chimney question for fireplace insert

[hammmitc]

I have a two story home with a brick exterior chimney with a standard (terra cota?) liner. The liner is in good shape, kept it clean, no creosote buildup at all. Chimney is about 25ft high and has an excellent draft. The house is about 20 years old, the fireplace was used maybe 4 times a year over that time period. Can I get away with not using a SS liner until the chimney needs it? I will use some flex liner to get past where the flue is located and plan on using a block off plate.

I am looking at a Napolean 1201P or a Regency I3100 for a 2700 sq ft home.

 

[Mike Wilson]

Depending on the size of your flue, the answer would be either absolutely not, or probably not.

Modern stoves aren't meant to have flues larger than about 6" diameter. I used my regular clay flue for year one, and had a below average experience... burned a lot of wood, and the burns were inconsistent. The difference with the 6" liner I had installed was literally night and day. I had increased burn times, consistent burns, hotter burns, and used less wood. Plus the stove was less effected by wind.

Bottom line, don't waste your time, line the flue, and you will be happy.

-- Mike

 

[MrGriz]

I would recommend lining the entire chimney. With a full liner, your system will draft better and be much easier to clean.

 

[JimWalshin845]

Welcome aboard,

You will get the pros and cons. As far as draft, do you know the size of your existing flue?

If you decide not to line the flue, a block off plate with a pipe extended past the first flue tile is code from what I understand in the US.

If you do not line the chimney I would suggest that you at least have it inspected by a Sweep or a ME.

Good luck with the project!

 

[Gooserider]

I have a two story home with a brick exterior chimney with a standard (terra cota?) liner. The liner is in good shape, kept it clean, no creosote buildup at all. Chimney is about 25ft high and has an excellent draft. The house is about 20 years old, the fireplace was used maybe 4 times a year over that time period. Can I get away with not using a SS liner until the chimney needs it? I will use some flex liner to get past where the flue is located and plan on using a block off plate.

I am looking at a Napolean 1201P or a Regency I3100 for a 2700 sq ft home.

There are three issues - chimney condition, flue size, and climate

1. Chimney condition - If a flue is not up to NFPA standards, it must be lined, normally with an insulated liner to bring it up to code. - this doesn't sound like a problem for you.

2. Flue size - VERY likely a problem - current code says that an external chimney flue may not have a cross section area more than twice the area of the stove flue outlet. I don't memorize stove specs, but I think the two you mention use 6" flues, as do all but the largest of modern stoves. This means about 28 sq" - any clay liner larger than a nominal 8"x 8" will not be w/in that 2x 28" limit, and therefore you must install a full length liner to reduce the size to an appropriate number. Code does not "require" liners installed to meet cross section requirements in otherwise sound chimneys to be insulated, though it's a good practice.

3. Climate - An external chimney tends to have a problem with creosote buildup during stove operation, and with draft reversals any time you try to get it started. It can also have problems with poor drafting in general, draft works on heat differential, and an external chimney can cool a stoves exhaust enough to cause it to draft poorly, especially when it is cooling off towards the end of a burn. Many refer to them as "Evil Chimneys". The colder the climate, the more problems, and most of PA is cold enough to be considered a problem. Insulating the liner is not cheap, but it doesn't add that much to the job as part of the overall cost of a stove installation, and can result in major improvements in stove performance. General concensus is that if you can insulate (you may not have room, though there are things that will help even then) you should.

There are a couple side benefits to the liner however,
1. You will find that it makes chimney cleaning FAR easier if you do it yourself, and usually cheaper if you have it done.
2. In the unlikely event of a chimney filre, the liner will significantly increase your odds of riding it out without any damage - this is greatest with an insulated liner, but any liner will help contain the fire.

Gooserider

 

[hammmitc]

was up on the roof on Saturday measuring everything. The existing opening for the chimney is 12 x 9, so I know I will have to get a SS liner.

Another question - I measured from the top of the existing chimney down to the flue and came up with 22 feet, can I get away with using a 25 section of chimney liner or will I have to get a 30 ft section and trim it down.

thanks in advance

 

[Gooserider]

was up on the roof on Saturday measuring everything. The existing opening for the chimney is 12 x 9, so I know I will have to get a SS liner.
Another question - I measured from the top of the existing chimney down to the flue and came up with 22 feet, can I get away with using a 25 section of chimney liner or will I have to get a 30 ft section and trim it down.
thanks in advance

12 x 9 definitely means a liner is needed, and you have plenty of room to get the insulation kit for it as well. Should be a very easy install to get the liner down such a big tube.

As to the length question, the key factor is being able to reach the stove connector and still have a bit of liner sticking out the top of the chimney to attach the top plate and cap. I would say the measurement you should have gotten was from the chimney top down to the bottom of the fireplace, then subtract the approximate height of the stove. Remember that it is better to be overlength and have to trim than it is to be to short, so if in doubt go for the longer length. (I haven't priced the kits, but as I understand it the difference isn't that much...)

Gooserider