HVAC - modifying cold air return while finishing basement

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jfreeman
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Joined: Wed Sep 25, 2019 7:48 am

HVAC - modifying cold air return while finishing basement

Post by jfreeman » Mon Jan 06, 2020 11:40 am

Hi all,

I'm nearly done the framing portion of my basement-finishing project, and I'm trying to figure out the cold air return. We divided our basement into 3 rooms, and luckily the builder provided output vents for each area already.

For cold air return I have a single 6" pipe with a vent near the floor. Our walls worked out nicely in that the existing cold air return is very close to the T-intersection of two dividing walls. (See attached pic)

I *believe* a cold air return is needed for each habitable room, but my HVAC code knowledge is limited. My current idea is to split off the 6" pipe, and add ducting to 2 new vents. I'll add a valve in the existing vent to allow for some balancing. I'm assuming if the existing 6" return was sufficient for the volume of air of the entire basement, dividing it up between rooms should be okay, but this is an assumption.

As I am out of my element, if I might ask:

• Are cold air returns required for habitable rooms (TV room and office in this case)?
• Does this strategy seem okay or would you suggest something else?
• Can I split off of the existing 6" line, or do I need to tap into the main return trunk?

Any suggestions or advice would be welcomed. I may have to call in a pro but I wanted to check here first. Thank you all in advance for your help.
hvac return.png
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A. Spruce
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Re: HVAC - modifying cold air return while finishing basement

Post by A. Spruce » Mon Jan 06, 2020 7:19 pm

I do not know what the current codes are, but returns in every room seems redundant, overkill, and completely unnecessary. Generally, you only have a supply in rooms and have a 1" gap under doors for air to pass, thus giving you the "return" the system needs, and the actual return vent is place in a common area
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Shannon
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Re: HVAC - modifying cold air return while finishing basement

Post by Shannon » Mon Jan 06, 2020 8:12 pm

I actually don't know that it is code anywhere to have one in each room but it will increase efficiency of the forced air system. In most cases like Spruce said you want at least one per floor and centrally located. Leaving doors open as often as you can is great also if you have C/A returns centrally located.
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jfreeman
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Joined: Wed Sep 25, 2019 7:48 am

Re: HVAC - modifying cold air return while finishing basement

Post by jfreeman » Wed Jan 08, 2020 8:39 am

Thank you both for the feedback. It sounds like I might be over-thinking this. That makes sense about using the doors as a natural return path. I might still include the vents, but the ducting may be unnecessary - I guess as long as there is a path back to the existing return. Thanks guys, I'll check with the inspector and let you know how it turns out.

jfreeman
Posts: 14
Joined: Wed Sep 25, 2019 7:48 am

Re: HVAC - modifying cold air return while finishing basement

Post by jfreeman » Thu Jan 09, 2020 11:17 am

Hi again,

I just wanted to let you guys know I spoke with my inspector and he said the vent-only option is okay. So it looks like I was over-complicating things a bit. :) Thanks again for the feedback.

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Shannon
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Re: HVAC - modifying cold air return while finishing basement

Post by Shannon » Thu Jan 09, 2020 7:15 pm

perfect!
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