fireplace draw problem

[burr]

New member, stumbled on it searching for answers; although I've been in my single story house for twenty years, I've never used the fireplace. It doesn't draw. Hearth is at floor level, box is 34x34x19dp., 30w at the back, with 8x13 clay tile flue, and at the top, a 7" dia stovepipe about 18" long, is set and mortared over the flue opening.

I'm gonna burn wood this winter for heat, although I realize a open fp isn't going to get it. I would like to achieve a good draft, with no smoke when door closes, no strong smoke odor. This year, to improve the draft, I am installing a 'smoke guard' (5" wide), and building up the hearth two or three courses. A set of fireplace doors will act as the damper when retiring for bed. I had a chimneysweep over to inspect and he said a smaller firebox opening into the house should help the draft problem.

Can you advise on what I need to use this fireplace ? Eventually, I'm gonna find a used insert and heat the house, only 1,000sf.

I really need advise on:

smoke guard size, do they work, improve draft ? If I use thick gauge, will it be an effective heat sink to radiate into the room ?

Is there an ideal firebox opening size for this type description ?

What can I do with what I've got ?

 

[begreen]

Welcome burr. Let me guess, is this an exterior wall fireplace? How tall is the chimney and how high over the roof does it go? Is it a straight up flue or does it have an interior offset?

It's hard to say whether the smokeguard will make a big difference. If there are core issues with the chimney design, then a smokeguard may not help much. There are tricks for getting a balky chimney to start drafting like burning balls of newpaper up on the smoke shelf. If it were me, I wouldn't waste a lot of money on temporary fixes. Instead, I would be sure that everything I do is a step towards the final installation of an insert, with a proper liner.

If you can post pictures of the fireplace and another of the chimney, perhaps we can be of greater help.

 

[cmonSTART]

My thoughts exactly. Why pour money into something that isn't going to work well in the first place.

 

[Dix]

Burr, these guys are dead on, and telling you straight.

I danced with the FP last year.... it was a losing proposition.

Git 'er dun

 

[fossil]

Welcome, burr. I really don't think it much matters what you do with what you've got, it's not gonna get the job done for you. Even if you get it to draw, it's gonna just eat wood and expel the vast majority of the heat produced right up the chimney and out. After a good fire's been burning in it for a while, you'll get some radiant heat into the room, for sure, but you will have thrown away a whole lot more getting it to that point. Pretty late in the game this year to do anything dramatic with it, but I wouldn't put a lot of money & effort into it if it were mine and I was considering my options for the future. Chances are that whatever you do to it now you'll just turn around and rip out when the time for real improvement comes. Start learning about inserts and hearth stoves and finding out what your options are. A real useful appliance can be installed there, I'm sure. Rick

 

[jtp10181]

If you try to burn wood in that fireplace for heat, you will be very disappointed. It may heat the immediate area around the fireplace but it is also sucking so much air out of the house that cold air is going to leak in all over the house. This will actually cool off the rest of the house.

 

[burr]

Being down in SC, my heating needs are a little different from most of you all, it seems. Wood heating is the ultimate goal; having a workable firebox is the immediate goal. Firewood is available and free (well, not free, but mine). Woodheating / fireplace retail stores are far and few down here, not much choices except what one can find online. Same with wood heat knowledge and experience, some do it, but few do it as primary heat source. I know a couple or three, and two of those use wood as secondary heat source. This site is going to be a main source of learning thru experience of all the members and the comments and suggestion. That being said, I am not really in the position (at this time) to sink several thousand on heat source; now several thousand on cooling makes sense as we have all the summer I can handle nowadays.

OK, the particulars you were needing, single story brick home, exterior wall fireplace, chimney runs straight up, with iron damper in place, is app 18' above hearth, including a 2' stovepipe extension and common chimney cap, ending up 4' above roofline. As I said, house is only 1,000sf and living room that has fireplace is not big enough to hold a free standing wood heater; a small stander, backed up to the fireplace could work if I could tie into the existing chimney.

From what I understand with this topic so far, existing chimney is only useful for holding a SS liner, unless I am missing something. And from what I've read here already, the flue would be sealed with light gauge sheet metal skirt around this liner. After removing the damper, does the liner end after extending into the existing, or run to the top of chimney ?

Last night, I lit a fire with some nice small dry pine (from rough cut lumber scrap) and small dry split oak on a grate and it started nicely, and after starting good, I added a few pieces of split oak to build up the fire. After two hours, it seems that the fire had faded, and I was getting smoke into the room to an uncomfortable level. From what I have read here, the flue may have lost its heat, just a WAG. I've also read onsite that if the weather is not significantly cooler (than it is here on the Savannah River), draft becomes a problem.

OK people, be patient with me, I am a firebug at heart, just don't have it quite like you - YET ! Have a great Thanksgiving, eat good, and warm by the heater. Looks like a middle 60s cloudless day down here.

 

[thechimneysweep]

Hey Burr,

A couple of things jump out upon careful reading of your posts:

First, unless yours is a Rumford fireplace design (which the shallow depth might indicate), your fireplace opening width/height ratio is taller than the 3/2 rule of thumb used by most Masons: normally, we'd expect a 34" wide fireplace to be just 22" to 24" tall. This is probably why your Sweep is recommending a smoke guard, which has the affect of shortening the opening height.

Second, another brickmasonry rule of thumb suggests that the cross-sectional area of a rectangular fireplace flue should be about 1/10th the CSA of the fireplace opening. Doing the math, your 34 x 34 fireplace opening (1156 sq.in.) would need a 116 sq.in. flue. The existing 8 x 13 flue, at 104 sq.in., should be close enough, BUT... the 18" length of 7" pipe mortared on at the top of the chimney reduces the flue size at that point to just 38.5 inches! This nearly 2/3 reduction in flue size has gotta be restricting the draft considerably.

Here's what I think might be happening: as your fire dies down and flue gas temperatures drop, updraft strength decreases to the point where your undersize flue extension provides more airflow resistance than your oversize fireplace opening. Following the path of least resistance, the wood exhaust flows into the room.

Here's what I'd do:

First, remove that 7" stovepipe flue extension: it is not only restricting the exhaust flow, but causing the exhaust to cool prematurely, compounding your problem. If yours is a properly built Rumfoord, that should solve your backdrafting problem.

If that doesn't work, install a smoke guard that reduces the opening height to about 24 inches.

Should you decide to install a hearth stove or insert, your existing 8 x 13 flue will be much too large: you'll need to install a stainless liner, the same size as the flue collar on the stove, all the way to the top of the chimney.