Insulating a liner, why does the insulation need to be overlapped?

[neverstop]

Assuming the insulation is 0.5" overlapping the liner increases the OD (at the overlap section) by 1.5". Is this overlap necessary?

My assumption is that the adhesive adheres to the liner better than the to foil insulation backer, but even if that is incorrect a 1" overlap isn't going to provide significant increase in holding force. If anything it could provide an easier point for peel-back of the insulation over time.

 

[EbS-P]

My kit came with spray adhesive sparky insulation and liner. It probably burns off the bottom. But it did a good job holding everything in place while wrapped. The taped over lapped seam is a bit bigger but once taped around every couple feet then taped the whole length it’s not really making it more difficult to install.

I’m guessing the reason is to ensure there is little chance of a the hot liner surface touching anything. It’s still is a bit fluffy/compressible. But if you think the extra 1/2” is going to be an issue you need to break out the clay liner. Just my thoughts.

 

[bholler]

Assuming the insulation is 0.5" overlapping the liner increases the OD (at the overlap section) by 1.5". Is this overlap necessary?

My assumption is that the adhesive adheres to the liner better than the to foil insulation backer, but even if that is incorrect a 1" overlap isn't going to provide significant increase in holding force. If anything it could provide an easier point for peel-back of the insulation over time.

It's to ensure complete coverage. The spray glue is only to help assemble stops working after the first fire or 2. That's why you need to tape well and cover with the stainless mesh

 

[neverstop]

It's to ensure complete coverage. The spray glue is only to help assemble stops working after the first fire or 2. That's why you need to tape well and cover with the stainless mesh

this is the information I was looking for @bholler, thank you.

I snapped the image below last night of my tee and then scaled it based on the tee cover diameter 5.5". The approximate width/length (yellow line shown in image) of the internal dimensions of the clay flue are 7.725/12in respectively. This is measuring internal joint surface to joint surface. Measuring internal dimensions without the joints its ~8.5x12.5(or 13, hard to find the surface in that part of the image). Using the same technique from my last inspection the external dimensions are ~ 9"x14"

Does that make sense for a rectangular clay flue tile? They're from the 80's.

I need to pull this 5.5" uninsulated liner and replace it with a 6" insulated liner. The chimney is straight.

What are chances of me having to break out the tiles to accomplish this? I have this inclination that the clay flue is mortared in place just because that's my luck.

 

[bholler]

this is the information I was looking for @bholler, thank you.

I snapped the image below last night of my tee and then scaled it based on the tee cover diameter 5.5". The approximate width/length (yellow line shown in image) of the internal dimensions of the clay flue are 7.725/12in respectively. This is measuring internal joint surface to joint surface. Measuring internal dimensions without the joints its ~8.5x12.5(or 13, hard to find the surface in that part of the image). Using the same technique from my last inspection the external dimensions are ~ 9"x14"

Does that make sense for a rectangular clay flue tile? They're from the 80's.

View attachment 297513

I need to pull this 5.5" uninsulated liner and replace it with a 6" insulated liner. The chimney is straight.

What are chances of me having to break out the tiles to accomplish this? I have this inclination that the clay flue is mortared in place just because that's my luck.

I can all but guarantee you will have to break out to fit a 6" round insulated liner in there. But you could use a 6" equivalent oval liner easily

 

[neverstop]

I can all but guarantee you will have to break out to fit a 6" round insulated liner in there. But you could use a 6" equivalent oval liner easily

I forgot about that option. In that case as long as the cross-sectional area is the same the draft should be the same correct? Do you have a preferred brand for oval?

To confound things I'm going to have to connect to Class A at the top of the chimney because I need to increase the height but I'm unsure about how much will fix my low draft issues. I know it has to be at least 5ft and I got a $2k quote to extend the chimney 5ft. Class A would almost be half the price and I could easily change height after the fact.

 

[begreen]

DuraLiner oval is preinsulated. They make a system for this, including the class A transition.

 

[bholler]

Duraliner would be a good option. I generally just ovalize my own liners because I have an ovalizer. Most manufacturers have adapters to get back to 6" round as well

 

[neverstop]

DuraLiner oval is preinsulated. They make a system for this, including the class A transition.

Duraliner would be a good option. I generally just ovalize my own liners because I have an ovalizer. Most manufacturers have adapters to get back to 6" round as well

I'm not seeing an oval option. I will admit that their website is not the most friendly

 

[begreen]

Download the DuraLiner catalog or the whole DuraVent catalog for parts details. There are also installation guides here. Twirl down the Resources section:

DuraLiner® | Duravent

Consistently the first to market with new innovations in venting systems, DuraVent has captured a leadership position in emerging markets.

duravent.com

It's not the only option, but a good working solution.

Weak draft can have multiple causes, including venting into too large of a chimney. Can you detail the current installation? How tall is the existing chimney?

 

[neverstop]

Download the DuraLiner catalog or the whole DuraVent catalog for parts details. There are also installation guides here. Twirl down the Resources section:

DuraLiner® | Duravent

Consistently the first to market with new innovations in venting systems, DuraVent has captured a leadership position in emerging markets.

duravent.com

It's not the only option, but a good working solution.

Weak draft can have multiple causes, including venting into too large of a chimney. Can you detail the current installation? How tall is the existing chimney?

i had downloaded the duraliner catalog, but only saw short sections of oval or an option to ovalize the first 4' of the liner.

• rear exit - ~30" horizontal run to tee - there is an adjustable 90 degree on that run so it's not all horizontal
• 16' 10" long 5.5" uninsulated liner
  • tee has a cap on it
• stove calls for 6" liner and in rear exit configuration minimum chimney height should be "16 feet 6 1/8 inches (5.2m) from the top of the stove"
• chimney is exterior extends to ground level, stove is on 2nd level

 

[EbS-P]

i had downloaded the duraliner catalog, but only saw short sections of oval or an option to ovalize the first 4' of the liner.

• rear exit - ~30" horizontal run to tee - there is an adjustable 90 degree on that run so it's not all horizontal
• 16' 10" long 5.5" uninsulated liner
  • tee has a cap on it
• stove calls for 6" liner and in rear exit configuration minimum chimney height should be "16 feet 6 1/8 inches (5.2m) from the top of the stove"
• chimney is exterior extends to ground level, stove is on 2nd level

You are doing a big project now. Have you considered moving the thimble up? Top vent is that an Option can’t remember from you post detailing the install and troubleshooting. Might just throw a link to it in your next post here.

 

[neverstop]

You are doing a big project now. Have you considered moving the thimble up? Top vent is that an Option can’t remember from you post detailing the install and troubleshooting. Might just throw a link to it in your next post here.

I'm sure there is a way to edit OP but I couldn't figure it out. Here is a link to a past post about the install https://www.hearth.com/talk/threads/poor-draft-or-negative-pressure-issues.189240/ - note liner was actually 5.5" not a 6".

I suppose there isn't a reason that the thimble couldn't be moved, but in order to get any appreciable vertical distance before an elbow the thimble would need to be relocated above the mantle of the hearth. That sounds like a much more extensive project vs. replacing the liner.

 

[EbS-P]

I'm sure there is a way to edit OP but I couldn't figure it out. Here is a link to a past post about the install https://www.hearth.com/talk/threads/poor-draft-or-negative-pressure-issues.189240/ - note liner was actually 5.5" not a 6".

I suppose there isn't a reason that the thimble couldn't be moved, but in order to get any appreciable vertical distance before an elbow the thimble would need to be relocated above the mantle of the hearth. That sounds like a much more extensive project vs. replacing the liner.

Moving thimble would be 1/2 -1 day job. But it almost certainly would improve draft. Two 45s vs a 90 and then the height right off the stove. At this point I’m not sure what would have more of an impact. Increase the diameter, insulation, increased height. They all have to help some.

 

[bholler]

Moving thimble would be 1/2 -1 day job. But it almost certainly would improve draft. Two 45s vs a 90 and then the height right off the stove. At this point I’m not sure what would have more of an impact. Increase the diameter, insulation, increased height. They all have to help some.

That depends what the wall you are going through is. If it's all masonry it's an hour and little to no materials. If it's combustible it will cost allot more.

 

[neverstop]

Moving thimble would be 1/2 -1 day job. But it almost certainly would improve draft. Two 45s vs a 90 and then the height right off the stove. At this point I’m not sure what would have more of an impact. Increase the diameter, insulation, increased height. They all have to help some.

I could take on the liner install myself. Moving the thimble I'd leave that up to someone who's done it before. Also, if the liner upgrade and height doesn't solve it i could always move it later and reuse the liner.

That depends what the wall you are going through is. If it's all masonry it's an hour and little to no materials. If it's combustible it will cost allot more.

This is what I'm working with. Unsure what it looks like behind the brick hearth but the external chimney is back there. Probably wouldn't be brick all the way back to the chimney right?

 

[bholler]

I could take on the liner install myself. Moving the thimble I'd leave that up to someone who's done it before. Also, if the liner upgrade and height doesn't solve it i could always move it later and reuse the liner.

This is what I'm working with. Unsure what it looks like behind the brick hearth but the external chimney is back there. Probably wouldn't be brick all the way back to the chimney right?
View attachment 297542

No there is probably framing between the 2 part way up

 

[neverstop]

No there is probably framing between the 2 part way up

That's what I figured.

So it sounds like installing an insulated ovalized liner (equivalent to a 6") and class A above the chimney is still the simplest/cheapest solution. I wouldn't have to relocate the thimble, or break out the clay flue in this scenario.

Can't the reduced draft from the rear exit just be compensated for by increasing the stack height?

 

[brenndatomu]

Can't the reduced draft from the rear exit just be compensated for by increasing the stack height?

Technically yes, but anytime you come straight out the back and then a hard 90* right away, you will very likely deal with smoke rollout when reloading, at least to a greater degree than if everything was set up per OEM recommendations....some models stoves have more issues than others as far as the smoke rollout problem.
Loading only after the wood is fully burnt down will minimize smoking...but if you have good dry wood and want to load on hot coals, its pretty hard to get fully loaded before the fire has reignited...also, you will have more flyash in the house too...

 

[EbS-P]

My F400 top vent with 15’ rolls much less smoke than my in laws same stove rear vented with 30+ feet. It changes the flow characteristics.

I think you are starting on the right path.

 

[begreen]

Our F400 was rear-vented to an elbow and straight up 20'. The connector is all double-wall. This was done to increase corner-install clearances for this radiant stove. Under 45ºF outside, there was no smoke rollout unless I was careless, but above that temp, I had to be careful when starting and reloading. Above 50º smoke rollout was almost guaranteed.

 

[neverstop]

Technically yes, but anytime you come straight out the back and then a hard 90* right away, you will very likely deal with smoke rollout when reloading, at least to a greater degree than if everything was set up per OEM recommendations....some models stoves have more issues than others as far as the smoke rollout problem.
Loading only after the wood is fully burnt down will minimize smoking...but if you have good dry wood and want to load on hot coals, its pretty hard to get fully loaded before the fire has reignited...also, you will have more flyash in the house too...

all i can go by is how the mfg says to install the stove in a specific configuration. I'm almost exactly at the minimum chimney height for a rear exit and I have an external chimney, undersized/uninsulated liner. I would expect a sizable increase in efficiency with an insulated liner, extra 4.5 sqin of liner, and an extra 4-5ft of chimney height.

I just measured the hearth; it looks like if I were to use double wall and top vent the stove the thimble center would be located ~19.5" above the top of the stove.

 

[brenndatomu]

would expect a sizable increase in efficiency with an insulated liner, extra 4.5 sqin of liner, and an extra 4-5ft of chimney height.

Efficiency, or draft? The 5.5" liner might actually have a bit more draft...the 6" might have a bit less smoke rollout though too. More height helps both...

 

[neverstop]

Efficiency, or draft? The 5.5" liner might actually have a bit more draft...the 6" might have a bit less smoke rollout though too. More height helps both...

I meant draft

 

[begreen]

With the proposed changes, the volume of gases will increase slightly. If the height remained the same, the velocity of the gases would decrease a little, but adding 4 ft and insulating the liner should make a notable improvement. Is there an insulated block-off plate sealing off the damper area?

Note that sometimes there are other issues like the location of the chimney with respect to the house roofline and geographic location. What is the current misbehavior that is being addressed? Does it always happen, or just under certain conditions? For example, if smoke rollout is a problem, is this mostly with cold starts when outdoor temps are milder? Or all the time?