Return duct options for bedrooms

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Old 12-22-16, 04:56 AM
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Return duct options for bedrooms

I have three upstairs bedrooms in a townhome. They have 1 or 2 supply ducts in the floor (6") each, however the only return duct is in the hallway. When BR doors are closed return air is very minimal, only what flows under the door. Would vents through the wall over the door provide adequate return air and improve comfort? If so, what size, and is there a vent style that would still guarantee privacy, too? Or would I need to look at going in to the attic and running additional return ducts?
 
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Old 12-22-16, 05:45 AM
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I have added return air flow paths several times and it works quite well. I locate the joist bays within the wall and cut a hole in the inside and outside the room within the same joist bay. Offset them so one is at floor level and the other near the ceiling for privacy and cover with a decorative grate.

My office has a similar problem and I had a lot of wall to work with so I installed two grates in the office side. One grate near the floor and one near the ceiling and the grates of closeable louvers. In summer I open the one near the ceiling and in winter the one near the floor.
 
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Old 12-23-16, 08:37 AM
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I don't have a lot of wall space to work with only the wall above the door. Is a 5/8 inch Gap under the door adequate return air flow for a 6 inch duct?
 
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Old 12-23-16, 10:00 AM
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It is far too common for homes to end up with insufficient return capacity. If you add up all of the current supply ducts and compare them to your return capacity it is already less. The 5/8" is shy of what you would want for one supply register and way shy for two. BUT, once the air gets to the hall is there currently enough return capacity.

Backing up, what concern are you addressing?

Bud
 
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Old 01-08-17, 09:39 AM
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Apologize for a late reply to your questions, but had to drop this project for a few weeks, although I have been thinking about your questions.

The return trunk is sized larger than the supply by about 10%, and the three return vents add up to the same area as the trunk. I measured the duct inside the grills.

I am trying to ensure adequate return air flow in this bedroom. I have concluded that summer vs. winter there are different return air requirements in this room. In the winter the return under the door is useful as falling cold air gets pushed under the door to the hallway. In the summer the effect is the opposite and the hot air rises and stays in the room and cooler air flows out under the door.

A vent above the door might be helpful in summer to vent the rising hot air out.

Would a damper system be needed to address the different seasons? e.g. to switch from venting return above door in summer, to below the door in winter.

Is there a neat-o design of such a system?

And I have another question regarding a basement room, but I will start a new thread...
 
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