What purpose does a chimney liner serve?

Question

we have to replace our old furnace, if we get a permit, we have to get a chimney liner, per town code(almost dbl. cost) The house is over a hundred yrs. old & we don't think it's had one thus far, so what purpose do they serve, what should we do HELP!!

This furnace in place right now is over 60 years old

Answer 1

You may be running into a problem far beyond your expectations, so read carefully...

To begin with, mortar holding your chimney together has cracked over the years as result of high temperature in the chimney and variable temperature outside the chimney, not to mention constantly changing humidity...all of which affects the lifespan of mortar...

The reason for the liner is to insulate the chimney itself from the variables causing mortar to age and deteriorate. These liners are usually made of clay and are not mortared...they are carefully lowered down into an existing chimney using strong string. Once seated, the string is cut and left inside the chimney to burn away eventually...

There is an alternative which you most certainly can do your own self but you will have to check with the building inspector to be sure it is acceptable for your state and local building code...

You could lower a stainless steel single wall stove pipe into the chimney in sections down into the chimney but keep in mind each section must be joined with screws. It can be a bit tricky, but can be done... At the very bottom you will have to install a "T" stove pipe, not an elbow, and you may have to enlarge the hole in the wall to accomodate getting that T inside the chimney... This can be done with a rotary drill but it sure can make a lot of dust...definitely wear head gear and a respirator...

I built my two chimneys using chimney block and installed the clay liners as the blocks were climbing upward. When the chimney height was reached, I then made my own stainless stove pipe and lowered that...2 four foot sections at a time and joined additional sections before the first ones dropped out of sight...

Now, problems you may have as result of your chimney being over a hundred years old...:

Is the chimney straight or is there a curve...? Installing straight pipe in a curved chimney doesn't go well and if the curve is at the bottom and you use flex pipe the weight of the pipe above will surely collapse it... I rather doubt flex pipe will pass the building code if there is no chimney liner.

Next...: Most chimneys made a hundred years ago had large holes in them...10 x 10, 12 x 12, and larger. Your furnace needs only the standard liner...6 x 6, which is almost 8 x 8 measured outside. If the hole in your chimney now is 10 x 10, you may have mortar hanging inside the bricks which will prevent a clay liner from passing thru...

Also, if your chimney is inside your home, as most were in that era, floor and ceiling joists were imbedded in the brick to help support the chimney when the house settles in order to prevent a wide gap which would allow fumes to enter the walls surround the chimney... Shifting of the house over the years may have moved the bricks inward to the chimney hole and adding additional blockage for a liner...

Depending on your own abilities, it can be somewhat costly and time consuming whether you do it or hire someone...

An additional option is to tear out the old chimney starting at the top and eventually working your way to the bottom if you have access to the chimney in the rooms or closets below. When below the roof line, you drop the bricks down (a few at a time) and remove them thru the cleanout at the bottom. If no cleanout...cut one in. When the chimney is gone, replace it with a stainless steel 3-wall chimney and you will just have to install a baffle on the roof to cover the square hole surrounding the new chimney... This will also comply to the building codes...

The remedy of all remedies is to install the latest hi-efficiency furnace which recycles it own exhaust and heat lost. Those do not require a chimney. The installer will drill a two inch hole in the foundation wall and run the exhaust thru that and vent cover the outside...

Guess what...? The exhaust tube is made of plastic...yeppers... And that, sir, complies to all the building codes in all the states. It adds a great deal of value to your home and most certainly will cost you less for heating as they are 98% efficient. Some insurance companies even offer an additional discount when a home has one installed...

Now, a question of you...why do you need a new furnace in the first place...? I just helped a lady whom was advised to replace her hot water furnace and her hot water heater and he gave her an outstanding price of $7000.00...GULP...!

I looked at the system myself and found the firebrick inside the combustion chamber were falling. A hot water boiler does not require a hot water tank either as the boiler heats water on demand year round for both heat and washing needs...

The results were to replace the firebricks, remove the hot water tank and clean the flue. The cost will choke you...$500.00 and less than a day of work...!

What I am saying sir, is you would be wise to get a second opinion before you go any further...

Also, in most states you may be allowed to do a lot of work usually done by licensed contractors if only your family lives in the home. This does not exempt you from inspection tho, that must be done regardless...

Hopefully, I have given you enough insight towards making the right decisions ahead...

Good luck...

Answer 2

Your old furnace probably used the principle of convection, (hot air rises), to get rid of the exhaust gases through the chimney, most of them did. However, if you're contemplating installing the same type of furnace, gas, fuel oil, wood, etc, then you're going to need to replace the flue, (chimney), liner. Odds are there's one in there now. They've been required for some time. My house was built in 1904 and it's got a chimney liner for a gas forced air furnace that's probably 30 years old. Rich is correct though, in his assessment that you should seriously consider a newer type hi-efficiency furnace. They don't just let the exhaust go up a chimney by convection, they use a fan to blow it up and out, so fast, in fact, that you can now use PVC piping to route the exhaust thru a wall somewhere instead of putting it in the chimney. The gases go thru the pipes so fast that they don't get hot enough to soften up. Hope that helps.

Answer 3

Sue B,
u answered ur own '?'.
the chimney is over 100yrs old?
do u really want HOT exhaust gases going up that old chimney?
the toxic gases enter into the house through the leaks in the mortar where they heat up the contents of the house until a fire breaks out while u sleep , if the toxic gases didn't poison u first.
sorry for the graphic answer but this is why the new liner is Required.
if u don't get a permit to do the work and the house burns down the insurance company isn't likely to pay.
if money is issue, second jobs help or budgets.

Answer 4

What you should do is get a high efficiency condensing furnace. It would not use the chimney and you would save on your utility bill. For more info, check out the furnace page at www.hvac-for-beginners.com

Answer 5

Does your furnace vent out the old chimney?? why type of furnace is it...

Answer 6

Function Of Chimney

Answer 7

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