Bad Return Air Duct in Basement

5 years ago

last modified: 5 years ago

Hello Guys,

I need some guidance.

I have an 1800 sqft house in Canada. I just moved in, it's a 19-year-old semi-detach.

In the basement I have 2 vents 1 for Supply Air(in the living room) and 1 for Return Air(in the bedroom), I removed the vent cover for cleaning and found the following:

The boot duct was not connected to the cover. there was around a 3-5 inch difference.
I removed the boot duct as it was kinda broken. and found the air duct had 20 inches of top part cut off.

now what's happening is, because this return air duct is wide open between the drywall(basement ceiling) and floor(living room 1st floor). This space also leads to the Furness room(basement), which has 2 doors(1 in the basement bedroom, second in the basement living room), so basically, all the air from the Furness room and basement bedroom are sucked back in from this duct.

1 more imp thing is there is no return vent in the first floor/living room. I have 3 return vents on the top floor though(1 in the hallway and 2 in rooms).

I have few questions:

Should I seal this opening and make a vent out of it. if vent then how big of boot I needed, 4/5/6 inches?
is it a good idea to have a return vent in the basement bedroom and a Supply in the Basement Living room? or no return vent in the basement will work? I will be renting the basement out, so it's separate from other parts of the house.

in your opinion is this a bad design? Please advise what should I do.

let me know if something is not clear and I will update you with more details.

Thanks

Featured Answer

PRO

Charles Ross Homes

5 years ago

High-efficiency furnaces have a dedicated, ducted supply of outside air for combustion air and a dedicated exhaust. Your Lennox furnace has a lifetime warranty on the heat exchanger, so a corroded-through heat exchanger is not likely. Bottom line: it's possible, but not probable that your heat exchanger has failed; accordingly, the likelihood of combustion gases entering your home is minimal.

Proper HVAC creates balanced flows of supply and return air. The supply and return ducts should be continuous with the goal of providing the same amounts of supply and return air.

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Comments (8)

vinamra bhatnagar
Original Author
5 years ago
Hi Austin, it's a natural gas furnace. What are my options here. Patch the duct and put a boot to it? Or close it all together. But if I close it, it will increase the pressure in return duct, if this is true, do I need another vent in other part of home like living room to reduce the pressure?

Thanks
PRO
Austin Air Companie
5 years ago
last modified: 5 years ago
I will be renting the basement out, so it's separate from other parts of the house.

Based on what you say above... you need professional help. Canada isn't really known for "mild" winters.

Rental Real Estate is a long term game. The number one killer in a real estate portfollio is "liability".

If you weren't renting this out, the people you endanger are your own. CO is a colorless, odorless gas that can kill you. Not to scare you, these are facts.

Do yourself a favor and get professional help in your area. That furnace needs "combustion" air to work safely. If you plan to be a successful rental real estate tycoon, that is your way forward.
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mike_home
5 years ago
I want to confirm the return vent in the basement is a separate room. Is this correct? Is your furnace the high efficiency type where the combustion air is going from the outside through a PVC pipe? Is there a nearby hot water heater near the furnace? You want to make sure there is no back draft of air occurring. If there is a concern, then the return in the basement could probably be eliminated. You have to determine if there is enough return air coming from the one on the second floor. What is the size of your furnace?

I am not following the issue with the vent connections. If you are going to have returns and supplies there should be not gap between the drywall and the duct. A return in the first floor would be good to have, but in your house the three on the second floor may be sufficient.
vinamra bhatnagar
Original Author
5 years ago
Thanks, Mike,

Yes, it's kind of a separate room, drywall on all 4 sides with 2 doors and a vent for inverse pressure(that's what one HVAC guy said)(it's just an opening on the furnace room and living room.

Yes, the furnace is high efficiency type. (Lennox EL196E)

Yes, there is a hot water tank next to it.

Yes, there is a Rubatex insul Tube 180 3/4. I think this is where it's getting air for combustion.

Not sure how to measure the size of the furnace.

I have closed the front opening in the duct. I have left the top opening, now I think the air will be sucked in from there. the area between the duct and wood you see in the image(i think its called joist) is leading to the furnace room,

My concern is, this big of an opening is sucking all the air and the vents on the 2nd floor is not able to suck or are low on return air. if there is low suction on the 2nd floor then no return vent on the 1st floor can cause issues???
mike_home
5 years ago
I am not following what is in the photo. Does the duct in the photo connect back to the furnace return in another room? Why is preventing you from closing the top that is exposed to the joists and drywall and pull air through a vent in the basement?

When the furnace is running, can you feel air being pulled into the second floor return?
vinamra bhatnagar
Original Author
5 years ago
I am unable to close that because it's a furnessed basement and I need to demo quite some drywalls in order to reach to that top opening.

Yes I can feel the air sucked into the second floor return. I did the paper test and it stuck on the vent. But not sure if the suction was enough or this basement opening is sucking every thing.
PRO
CoolAir Inc.
5 years ago
You need a professional contractor to repair this. Delaying will be more problematic.