When a Fireplace Smokes Indoors
LESLIE: Sandy in Texas is having some issues with the fireplace. Tell us about it.
SANDY: Yes, I have a fireplace that kind of goes through my living room and my kitchen; meaning you can see through it.
SANDY: And when I build a fire in the fireplace with logs and after it gets going a little bit it starts kind of smoking the house up and I want to know what is wrong with the fireplace. Do I need to lift the grate up and put some like fire bricks underneath it and get it up closer to the chimney or is there something wrong with the firebox through (ph) the opening’s not big enough or could you tell me what’s wrong?
TOM: It could be a number of things that are causing that. Do you live in a newer house, Sandy, or is it an older house?
SANDY: It’s an older house built back in the 60s.
TOM: Hmm. Well, because if you start to get a fireplace that’s smoking a lot then it’s a draft issue, obviously, and there …
LESLIE: It usually means the flue is cold.
TOM: Well, yeah. If it’s happening right on the startup, there’s a way to kind of work around that where you start the fire very slowly til you sort of heat the chimney up and that increases the draft. But if it’s happening after the chimney heats up there could be a number of issues. There could be a problem with the chimney design; it’s too high, it’s not high enough, it’s not capped properly. There could be an issue with the box design of the fireplace itself. There could be an issue with air pressures inside your house. If you don’t have enough makeup air, that could be causing the smoke to back up into the house as well. So this is a condition that takes a bit of experimentation. There are also ways that you can modify that firebox to increase the draft right there and help the air sort of speed up. I think what’s complicating it here for you – and if I’m understanding you correctly – is that you have, essentially, a two-sided fireplace. So it opens from two side.
SANDY: That’s correct. Yeah.
TOM: Yeah. So that makes it a little bit more difficult. So you’re going to have to try things one step at a time and see if it works.
Have you spoken with a certified chimney sweep on this?
SANDY: I had the chimney cleaned once and he said he didn’t see that there was any problem with it. And then I also had another person tell me that my return air unit on my air conditioner was too close.
TOM: Ah! That actually could be the cause.
LESLIE: That could be a major cause of it.
TOM: Have you noticed that when it starts to smoke that your HVAC system is on? When it starts to smoke the next time, I want you to turn your heating system off and see if it changes. Because if that’s causing it, it could be very dangerous. You could be sucking combustion gas into the house and that’ll make the whole house smoke up and it could also cause carbon monoxide to get into the entire house. So if that return duct is close to the fireplace, that could absolutely be causing this problem and if it’s inconsistent like that, you may find that it happens whenever the fan turns on and that return duct actually starts to draw house air back into the system.
SANDY: Mm-hmm. OK. How far should the return unit really be away from a fireplace?
TOM: Mm, at least on the other side of the room, I would think.
SANDY: OK. Well, it has – it’s on the other side of the room pertaining to the entry hall.
TOM: Listen, my recommendation is this. If you can – if you have a chimney contractor that you’re real comfortable with – and I’m talking about someone who’s a member of the Chimney Safety Institute –
TOM: – they should be able to diagnose this.
TOM: A second choice would be an HVAC contractor that can determine what’s happening with the air pressures in your house. Because for some reason, you’re not getting enough intake and that’s what the draft is – that’s why it’s backdrafting into the house.
LESLIE: Now the website for the certified chimney sweeps, Sandy, is CSIA.org and you should also, if you don’t already, get a carbon monoxide detector and place it somewhere on that first floor so that you know that you’re keeping your family safe.
SANDY: OK. Now, and he said something about the other one; about the air pressure in the house. Who would I contact about that?
TOM: Your heating and cooling contractors can test for that …
TOM: … and make sure you’re getting the proper draft.
SANDY: Oh, OK. OK.
TOM: See, houses always have air pressure. They have negative pressure, which means it’s less than the outside, or they have positive pressure; depending on how the winds are blowing over the house and things like that.
TOM: And what happens is if they get reversed you can get the draft on the chimney or even on the furnace or the water heater that gets reversed. If you have – for example, I’ve seen houses that have attic fans that when the attic fan is turned on, all of a sudden the fireplace stops working because it’s pulling so much air out of the house that it reverses the draft.
TOM: So making sure that the airflow is correct inside your house can prevent draft problems like that.
TOM: Start with a chimney sweep and take it from there. Sandy, thanks so much for calling us at 888-MONEY-PIT.