Heating & Air Conditioning Design Dilemma

Removing A Few Return Air Ducts

2 years ago

Hello We are renovating a townhouse that is very linear - almost like a shot-gun style house. The house is 11 years old. On the first floor we have four return air vents. (1000 square feet). On the first floor, the vents are along the shared wall of our townhouse, with maybe 25 feet between each one. On the second floor we also have four return air vents - one in hallway, and one in the center of the ceiling of each bedroom. They look terrible! As part of the renovation, I would love to remove a few of these vents. Is this possible? I am going to call an HVAC professional but thought I would ask if anyone has experience with this. I've been reading that you really only need one per floor. Thanks!

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Comments (6)

Elmer J Fudd
2 years ago
last modified: 2 years ago
The number and placement of the returns are for function, not appearance. It sounds like you have a well-designed system, one intended to operate properly. I wouldn't mess with them, you'll easily handicap the intended air flow. Not infrequently, people buy new homes and ADD returns when doing HVAC work to improve airflow and function.

PS - The ones in the bedrooms ensure good air flow with closed doors. A very useful feature.
arcy_gw
2 years ago
Code dictates such things for healthy air reasons. We all have them. No one focuses on them. I did see an idea where a designer took a thin piece of wall board, painted/wall papered to match the wall then put spacers in the four corners then attached it over the duct grates. If you really are that anal about them, try that.
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you need to go back to the main trunk line. air travels the path of least resistance. if you tap off of another return line and one is shorter than the other the air will mostly be drawn from that one. not to mention you are restricted by the size of the return run you are taking it from. it will work better coming off of main trunk line.
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Congratulations on your new house. I will start by saying I have merv6 pre-filter and merv10 high effeciency filter just as you describe. Were I having allergy problems I would go up to 8 & 15. I had/have benifit of air flow and tempature differential testing which shows there is no concurns with restriction. What those who rally against good filters fail taking in to consideration is that if you pull a pleat filter out flat,there is a lot of surface area. 1) Is this the installing contactor advocating the removal of pre-filters?????? I would think the collective square inches of pre-filter would alow free flow unless the returns are under size to begain with. The only way to know is by calculating minium return size then compare to what is in place. 10 to 15% extra return size is prudent just as insurance in case of mistake ( such as omitting a turn in data) while calculating duct work. The installer should have done the calculations. If a secound contractor is challenging those,you need more and different help than can be found on the net. Don't waste money on cheapies. 2) I see no advantage in removing 1 or 2 while leaving another in place,unless the single remaining filter is in an exceptionaly dirty area. 3) There is no "rule of thumb"interval. You can establish your model through inspection of the filter(s). On a pleated filter,the bottom of vees will collect 95% of impurities starting out. As time passes,you can easyly see the grey collection creep from bottom of pleat toward top of pleat. The filter should be changed before the upper 1/3rd of pleat is covered in enough dust to hide the color of filter. The time required for that transisition on 5" will be much longer i you choose to use pre-filters. There is a very real possibility that the installing contractor put filters in the intakes to prevent construction materials getting into returns. It is possible he intended to abandon the 3 intake filters after home was complete. Discuss this with the installer to get best answers.
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your hvac company that has seen you situation has a better view of what is going on than we do...just saying...but "First question, what should be done with this? I assume I should cap it off as low as possible since I cannot remove it from the cinderblock basement wall without leaving a hole. My HVAC contractor who replaced our AC last year said he can cap it with sheet metal." if it truly is abandoned then cap it off as close to the plenum as possible. insuate the cap (sheetmetal) and mastic seal the cap. fyi all ducts should be mastic sealed. "Second question, is there any purpose to this duct? I assume sucking in non-heated or non-AC air only makes the HVAC system work harder to maintain the appropriate air temp in the living areas since this area is not all insulated." hard to say without seeing the duct & surrounding areas. your assumption that the duct sucking in non filtered non conditioned air is right. 'Third question, should I insulate this space while I have it open? ' is this an exterior wall? I always insulate. Realistically I know that insulating one area of a wall when the rest of the wall may not have any insulation ..doesn't do a whole lot. its just the way I work. always air seal, always insulate. best of luck.
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Iowa, you must have a basement and returns could be "easier" to relocate. Hopefully, those are just returning the CFM required for that room and not the entire house. Be aware that with 18' walls there will be blocking somewhere above those vents or something framing in from whatever's on the other side of that wall which might prevent you from raising the vents up higher (at least easily). A well-advised HVAC designer (not equipment tech) can review the size of both stud space openings through the floor for each vent and possibly find another location/combine a couple if you can meet the CFM flow. The location to the left of FP is too close to the floor register IMO anyway.
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Elmer J Fudd
2 years ago
last modified: 2 years ago
I don't think building codes address the number or placement of return air ducts.

Those decisions are made in the design of each system. Knowledge and experience are involved along with industry tools (to calculate duct sizes, as an example) and with attention to equipment requirements to determine what is needed to handle required flow. But there's not anything more that I know of.
mike_home
2 years ago
It is possible to remove returns, but then you would need to increase the size of those that remain. Having a return is a bedroom provides good air flow with the door closed. That is a nice feature which most houses do not have.

You could move the vent from the center to the ceiling to a spot above the doorway. It would be less noticeable. Painting the vent cover the same color as the ceiling also makes it less noticeable.
littlebug zone 5 Missouri
2 years ago
A 25 x 35 family room was built on my house several years before we bought it. It has its own furnace. There are only 2 air returns (side by side in the floor) in the room.

Our HVAC man fusses about those returns every time he’s here checking the furnace. He says we need 2 more.

Could you take a picture? I can’t imagine what a ”terrible air return” looks like so that it annoys you so much.
kandrewspa
2 years ago
In addition to painting the vent cover to match the wall, painting the interior of the duct (just the part right behind the grill) makes it even less noticable. While you should definitely seek out the advice of a professional, I wouldn't remove any of them. Our first house was built in 1910 and thus the forced air system was added later. It had inadequate returns and it was impossible to get the temperature to be the same throughout the house. It was very annoying. Since your house is only 11 years old it was probably built state of the art at that time which is a good thing.

Removing A Few Return Air Ducts

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Elmer J Fudd

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