Chimney Lining necessary?

MP

Hello all,

I will be replacing my old gas-powered boiler which heats my 90-year-old house through hot water through radiators. My house is a "twin" which shares in inside wall with another house.

One contractor told me I would need to have my chimney lined (which was probably never lined) due to the new heater's efficiency causing eventual damage to the bricks (mostly due to excess moisture I believe). Another contractor told me that because the chimney isn't on an outside wall (it is on the inside wall shared with the other twin), it wouldn't need to be lined.

Opinions please.

Also, the price of aluminum lining is attractive, but would I be wasting my money?

Thanks,
Margie P.

Constantin

I'm a mere homeowner myself...

...but I would always line a chimney that was attached to a high-efficiency heating appliance. The potential problem your contractor is alluding to is the water in the exhaust gasses, a natural byproduct of combustion. The lower the flue temperature, the more likely the water is to condense on the chimney walls.

Granted, your chimney will be relatively "warm" due to its location, yet that alone will not protect it, particularly if you elect to install a condensing appliance. Such appliances have very low flue temperatures but also offer maximum thermal efficiency.

If you'd like to maximize your energy savings, you may want to investigate a direct-vent appliance like the Dunkirk Quantum Leap, HTP Munchkin, Monitor MZ, NTI Trinity, Viessman Vitodens, Weil-McLain Ultra, etc. There are a lot to choose from (all of the above run on natural gas). Direct vent appliances don't need a chimney, they can vent through the side of your house. The only caveat is whether you have enough room on the side (without windows being too close).

I would also install a liner for other reasons, such as a better draft. The flues found in older chimneys are usually much bigger than the ones needed for the modern combustion appliances that are now hooked up to them. For example, my old chimney had two 12" square flues while the new one will have two 8" round and one 6" round.

As to what material is most suitable, that is a question that is highly dependent on what kind of a boiler you are installing. For example, if I recall correctly, 304 or 316-based stainless liners will usually work great with non-condensing heating appliances. Due to the condensation issues associated with condensing appliances, liner-manufacturers tend to recommend Al29-4C alloys for those applications instead. See the HomeSaver website for more info on your options.

dave connors

Chimney liner

Line the chimney with an aluminum liner and insulate if possible. Other option could be a Buderus GA124 series direct vent boiler.

Al Letellier

chimney lining

Definitely line the chimney, but take a good look at stainless. It will last longer and will give you more options down the road. I don't know if you live in oil country, but you would have the option of switching if gas gets to expensive. Oil or wood or coal or any other fuel other than gas require stainless. And if oil is every an option, consider a boiler that can be converted. You may sacrifice a little efficiency, but would save the cost of replacing the boiler if you ever switched.
If gas is the only foreseeable fuel, go high efficiency or condensing and line that chimney...stainless is best if you can afford it in your budget.

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Brian_24

chimney liners

If the chimney is in good shape I would not line it. If it is in poor condition I would still not line it but abandon it alltogether. A properly installed appliance will not attack the chimney and destroy it. IMHO a chimney liner is just asking for trouble. Good luck,
Brian

Jamie_6

MP,

I definitely agree with AL. You really should line that chimney. It’s always better to be safe then sorry, especially with all the press on Carbon Monoxide the last couple of winters.

If you do have a stainless liner pulled it will most likely never have to be addressed again. Although, price can play a large portion in the purchasing decision and an aluminum liner might have to be used.

Just make sure that the "chimney guy" puts in the right size liner. This should be done by checking the amount of BTU's going up that chimney, the height of the chimney, and if the appliances entering the chimney are fan induced or atmospheric.

Jamie


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Dean_7

Chimney liner

I once had an unlined brick chimney when the old boiler was coal fired it was fine, it was fine when the boiler was converted to oil, however when the old boiler was converted to gas the condensation destroyed the chimney from the inside out.The mortor was all eaten away. This is why I now have a Burnham boiler that is directly vented. The old chimney had to be removed because bricks were falling out of it. If it had been lined properly when the old boilers gas conversion was done It probably would still exist.

lchmb

code requires

If you are using a gas unit then code will require that the chimney be lined. It is being done for your safety as well as saving the system. I personally would go with the stainless. You will pay more now but save more later. JMHO

S Ebels

Line it.

Two outstanding reasons.

1. Proper sizing of the flue creates the conditions you need for the correct flue velocity. This keeps your boiler more efficient and mor quiet. An oversize lue will draw more air than is needed from your house, thereby wasting heated air.

2. Condensation of newer medium efficency appliances will kill a chimney in a matter of just a few years. (Ask me how I know this) Even a clay lined flue in good condition will succumb and rot from the inside out with an 83% efficient boiler. The effect is even more pronounced when you go with a boiler capable of running at low water temps (ala Buderus or Viessmann)

Stainless is the only logical choice BTW.

Dean_7

liner

Go with the stainless. These people are right. It's more money initially but a lot less in the long run.

Brian_24

Just because code requires doesn't make it right. Does the code official have to back the performance of the system up? I think not, his job ends when he walks away. A properlt tuned non-condensing appliance will not destroy a clay lined chimney. It will actualy put more heat up the chimney. I would rather vent into a relativly smooth clay chimney than try to get a proper draft from a twisted piece of flex. A barametric control will do wonders on gas. JMHO.
Brian

Jack_21

First code change on liners was the 92

edition of NFPA 54. Since that time the field experience and research have continuously supported a tighteneing of the venting code requirements in support of lining with Cat I equip. If you compare the 92 edition to the current edition it basically says that masonry chimneys are not suitable for venting cat I equipment...period! it isn't just that you can tune the equipment to work. The breeching on most appliances is significantly smaller than the cross section of the chimney. Masonry chimneys do nothing but absorb every btu that comes their way. The Cat I stuff is all single stage (I think) which exacerbates the problem of shortcycles never giving the flue the opportunity to warm up and really work well. You overlay that condition with the oversizing that is so typical in the business and you end up with a system that cannot work well. JMHO,also!

Mark Hunt

I agree with Brian


"One size fits all" codes can actually cause more problems and often ignore larger issues.

Draft is draft. The only way flue gas can destroy a chimney is if the draft is off, and it will destroy liners as easily as it will masonry.

If the unit is underfired for example, the stack temps will be low.

Fire it right and these problems go away. If there is an issue with draft (depressurization), how do liners solve that? They can't.

But big brother did a study and liners supposedly solved the problems. I can show you instances where they didn't.

No two cases are exactly alike. Without testing, no-one knows for sure.

Mark H

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Brian_24

Use a barametric and control the draft yourself. No two installs are the same so how can a sizing chart developed by people who don't install equipment be right? You should read the disclaimers in the gama tables. Basicly tells you that you are on your own to make the chimney work, but yet we are forced to install equipment to meet this table. Line all you want I quit using them after Jim Davis's class opened my eyes. Fact.

Mark Hunt

You're 100% correct Brian


Testing proves everything.

Mark H

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Dave Ewald

To Line or Not to Line

My inexpert (homeowner) comments: A building code may require a lining, but here in Pennsylvania some municipalities still don't have a building code. The "statewide building code" law recently passed only "required" municipalities to adopt the 1999 BOCA or subsequent International code - but if the municipality didn't do what it was "required" to do, there is no code.

I discovered my chimney's flaws when I climbed up on the roof to clean it. No code officials or inspectors had looked for or found the problems, and none were informed of them. I did what I could reasonably do to correct what I believed was a safety problem.

My chimney is pretty bad, corbelled out of a brick party wall and the flue so narrow (about 4.5 inches by 15") that I didn't believe there would be sufficient draft with any lining (though there were contractors willing to line it anyway). Bricks had fallen into the flue, resulting in the loss of a partition between my flue and that of the house next door. Some bricks had partly crumbled, thining the chimney wall which was also, of course, a part of the wall of a third floor bedroom. Damage was from the top of the chimney to a few feet below the roof line. I removed the fallen bricks and hired a mason to restore the chimney as it had been built.

I could not convert from oil to gas, as I would have needed an up-to-code chimney (gas company or Norristown code, I forget which). With a 14-foot wide row house it would be difficult or impossible to site a new chimney or a direct vent where it wouldn't be too close to a window. It would also have been a major expense.

Be sure that you will have an adequate cross section in your newly lined chimney, and don't rely on the opinion of the guy selling you the liner.

If I could have, I would have lined my chimney with a poured liner. This is being done either with an inflatable bladder to form the flue (removed after the liner hardens) or with the flue formed by a stainless steel liner (which remains). I think the poured liner helps stabilize the chimney structure and lasts longer than metal liners.

Regardless of actual legal codes in your area, try to get a job done according to the National Fire Protection Academy (NFPA) code for chimneys, and beware of incompetent, unlicensed, or uninsured contractors.

lchmb

May be wrong

But he indicates the house is 90 year's old and original chimney and was "never lined in the first place". I believe that mean's it is just a brick formed chimney without a clay liner. If this is the case then code will require it be lined in some manor. I agree that code does not work for everything but in this case it will make it much safer...JMHO..:)