Large Fireplace - Efficiency Options

[dvdeusen]

I have an old large masonry fireplace (Front opening dimensions 50" Wide X 36" Tall (slightly shorter at the back of the fireplace) X 25" Deep). I'm in the process of doing a bunch of insulation and air-sealing to make the house more energy-efficient and I am a bit at a loss as to the best way to handle such a large fireplace while preserving as much character as possible.

My main goals:

• Ability to have fires in this room without worrying about huge amounts of conditioned air running out of the house
• Keeping the existing tile & mantel
• Large fire "viewing area" for ambience

I am looking for more heat output efficiency than a standard open fireplace, but this fireplace is not meant to be a significant source of heat for the home. (I am converting a smaller fireplace in the home to a Blaze King Ashford 25 for that purpose)

I have some different options and I'd love input. Willing to invest a good amount of money for this project so budget is not the primary consideration.

1) Attempt to make current fireplace more "efficient" (although I'm well-aware that this efficiency won't get anywhere close to an insert or stove)
I would install some combination of:

• air-sealed pyro ceramic doors with a bottom damper (from Stoll)
• outdoor combustion air kit
• catalyst

Would this accomplish anything? My hope would be the combination of the doors and outdoor air would allow me to reduce the amount of conditioned air sucked up the chimney, but my hunch is from reading through other posts on this forum that this might be a doomed avenue.

2) Install an Insert
Is there any option for an "interior install" that wouldn't damage/alter the tile? Are there any inserts large enough such that there wouldn't be a large gap to fill around the insert? (Or is there a more attractive option to fill this gap than the plain black steel border?) The fireplace is so large I am having a hard time envisioning how the smaller inserts would look.

3) Install a stove in the fireplace
I don't see this option pursued that often - are there any important considerations to keep in mind? My hope here would be to get as large of a stove as possible with a large window to maintain ambience.

Thanks in advance for all input!

 

[stoveliker]

A fireplace will always suck large, LARGE amounts of air out.
I don't think installing a catalyst is possible - temps will likely be too low to get into the active zone (see large amounts of air).
Doors may be possible to close off the fire place when not in use. Not sure if you can (should) have them closed (plus air inlet) when burning.

Inserts: not enough knowledge (me). Mantel etc will be affected.

Stove inside (plus insulated block-off plate and stainless liner in the chimney?): best option for having fire and keeping mantel. Fireview will be smaller, but could be fair given the 3' tall and 4' wide space there.

I would go this route, if you can find a (pleasing to the eye) stove that fits. But then I am "stove-biased".

 

[EbS-P]

From what you have said that heat really isn’t all that important why are you pushing for more efficiency?
We had two open fireplaces one with the white stove is 42”wx29h. The one with the insert is 36”wx28”h.

I really like the stove inside a fireplace look. It heats good enough for us. I don’t care for a large surround. I may try to install a surround inside my brick opening for the insert but I think I will try to conceal the liner. With some black stove pipe or similar.

Doors are just a way to keep kids out of the fireplace I found We got rid of them after 5 or six fires. Just was too much smoke In the house. Draft was fine I’m just pretty sensitive.

At 36” high you have more choices than I did for stoves.

Mantle clearances could/will be an issue. Stove or insert. I think a pacifier energy T5 could look very nice but I’m not sure how to fill all the space. Or if it even needs to be to look good. Mantle clearance will dictate choices I believe.

 

[begreen]

The mantel could be an issue for a freestanding stove, especially if the stovetop projects out of the fireplace even an inch or two, which seems likely. Many freestanding stoves only have ceiling height listings because they are rarely put in fireplaces. If the mantel is entirely non-combustible, like EbS-P's then it is not an issue.

Some flush inserts have lower clearances that might work here. It looks like a custom surround would work best for this fireplace so as to not cover the tiles. This would be with the insert inset slightly. The fireplace is deep enough to provide some room for recessing some inserts so an insert could be installed without the surround. Some inserts look better than others when this approach is taken.

 

[Drewby]

You need to make it into a retrofit rumford fireplace.
Look on Rumford.com website on the plans for those units.
Anyone who say a fireplace can’t heat a house has never owned a Rumford.
I am sitting in front of my 60”x54” Rumford that I built 4 years ago and it’s my only source of heat currently. It is keeping my 4200 foot house in the high 60’s this week in wisconsin. Last winter I wanted to test it out and it kept the house in the low 60’s when the outside air was 15 degrees for a week solid. It was the only heat source running. It does like wood though but then again most large houses do. This fireplace will heat a wall up that is 52 feet away to over 80 degrees according to my laser thermometer. It will heat my leather couch up to 120 and it’s over 10 feet away.
The make up air currently is just a slightly open window next to the fireplace and rest of the house warms up nicely.

 

[begreen]

It can be a good radiant heater if one keeps a good fire going, but they are very inefficient and dirty, thus the high wood consumption.

 

[Drewby]

It can be a good radiant heater if one keeps a good fire going, but they are very inefficient and dirty, thus the high wood consumption.

This unit basically heats all the walls and everything else up and then we go to bed. In the morning the temp drops 2-4 degrees and we start all over. Those firebrick throw heat all night even after the fire is out.
This crackling fire will literally hypnotize you to sleep. It never gets old.
once I get the screen it won’t be too messy either.
As far as wood consumption it is higher but we’ll worth it IMO. If you get it roaring it’s putting out around 80-100k btus an hour on around 25lbs of wood so about 50% efficiency which is on par with what the designer says also. That includes the heated air getting removed from the room. If it wasn’t for that it would be much much higher. They do burn very clean.

 

[bholler]

This unit basically heats all the walls and everything else up and then we go to bed. In the morning the temp drops 2-4 degrees and we start all over. Those firebrick throw heat all night even after the fire is out.
This crackling fire will literally hypnotize you to sleep. It never gets old.
once I get the screen it won’t be too messy either.
As far as wood consumption it is higher but we’ll worth it IMO. If you get it roaring it’s putting out around 80-100k btus an hour on around 25lbs of wood so about 50% efficiency which is on par with what the designer says also. That includes the heated air getting removed from the room. If it wasn’t for that it would be much much higher. They do burn very clean.

Rumfords are about the best fireplace design around the only thing better is a prior fire. But they are still really far behind a woodstove even old ones. Modern woodstoves are vastly better in every way.

Yes one could spend a huge ammout of money to modify their fireplace into a Rumford to maybe get to 50% and still burn pretty dirty. Or you could spend half the money and install an insert or stove.

 

[begreen]

This fireplace will heat a wall up that is 52 feet away to over 80 degrees

That's a large room or area. Every room or home is a good set up for them. Radiant heaters are best in large open areas.

dvdeusen, how large is the room this fireplace is in and how open is it to the rest of that floor?

 

[bholler]

One also needs to be able to run a very large fresh air supply to the fireplace in order to get any real efficency. In many cases that simply is not possible with a retrofit

 

[Drewby]

Rumfords are about the best fireplace design around the only thing better is a prior fire. But they are still really far behind a woodstove even old ones. Modern woodstoves are vastly better in every way.

Yes one could spend a huge ammout of money to modify their fireplace into a Rumford to maybe get to 50% and still burn pretty dirty. Or you could spend half the money and install an insert or stove.

You are right they do not come cheap and the fuel mileage sucks.
A $25,000 dollar rumford like the one shown in my pic is not to be compared to a $2,000 wood stove. They are to serve a much different purpose. It’s just like comparing a Ferrari to a Ford.
I’ve had over 50 fires in this one already and everytime sitting in front of it is truly the highlight of my day. I will never build another house without one. They are simply too amazing. If economics is what your after a wood stove all the way.

 

[bholler]

You are right they do not come cheap and the fuel mileage sucks.
A $25,000 dollar rumford like the one shown in my pic is not to be compared to a $2,000 wood stove. They are to serve a much different purpose. It’s just like comparing a Ferrari to a Ford.
I’ve had over 50 fires in this one already and everytime sitting in front of it is truly the highlight of my day. I will never build another house without one. They are simply too amazing. If economics is what your after a wood stove all the way.

I get the appeal of open fireplaces for sure. And honestly I make allot of money when I build them. So I have absolutely no issue with people who like them. But the comparison of Ferrari to Ford isn't very accurate. Because with a Ferrari you also get a big performance advantage.

 

[dvdeusen]

The mantel could be an issue for a freestanding stove, especially if the stovetop projects out of the fireplace even an inch or two, which seems likely. Many freestanding stoves only have ceiling height listings because they are rarely put in fireplaces. If the mantel is entirely non-combustible, like EbS-P's then it is not an issue.

Some flush inserts have lower clearances that might work here. It looks like a custom surround would work best for this fireplace so as to not cover the tiles. This would be with the insert inset slightly. The fireplace is deep enough to provide some room for recessing some inserts so an insert could be installed without the surround. Some inserts look better than others when this approach is taken.

I have realized I put the wrong depth measurement. The correct depth is 29.5" (not 25). If I did something like the Hearthstone Manchester (21.5" depth) would the stove have to project at all? (The mantel is wood so is definitely combustible)

I didn't know that inserts could be inset (I was worried that the installs would all involve covering up the tile). Should most inserts have an inset option or should I start digging through the installation docs for details?

 

[dvdeusen]

From what you have said that heat really isn’t all that important why are you pushing for more efficiency?
We had two open fireplaces one with the white stove is 42”wx29h. The one with the insert is 36”wx28”h.

I really like the stove inside a fireplace look. It heats good enough for us. I don’t care for a large surround. I may try to install a surround inside my brick opening for the insert but I think I will try to conceal the liner. With some black stove pipe or similar.

Doors are just a way to keep kids out of the fireplace I found We got rid of them after 5 or six fires. Just was too much smoke In the house. Draft was fine I’m just pretty sensitive.

At 36” high you have more choices than I did for stoves.

Mantle clearances could/will be an issue. Stove or insert. I think a pacifier energy T5 could look very nice but I’m not sure how to fill all the space. Or if it even needs to be to look good. Mantle clearance will dictate choices I believe.

View attachment 284197 View attachment 284198

Good opening question! My impression is that a large open fireplace is not only a poor provider of heat for the room that it is in, but could draw so much air up the chimney that it could make other rooms in the house cold (wherever the air gaps might be) and potentially cause backdrafting issues in tighter homes. So my "efficiency" word choice was a bit poor. I'm more worried about the air exhaust with such a large fireplace than I am about the BTU output. I could always open a window in the same room as the fireplace and avoid some of these issues, but I was hoping for a more elegant solution.

Thanks for the photos! The "stove in fireplace" is looking like a compelling solution and it's good to see examples.

 

[dvdeusen]

That's a large room or area. Every room or home is a good set up for them. Radiant heaters are best in large open areas.

dvdeusen, how large is the room this fireplace is in and how open is it to the rest of that floor?

The room is only 23' by 14' , and I'd say somewhat open. There are walls between it and other rooms, but with large molding/framed openings rather than doorways (and opens to rooms on three sides)

 

[dvdeusen]

One also needs to be able to run a very large fresh air supply to the fireplace in order to get any real efficency. In many cases that simply is not possible with a retrofit

I think I probably already know the answer to this, but just in case: I'm assuming installing 1-2 of these vestal kits doesn't constitute a "very large fresh air supply"?

 

[dvdeusen]

A fireplace will always suck large, LARGE amounts of air out.
I don't think installing a catalyst is possible - temps will likely be too low to get into the active zone (see large amounts of air).
Doors may be possible to close off the fire place when not in use. Not sure if you can (should) have them closed (plus air inlet) when burning.

Inserts: not enough knowledge (me). Mantel etc will be affected.

Stove inside (plus insulated block-off plate and stainless liner in the chimney?): best option for having fire and keeping mantel. Fireview will be smaller, but could be fair given the 3' tall and 4' wide space there.

I would go this route, if you can find a (pleasing to the eye) stove that fits. But then I am "stove-biased".

My plan was definitely to have the doors closed while burning, so thanks for the feedback that it might not be the best idea. Is the issue that there wouldn't be enough air?

 

[EbS-P]

Good opening question! My impression is that a large open fireplace is not only a poor provider of heat for the room that it is in, but could draw so much air up the chimney that it could make other rooms in the house cold (wherever the air gaps might be) and potentially cause backdrafting issues in tighter homes. So my "efficiency" word choice was a bit poor. I'm more worried about the air exhaust with such a large fireplace than I am about the BTU output. I could always open a window in the same room as the fireplace and avoid some of these issues, but I was hoping for a more elegant solution.

Thanks for the photos! The "stove in fireplace" is looking like a compelling solution and it's good to see examples.

If you don’t want the fireplace sucking lots of room air out I see a stove or insert as the only real solution.

I was trying to think of stoves that had a big and more rectangular window. To visually fill out the width. Blazeking boxer on legs comes to mind. Jotul F500 but we need another season or two of data to see if it’s a good stove or not. Pacific energy has some that would look good and are good performing stoves.

The Blaze king stove in a fire place has me wondering if it’s a good idea with the thermostat.

 

[bholler]

I think I probably already know the answer to this, but just in case: I'm assuming installing 1-2 of these vestal kits doesn't constitute a "very large fresh air supply"?

Maybe 4 of them depending on the size of the liner

 

[Drewby]

My impression is that a large open fireplace is not only a poor provider of heat for the room that it is in,

A large open fireplace like a rumford will cook you out of the room. When people say they rob a house of heat it is simply not true. They are not as efficient as a sealed stove but I believe based on my experience is that they put out much more heat. My calculations show that the 60” unit that I have is around 50% efficient based on providing 80,000 btus an hour for my heat needs on a 15 degree day in a 4200 foot house. I used around 20-25 lbs of wood an hour at full burn. All these numbers are including the air they remove from the house as the calculation was done when no other heat source was present for 7 days straight.
Large open rooms are the best for fireplaces.
Stoves are much easier and cheaper however. I have to add wood to the fireplace every hour or so.

 

[stoveliker]

The Blaze king stove in a fire place has me wondering if it’s a good idea with the thermostat.

Depends on how much space there is, but I agree having the Tstat in the back of a stove in a fireplace (i.e. a really small alcove) seems like asking for trouble with the Tstat never opening the air supply enough because it remains too warm.
One could look at the alcove clearance requirements for such a stove to gauge this - but I think it's better to stay away from this here.

 

[stoveliker]

My plan was definitely to have the doors closed while burning, so thanks for the feedback that it might not be the best idea. Is the issue that there wouldn't be enough air?

Fireplaces run because there is a large flow of air coming from everywhere. Closing doors (with a small hole someplace for air) changes that considerably. A (bunch of, I read above) OAKs may make this workable though.
Glass needs to be special glass (not just window). I'm not sure what code says about this - likely you'l be making your fireplace hotter than it was designed for...

However, I'm in general weary of adapting solid-fuel burning appliances. Maybe because I'm not knowledgeable enough of the engineering (or, for fireplaces, centuries of accumulated empirical knowledge) that went into their design, and thus the requirements for them to work well. But I gather you and I are in the same boat there (so I hope I'm not offending you - and at least I'm offending myself to the same level ..)

 

[weatherguy]

I have a big fireplace and put a Progress Hybrid in it, heats the house just fine. I have another see through fireplace that I'd like to use but haven't come up with a solution yet. If I built a new house I'd have a Rumford and a hearth for a free stander.

 

[dvdeusen]

Thanks everyone for feedback!

I've decided to move forward with scoping out a wood stove installation in the fireplace.

One thing I've noticed is that the flue pipe outlet is at the very rear of most stoves yet the flue of the fireplace is roughly centered in the firebox. Does this have to be perfectly aligned so that the flue pipe is a straight vertical for some minimum distance? (which probably means that most stove would stick out of the front of the fireplace, causing issues with the combustible mantel) Or is there a way to install the pipe so it has a bend or curve to exit the flue?

(trying to figure out a way to have the largest stove I can without protruding from the fireplace and having to replace the mantel)

 

[EbS-P]

If you don’t want the stove to stick out of the fireplace very far you need to get a top vent stove. You can hook a rear vent up to a T but it will stick out 12-18” further. They make angled appliance adapters and bends in stove pipe. Your existing flue will dictate is your can use a rigid liner most common to use flexible liner but it’s not super flexible 18-24” minimum radius bends. If you have shorter stove think about how to make the liner connection pretty as it will be seen. The liner connects directly to my appliance adapter on the stove. Same on the insert. The insert connection is ugly and needs addressed. The stove connection you can’t see. With 36” height you have many more options than I did.

Think about if you want a catalytic stove and where the bypass handle is. With your width it’s not that big of an issue. Just something to consider.

Depending on firebox construction you can make a little room by altering the top course of fire bricks. Grinding, or resetting different angle or further back.

Start by making good measurements so you can see just how deep the firebox is at different heights. The angled connections can give you a couple more inches but that depends on a many factors.

Let the stove shopping and manual reading commence. For looks check out Stuv (single burn rate not much feedback about quality or function). MF nova falls into that catagory (it’s catalytic). 25” dearth is a limiting factor.

Another course of brick could be laid down on the floor to raise up the stove to center it.

That 25” depth is gonna be tricky

Evan