I'm about to post finish product pictures in my basement finishing project.

I have a question though. When putting in duct covers my builder noted there was a cover for a return duct but no return. Only 4 hot air supplies. We also noticed when the heat is on in the basement the door from the basement going to our main floor basically flies open because of air pressure from the basement.

So a call to the original HVAC guy that did the original heating system(new construction a year ago) and he said the furnace gets air from outside, it doesn't need a return in the basement. A bit of reading and I also saw that returns in basements can cause backdrafting (a carbon monoxide concern).

So is this all legit? I'm not concerned unless this really would affect efficiency.

Update: I’m so glad I called the HVAC company that installed my system. They said they were waiting for the wall to be put in to connect the return. Even though it’s been a year they will be connecting it for me early next week at no charge since it was included in the price when built.

This message has been edited. Last edited by: frayedends,

I will let our resident HVAC guru comment but in all the houses we built we always had a return air in the lower level if it had supplies.

Do you have just one system for both levels and/or do you have more than one zone?

Never heard of any house not having a return per floor, but I am not an HVAC person and have no experience.

It is one system with 3 zones. We have the main floor (living room/kitchen), upstairs (bedrooms, bath), and basement. We had them add the basement zone when they built the house as we anticipated finishing the basement. There are 4 supplies to the basement and the controller separates the zones.

quote:

Originally posted by frayedends:
It is one system with 3 zones. We have the main floor (living room/kitchen), upstairs (bedrooms, bath), and basement. We had them add the basement zone when they built the house as we anticipated finishing the basement. There are 4 supplies to the basement and the controller separates the zones.

Then yes. Each zone should have at least one return if not more.

quote:

So a call to the original HVAC guy that did the original heating system(new construction a year ago) and he said the furnace gets air from outside, it doesn't need a return in the basement. A bit of reading and I also saw that returns in basements can cause backdrafting (a carbon monoxide concern).

You should probably find out what the code for HVAC is in MA.

Why would he put the vent in but not the line itself? Sounds like he tried to cut a corner. If you're within your 1 year builder's warranty, I'd have his butt out there installing a return.

Any floor that is supplied has to have at least 1 return duct, but that is the bare minimum. I have no idea what your local codes are. It’s best to have as close to one return per room as possible. And yes, it does affect efficiency and comfort, a lot.

You cannot put air into a room unless you can get it back out. Right now, your stairwell is functioning as your return, thus pushing the door open. As for the so called, “HVAC guy” that told you the system gets is air from the outside; he’s an idiot.

In commercial buildings, a percentage of outside air is required to be pulled in, but not so in residential systems. Put in a return equal in capacity to the sum total of supply feeding the space. If that’s not possible, and you want the door to stay closed, you can cut a return opening In The door and cover it on both sides with a return grill.

quote:

Originally posted by Nick:
You cannot put air into a room unless you can get it back out. Right now, your stairwell is functioning as your return, thus pushing the door open. As for the so called, “HVAC guy” that told you the system gets is air from the outside; he’s an idiot.

In commercial buildings, a percentage of outside air is required to be pulled in, but not so in residential systems. Put in a return equal in capacity to the sum total of supply feeding the space. If that’s not possible, and you want the door to stay closed, you can cut a return opening In The door and cover it on both sides with a return grill.

This, you can't push air into a room without some way for it to return. You didn't mention the size of the 4 ducts, but they would need a return, or in the old days they'd cut the bottom of the door to the basement 3/4" and it would return that way.

I believe you probably have several concerns.

Who talked with the HVAC guy?
I believe the question wasn't understood by the tech or the question wasn't relaying the exact concern.

I believe the tech was thinking 'combustion' air and not 'return' air. As 90+ furnaces can be piped to bring in outside air for combustion. Which is the way it should be done.

Return air is completely different. It comes from the structure.
The only outside air to possibly enter this duct would be for 'make-up or fresh' air intake. As stated above, required for commercial, not residential.

The real concern I have, is questioning whether the zone system is designed correctly. Is it allowing the proper air flow during a single call for heat from each zone. I'm willing to bet the basement isn't and highly doubt the other two are correct either.

What's the model number on the furnace?
What's the model number for the outside air conditioner?
What size is the 4 ducts in the basement?
Size of ducts for the main floor?
Size of ducts for the upstairs?
Is the supply ducts metal or flex?

The concern is equipment longevity!

Okay so without going crazy first I put a call into the company that installed the system. When it was installed they went over the aprilaire controller and explained it all to me. So I trust them. What I did just find (and no idea how I missed) is the return duct has an extra stub off of it that is sealed. I’m guessing this was meant to be the return for the basement.

From my reading about backdraft concerns it said there usually isn’t a return in open unfinished basements because return air too close to supply can be an issue. So I’m thinking this should have been connected once the rooms were separated. If I’m right this could be a very easy fix. The return stub is right near a wall that separates the basement rooms. I just need to make sure there is some zone control for the basement return so it doesn’t steal air from upstairs return when running. Other than that I could do this install.

Your assumptions are correct.
You can NOT pull return air from bathrooms, kitchens, utility or equipment rooms.

quote:

Originally posted by frayedends:
Okay so without going crazy first I put a call into the company that installed the system. When it was installed they went over the aprilaire controller and explained it all to me. So I trust them. What I did just find (and no idea how I missed) is the return duct has an extra stub off of it that is sealed. I’m guessing this was meant to be the return for the basement.

From my reading about backdraft concerns it said there usually isn’t a return in open unfinished basements because return air too close to supply can be an issue. So I’m thinking this should have been connected once the rooms were separated. If I’m right this could be a very easy fix. The return stub is right near a wall that separates the basement rooms. I just need to make sure there is some zone control for the basement return so it doesn’t steal air from upstairs return when running. Other than that I could do this install.

Yep, that makes sense... and I think most of us missed it that when the HVAC work was intially done the basement was unfinished...

I'm not the expert on this but some systems do bring outside air in (when needed) for the simple reason the industry has gotten this crazy idea that houses need to be air tight.... which in my limited opinion is stupid... in a 'perfect' (not) house that is 'air tight' then things like your kitchen and bathroom exhaust vents ... clothes dryer and fireplace or wood stove will not work. think about it they all require make up air to replace the air they are removing .... on top of that regardless of one's life style the air in a home is dirty and if you don't allow an air exchange ever couple of hours it can get down right dangerous....

Ahh I see. My original post wasn’t clear. When we built the house we anticipated finishing the basement so we had the heating zone put in to save time and money later.

Update in original post.

Nice! Your situation is actually quite common. Many not so good contractors that finish basements will only put a couple vents in with no return. Why? Because it is cheaper and easy and the WRONG way to do it. I have seen at least 10 finished basements that were one big room (home theater) with no return. Not the right way to do it but in a single zone house it will keep the basement warm although far from optimal.