Basement vent and return sizing question


  #1  
Old 02-01-22, 07:31 AM
A
Member
Thread Starter
Join Date: Dec 2009
Location: Virginia
Posts: 138
Upvotes: 0
Received 0 Upvotes on 0 Posts
Basement vent and return sizing question

Hi All,
Doing a small basement finishing project. About 500 sqft, divided off from the HVAC/shop/storage area.

Basement fluctuates from 60F in the winter to 72F in the summer. Summer brings more humidity than I like, but wall panel insulation (with some vapor restriction) and a full vapor barrier on the floor before the LVP flooring should tamp that down. Really I just want some air movement with possibly a little heat in the winter.

Based on that, I'd like to tap the hot side trunk (main floor) and do a single vent at the far end of the room and then cut a return at the other end towards the floor. The hot side gets about 25% flow during the cooling season when I flip the dampers.

I had some questions:
Should the vent and return be the same size in this setup?
What size return should I use for the basement? My main floor has 290 sq-in return and the 2nd floor has 370 sq-in one. Since the basement return will be much closer to the furnace, I don't want it to pull too hard from the other floors.
I was going to put a damper on the air return to help balance the load, but never see this done (only trunk line and register dampers). Will that work, or is there a reason to never constrict the return air flow?

I'm sure I'll have more questions. Again, not looking to get the basement to 70 degrees, just keep air moving.
Thanks.
 

Last edited by arc2v; 02-01-22 at 07:33 AM. Reason: typos
  #2  
Old 02-01-22, 02:21 PM
coolmen's Avatar
Member
Join Date: May 2006
Location: usa
Posts: 126
Received 5 Upvotes on 5 Posts
Basements if 5ft or more below grade dont need many btus.
I would run a low 7" or even 8" pipe and connect with a say 14x8 low on wall. ( cold winter air traps)
2 supply runs 5" 6x10 ceiling boots with balancing dampers.
 
  #3  
Old 02-02-22, 06:01 AM
A
Member
Thread Starter
Join Date: Dec 2009
Location: Virginia
Posts: 138
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thanks.

Looking at the joist layout and such, I think I can get a 6" duct to the far corner (have to do flexible or else I'd have three takeoffs in a 2' stretch, with flexible, I can go upstream and still get around some obstacles).

Still looking for where I can tap a second duct.

The return will be right next to the furnace but opposite a full wall.
 
  #4  
Old 09-28-22, 06:30 AM
A
Member
Thread Starter
Join Date: Dec 2009
Location: Virginia
Posts: 138
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thanks again for the advice.

With the return so close to the air handler, should I use excess flex duct for noise mitigation?
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: