Heat Escaping Up Chimney?

[ryanm527]

I recently had a hearthstone mansfield installed. Been pretty happy with it overall, however the only way we're able to keep the room, let alone any adjacent rooms warm is by placing a fan next to the unit. The house is 135 yrs old and very poorly insulated, and has LOTS of single pane windows. Even with the fan, the unit only keeps the one room 'comfortable' and its a 18x18 or so sized room.

The Mansfield is installed in an old open fireplace, with the flu running up the chimney. I am concerned that a lot of the heat is going up the chimney instead of out into the room. I asked the installer if he should seal the bottom of the chimney and he said this was a typical installation and since the chimney was sealed at the top the heat was not technically lost; it would just heat up the structure, and thus warm the house. Which makes sense to a degree, but i think he is underestimating just how drafty and cold this old stone house gets and how hard it is to keep it warm once it gets cold.

Not sure if I should pressure him to come back and seal the bottom of the chimney, or if I need to consider a blower or if perhaps a radiant type wood stove was not the ideal fit for this house. Anyone have any thoughts or experience with a similar installation?

 

[BrotherBart]

I have a stove in a fireplace and cannot imagine not having a block off plate at the damper frame. Info here:

https://www.hearth.com/econtent/index.php/wiki/Why_damper_seal_is_needed/

 

[heatwise]

we have our phoenix out in the room on a hearth pad with a tee connected to the liner and a couple feet of pipe running to the stove. our installer also share's the same theory yours does and we dont have a block off plate either. our place is very drafty and poorly insulated but we are able to raise the temps inside to battle the coldest of days. this takes up a bit of space in the room but i feel it lets the heat rise and circulate extremely well. i must add that you have a nice stove that looks great. best of luck on getting the most heat from it . pete

 

[ryanm527]

Thanks guys for the input. I wouldn't be quite as concerned about it if it were further out into the room like the setup you are describing. But being almost completely inside the fireplace opening it just seems like so much of the heat is going straight up the chimney instead of into the room.

Is it typical to need a fan to get any substantial heat from the unit into the room? Even right now i've got a roaring fire going and if I open the door to add wood it nearly burns my arm off but sitting on the couch 5 feet away we're still chilly.

 

[shawneyboy]

I have the Mansfield and I can tell you if you are burning correctly your heat must be going somewhere. I burn with a stove top temp about 525 on a full load and easily heat my 2 story home. I am wondering if you have a thermo and what temps you hit. I would think since you do not have the stove fan, which would move warm air into the room, the majority of your BTUs are going up the chimney. Granted the BTUs may not be escaping since it is "sealed" at the top but........ you are expending an awful lot of those BTUs to warm the mass of the chimney. What type of chimney is it?? Is it on an external wall of the building? If so you are losing all sorts of heat there. The blower fan will most definately help but you also NEED a blockoff plate IMHO.

 

[Huskyforlife]

Add a blockoff plate and insulate with rock wool above it. You will notice a large difference.

 

[CTYank]

You're trying to "shovel s#it against the tide" so to speak, trying to heat a leaky uninsulated house. Simply throwing away lots of fuel. Until you can properly address the real issues, you might try partitioning off part of the house- like a few rooms adjoining the one with the stove - with curtains, so you're trying to heat only that space.

Given that your fluE ("flu" is short form for influenza, a viral disease) is sealed at the chimney top, most all of the heat lost through the chimney is radiated/conducted from the flue pipe in the chimney. Sealing the flue in the chimney at the damper would then have no effect on losses.

Your losses are addressed up top.

Meanwhile layers of clothing will help retain heat released by body. You could increase both.

 

[mellow]

Given that your fluE ("flu" is short form for influenza, a viral disease) is sealed at the chimney top, most all of the heat lost through the chimney is radiated/conducted from the flue pipe in the chimney. Sealing the flue in the chimney at the damper would then have no effect on losses.

I disagree, the heat generated by the stove is going up the chimney as well, a block off plate at the damper will radiate the heat back out of the fireplace into the house.

 

[ryanm527]

I don't yet have a thermometer but I am confident I'm getting it plenty hot. When I restock it, the thing is so hot I have to wear gloves to move stuff around, even with a 2' long poker. I've been burning a mix of hackberry, honey locust, and osage orange ("hedge").

Currently we do feel like we're shoveling against the tide and as such closed off as much of the house as we can so we could at least have a small warm space. We're heating maybe 1200sf (family room, kitchen, living/dining room) and if you count the upstairs maybe another 800 (although it makes no difference up there - the furnace runs upstairs regardless). The stove is located in the "family" room, which is right in the middle of the other rooms. Still, we're within the typical SF range of the unit and the installer said our setup was pretty ideal for a wood stove.

I blew a ton of insulation in the attic and done all the cheap(er) things i can do as far as sealing the place up. The windows are single pane but almost all of then have storm windows over them which i would think to help. Not really sure if its just the old masonry walls or what. I know the house is not ideally insulated but i wouldn't think it would be THAT bad. The walls are about 20" thick so i would think that would count for something.

Also, the chimney is built into the interior side of an exterior wall (if that makes sense), until of course it goes through the roof. They actually had to order more liner because the chimney is so tall.

 

[firefighterjake]

Strike One: Old house that is poorly insulated with single pane windows . . . although it sounds as though you're making some headway here by adding insulation and putting on storm windows.

Strike Two: No block off plate . . . heat rises . . . and generally takes the path of least resistance . . . I could easily see a lot of heat going right up the chimney.

Strike Three: To move the heat to the rest of the house try positioning the fan on the floor in an adjacent room with it pointing towards the woodstove . . . the idea being that it will move the cool air to the stove, the air will be heated and then flow out to the areas vacated by the cooler air. I heat my house in this fashion . . . it really works.

And the three questions that need to be asked . . .

1) How well seasoned is your wood . . . i.e. when was it cut and split?

2) How hot are you running your stove . . . what are you getting for temps? Some folks think their stove is running a lot hotter than it actually is.

3) How do you run your stove . . . once you get the stove hot enough do you start shutting down the air to achieve a secondary burn . . . many newbies think more heat = more air = more flames. However, in the case of these secondary burn stoves . . . more heat usually is brought on by reaching temp and then cuting back the air to get the secondary burn . . . which often results in the Bowels of Hell, Northern Lights or Propane BBQ Jets Effects.

 

[firefighterjake]

Just re-read a post . . . I would suggest getting a thermometer . . . my stove may seem pretty hot when it has a bed of coals . . . but it may not truly be all that hot.

 

[CarbonNeutral]

Is this chimney on the outside of the house, rather than centrally? If yes I may consider looking to create a radiant barrier/insulate the bricks - lots of heat will be sucked away. Also a fan pointed into the hearth may help recover some heat. And, yes, I would also block it off.

 

[ryanm527]

Most of the wood has all been down and cut to length for about 2 years. I split it all in the fall and some more a few weeks before the stove was installed.

I'll have to pickup a thermometer to verify temp. I realize I am kind of flying blind in that regard. Though I do operate it in the fashion where I get a good fire going and then slowly close it down - the installer gave me a pretty good tutorial on how to use the stove properly. I rarely see smoke from the chimney unless I've just restocked it. I have also noticed that it seems the hottest after the big flames die down - however this is the point at which the room starts cooling off. It strikes me as odd that when the fire appears to be at its hottest, the room starts cooling off. Not being an expert in thermodynamics, my theory was that more heat is rising with more force and thus creating more draft up the chimney and taking more heat with it. For about 80% of the stove surface, the path of least resistance for the rising heat would be up the chimney.

I have the fan blowing on the stove at an angle, into the fireplace. The air deflects and blows back out the other side of the fireplace and it's pretty warm. Until I started doing this I was totally unhappy with the stove. We've also got a couple ceiling fans operating (reverse).

I'll post a pic of the exterior of the chimney. This was taken before I bought the place so the cap is different now with the hearthstone installed. The house actually has 2 chimneys (the more distant one has two flues - a nearly useless buckstove insert in the living room and a coal boiler than used to be in the basement).

 

[gandrimp]

I blew a ton of insulation in the attic and done all the cheap(er) things i can do as far as sealing the place up. The windows are single pane but almost all of then have storm windows over them which i would think to help. Not really sure if its just the old masonry walls or what. I know the house is not ideally insulated but i wouldn't think it would be THAT bad. The walls are about 20" thick so i would think that would count for something.

.

Are you talking about concrete blocks or concrete when you say " the old masonry walls" ? It takes alot of heat to heat that up. If it was me I would block off the chimney and aim a fan at the stove.
I am on my first year of heating with an EPA free standing stove and I cant believe how much better the wood quality has to be for these than say an old ashley type stove.

Dry wood will heat better and last longer than wood that isnt seasoned long enough.

Im actually about out of properly seasoned wood, so within a couple of weeks its back to less heat and more consumption for me.

 

[BrotherBart]

The seven dollar challenge:

Go down to Lowe's and in the duct work section buy the sheet of galvanized steel they sell for seven or eight bucks. Shape a block-off plate but cut the hole as a "U" shape to allow you to install it without pulling the liner. Stuff it up there and notice the difference it makes.

 

[ryanm527]

The walls are limestone blocks quarried from a nearby bluff and I believe there is roughly 2" of dead air space and then plaster/lath on the inside. But that is a guess since I haven't actually torn one open to verify. I haven't measured but I believe they are about 20" thick in total. The upside is that the house stays cool well into the late spring, sometimes early summer before I ever turn on the A/C. They seem to absorb every bit of heat you throw at them.

 

[shawneyboy]

by that picture... It seems to me that the chimney runs up the side of the house. Not as is typically seen as a bump out but it does look like it runs up the side of the house. If this is correct that means that it is basically at least partially outside the insulation envelope. If this is the case, a block off plate would most certainly help. Think of it this way, all that air and all of that cold/cool masonary mass is sucking up the heat in a way that an uninsulated block wall in a basement would do. Maybe not to the extreme of a basement but similar in mode.

So I would say get a block off plate, blow cold towards stove room, get blower/heat shield (heat shield needed for blower install) to allow stove to use convection heating as well. You definately need a stove top thermo, really hot may not be heating the house hot. The difference between the BTUs you get from a stove at 400 (really hot) and what you get at 500 ( really freeking hot) is amazing, I know there is a thread on this subject here, but I believe the difference from 400 - 450 was a 25% increase in actually heating capability..... I couldn't find the thread, maybe someone else can...

Edit... You will have to pull the stove out for a blower install, may be tough to do but will make a difference IMHO. .... End Edit

 

[ryanm527]

The walls near the stove do not get hot at all. The fireplace structure immediately surrounding the stove gets warm, especially above the stove. The floor near the stove is also warm. The only thing i would describe as hot would be the stove itself. I'll try the $7 experiment and probably discuss the block plate w/ my installer. I am not familiar with how the heat shield and blower attach but the rear of the unit is maybe 1-2" from the back wall of the fireplace so there may be a clearance issue, at least with the current positioning. I was hoping to avoid a blower because of the noise and electricity use, but that's still better than using the old electric furnace.

Hopefully we'll be able to replace most of the windows later this year. It's an evolving project and nothing is ever straightforward (or cheap) in a house of this age. The previous owner lived there for 35 years and managed to screw the place up beyond belief with additions and DIY projects well outside his ability.

 

[szmaine]

We don't have a block off plate either. My husband is with the "heat can't be lost up the chimney with a top plate" faction. I've resolved to give it a try myself even though
it looks like a bugger to do because our flue is offset and the liner exits in the far left corner.

Another thought I have been toying with for a long time is doing a reflective backing in the fire place with tin ceiling panels - but could not think how to support/attach them until some one recently showed their hearth install using a skeleton of metal studs to attach cement board for slate tiling - so I'm thinking about giving that a go as well.

Found a picture of a fire place and stove that looks like yours, it's painted panels in this picture - but I bet lining it with shiny panels would reflect alot of heat.

Opinions people? More heat in the room by reflecting or letting the masonry warm up - or no difference...

Edit- there's my fireplace with the funky green hearth..

 

[CarbonNeutral]

The walls near the stove do not get hot at all. The fireplace structure immediately surrounding the stove gets warm, especially above the stove. The floor near the stove is also warm. The only thing i would describe as hot would be the stove itself. I'll try the $7 experiment and probably discuss the block plate w/ my installer. I am not familiar with how the heat shield and blower attach but the rear of the unit is maybe 1-2" from the back wall of the fireplace so there may be a clearance issue, at least with the current positioning. I was hoping to avoid a blower because of the noise and electricity use, but that's still better than using the old electric furnace.

Hopefully we'll be able to replace most of the windows later this year. It's an evolving project and nothing is ever straightforward (or cheap) in a house of this age. The previous owner lived there for 35 years and managed to screw the place up beyond belief with additions and DIY projects well outside his ability.

The fact that the walls don't get hot is a real indicator that they are doing a great job of wicking away the heat. If I stacked bricks at the side of my stove, you better bet they are going to get hot. Assuming you're getting the stove to temperature, block off plate first, then some sort of barrier..

 

[SPhill]

I don't think the concept of warm air in the chimney heating the house, is sound in this case, partly due to chimney location, and the top block-off may not be sealing well at all. Experiment with incense smoke and see if air is flowing from the room into and up the chimney. If there is flow, then it's exiting up there as well.

Additionally, hot exhaust gas in the flue is far more effective at transfering heat than room temperature-ish air -- there has to be a temp gradient for heat transfer. I would add the lower block off plate and keep that warm air in the house.

I wouldn’t be quite as concerned about it if it were further out into the room...

From the picture, it looks as if you may be able to move the stove farther into the room (or possibly build the hearth out a little farther) for better heat distribution. You could add the block-off while the pipes are apart.

 

[firefighterjake]

Most of the wood has all been down and cut to length for about 2 years. I split it all in the fall and some more a few weeks before the stove was installed.

I'll have to pickup a thermometer to verify temp. I realize I am kind of flying blind in that regard. Though I do operate it in the fashion where I get a good fire going and then slowly close it down - the installer gave me a pretty good tutorial on how to use the stove properly. I rarely see smoke from the chimney unless I've just restocked it. I have also noticed that it seems the hottest after the big flames die down - however this is the point at which the room starts cooling off. It strikes me as odd that when the fire appears to be at its hottest, the room starts cooling off. Not being an expert in thermodynamics, my theory was that more heat is rising with more force and thus creating more draft up the chimney and taking more heat with it. For about 80% of the stove surface, the path of least resistance for the rising heat would be up the chimney.

I have the fan blowing on the stove at an angle, into the fireplace. The air deflects and blows back out the other side of the fireplace and it's pretty warm. Until I started doing this I was totally unhappy with the stove. We've also got a couple ceiling fans operating (reverse).

I'll post a pic of the exterior of the chimney. This was taken before I bought the place so the cap is different now with the hearthstone installed. The house actually has 2 chimneys (the more distant one has two flues - a nearly useless buckstove insert in the living room and a coal boiler than used to be in the basement).

Hmm . . . wood being cut to length for two years before use is good . . . but not splitting the wood until the Fall is not all that great . . . in "log" form the wood takes a while to really season in some cases . . . depending on the weather your wood may be great or not good at all . . . but my guess would be somewhere in the middle.

Sounds like you're running the stove properly which is good.

Have you tried changing the direction of the fan . . . blowing it towards the stove as an experiment? That said I suspect like many others that the real key here may be getting a block off plate in place . . . if your surrounding walls are not at least warm to the touch the heat is going somewhere . . . I know my surrounding dry wall and slate hearth are sometimes quite warm . . . bordering on hot . . . when the stove is cranking.

 

[ryanm527]

Yeah I've tried experimenting with the angle of the fan. To clarify, the stone surrounding the stove is quite warm, the nearest actual "walls" are several feet away and they are slightly warm at best. Last night I burned a load of 3 hackberry splits and 2 short osage orange logs. The floor immediately in front of the stove was very hot.

I know the wood I currently have is probably not ideal but I didn't realize this time last year I would have a wood stove. Until now I've only burned wood for ambiance using the old insert in the other room. Unfortunately I'll probably be buying most my firewood for the rest of this winter since the small amount of my remaining wood is buried under nearly 3' of snow.

 

[CTYank]

Given that your fluE ("flu" is short form for influenza, a viral disease) is sealed at the chimney top, most all of the heat lost through the chimney is radiated/conducted from the flue pipe in the chimney. Sealing the flue in the chimney at the damper would then have no effect on losses.

I disagree, the heat generated by the stove is going up the chimney as well, a block off plate at the damper will radiate the heat back out of the fireplace into the house.

That might be so, if there were airflow up the chimney, but it's capped at the top. So, at most, it'd be minimal, and flipping NOTHING compared to what the walls and windows are doing. In the chimney, consider that air is a lousy conductor of heat, and, with the small space between liner and metal flue, you can forget about convection currents.

 

[ryanm527]

Just a quick update - I did talk to my installer and he said he would be happy to come back out and install a block plate. So once that's complete I'll report back on what, if any difference it makes.

Also I did pickup a thermometer and I've been getting stove temps in the 475-575 range pretty regularly from wood i've scrounged around the property (mostly ash and locust and some hedge). The weather has also been warmer lately so there have been a couple days the wife has actually complained it's too hot. So that was music to my ears!

At the time I posted we were having a very unusual cold snap here... -12 one night. I don't recall it ever being anywhere close to that cold here. A town about an hour west of here in Oklahoma recorded -31. A normal winter we usually bottom out in the single digits (above 0)... if there is such a thing as "normal" anymore!