First time poster needs info on bsmnt ducts

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Old 08-19-06, 11:43 AM
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First time poster needs info on bsmnt ducts

I am finishing a basement and creating three new rooms separate from exisitng ducts. I am planning on running stack ducts in the framing bays in two of the rooms getting the supply close to the floor. I have no way of getting the duct into the wall in the bath, so I am just running a ceiling duct. The basement is a walkout with two exposed sides. the existing ducts are run in the floor joists blowing out of the ceiling. I am afraid this will not be conducive to heating in the winter. Some posts have said that supply should be run out of the ceiling in basements.

should i also place the supply in the ceiling as opposed to the walls for the other two rooms? Also, I am only going to put one cold air return in the basement. Is this sufficient or does each room need one?

Thanks for your replies.
 
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Old 08-19-06, 01:50 PM
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Generally speaking supply registers go low and returns are high, this is to ensure mixing of the air in the room and prevent stratification. Obviously this cannot always be done as in the case of your bathroom. Be sure to install balancing dampers in the new supply ducts where they "take off" from the existing main duct.

Return air ducts are not installed in bathrooms...for obvious reasons. You do want a ventilation system (exhaust fan) in the bathroom exhausting to the outside air.

The other two rooms would best be served if they each had a return air duct. Generally, the RA duct will have a cross-sectional area of 1-1/4 to 1-1/2 times the combined cross-sectional area of the supply ducts in the particular room it serves.

Are you sure that your present furnace has the capacity to heat these rooms?
 
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Old 08-21-06, 11:26 AM
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Thanks for the reply. Yes the system has plenty of capacity. The builder was ggoing to finish the basement. In the bedroom I have a 12x6 supply takeoff. it is the last duct on the run so I am not robbing anything else. It pushes plenty of air. I have a 12 inch wall stack I am locating in the stud bay to take the air flow down to ground level. Before I did that I wanted to make sure that the supply was low and return high. Just wnated to make sure I wasn't confused about that.

I am putting an equal size return flow in that bedroom at ceiling level. It runs right into the cold return duct.

I am placing a small supply duct in the other closed room. Mostly because it does not have an outside wall that it above ground level so it should stay warmer. Also there is a lot of runs off that trunk line, including the master bedroom, that I don't want to rob airflow from. I have a cold return in that room I had to build a soffit around.

So hopefully i have done the job. Only other question is why do I need a dmaper in the run for the bath?
 
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Old 08-21-06, 12:30 PM
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You need balancing dampers in ALL of the supply ducts so that you may properly adjust the airflow into each room. This is necessary to keep some rooms from overheating while other rooms never heat enough.
 
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Old 08-22-06, 08:39 PM
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Wink

We run almost all basement runs to just off the outside walls in the ceiling. Most time a 2X12 register This will give you about a 14 ft spread over the wall blowing down. The air then has to come back to the cold air return near the floor. Or under the door to a central return in the cold air drop.

Before I did that I wanted to make sure that the supply was low and return high. Just wnated to make sure I wasn't confused about that.

In the basement you want the air to blow down and the return down low.

ED
 
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