Basement air return...

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  #1  
Old 01-09-21, 09:02 PM
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Basement air return...

I've seen this topic come up in a few searches but none seem to fit this situation. I understand that each floor should have at least one return and that this includes the basement.

I'm finishing half of my 900 sq ft basement. Half fully finished and half unfinished utility/work room.

There is a wall basically down the middle that I framed and (mostly) insulated. There are no forced air heating vents in the utility area.

In the finished zone I have in-floor heating. There is a the original ceiling heat vent serviced by a 4 inch duct. Additionally, I added a floor level heat vent serviced 5 inch duct.

In the unheated utility room where the furnace is located, is original, ceiling mounted air return.

Questions:

- I assume I should at least bring the return vent in the unheated utility room down to near floor level?

- Does the heated, finished room require its own return vent connected to the return duct? (not sure if that's possible)
or
- If not should I install a grille at floor level... allowing return air to flow from the heated finished room to the unheated utility room? (along with lowering the return in the unheated room)

- Are there any potential problems that could arise from leaving a basement room unheated? Primarily on the dividing wall?

Thanks as always.... I'm putting a lot of time and effort into this basement and I don't want to fall down because I overlooked some detail.


 
  #2  
Old 01-10-21, 02:02 AM
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In the finished zone I have in-floor heating.
If you have in floor heating then technically you do not need any venting!

I assume I should at least bring the return vent in the unheated utility room down to near floor level?
You can, its not critical, air will be pulled from either location.

Are there any potential problems that could arise from leaving a basement room unheated?
Room will maintain a basic ground temp, approx 55-60 degrees.
 
  #3  
Old 01-10-21, 08:19 AM
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Thanks. I would have though leaving the return on the ceiling would have it pull in the warmer air. I suppose given that room isnít heated makes it less of an issue

I had no idea the floor heating made the return unnecessary. I assumed it was a must regardless
 
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Old 01-11-21, 08:41 AM
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Despite the floor heating, air circulation, filtration, and removal of humidity are all things you would want in a basement. At the very least, I would move the return in the utility room down to floor level then install a louvered door or cut a hole in the existing door and install a grill. Second best, in my opinion, would be to block off the utility return and install a new one in the finished area at floor level and across from the supply registers so you're pulling air across the room.

I was in a similar predicament when I bought my home, except there was no return in the basement at all (basement is 3/4 finished with 1/4 being a utility room). I initially planned on installing a return in the utility room and installing a grill in the door, but decided against it because I use the utility room for woodworking on occasion, so I put the return in the finished area. I leave the utility room door cracked for circulation and close it when woodworking. Has worked fine.
 
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Old 01-11-21, 10:38 AM
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I really would like to have some air flowing through. I'm thinking along the same lines of blocking the return in the utility room and installing one in the finished area. The only thing is that the layout makes if very tricky. I may need to install a return duct in the riser of the bottom step on the stairs. Even with that I doubt I'll be able to fit more than a 2-1'4" by 12" grill serviced by 4" duct back to the return. It's significantly less than what's feeding into the finished areas, but there will be air flow at least.
 
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Old 01-11-21, 11:33 AM
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2-1/4" x 12" with a 4" duct isn't going to cut it. Can you post pics of your area or a sketch so we can see what you're working with?
 
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Old 01-11-21, 12:21 PM
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mossman Thanks. I just went back to take a look. Outside of the stair riser I have one, pretty small spot where I can go through. I hope these pics illustrate it.

I can put a takeoff at this spot on the return near the top of the stairs.



I run that across the top riser and down the stringer on the wall that divides the finished and unfinished spaces.



Then down near the bottom there's a small space between the post on the left and stud on the right where I can poke through. The space between the two is 10".



I think I have enough room to do the whole thing with 8" round duct. I'm hoping that's big enough.

This spot would place the return roughly in the middle of the room.... The supply vents are on either end of the room so this would pull air from either to the middle.

On a quick look the only boot I can find is this expensive thing but I suppose I can even just fasten another 8" takeoff to the drywall and put a grill on the other side?

I'd appreciate your thoughts.
 
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Old 01-11-21, 01:09 PM
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To add to the frustration.... I can't find 8" takeoffs and unions anywhere. 6" is the best I can do at the big box stores. I'm calling around to local sheet metal shops not.
 
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Old 01-11-21, 06:40 PM
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I'm confused as to what your layout is and why the stairs is the only option to install a return duct. Is there a block wall separating the utility room from the finished area?
 
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Old 01-11-21, 07:31 PM
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Maybe this will better illustrate.

 
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Old 01-11-21, 11:29 PM
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Ah, I see the issue now. That's a tough one. I'm thinking a properly sized return in the utility room with a fully louvered door may be your best bet.
 
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Old 01-13-21, 10:07 AM
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With the finished section heated and the unfinished section not heated, have the return vent (as well as the heat registers) all in the finished section. Close off the return vent in the unfinished area.

Returning air from the unheated section means heated air has to be added to that section for make up. This will increase the heatable square footage and in turn increase your heating bill possibly unnecessarily.

(Without solid doors that can close off the finished area, scratch the preceding.)
 

Last edited by AllanJ; 01-13-21 at 10:22 AM.
  #13  
Old 01-13-21, 11:56 AM
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I do spend a little time in the utility room so I donít have a problem allowing some return air pass through there.... it wonít be quite as cold and Iím hoping provide for a bit of air flow.
 
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Old 01-21-21, 01:06 PM
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I just noticed the insulation in the wall separating the utility room from the rec room. Is this a below ground basement? Are the foundation walls not insulated? I would think you'd want the temperature in your utility room to be comfortable as well.
 
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Old 01-21-21, 03:40 PM
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Thanks. Yes, the foundation walls and rim joists have 3 inches of spray foam
 
 

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