should insulating my masonary chimney help draft?

[pro5oh]

I just insulated around my 18x18 interior masonary chimney in the attic space, only about 30" or so. I cut 1/2" foam to fit around it leaving a 2" air gap. I have low draft due to short chimney. I have a ranchstyle home and I have already added 3' to my chimney giving it 15' from top to stove with 2 90 degree elbows. each 90 is said to be equvalent to 3ft of chimney loss. My englander doesnt get over 400 degree flue temp ever, even wide open with 25 degrees outside. Think I'm screwed with out a draft inducer.

 

[BrotherBart]

Two questions. Do you have a six inch liner in that chimney? Is that 400 degrees the surface temperature of the pipe?

If you don't have a liner in that chimney, get one. That will fix your draft.

 

[pro5oh]

Two questions. Do you have a six inch liner in that chimney? Is that 400 degrees the surface temperature of the pipe?

If you don't have a liner in that chimney, get one. That will fix your draft.

Yes it has a 8x8 clay liner, yes 400 degres is the surface temp usually 250-300 average

 

[Redox]

It takes forever to get that clay hot enough to draw well. You might want to consider a 6" liner with insulation inside the clay. It will get hotter faster and draft much better.

Chris

 

[begreen]

Make sure that the horiz. run from the 90 to the chimney is running uphill at least 1/4" per ft.

Can you change out the first 90 elbow for a 45, then a diagonal pipe connected to another 45? That should help improve draft a bit. Adding a 6" liner inside that 8x8 should help some more.

 

[Cluttermagnet]

Greybeard asked a question that got my curiousity going. Is it either safe or helpful to apply foam board (say the pink stuff) around the outside part of a masonry chimney where it is within an attic? The advice about adding an insert is standard and makes good sense, of course. I guess my question would apply more to fireplace applications than wood stoves. I notice he says he allowed a 2in space between the foam and bricks. What happens in the event of a chimney fire, if the foam is hugging the bricks? And what if the 2in spacing is there- any difference? BTW I would assume that the only safe way to do this (considering the possibility of a chimney inferno) would be a wrap of some truly heat resistant material hugging the bricks- in which case the foam becomes unnecessary anyways. Would fiberglass stand up to that sort of heat? (I doubt it). Materials really designed for this sort of thing tend to be real pricey.

 

[BJN644]

I just had an 8x8 clay tile chimney relined. The mason used a tool on cleaning rods and broke up the clay liner into pieces, and then installed a rigid stainless liner and used a pour in insulation mix around it. It works great! that would be the way to go and I've been told it should last forever.

 

[PS3696]

Make sure that the horiz. run from the 90 to the chimney is running uphill at least 1/4" per ft.

Can you change out the first 90 elbow for a 45, then a diagonal pipe connected to another 45? That should help improve draft a bit. Adding a 6" liner inside that 8 should help some more.

This was the answer I was looking for. I was just about to post this same question. I have the same issue with low temp with the damper shut and air wide open I can only get the stove-top up to 425. It averages 325 - 350. I have 30" to a 90 then another 36" then into a 20' 8"x8" clay lined masonry chimney. all pipe is 6" DSP. Is there anything else that can be done to improve the draft?

Does anyone have a rough idea how much it will cost to have a 6" liner installed? or which brand to get?

Please oh wise ones with the wood this newbie needs help! :down:

Thanks!

 

[branchburner]

You should be able to find a liner kit for $400-500, double that to have it installed, add a few hundred to have it insulated unless you do one of a few DIY cheapo insulation methods.

 

[BJN644]

I just had an 8x8 clay tile chimney relined. The mason used a tool on cleaning rods and broke up the clay liner into pieces, and then installed a rigid stainless liner and used a pour in insulation mix around it. It works great! that would be the way to go and I've been told it should last forever.

$50 to $60 a foot is the going rate in my area to have this done by a professional mason.

You have to remove the original 8x8 liner if you want to insulate the new 6" liner.

 

[pro5oh]

Greybeard asked a question that got my curiousity going. Is it either safe or helpful to apply foam board (say the pink stuff) around the outside part of a masonry chimney where it is within an attic? The advice about adding an insert is standard and makes good sense, of course. I guess my question would apply more to fireplace applications than wood stoves. I notice he says he allowed a 2in space between the foam and bricks. What happens in the event of a chimney fire, if the foam is hugging the bricks? And what if the 2in spacing is there- any difference? BTW I would assume that the only safe way to do this (considering the possibility of a chimney inferno) would be a wrap of some truly heat resistant material hugging the bricks- in which case the foam becomes unnecessary anyways. Would fiberglass stand up to that sort of heat? (I doubt it). Materials really designed for this sort of thing tend to be real pricey.

Last winter the snow on my roof would melt around the chimney and cause ice to build up. There must be a considerable heat loss through the bricks when burning 24/7. I figured insulating would help the draft and keep the ice from forming so much. 2" is the firecode for any combustables near a masonary chimney. I used foil-faced foamboard 1/2". Got up in the attic last night and it was containing the heat nicely. I dont think even with a chimney fire there is any risk of the concrete chimney getting hot enough to catch fire to the structure, I beleive its the flaming creosote flying around that causes fire to spread. But I'm not a fire expert. The fireman I work with says chimney fires usually start when theres so much build up the person has to notice theres little to no draft. Something like a 3" hole in a 8x8 liner.

 

[PS3696]

I just had an 8x8 clay tile chimney relined. The mason used a tool on cleaning rods and broke up the clay liner into pieces, and then installed a rigid stainless liner and used a pour in insulation mix around it. It works great! that would be the way to go and I've been told it should last forever.

$50 to $60 a foot is the going rate in my area to have this done by a professional mason.

You have to remove the original 8x8 liner if you want to insulate the new 6" liner.

Does it make a huge difference in draft between the insulated and non insulated liners?

 

[sullystull]

Greybeard asked a question that got my curiousity going. Is it either safe or helpful to apply foam board (say the pink stuff) around the outside part of a masonry chimney where it is within an attic? The advice about adding an insert is standard and makes good sense, of course. I guess my question would apply more to fireplace applications than wood stoves. I notice he says he allowed a 2in space between the foam and bricks. What happens in the event of a chimney fire, if the foam is hugging the bricks? And what if the 2in spacing is there- any difference? BTW I would assume that the only safe way to do this (considering the possibility of a chimney inferno) would be a wrap of some truly heat resistant material hugging the bricks- in which case the foam becomes unnecessary anyways. Would fiberglass stand up to that sort of heat? (I doubt it). Materials really designed for this sort of thing tend to be real pricey.

Last winter the snow on my roof would melt around the chimney and cause ice to build up. There must be a considerable heat loss through the bricks when burning 24/7. I figured insulating would help the draft and keep the ice from forming so much. 2" is the firecode for any combustables near a masonary chimney. I used foil-faced foamboard 1/2". Got up in the attic last night and it was containing the heat nicely. I dont think even with a chimney fire there is any risk of the concrete chimney getting hot enough to catch fire to the structure, I beleive its the flaming creosote flying around that causes fire to spread. But I'm not a fire expert. The fireman I work with says chimney fires usually start when theres so much build up the person has to notice theres little to no draft. Something like a 3" hole in a 8x8 liner.

In the event of a fire, the stack temps could increase enough to cause the liner, mortar, and brick/block to crack. This would then create a space for flames to catch the insulation or framing of the house on fire. This is what I have heard from some of the local firemen around these parts. A SS liner may be the way to go.

 

[BJN644]

I just had an 8x8 clay tile chimney relined. The mason used a tool on cleaning rods and broke up the clay liner into pieces, and then installed a rigid stainless liner and used a pour in insulation mix around it. It works great! that would be the way to go and I've been told it should last forever.

$50 to $60 a foot is the going rate in my area to have this done by a professional mason.

You have to remove the original 8x8 liner if you want to insulate the new 6" liner.

Does it make a huge difference in draft between the insulated and non insulated liners?

It does make a difference, I won't know for sure how huge until the cold temps are more consistent. I know when we get a cold night in the 20's now my Oakwood really cranks. I can open the top loading door without a hint of smoke coming out.

 

[CT-Mike]

BJN,

What was the name of the product used to insulate around your liner?

Thanks,

Mike

 

[jqgs214]

Its call thermix I think, couple of brands out there. I have a 8X8 and did not remove the clay. Slid S.S. flex liner down. Installed and sealed block-off plate, mixed and poured insulation down around liner. Worked like a charm!

 

[BJN644]

BJN,

What was the name of the product used to insulate around your liner?

Thanks,

Mike

It's called Everguard, a vermiculite and mortar mix. I opted for this instead of the wrap insulation because I liked the idea of the mix filling any cracks and voids in the cement block as well as insulating. The system I have is UL 1777, which is zero clearance, the best you can have as far as I'm concerned.

I think Thermix is basically the same thing.

 

[PS3696]

Its call thermix I think, couple of brands out there. I have a 8X8 and did not remove the clay. Slid S.S. flex liner down. Installed and sealed block-off plate, mixed and poured insulation down around liner. Worked like a charm!

Where do you install the block-off plate? and how do you install it? through the cleanout door?

 

[BJN644]

Its call thermix I think, couple of brands out there. I have a 8X8 and did not remove the clay. Slid S.S. flex liner down. Installed and sealed block-off plate, mixed and poured insulation down around liner. Worked like a charm!

The reason I had my liner removed was because the mason said there wouldn't be enough space to insulate enough to do any good. That 6" round liner must be tight inside your clay liner.

 

[jqgs214]

A little tight, but I've got the inch required all around for the thermix, I really didnt need to do it but figured with that all round the liner and like you said filling the cracks in the block if there were any its just going to help solidify the whole thing. The block off plate is installed where the damper used to be. Do a search on this site for it and you'll find many (100's) of threads on block-offs.) There is a sticky some where on here too on how to make one.

 

[branchburner]

Yes, it's good to fill in even a little, narrow space - any convective air flow can cause heat transfer/loss.