Overcoming Bad Chimney Designs

[farmerandy7481]

I have a fireplace that violates most of the rules discussed in this article:

http://www.woodheat.org/best-practices.html

The firebox is a manufactured metal box about 18" deep and 42" wide with a triple lined straight flue pipe inside an uninsulated framed enclosure which is on the outside of the house. The flue exhausts above the ridge-line. Even though the house is 23 years old, I built it to minimize air infiltration and it is still tight. The few times I built an actual fire, smoke filled the house which I attributed to very little available combustible air and dense cold air in the chimney. Regardless, it smokes which is why soon after I built the house, I installed gas logs which I rarely use because it sucks propane and produces very little heat. While the fire is nice to look at, the pleasant thoughts are extinguished by the thought of my 500 gallon propane tank draining.

Will the new wood burning inserts be able to overcome my poor drafting issues or will I be better off with a pellet insert with forced air exhaust?

 

[farmerandy7481]

I have a fireplace that violates most of the rules discussed in this article:

http://www.woodheat.org/best-practices.html

The firebox is a manufactured metal box about 18" deep and 42" wide with a triple lined straight flue pipe inside an uninsulated framed enclosure which is on the outside of the house. The flue exhausts above the ridge-line. Even though the house is 23 years old, I built it to minimize air infiltration and it is still tight. The few times I built an actual fire, smoke filled the house which I attributed to very little available combustible air and dense cold air in the chimney. Regardless, it smokes which is why soon after I built the house, I installed gas logs which I rarely use because it sucks propane and produces very little heat. While the fire is nice to look at, the pleasant thoughts are extinguished by the thought of my 500 gallon propane tank draining.

Will the new wood burning inserts be able to overcome my poor drafting issues or will I be better off with a pellet insert with forced air exhaust?

This is an old post that needs updating. After 4 years I'm about to launch the wood burning stove project. The attached file is my plan for replacing the original junk fireplace. My basic question is can I get away with double wall insulated chimney pipe or do I need to insulate the chase and porch attic space for proper draw? I know without more detail this would be an educated guess but your observations would be appreciated.

 

[bholler]

This is an old post that needs updating. After 4 years I'm about to launch the wood burning stove project. The attached file is my plan for replacing the original junk fireplace. My basic question is can I get away with double wall insulated chimney pipe or do I need to insulate the chase and porch attic space for proper draw? I know without more detail this would be an educated guess but your observations would be appreciated.

Does that opening meet the alcove clearance requirements of the stove?

 

[farmerandy7481]

Does that opening meet the alcove clearance requirements of the stove?

Thanks bholler. The alcove doesn't exist yet. It can be anything required to meet code.

 

[kborndale]

Got your wood yet? Need it 2 years in advance to burning. You will be very disappointed in your stove if you don't.

 

[farmerandy7481]

Got your wood yet? Need it 2 years in advance to burning. You will be very disappointed in your stove if you don't.

I have a local source for seasoned Post Oak here in north central TX.

 

[bholler]

Thanks bholler. The alcove doesn't exist yet. It can be anything required to meet code.

Check the alcove requirements for the stove you chose.

 

[begreen]

Trying to make this look like a brick fireplace is going to be the gotcha. No stove is going to accept a low lintel like that unless the entire construction is non-combustible, not only on the surface but right down to the studs.

The drawings show a VC stove. Is this the choice? I ask because it's not great for this situation being primarily a top loader.

 

[farmerandy7481]

Trying to make this look like a brick fireplace is going to be the gotcha. No stove is going to accept a low lintel like that unless the entire construction is non-combustible, not only on the surface but right down to the studs.

The drawings show a VC stove. Is this the choice? I ask because it's not great for this situation being primarily a top loader.

Thanks for the reply. The VC stove was just to show the idea clearer; I won't be using a top loader. I can see how all the heat could be concentrated in the alcove so even if I sheathed the walls with cement backer board and then applied thin veneer brick (is that even code?) I'd have an inefficient distribution system. I guess that puts me back to a fireplace (not an insert).

The existing cutout in the brick veneer interior wall is the problem. There doesn't appear to be one on the market big enough to cover the hole. I may have to get more creative on decreasing the size of the opening and making it look right versus clearly an add on.

When you say no stove is going to accept a "low lintel like that" I've assumed you mean that the alcove will essentially become an oven and thus even the sheathing behind the non-combustible finish surface (tile, brick, rock, etc.,) will also have to be non-combustible? Or are you saying since 3 of the radiant surfaces (top and sides) will only emit to the walls of the enclosure that I'm defeating the purpose of a stove? Or was this an observation about combustion air? Whatever the issue, can I overcome it with a change to the design?

 

[bholler]

Thanks for the reply. The VC stove was just to show the idea clearer; I won't be using a top loader. I can see how all the heat could be concentrated in the alcove so even if I sheathed the walls with cement backer board and then applied thin veneer brick (is that even code?) I'd have an inefficient distribution system. I guess that puts me back to a fireplace (not an insert).

The existing cutout in the brick veneer interior wall is the problem. There doesn't appear to be one on the market big enough to cover the hole. I may have to get more creative on decreasing the size of the opening and making it look right versus clearly an add on.

When you say no stove is going to accept a "low lintel like that" I've assumed you mean that the alcove will essentially become an oven and thus even the sheathing behind the non-combustible finish surface (tile, brick, rock, etc.,) will also have to be non-combustible? Or are you saying since 3 of the radiant surfaces (top and sides) will only emit to the walls of the enclosure that I'm defeating the purpose of a stove? Or was this an observation about combustion air? Whatever the issue, can I overcome it with a change to the design?

The issue is that every stove will require a much higher opening for fire safety. This isn't about performance it is about keeping your house safe.

 

[EbS-P]

Doing this much work have you considered a new high efficiency zero clearance unit? Have you found any stoves that will fit width wise with alcove clearances? Or what is the width of the chase?

 

[begreen]

What covers the surface is somewhat irrelevant. It is the nearest combustible behind whatever veneer is used that is the gating factor. It can be done, but only if everything in the structure surrounding the alcove is non-combustible. Even then only some stove manuals will make an exception for this. Also, one then needs to understand the compromises necessary if the goal is to have the stove provide good heat and not trap it in the alcove. There have been some clever solutions to these design problems over the years, but it takes careful planning with an eye on safety at every step.

I went through this exercise a couple years ago with a family that wanted just what you are trying to design. But they wanted a specific stove which did not fit well with their design. In the end they surprised me and came up with an alternate design that they have grown to love. The stove has the required ceiling height and clearances, though they hung the steel veneer on 1" spacers with the proper bottom and top gaps just as an extra measure of safety. This install could have just as well had a brick veneer on the alcove walls.