013, 12:14 PM   #24
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Return Air in the basement


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Trying to add something to the stairwell is overkill. If your AC is off, having a return or supply in that area wouldn't do anything. When your system is on, there will still be air circulation up the stairs and under the door.

My basement isn't finished but I run a dehumidifier all the time. When my AC is off, the top of the stairs does smell a bit stale. However, the stale air quickly dissipates once the door is opened.

As a side note, have you measured the humidity levels in your basement?
I run a dehumidifier constantly. The humidity level in the basement is 45-50%, but at the top of the staircase, it is 60%. This is why I am worried because I do not want mold to grow there.

I am thinking about putting a return close to the opening at the right end of the staircase in the basement. Maybe it will help moving air in the staircase?
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Old 08-23-2013, 12:25 PM   #25
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Return Air in the basement


By the way, the contractor will use flex rather than duct to pull the 3 return airs from the 1st floor. Should I ask him to use duct instead?
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Old 08-23-2013, 01:31 PM   #26
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Return Air in the basement


With the 3 new returns upstairs you should have enough airflow to keep the staircase air moving. When your AC is not running is when the air will stagnate. Going in and out of the basement should give you enough air movement to prevent mold. Every situation is different, but my basement door gets opened at least once a day.

Flex is more restrictive and causes more air noise. Did your HVAC contractor do duct calculations to determine the number and size of the returns?
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Old 08-23-2013, 03:24 PM   #27
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Return Air in the basement


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With the 3 new returns upstairs you should have enough airflow to keep the staircase air moving. When your AC is not running is when the air will stagnate. Going in and out of the basement should give you enough air movement to prevent mold. Every situation is different, but my basement door gets opened at least once a day.

Flex is more restrictive and causes more air noise. Did your HVAC contractor do duct calculations to determine the number and size of the returns?
The contractor was rushing through my house and I am concerned that he may not do the correct calculation. It is a 4-ton system. The return is the size of the filter, which is 20 by 25. Please see the picture below. What should be the correct duct size and size of return register? Thanks a lot!
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Last edited by kgkg; 08-23-2013 at 03:28 PM.
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Old 08-23-2013, 03:51 PM   #28
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Return Air in the basement


A 16X24 floor register would work
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Old 08-23-2013, 10:16 PM   #29
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Return Air in the basement


I have a pretty lousy house with no insulation around the basement (concrete block) walls. I insulated with xps on the insides of the rim joist as well as some fiberglass on top of that.

Anyway, I keep it decent down there with a return in the middle of the basement and a supply as far to either end as possible.

I leave the fan running continuously.

Obviously, things are drier down there when the ac is on, but I think keeping the air moving all the time when the ac is off helps a lot.

I set the AC at 76 degrees because I'm not made of money and that is plenty comfortable with some ceiling fans going. RH is running 55-60%. The RH will decrease as the outside temperature increases (AC is running more), so I could probably step up the set temp a bit.
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Old 08-23-2013, 10:31 PM   #30
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Return Air in the basement


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I set the AC at 76 degrees because I'm not made of money and that is plenty comfortable with some ceiling fans going. RH is running 55-60%. The RH will decrease as the outside temperature increases (AC is running more), so I could probably step up the set temp a bit.

Put an RH meter in the corner of your basement. And see what the RH is there.

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