Home chimneys

[John Terefenko]

For those in the know about chimneys, a few questions. First I am talking homeowner chimneys. Forgive the not knowing names. But what are the red blocks that line the interior of a chimney. They are square and stack on top of each other and then block and or brick is built around them.

The reason I am asking is there now a law that if you replace your boiler or hot water heater and it is piped into the chimney then you need to have a steel liner inserted??? I have conflicting reports that if you chimney is lined with terracotta bricks then it does because they can leak gases. But if you have these red blocks and for a lack of a better name clay blocks you do not. Anyone with knowledge of new rules when installing a new furnace and or water heater. Or do you know the rules to when you need to install a steel liner?? I will be needing to do this next year. Thanks.

[Tom M King]

Flue liners. I've never heard of steel liners being required in a properly built chimney with flue liners.

[John Terefenko]

Flue liners. I've never heard of steel liners being required in a properly built chimney with flue liners.
Flue liners is that the proper name for those red or orange colored blocks that stack?? What are they made from?? I am saying steel liners, they I think are stainless steel flexible liners that they snake down a chimney if you have a poor chimney.

[Jim Becker]

The red tile flue liners are fine for more traditional, lower efficiency burning appliances, but many mid-efficiency devices require stainless steel flues because of the chemical natures of the stuff that has to flow through them. The most efficient devices can vent through PVC and cannot be routed through an existing chimney. So the bottom line is, yes, if you replace and existing device, you may very well have to have a stainless steel flue installed. There are also multiple types and the correct one for the appliance has to be employed.

The HVAC in our addition has a SS flue...I made the mistake of accepting the proposal for an 80% system at the time not knowing any better. That SS stuff is darn expensive and honestly, it would have been about the same cost to install the more efficient unit that used PVC! It was an expensive lesson. The same unit, but 95% efficiency in the other part of the house that was installed after a basement flooding uses PVC vented out the side of the house and the original flue was closed off. Both of my tankless water heaters use PVC.

[Paul F Franklin]

In our area (NE Ohio), if you change your water heater or furnace you will have to have the chimney lined, period (unless you DIY and don't pull a permit). Unless you change to a model that is power vented through PVC, as Jim mentions. The main reason, as I understand it, it that today's more efficient water heaters and furnaces have lower flue gas temperature and it's just not enough to warm flue tiles enough to reliably generate the draft needed when it cold outside.

[Jim Matthews]

I replaced my ancient Burnham boiler with a Vitodens 100W.

It vents directly out of the house just above the sill line.
The old chimney is now sealed at the bottom with an inverted U cap. This meets code and was considerably less expensive than relining the (now redundant) chimney.

[Jim Koepke]

The reason I am asking is there now a law that if you replace your boiler or hot water heater and it is piped into the chimney then you need to have a steel liner inserted???

Isn't this an issue that differs by state code?

Some states will not allow running the exhaust from a water heater or boiler through a fireplace or wood stove chimney.

jtk

[Jim Becker]

I've never seen them combined to use the same flue, even if they are parallel up the overall chimney, Jim.

[John Terefenko]

Getting an education and yes when it comes time I will check with building codes and hopefully contractor knows them as well. Thanks every one. Mkes sense about more efficient models today.

[Myk Rian]

Our chimney, built in 1972, is as OP describes. With the flue liners stacked to the top, and brick.
It had a lot of problems keeping the bricks in place. Freeze thaw cycles popped the mortar loose.
After a few chimney repairs a hole was found in one of the liner blocks. Water got behind the bricks from the exhaust vapor.
A flexible hose liner was installed, end of the problem.

[Stan Coryell]

In our area (NE Ohio), if you change your water heater or furnace you will have to have the chimney lined, period (unless you DIY and don't pull a permit). Unless you change to a model that is power vented through PVC, as Jim mentions. The main reason, as I understand it, it that today's more efficient water heaters and furnaces have lower flue gas temperature and it's just not enough to warm flue tiles enough to reliably generate the draft needed when it cold outside.

It's not the draft so much as the lower temperature flue gas condenses. The condensation may eventually deteriorate a terracotta liner.
80% gas fired appliances use flexible aluminum liners. Oil fired appliances use flexible stainless steel liners. A +90% is direct or indirect vent and uses PVC pipe (low exhaust temperature and a lot of condensation). At least in New Jersey. Philadelphia use to require hard stainless liners, I am not sure if the still do.

Aluminum liners are cheap. I replaced mine along with the water heater right after Christmas. The 4" liner was about $115. I would expect the contactor to charge about $500 with installation. Well worth it.

[Ole Anderson]

After I went to a high efficiency furnace with PVC venting, all that was left using the old 8"x8" vitreous flue was my water heater with a 3" vent. Not enough heat to generate a draft so I was getting fumes in the basement. Solved by inserting a 4" aluminum flexible flue liner with a proper cap, sealing each end of the unused portion of the old flue. At the same time I sealed off another 8"x8" unused flue that tended to bring smoke from my fireplace into the basement via a backdraft.

BTW, those red blocks inside the other masonry would likely be fire bricks, or refractory, designed for much higher temps than ordinary portland cement masonry.

[Mike Cutler]

For those in the know about chimneys, a few questions. First I am talking homeowner chimneys. Forgive the not knowing names. But what are the red blocks that line the interior of a chimney. They are square and stack on top of each other and then block and or brick is built around them.

The reason I am asking is there now a law that if you replace your boiler or hot water heater and it is piped into the chimney then you need to have a steel liner inserted??? I have conflicting reports that if you chimney is lined with terracotta bricks then it does because they can leak gases. But if you have these red blocks and for a lack of a better name clay blocks you do not. Anyone with knowledge of new rules when installing a new furnace and or water heater. Or do you know the rules to when you need to install a steel liner?? I will be needing to do this next year. Thanks.

John

It's based on flue sizing requirements. I don't know about "laws", but the code may be requiring a smaller flue and chimney for the appliance than what you currently have.
There are Chimney liners, which is an uninsulated stainless steel liner that is sized for chimney and inserted. It will be either a long flexible "snake", or individual, interlocking, gas sealing, sections installation. A new chimney built today will more than likely have a stainless steel liner.
There are also chimney adapters, which will be an insulated flue pipe dropped down your chimney sized for the appliance. It will terminate at the top and through your existing thimble.
Bottom line is that they are not a bad thing to have, especially if you have an older chimney. They're actually a very safe addition. You need to know which one New Jersey is requiring. I'm going to guess, it's the second example.

[Brian Elfert]

My parents put a wood burning stove insert into a masonry fireplace way back in the mid 1980s. It turns out they needed to have a stainless liner put in the masonry chimney at the last minute and it was a major expense my parents did not expect.

I ended up removing the chimney in my current house. The roof was leaking around it and the only thing it had ever been used for was a wood stove in the basement that was long gone.

[John Terefenko]

Thanks Mike Cutler.

[Steve Demuth]

Sounds familiar. The first tankless water heater I installed here required stainless steel, insulated venting. Gases hot enough to be a hazard, but cool enough to be highly condensing, and thus acidic. Also had to be horizontal, and sloped to the outside to drain. The one I just installed is fully condensing, and vents through PVC. Just a way better solution.

[Mike Cutler]

Thanks Mike Cutler.

You're welcome John.
A coworker just had their chimney remediated and sleeved last summer. I think it was about $1500- $1800.00 for an insulated chimney insert.It took less than a day to install.They have a single story dwelling.
There is also a process where they break out all the chimney tiles and pour a new single,no seam, liner, but it's wicked expensive, and may not meet needs such as your requirement for a smaller flue.
What you will probably end up having done is an insulated corrugated stainless steel liner. It will be a long snake looking thing wrapped in chicken wire. It will be sized to your existing chimney dimensions.
It goes in from the top and will have the clean out port already attached. The location where it meets your existing thimble will have a hole and flange precut. A birds mouth adapter and strap( giant hose clamp), will be inserted through your existing thimble and the liner will go through the strap. Then the thimble adapter will be tightened to the flue pipe giving you a seamless installation. They're really pretty slick.
There is a whole cottage industry to personalize the chimney termination cap. The sky is the limit to personalize your chimney cap.
Be sure to inform your insurance company that an insulated liner/flue was installed. You may get a few bucks off your yearly premium. Insurance companies hate chimneys. ;)

[roger wiegand]

You're much better off at this point replacing appliances with sealed combustion condensing units. These draw makeup air from outside and are power vented through PVC pipe at near ground level. You avoid the expense of a stainless liner and eliminate the potential for backdrafting combustion gasses back into your house. Installation is typically quite easy, and the efficiency is great.

[Scott Winners]

Jim Becker (and company) are repeating what I have learned burning about 8 cords annually in my wood stove. The new more efficient appliances have lower exhaust gas temps, and perform best with right sized chimney diameter and insulation.

On my wood stove it is beneficial to keep the exhaust gas temperature pretty hot right up to the chimeny exit so the water vapor in the exhaust stream does not condense on the inside of the chimney pipe.

[Brian Elfert]

You're much better off at this point replacing appliances with sealed combustion condensing units. These draw makeup air from outside and are power vented through PVC pipe at near ground level. You avoid the expense of a stainless liner and eliminate the potential for backdrafting combustion gasses back into your house. Installation is typically quite easy, and the efficiency is great.

The federal government mandated 90% furnaces in 30 states back in 2013. The regulation was rescinded later and it is unclear if it was reinstated. The issue was a lot of houses it was very expensive or impossible to install the PVC exhaust. Condos and townhouses were especially bad. It isn't always practical or possible to install a 90% furnace.

[roger wiegand]

The federal government mandated 90% furnaces in 30 states back in 2013. The regulation was rescinded later and it is unclear if it was reinstated. The issue was a lot of houses it was very expensive or impossible to install the PVC exhaust. Condos and townhouses were especially bad. It isn't always practical or possible to install a 90% furnace.

I don't think anything precludes running the PVC up the original chimney in such a case (I could be wrong, I don't know the code). Condo rules may well make life difficult, I was thinking single family houses. You have so much flexibility in running the PVC I have trouble imagining a situation that makes an install impossible, but if the combination of circumstances makes it impossible then it is. I've only done it a few times, so clearly haven't encountered all the possible barriers. My son's house required some out-of-the box thinking to meet all the requirements.

Sealed combustion doesn't have to be 90+%, though most are. My shop heater uses outside makeup air but is only an 85% furnace. It vents with conventional metal flue pipe, double walled to provide the return path. I didn't want to be sucking dust and fumes into the burner.

[Brian Elfert]

The mandate was 90%, not sealed combustion. I don't think there is a 90% furnace that is not sealed combustion which is why there was such a fuss. It wasn't that the installations were impossible in all cases, but impractical due to the cost and length of runs. I believe I have seen PVC exhaust run up a chimney, but if the water heater also was going up to chimney then it might need to be replaced with a PVC vented model. I'm sure going up a chimney instead of another 80% furnace is not cheap.

My house had electric baseboard heat when purchased. I had ductwork installed for a furnace. I didn't have a flue of any kind and I wanted a 90% furnace anyhow so everything was done in PVC. I was lucky that it was easy to do. My water heater is power vent so it is also PVC exhaust.

[Jim Becker]

Roger, my understanding is that you cannot route the PVC up an existing chimney and one factor is likely distance. Just like with our dust collection systems, the high efficiency furnaces and water heaters need to move a minimum amount of air at a given velocity to do their jobs and distance matters in that respect. (so does directional changes)

[Stan Coryell]

Roger, my understanding is that you cannot route the PVC up an existing chimney and one factor is likely distance. Just like with our dust collection systems, the high efficiency furnaces and water heaters need to move a minimum amount of air at a given velocity to do their jobs and distance matters in that respect. (so does directional changes)

It's not always possible to vent a 90%+ horizontally and maintain the required distances from doors and windows. Picture a 12' wide row home. In the front, a door and 3 windows. The rear: a door, two windows, and a basement window.

The PVC flue can be run vertically through an existing chimney. Although most installations require direct venting. Direct venting requires intake combustion air and flue exhaust. Most chimneys won't have enough room for two 3" or even two 2" pipes. Even if it did what about the water heater? They can not be combined.

Also, to remove the furnace from the flue shared with the water heater, requires the flue be changed to the correct size for the water heater. 4" in New Jersey.

It isn't always practical to replace an 80% with a 90+%

[Jim Becker]

Yes, I've done this dance over the years, Stan. You are absolutely correct that a horizontal penetration is sometimes difficult and going more efficient tough. This actually delayed getting tankless in the 250 yo side of our home because early on, the units required SS flue and the distance was too great to use the existing chimney from that area. Once I could use PVC, that happened. But with 24" thick stone walls, the pathway was through a window-well. HVAC was done the same way when that unit was replaced with high-efficiency. The tankless unit in the addition side of the house vents vertically through the roof, albeit with a sloped horizontal pathway to the penetration points in the attic. That one was much easier as can be imagined.

[Stan Coryell]

Jim,
I feel your pain with the field stone walls. I've core drilled a few holes through them. I did a job in Manyunk that required 12 16" holes, the walls were about 30" thick.

[Jim Becker]

Jim,
I feel your pain with the field stone walls. I've core drilled a few holes through them. I did a job in Manyunk that required 12 16" holes, the walls were about 30" thick.

Yes, when we had the electrical upgraded in 2005, the contractor had to core drill through about 20" of limestone wall...twice. He went through two rented 3" diamond core drills to complete the task as there were two 200a feeds down from the meter; one for the house main panel plus the disconnect for my shop and then another core drill deeper down for the conduit to the shop's panel. That was a day filled with very colorful language! Fortunately, when I did the water heater, I could use that existing window-well...

[John Terefenko]

Being I will be changing the furnace and the hot water heater, will I need 2 liners or do they tap off and just one?? This is a ranch house so the roof line is not far.

[Jim Becker]

John, AFAIK, each appliance has to have it's own inlets/outlets and they have to be sized specifically for the unit and sometimes for the distance. I would imagine they can follow a similar path, but the installing company will have to verify that. For the 90%+ efficient products that have separate intake/exhaust, there are also very specific rules about proximity at the termination point outside and that could be fun when utilizing an existing chimney structure as a pathway.

[John Terefenko]

John, AFAIK, each appliance has to have it's own inlets/outlets and they have to be sized specifically for the unit and sometimes for the distance. I would imagine they can follow a similar path, but the installing company will have to verify that. For the 90%+ efficient products that have separate intake/exhaust, there are also very specific rules about proximity at the termination point outside and that could be fun when utilizing an existing chimney structure as a pathway.

Thanks Jim. I guess all this will be more clear once I have the people down.

[Jim Becker]

Thanks Jim. I guess all this will be more clear once I have the people down.
Yup...the actual specifications for the units you choose for heating and making hot water matter.

[Stan Coryell]

If you stick with 80% gas equipment, you only need one liner. 100k furnace and 40 gallon water heater would be 5" aluminum flexible chimney liner.