Is fireplace efficiency really that bad?

[Seasoned Oak]

I was always under the impression fireplace efficiency was horrible hearing single digits and some claims that you lose more heat than you gain. Friend of mine had his fireplace going yesterday one of those with the steel lined firebox but no double wall or fans or vents,just the lever to close off the chimney when not in use. THis thing was throwing so much heat that he had to open the main entrance door to let some outside. Was about mid 30s outside and the house was 80+ with just a few small logs burning slowly. House is split level about 2000 SF so-so insulation none between the floor and an unheated BSMT. 40 Year old house with heat pump and electric BU.
He claims the trick is to just open the flue just enough so the smoke exits but not too much so all your heat goes with it.

 

[branchburner]

He claims the trick is to just open the flue just enough so the smoke exits but not too much so all your heat goes with it.

The key is how much air is consumed by combustion and/or goes out the chimney, because that equals the amount of cold air coming in (through cracks, etc.). When we had our oil forced hot air running with the fireplace going full bore on a cold day, I'll bet there were times we had a negative efficiency (if you count the oil).

 

[RedGuy]

I was always under the impression fireplace efficiency was horrible hearing single digits and some claims that you lose more heat than you gain. Friend of mine had his fireplace going yesterday one of those with the steel lined firebox but no double wall or fans or vents,just the lever to close off the chimney when not in use. THis thing was throwing so much heat that he had to open the main entrance door to let some outside. Was about mid 30s outside and the house was 80+ with just a few small logs burning slowly. House is split level about 2000 SF so-so insulation none between the floor and an unheated BSMT. 40 Year old house with heat pump and electric BU.
He claims the trick is to just open the flue just enough so the smoke exits but not too much so all your heat goes with it.

It's really bad! Last year I experimented heating my home with the fireplace alone. In 2 days I burned a whole face cord! This was furnace off, 1,800sqft in January with the temps in the mid 20's. To keep the whole house warm with that fire place there had to be a ROARING fire 24/7. Now take into the effect that that when a fire dies out at night and the damper is still open when you go to bed, come morning I'd be willing to say your actuall efficency is negative with the heat you lost up the chimney at night.

 

[peakbagger]

While the fireplace is running, it can give off reasonable heat, but when the fire starts to go out, the damper has to be left open for a long time until the fire is completely out. That is when the chimney really sucks the heat out of the house. My father used to have a asbestos cement board "plug" that he could install in the fireplace opening when the fire was going out. He would leave it overnight and then shut the damper in the morning when the fire was complety out. It made a big difference.

 

[Dakotas Dad]

Ice storm of '09. No electricity for 8 days. Fireplace only. Burned nearly a full cord, kept house above freezing. Feb. '10, same time of year, but now with wood stove. For that "same" week, we never had the heat pump on, burned less than a half a rick, house at 72+ degrees the whole time.

Yes their efficiency really is that bad.

 

[ansehnlich1]

I was always under the impression fireplace efficiency was horrible hearing single digits and some claims that you lose more heat than you gain. Friend of mine had his fireplace going yesterday one of those with the steel lined firebox but no double wall or fans or vents,just the lever to close off the chimney when not in use. THis thing was throwing so much heat that he had to open the main entrance door to let some outside. Was about mid 30s outside and the house was 80+ with just a few small logs burning slowly. House is split level about 2000 SF so-so insulation none between the floor and an unheated BSMT. 40 Year old house with heat pump and electric BU.
He claims the trick is to just open the flue just enough so the smoke exits but not too much so all your heat goes with it.

AMAZING :roll:

I'm an old opinionated Pennsylvania Dutchman and I say BS.

 

[blades]

The mfg's of the newer prefab units are aware and are addressing that issue. In one of my homes, in the past, I had an absolutly great looking fireplace. It also had a 13" diameter flue ( Inside Dia.) It would create a gale force breeze across your feet when used. I installed an insert ( box store unit, no idea as to mfg anymore , inexpensive $ 350) to reduce the size of it and it did help as it would circulate air around the firebox and back into the room, but I still had the issue of combustion air being drawn from inside the house although much reduced.

 

[fishingpol]

I've read on different websites that the efficency can be between 10-15%. I did a bit of research before deciding on a wood stove. There is something pretty cool about big open flames in the firebox with the snapping and crackle of the fire.

I do miss using the fireplace, but I feel the money is better spent on a stove with secondary combustion. Neighbor commented one night several years ago that the embers exiting the chimney reminded him of visiting his grandparents house when he was little. I think he meant put a screen cap on it before you light the neighborhood on fire in a friendly neighborly way.

You can sit anywhere in a room with a wood stove and feel the warmth. The fireplace required you to sit in front of it to feel the warmth. One mason told me that a russian fireplace is designed to slow flue gases down exiting the chimney radiating heat to the brick and into the room like a heat sink.

 

[My Oslo heats my home]

I think todays stoves are incredible, they have come so far over the years. To comment on efficiency just a bit. To be a stove owner/user over a period of years and to know the pros and cons of stove use is to be the efficient user. My first year of burning compared to my 5th year of burning is like night and day in the efficiency department and thats with no credit to the stove. Things learned here and things learned by trial and error make the user the more efficent burner in my opinion.

 

[weatherguy]

What would the efficiency be if you installed an air tight door? Anyone try this or have any idea?

 

[fjord]

Yes, often negative efficiency, since air is literally sucked out of the room with little transfer.

 

[BrotherBart]

I had my last fireplace in 1976. Went through a whole lot of wood with that thing in a two story condo we rented and got zip for heat except in the room it was in. When we had the first house built in 1977 it was the only one for miles without a fireplace. The builder and I fought daily about that. I had it built with a hearth and double wall pipe through the roof. Had the wood stove installed the day after closing. So I can't tell you of any tests I have done of fireplace efficiency in the last 35 years.

This house had a fireplace already and was about half finished when we bought it. Again, the big honkin insert was installed the day after closing.

 

[Todd]

What would the efficiency be if you installed an air tight door? Anyone try this or have any idea?

I did this with my old 1975 Superior Heatform masonry fireplace. It had the lower return vents and top supply vent and along with outside combustion air and airtight doors I could get the house up to 90 if I wanted. It ate wood fast but it was nice to have a back up for the basement Fireview at times. I'm guessing it had to be close to 50% efficient? I replaced the fireplace with a Woodstock Keystone this year because the old fireplace rusted out.

 

[nola mike]

well, i just replaced my heatilator with a stove insert, and it's night and day in terms of output, even with the new smaller firebox. with the heatilator, it took a lot of wood and a roaring fire to get anything except the radiant heat--even then, i couldn't keep the house warm. still haven't had any real cold nights yet, but this thing warmed the house with a hot fire, and kept the temp maintainted with it choked off with temps in the mid-30's. heatilator + 30' temps= heat pump on all the time.

 

[midwestcoast]

I've seen everything from 15% to -10% sighted. My take is that the lowest #'s are ussually from articles about ways to save energy & they really have to work to get down into the -digits. assume you leave the damper open all night with a dead fire, include significant air leakage past the closed damper continuously, that sort of thing.
I think what you witnessed was your friend burning a lot of wood at low efficiency to heat the house.
Also the FP wasn't designed to run with the damper part closed, that's a bit of a dangerous game IMO.

 

[Seasoned Oak]

I've seen everything from 15% to -10% sighted. My take is that the lowest #'s are ussually from articles about ways to save energy & they really have to work to get down into the -digits. assume you leave the damper open all night with a dead fire, include significant air leakage past the closed damper continuously, that sort of thing.
I think what you witnessed was your friend burning a lot of wood at low efficiency to heat the house.
Also the FP wasn't designed to run with the damper part closed, that's a bit of a dangerous game IMO.

The Damper was not closed but just open enough to pull the smoke out probably about 1/3 open. Judging from the replies here i probably should forget about any thoughts of putting in a fireplace as a Home Heater, but they are nice for the ambiance.

 

[Seasoned Oak]

So Where do Inserts fall in the efficiency scale somewhere in between a fireplace and a secondary burn stove? Im sure they are not quite as good a heater as a stand alone stove, unless the have a good fan forced air system to get the heat out into the room.

 

[Seasoned Oak]

I've read on different websites that the efficency can be between 10-15%. I did a bit of research before deciding on a wood stove. There is something pretty cool about big open flames in the firebox with the snapping and crackle of the fire.

I do miss using the fireplace, but I feel the money is better spent on a stove with secondary combustion. Neighbor commented one night several years ago that the embers exiting the chimney reminded him of visiting his grandparents house when he was little. I think he meant put a screen cap on it before you light the neighborhood on fire in a friendly neighborly way.

You can sit anywhere in a room with a wood stove and feel the warmth. The fireplace required you to sit in front of it to feel the warmth. One mason told me that a russian fireplace is designed to slow flue gases down exiting the chimney radiating heat to the brick and into the room like a heat sink.

I guess ill have to settle for the next best thing which is my harman TL-300 which has an option to use it as an open flame stove when using the fireplace screen which i purchased along with the stove. You just open the bypass,then the front door,popin the screen and Wala open fire

 

[mcollect]

We have a modern home with 10 to 14 foot window walls. We have a double sided fireplace between the living room and dining room. For the first twelve years we used the fireplace for ambiance, the house has infloor heat and starting at 70' the fires would lower the temps to 65 but by morning the main floor would be at 60. I got grief about not allowing spousal unit to light a fire on cold nights. Two Christmases ago I gave her a choice of a wood stove or an insert. She fell in love with the Jotul 550. It was installed in Feb and the learning curve began. Now we have a fire all the time and the propane heating system hardly ever comes on. Wood is cheap here at $150 a cord delivered. I also cut and she splits our wood. Never look back on"her" present. five cords split and ready for next year!

 

[Seasoned Oak]

Yes, often negative efficiency, since air is literally sucked out of the room with little transfer.

I get your comment to mean the heat you get is less than the warm air you lose up the flue. But as far as air goes
Air is sucked out of the room by every fuel burning furnace. Unless you have one of those expensive air to air exchangers they put in new airtight houses,or a direct outside air supply pipe going to your stove.
Probably the closest you can get to the fireplace magic while still getting significant heat output is a good insert.

 

[gibson]

So Where do Inserts fall in the efficiency scale somewhere in between a fireplace and a secondary burn stove? Im sure they are not quite as good a heater as a stand alone stove, unless the have a good fan forced air system to get the heat out into the room.

Inserts are OK in "shoulder season" and great in cold weather when burned 24/7. Since they are in the hearth, they have to heat up all of that wall mass and stone to get any kind of radiance, convective heat with the blower is good always. Conversely, a stove provides so much radiant heat, you may not be able to be in the room with it. A fireplace is nice to look at, but I burned in mine for one year before I said "enough". The draft going into the fireplace was enough to freeze your feet. Waste of wood as well.

 

[Seasoned Oak]

So Where do Inserts fall in the efficiency scale somewhere in between a fireplace and a secondary burn stove? Im sure they are not quite as good a heater as a stand alone stove, unless the have a good fan forced air system to get the heat out into the room.

Inserts are OK in "shoulder season" and great in cold weather when burned 24/7. Since they are in the hearth, they have to heat up all of that wall mass and stone to get any kind of radiance, convective heat with the blower is good always. Conversely, a stove provides so much radiant heat, you may not be able to be in the room with it. A fireplace is nice to look at, but I burned in mine for one year before I said "enough". The draft going into the fireplace was enough to freeze your feet. Waste of wood as well.

Im thinking about building a fireplace just to use an insert in it.
I like the look of an insert but im wondering if the heat output is close to that of a free standing stove.
THe insert cousin of my stove THe TL-300 is the 300i.Its the same weight,the same size firebox, Its rated the exact same BTU factor 75000,and also the same heating capacity 1500-3000 Sq Ft.Can i take this to mean both stoves will throw the same amount of heat from a given amount of wood? Its got dual 120 cfm blowers to push the heat out the front and into the room. I guess only a chimney temp gauge would tell the tale. Both stoves allow the option to open the door and use an optional spark screen for that open fire feel

 

[nate379]

I was at my friends for Thanksgiving meal last weekend (yeah did it early) and in the 4-5 hrs I was there he ran through more wood in his fire place than I'd use in 2-3 days in my stove.

 

[weatherguy]

Im thinking about building a fireplace just to use an insert in it.
I like the look of an insert but im wondering if the heat output is close to that of a free standing stove.
THe insert cousin of my stove THe TL-300 is the 300i.Its the same weight,the same size firebox, Its rated the exact same BTU factor 75000,and also the same heating capacity 1500-3000 Sq Ft.Can i take this to mean both stoves will throw the same amount of heat from a given amount of wood? Its got dual 120 cfm blowers to push the heat out the front and into the room. I guess only a chimney temp gauge would tell the tale. Both stoves allow the option to open the door and use an optional spark screen for that open fire feel

Im doing the bulk of my heating with my BK Princess insert and I have about 2800+ sf.

 

[Seasoned Oak]

Im thinking about building a fireplace just to use an insert in it.
I like the look of an insert but im wondering if the heat output is close to that of a free standing stove.
THe insert cousin of my stove THe TL-300 is the 300i.Its the same weight,the same size firebox, Its rated the exact same BTU factor 75000,and also the same heating capacity 1500-3000 Sq Ft.Can i take this to mean both stoves will throw the same amount of heat from a given amount of wood? Its got dual 120 cfm blowers to push the heat out the front and into the room. I guess only a chimney temp gauge would tell the tale. Both stoves allow the option to open the door and use an optional spark screen for that open fire feel

Im doing the bulk of my heating with my BK Princess insert and I have about 2800+ sf.

That answers the question of "are they capable"
What im wondering is would you use the same amount of wood and get the same heat output if you were using the same stove in a free standing model?
In other words is there an efficiency penalty using an insert vs a free standing and if so what is it?