What would require an wood burning insert to have a block off plate Vs. not requiring it to have one
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hard wood slow day looking for excitement trying to bait me aye
Its required for the same reasons I posted back 4/5 years ago
Do a sight search aught to keep you busy for quite some time
Finally because I said so Elkimmeg'code
Its required for the same reasons I posted back 4/5 years ago
Do a sight search aught to keep you busy for quite some time
Finally because I said so Elkimmeg'code
Not trying to bait here either, but the Lopi install manual clearly states that a blockoff plate is only required for a direct connection to the existing chimney, not for a full re-line.
Eric said:
Eric - is the stove in yet? pics? And, I assume that you didn't get a block off plate for your install???
Chococat According to the international Mechanical code it is required to block intrusion of room air. I posted that code a while back Since is is a code requirement One does not have to defere to manufacture's listing to require it, Plus all listings reference installations to code compliance Here is a post I presented a while back It might help readers think threw the process a little clearer
his is a reprint of the post I presented in June. By code it is required. I don’t care what some installer or retailer tells you. Believing and putting your complete trust in them could make you dead wrong. Hearthnet would not exist if all went well. This is the one place where good advice code and safe installs are discussed.
Guy and his wife are sitting in the insurance office, negotiating the final payment settlement. I still remember those events in the early morning three weeks back. It happened so quickly. Sounded like a freight train was coming threw the house. Woke me up from a deep sleep. No sooner did the noise start when all the smoke alarms went off
The smoke was everywhere. Me and the misses, grabbed the cell phone and a couple of blankets and made our exit. The smoke was so thick by now; we could not see anything we had to feel our way out. The fire dept arrived to our home fully engulfed in smoke. They started breaking out all the windows then axing holes in the roof . The paramedics checked us out to see if we were ok. Finally the chief informed us everything was under control. And that we better make plans to find another place to stay. The smoke damage rendered the home uninhabitable. My wife asked if they found Rover, our 5 year old yellow Lab? The news was not good. Rover died instantly, when that first 2100-degree hot flash back blew out the bottom of the chimney. Rover too enjoyed the comfort and warmth of our wood stove; He would sleep right on the rug in front of it.
Flash back 7 years earlier. The installers seemed knowledgeable. I posted questions on Hearth.com One reply recommended that a damper block off plate was needed. No one ever went far enough to point out the blocker plate prevented flash back. Everybody was only concerned about preventing room air from escaping up the chimney. It was never explained that these bats are not a permanent solution. Condensation from normal humidity forms in the chimneys in the summer this moisture gets into the batts and causes them to sag. Once they sagged they no loner prevented the intrusion of room air. That cooled my uninsulated liner, to initiate and accelerate the formation of creosote. I remember the poster said it should be of ridged material and recommended at using 26 gage metal. They recommended using the full liner and all agreed the 316ti was the superior product. So why did it fail? I thought it was installed to prevent this from occurring? Unknown to all till the incident happened. The chimney had an offset. The installers had a hard time getting the liner threw the offset. They used excessive force and weaken the structural integrity of the liner.. The latest batch of wood could have been a bit dryer and with an offset, a natural shelf for creosote build up, disaster was imminent.
Back to the insurance office:. Here is your check for $50,000 to repair your home. You complain it’s not enough and produce your estimates. The agent is apologetic and explains his hands are tied and that the decision was not his. He then claims how he went to bat for you, to get you this much. Really it was the best he could possibly recover, for an un-permitted un- inspected installation that failed.
I did not take the time to explain the reasons of blocking off the damper, if I felt it un necessary. For those that put in batt insulation, I would not post that info and expose your shortcomings. I would be ashamed to admit I’m a cutting corners and advocating it is ok for others to follow suit. The installer this guy talked to , recommended this being an accepted, practice needs to get re-educated in a hurry. It’s installers like this, that guarantee my job security
his is a reprint of the post I presented in June. By code it is required. I don’t care what some installer or retailer tells you. Believing and putting your complete trust in them could make you dead wrong. Hearthnet would not exist if all went well. This is the one place where good advice code and safe installs are discussed.
Guy and his wife are sitting in the insurance office, negotiating the final payment settlement. I still remember those events in the early morning three weeks back. It happened so quickly. Sounded like a freight train was coming threw the house. Woke me up from a deep sleep. No sooner did the noise start when all the smoke alarms went off
The smoke was everywhere. Me and the misses, grabbed the cell phone and a couple of blankets and made our exit. The smoke was so thick by now; we could not see anything we had to feel our way out. The fire dept arrived to our home fully engulfed in smoke. They started breaking out all the windows then axing holes in the roof . The paramedics checked us out to see if we were ok. Finally the chief informed us everything was under control. And that we better make plans to find another place to stay. The smoke damage rendered the home uninhabitable. My wife asked if they found Rover, our 5 year old yellow Lab? The news was not good. Rover died instantly, when that first 2100-degree hot flash back blew out the bottom of the chimney. Rover too enjoyed the comfort and warmth of our wood stove; He would sleep right on the rug in front of it.
Flash back 7 years earlier. The installers seemed knowledgeable. I posted questions on Hearth.com One reply recommended that a damper block off plate was needed. No one ever went far enough to point out the blocker plate prevented flash back. Everybody was only concerned about preventing room air from escaping up the chimney. It was never explained that these bats are not a permanent solution. Condensation from normal humidity forms in the chimneys in the summer this moisture gets into the batts and causes them to sag. Once they sagged they no loner prevented the intrusion of room air. That cooled my uninsulated liner, to initiate and accelerate the formation of creosote. I remember the poster said it should be of ridged material and recommended at using 26 gage metal. They recommended using the full liner and all agreed the 316ti was the superior product. So why did it fail? I thought it was installed to prevent this from occurring? Unknown to all till the incident happened. The chimney had an offset. The installers had a hard time getting the liner threw the offset. They used excessive force and weaken the structural integrity of the liner.. The latest batch of wood could have been a bit dryer and with an offset, a natural shelf for creosote build up, disaster was imminent.
Back to the insurance office:. Here is your check for $50,000 to repair your home. You complain it’s not enough and produce your estimates. The agent is apologetic and explains his hands are tied and that the decision was not his. He then claims how he went to bat for you, to get you this much. Really it was the best he could possibly recover, for an un-permitted un- inspected installation that failed.
I did not take the time to explain the reasons of blocking off the damper, if I felt it un necessary. For those that put in batt insulation, I would not post that info and expose your shortcomings. I would be ashamed to admit I’m a cutting corners and advocating it is ok for others to follow suit. The installer this guy talked to , recommended this being an accepted, practice needs to get re-educated in a hurry. It’s installers like this, that guarantee my job security
Elk- I do not doubt that a block off plate is a good idea. I was just reading another post where someone stated that the manuel said the stove required a plate and was just wondering what differences would make one stove's manuel say it's required while anothers may not say it's required....
Elk, did you write that whole diatribe? Wow......you must have it stored somewhere and break it out.....
Choco - here is the simple answer. It is almost impossible to correctly seal most insert panels to the fireplace front. A lot of air can get through them - this works both ways.....hurts the draft when stove is being used, and can leak cold air into the home when it is not in use.
Now go back in time a few years when most inserts were not lined to the top. This made the lack of a plate even worse as soot from the chimney could easily fall down onto the insert and also even more draft from and to the home (because of no seal at the top)...
Then there is the issue of keeping as much heat in the "home space" as possible.... if the plate is properly installed, everything below it becomes part of the home space and the panels are purely decorative.
So, while it is possible that an full liner installation might be legal (with tight front panels and top seal), it is not the right way to do it. I'm not being a stickler about this - the easiest thing I can relate it to is making furniture. Certainly a nail might do the job - but screws, glue and notches do the job better!
I don't think it is going to burn any houses down not to have a metal plate (with full reline) - can't see how it would, as the liner system is still 100% contained.
Choco - here is the simple answer. It is almost impossible to correctly seal most insert panels to the fireplace front. A lot of air can get through them - this works both ways.....hurts the draft when stove is being used, and can leak cold air into the home when it is not in use.
Now go back in time a few years when most inserts were not lined to the top. This made the lack of a plate even worse as soot from the chimney could easily fall down onto the insert and also even more draft from and to the home (because of no seal at the top)...
Then there is the issue of keeping as much heat in the "home space" as possible.... if the plate is properly installed, everything below it becomes part of the home space and the panels are purely decorative.
So, while it is possible that an full liner installation might be legal (with tight front panels and top seal), it is not the right way to do it. I'm not being a stickler about this - the easiest thing I can relate it to is making furniture. Certainly a nail might do the job - but screws, glue and notches do the job better!
I don't think it is going to burn any houses down not to have a metal plate (with full reline) - can't see how it would, as the liner system is still 100% contained.
mind you 2006 direct cut and paste
RESIDENTIAL
CODE®
FOR ONE- AND TWO-FAMILY DWELLINGS
Part V — Mechanical
CHAPTER 18 Chimney& Vents
MECHANICAL
M1803.4 Connection to fireplace flue. Connection of appliances
to chimney flues serving fireplaces shall comply with
Sections M1803.4.1 through M1803.4.4.
M1803.4.1 Closure and accessibility. A rigid noncombustible
seal shall be provided below the point of connection to prevent
entry of room air into the flue. Means shall be provided
for access to the flue for inspection and cleaning
RESIDENTIAL
CODE®
FOR ONE- AND TWO-FAMILY DWELLINGS
Part V — Mechanical
CHAPTER 18 Chimney& Vents
MECHANICAL
M1803.4 Connection to fireplace flue. Connection of appliances
to chimney flues serving fireplaces shall comply with
Sections M1803.4.1 through M1803.4.4.
M1803.4.1 Closure and accessibility. A rigid noncombustible
seal shall be provided below the point of connection to prevent
entry of room air into the flue. Means shall be provided
for access to the flue for inspection and cleaning
Its a 30 dollar item... install the damned blocking plate. Its costing Craig more than that just to host all the bytes on this thread.
-- Mike
-- Mike
>M1803.4.1
These codes cannot be interpreted without seeing the entire context. For instance, there used to be a section relating to fireplace flue connections like this which dealt with putting a pipe through the wall above the mantel....this, of course, would require a seal below the point of connection...i.e, the damper area.
Then there is the question of whether the metal front panels are termed a "seal". My guess is that they are, which is why many manufacturers manuals have been approved by the test labs and don't show the plate.
The plate is the right way to go.....
It would be so nice if those codes had a simple diagram of an insert with front plates AND a damper seal.
I'll have to read some modern manuals to see what they are showing these days...
These codes cannot be interpreted without seeing the entire context. For instance, there used to be a section relating to fireplace flue connections like this which dealt with putting a pipe through the wall above the mantel....this, of course, would require a seal below the point of connection...i.e, the damper area.
Then there is the question of whether the metal front panels are termed a "seal". My guess is that they are, which is why many manufacturers manuals have been approved by the test labs and don't show the plate.
The plate is the right way to go.....
It would be so nice if those codes had a simple diagram of an insert with front plates AND a damper seal.
I'll have to read some modern manuals to see what they are showing these days...
Just dug around the Vermont Castings, Jotul and Duraliner manuals - between these three, you'd think they were up to date....
As I suspected, they say:
1. Is using a direct connect to first flue tile, then a damper seal must be used.
2. If using a full liner, EITHER a damper seal or fireplace front seal may be used.
Vermont castings, specifically, says it this way:
"The chimney must be sealed off from room air,
either by a plate at the damper level or by sealing
the fireplace opening. "
So, considering a full liner and a decent seal on the front panels, these inserts all meet manufacturer specs. My opinion is still that a damper seal is best, but that does not overshadow the manufacturers manual.
As I suspected, they say:
1. Is using a direct connect to first flue tile, then a damper seal must be used.
2. If using a full liner, EITHER a damper seal or fireplace front seal may be used.
Vermont castings, specifically, says it this way:
"The chimney must be sealed off from room air,
either by a plate at the damper level or by sealing
the fireplace opening. "
So, considering a full liner and a decent seal on the front panels, these inserts all meet manufacturer specs. My opinion is still that a damper seal is best, but that does not overshadow the manufacturers manual.
Mike Wilson said:
Thanks Mike, although it has nothing to do with the question I was asking. All I wanted to know was what would make one stove's manuel require it while the next stove might not. As I stated, I do not doubt the importance of a block off plate, just thought that there might be differences between inserts that caused discrepencies in the manuel.
Crqaig, thanks for the answer!
Im going to try to answer your question. Every stove is tested and and certified.
The EPA requires re-certification every 5 years. In VC case, the non cat intrepid would not meet the EPA phase II regs,
so therefore not being a good seller they opted to drop that model. When the stove line is certified so are the manuals and recomended installations
/ manufactures specs. In order to cover changing codes the listing will have language that requires adhearance to code or NFPA211
For example a dramatic code change occured in 2003 NFPA 211. The manuals with that stove, could be printed in 2001 and they will not update the manual till re-certification occures
NFPA 211 changed the Cross-sectional code for venting in to a larger flue. The former code allowed 3x the flue collar cross-sectional area .
2003 change that to 3x for chimney locations within the building structure and 2x for chimneys exposed to exterior. The ramifications of this change,
meant that almost all inserts with 6" flue collars had to be lined if installed in an exposed chimney. using the existing fireplace flue
Most fire place flues were now ,larger that 2x 8/12 or 12/12 are the common ones used.
The point being, most manufactures s listings still show direct connect in exterior locations, as perfectluy acceptable because, when the manual was published in 2001, it was
All manuals call in compliance to NFPA211, in which the latest code can be applied. I inspect according to the code at the time of installation, not when the manual was published
Many here will tell you manufactures listings / specs trumps code. To an extent that is correct.. What manufactures specs can not do, is make me sign off a direct connect, even though the outdated manual tells me it is ok, in the case of the cross-sectional code. Yes I can hide behind the manufactures specs and approve the direct connect in an exterior fireplace.
If I go counter to manufactures specs I have to have a code base to back up my decision ,in this case I have 2003 NFPA 211
Lets face the manufactures fudge the BTUs and areas that a stove will heat. They know more stoves will sell if the cost of installation is less. Telling an potential owner the cost just went up
$1000 for the liner and installs will reduce sales. This week we had two post where the installer was going to direct connect into an existing exterior fireplace flue and stuff insulation to block the damper plate . It happened to one of my pellet inspections last week, plus the installed also ended the outside air feed within inches of the exhaust, inside the first clay flue liner
The installer was paid for the blockoff plate and a full liner.
Here is another way to look at the block off plate issue, something has to prevent the loss of room air up the chimney. A product used to make the block off has to be noncombustiable.
The product or material has to be listed by the product manufacturer for that application
An example of this is the high effeciench gas furnaces and hotwater heaters, use schedule 40 PVC drain pipe to direct vent there furnaces. The pvc pipe manufactures only test and certify their pipes for water flows and pressures. ITs up to the furnace manufactures to test the drain PVC pipe for their application.
Back to the block off area, common fiberglass insulation is only listed to insulate walls and floors There is no listing from the fiberglass manufactures, where its use is listed, to form the block off area of the damper . Manufactures do make and list metal damper block off plates. None make fiberglass ones. This probably does not completely answed your question but hopefully give you some insite how things are tested and can become out dated as code changes. I tried ,If I had all the answers I probably would not ne hanging out here. I'm still learning
The EPA requires re-certification every 5 years. In VC case, the non cat intrepid would not meet the EPA phase II regs,
so therefore not being a good seller they opted to drop that model. When the stove line is certified so are the manuals and recomended installations
/ manufactures specs. In order to cover changing codes the listing will have language that requires adhearance to code or NFPA211
For example a dramatic code change occured in 2003 NFPA 211. The manuals with that stove, could be printed in 2001 and they will not update the manual till re-certification occures
NFPA 211 changed the Cross-sectional code for venting in to a larger flue. The former code allowed 3x the flue collar cross-sectional area .
2003 change that to 3x for chimney locations within the building structure and 2x for chimneys exposed to exterior. The ramifications of this change,
meant that almost all inserts with 6" flue collars had to be lined if installed in an exposed chimney. using the existing fireplace flue
Most fire place flues were now ,larger that 2x 8/12 or 12/12 are the common ones used.
The point being, most manufactures s listings still show direct connect in exterior locations, as perfectluy acceptable because, when the manual was published in 2001, it was
All manuals call in compliance to NFPA211, in which the latest code can be applied. I inspect according to the code at the time of installation, not when the manual was published
Many here will tell you manufactures listings / specs trumps code. To an extent that is correct.. What manufactures specs can not do, is make me sign off a direct connect, even though the outdated manual tells me it is ok, in the case of the cross-sectional code. Yes I can hide behind the manufactures specs and approve the direct connect in an exterior fireplace.
If I go counter to manufactures specs I have to have a code base to back up my decision ,in this case I have 2003 NFPA 211
Lets face the manufactures fudge the BTUs and areas that a stove will heat. They know more stoves will sell if the cost of installation is less. Telling an potential owner the cost just went up
$1000 for the liner and installs will reduce sales. This week we had two post where the installer was going to direct connect into an existing exterior fireplace flue and stuff insulation to block the damper plate . It happened to one of my pellet inspections last week, plus the installed also ended the outside air feed within inches of the exhaust, inside the first clay flue liner
The installer was paid for the blockoff plate and a full liner.
Here is another way to look at the block off plate issue, something has to prevent the loss of room air up the chimney. A product used to make the block off has to be noncombustiable.
The product or material has to be listed by the product manufacturer for that application
An example of this is the high effeciench gas furnaces and hotwater heaters, use schedule 40 PVC drain pipe to direct vent there furnaces. The pvc pipe manufactures only test and certify their pipes for water flows and pressures. ITs up to the furnace manufactures to test the drain PVC pipe for their application.
Back to the block off area, common fiberglass insulation is only listed to insulate walls and floors There is no listing from the fiberglass manufactures, where its use is listed, to form the block off area of the damper . Manufactures do make and list metal damper block off plates. None make fiberglass ones. This probably does not completely answed your question but hopefully give you some insite how things are tested and can become out dated as code changes. I tried ,If I had all the answers I probably would not ne hanging out here. I'm still learning
Excellent info in this thread. Before I got to this post, I was wondering about why to use a block-off plate.
Can I make a suggestion? Can some of this information be incorporated into the article on how to make a block-off plate? As a newbie, I've have read dozens of posts where members remind people to use a block-off plate. Not knowing what one was, I read the how-to article where I learned what a block-off plate is. It then took quite a bit of hit-or-miss searching through forum posts to find this thread about WHY to use a block-off plate. And maybe there is plenty of other good WHY information that I still haven't found. If it's too much info to add to the HOW-TO, maybe a WHY article could be compiled and the articles could cross-reference each other?
I don't have sufficient knowledge and experience to compile or revise articles on this topic, so I thought I'd throw this out there for those who do. From what I've read, it seems like some installers don't buy into the need for a block-off plate and this info could help prospective buyers ensure they don't get talked out of one. Maybe this is the idealist in me talking, but it might even lead to the conversion of some installers who feel it's unnecessary. I started looking for info on WHY because I haven't discussed this yet with my potential dealer/installer and I prefer to know why I need something before I argue with a pro about how they should do something! My next step will be to take the code info and other pro-plate arguments here to my dealer and ask what they think about block-off plates and if they install them as part of the installation.
Just some suggestions from a newbie's perspective. Thanks again for all the help!
Can I make a suggestion? Can some of this information be incorporated into the article on how to make a block-off plate? As a newbie, I've have read dozens of posts where members remind people to use a block-off plate. Not knowing what one was, I read the how-to article where I learned what a block-off plate is. It then took quite a bit of hit-or-miss searching through forum posts to find this thread about WHY to use a block-off plate. And maybe there is plenty of other good WHY information that I still haven't found. If it's too much info to add to the HOW-TO, maybe a WHY article could be compiled and the articles could cross-reference each other?
I don't have sufficient knowledge and experience to compile or revise articles on this topic, so I thought I'd throw this out there for those who do. From what I've read, it seems like some installers don't buy into the need for a block-off plate and this info could help prospective buyers ensure they don't get talked out of one. Maybe this is the idealist in me talking, but it might even lead to the conversion of some installers who feel it's unnecessary. I started looking for info on WHY because I haven't discussed this yet with my potential dealer/installer and I prefer to know why I need something before I argue with a pro about how they should do something! My next step will be to take the code info and other pro-plate arguments here to my dealer and ask what they think about block-off plates and if they install them as part of the installation.
Just some suggestions from a newbie's perspective. Thanks again for all the help!
Good suggestion - will have to add an entry on this to the wiki and then link to it from the article.
BTW, we should keep in mind that EPA regs and mechanical codes have NOTHING (or little) to do with each other. EPA only cares about the smoke or lack thereof.
BTW, we should keep in mind that EPA regs and mechanical codes have NOTHING (or little) to do with each other. EPA only cares about the smoke or lack thereof.
[quote author="chemist44286" date="1166741884"]Excellent info in this thread. Before I got to this post, I was wondering about why to use a block-off plate.
Can I make a suggestion? Can some of this information be incorporated into the article on how to make a block-off plate? As a newbie, I've have read dozens of posts where members remind people to use a block-off plate. Not knowing what one was, I read the how-to article where I learned what a block-off plate is. It then took quite a bit of hit-or-miss searching through forum posts to find this thread about WHY to use a block-off plate. And maybe there is plenty of other good WHY information that I still haven't found. If it's too much info to add to the HOW-TO, maybe a WHY article could be compiled and the articles could cross-reference each other?
I don't have sufficient knowledge and experience to compile or revise articles on this topic, so I thought I'd throw this out there for those who do. From what I've read, it seems like some installers don't buy into the need for a block-off plate and this info could help prospective buyers ensure they don't get talked out of one. Maybe this is the idealist in me talking, but it might even lead to the conversion of some installers who feel it's unnecessary. I started looking for info on WHY because I haven't discussed this yet with my potential dealer/installer and I prefer to know why I need something before I argue with a pro about how they should do something! My next step will be to take the code info and other pro-plate arguments here to my dealer and ask what they think about block-off plates and if they install them as part of the installation.
Just some suggestions from a newbie's perspective. Thanks again for all the help
Ok, let me throw another log onto the fire and ask, is their a difference between a wood burning inserts in a masonry fire place VS a ZC fireplace when it comes to block off plates???? I know the install that the dealer just did on my ZC did not include a block off plate, however I have a full surround covering the front of the fireplace. Not sure if this applies or not
From the view point of a long-time dealer/installer:
In the old days, it was understood that a damper block-off was needed in all direct connect installs (pipe up and into the first/bottom flue tile). Most insert manufacturers also allowed for a "slammer" install, where the surround panels were used to seal off the fireplace and a pipe may not even be inserted into the collar and up through the damper. Then reality stepped in and it was discovered that these types of installs were assinine (dangerous, life threatening, etc. - you don't know what you don't know).
When we started doing full relines we reasoned that as long as the top was blocked off we had our block-off in place. With inserts, the surround panels were not "sealed" anymore because the liner went all the way up and was "sealed" at the top. Again, reality set in and stupidity was evident. With and outside fireplace there was no stopping the loss of warm room air and this was competing for draft and contributing to poor efficiencies. Then the energy codes kicked in. All fireplaces required sealed dampers or doors and all re-lines required block-offs at the bottom, not just the top. It turned out that this was the best install, and not directly encouraged by our industry but came out of the practice to control air exchange and energy use in our homes.
About 10 years ago we started refusing to install "direct connects". Shorly after that we sarted insisting on a block off plate at the damper level in ALL installations. This policy has turned out to be a benefit to thousands of new installs and we continue to upgrade old direct connects when we get the opportunity. Most of our manufacturers still show direct connects as allowable and we do end up arguaing a little about this topic from time to time. But we simpley refuse to install a direct connect or eliminate the block-off when a full liner is installed. The surround panels are considered decorative in most cases. This goes for wood, coal, gas, or pellet. It just makes sense to block off the fireplace flue. The stove gets full benefit of the draft up the stack and the house air exchange and energy efficiency is not negatively affected.
Note that in the case of a wood or coal insert we do feel it is an acceptable alternative to seal the panels to the front of the fireplace (with a full reline). It is not always possible or desirable. The damper/lintel block-off is usually the best solution.
Sean
In the old days, it was understood that a damper block-off was needed in all direct connect installs (pipe up and into the first/bottom flue tile). Most insert manufacturers also allowed for a "slammer" install, where the surround panels were used to seal off the fireplace and a pipe may not even be inserted into the collar and up through the damper. Then reality stepped in and it was discovered that these types of installs were assinine (dangerous, life threatening, etc. - you don't know what you don't know).
When we started doing full relines we reasoned that as long as the top was blocked off we had our block-off in place. With inserts, the surround panels were not "sealed" anymore because the liner went all the way up and was "sealed" at the top. Again, reality set in and stupidity was evident. With and outside fireplace there was no stopping the loss of warm room air and this was competing for draft and contributing to poor efficiencies. Then the energy codes kicked in. All fireplaces required sealed dampers or doors and all re-lines required block-offs at the bottom, not just the top. It turned out that this was the best install, and not directly encouraged by our industry but came out of the practice to control air exchange and energy use in our homes.
About 10 years ago we started refusing to install "direct connects". Shorly after that we sarted insisting on a block off plate at the damper level in ALL installations. This policy has turned out to be a benefit to thousands of new installs and we continue to upgrade old direct connects when we get the opportunity. Most of our manufacturers still show direct connects as allowable and we do end up arguaing a little about this topic from time to time. But we simpley refuse to install a direct connect or eliminate the block-off when a full liner is installed. The surround panels are considered decorative in most cases. This goes for wood, coal, gas, or pellet. It just makes sense to block off the fireplace flue. The stove gets full benefit of the draft up the stack and the house air exchange and energy efficiency is not negatively affected.
Note that in the case of a wood or coal insert we do feel it is an acceptable alternative to seal the panels to the front of the fireplace (with a full reline). It is not always possible or desirable. The damper/lintel block-off is usually the best solution.
Sean
Elderthewelder said:
You are not alone in wondering. We just came accross this very issue and it re-inforces our policy to block-off the damper/lintel. We installed a wood insert with a full set of surround panels into a Majestic ZC fireplace (both units are approved for this use). We relined the entire flue and used a UL approved block-off plate at the top (specifically for use with ZC air-cooled chimneys). We knew the panels would not completely cover the opening of the fireplace. The owner was planning to add surround extensions to finish colsing the gap. He wanted something specially designed to preserve the architectural look. We finished up the install but neglected to put a block-off at the bottom. (An oversight - we should have done it).
After a couple of days I got a call from the owner. His stove was not drafting. It was taking too long to start up and get up to temperature. I went over and did a test burn. Sure enough. It was sluggish. I used a smoke pencil to check for draft. I noticed the draft was strong around the panels. What was happening was the stack was thermosyphoning and copmpeting for draft. I told the owner we would return to install a proper block-off and see if it helped. After we installed the block-off the draft at the panels was significantly reduced - but still visible. But the stove was drafting much better and it took half the time to get up to temperature.
We could not seal off the fireplace entirely. With a zero clearance you are not supposed to block off the circulator around the firebox. But by blocking off the flue pipe we achieved better results. With zero-clearnances it can be tricky because you can't totally block off the fireplace in most cases. But, we maintian that is the best practice to block off the flue at the damper/lintel. This will allow for the best draft through the insert and allows the use of panels to be optional, which may be needed with some ZC installs.
I added a simple entry to the wiki and then linked it both ways to the block off article.
https://www.hearth.com/econtent/index.php/articles/making_a_block_off_plate/
see link at second sentence.
https://www.hearth.com/econtent/index.php/articles/making_a_block_off_plate/
see link at second sentence.
Elderthewelder said:
In my opinion using a tightly sealing front panel on a prefab installation is a no-no.
Many of the older units have cooling vents INSIDE the firebox which help the chimney and firebox stay at lower temps - in other words, not burn the house down.
I would say that a plate of some type (We often used metal trim rings) would be the best way to do this job. If I am not wrong, code forbids the tight sealing of the top of prefab lining jobs. That means if it is not sealed at bottom, there will be cold air leakage one way or the other.
elkimmeg said:
Elk, Web
Two questions:
1) what is the method (at the top exterior of the chimney) one uses to support the weight of the liner and do you have any photos of this? Is there some type of "collar" you clamp to the insert with "ears" on both sides that you support on the outer edges of the liner?
2) If I understand this correctly, once the liner is placed down the flue and put through the hole in the block-off plate, the plate is then sealed around the edges of the chimney with silicon and the hole where the liner pierces the plate is sealed with furnace cement. How then do you get enough "flex" or give in the liner to connect the insert and then shove the insert back into place without putting too much pressure on the blockoff plate and causing the liner to be shoved back through the hole in the block-off plate and therefore loosening the seal you made with furnace cement? That is, it would seem that the liner would need to "compress" in the short distance between the firebox connection point and the point where the liner pierces the block-off plate yet not put enough pressure on the liner to loosen the furnace cement seal to the block-off plate.....is there that much "give" in that short a distance in a SS liner? You'd also need this "give" when you pull the insert for any inspections
thanks
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