Chimney insulation?

[vwboomer]

I have a ranch house with an inside chimney. Through the attic - maybe 10 ft - it's of course uninsulated. Anyone ever insulate the brickwork in an attic to keep the temp up? Any benefits?
Gave the chimney a brief sweep yesterday after about 2 months of burning and got maybe a quarts worth of creosote FWIW.

 

[jtp10181]

A masonry chimney structure should have 2" clearances from it to meet code. So insulating it would violate that.

 

[vwboomer]

It was just kind of an oddball question since hearing of SS liners that are insulated.
As for the clearance, I'm not sure when that code requirement was put into effect but I really doubt that there is that much space between my drywall and the chimney. Possible. I'm not going to open up the wall to satisfy my curiousity. the wall is nice n toasty which helps to keep the bedroom a little warmer so that's a plus.
My last house that I did remodeling on, the plaster was tight on the chimney on all sides - I have no reason to believe this would be any different.

 

[jtp10181]

Its very common for that do be done (drywall or plaster right on the brick), it does not meet the nationaly accept code in NFPA 211 which has been in effect for a long time (not sure how long though).

This is why when installing a new liner for an insert we always wrap it in insulation, that way it is self reliant to meet the 2100F rating. Without insulation you rely on the old masonry structure and if its not code its not safe.

If the clearance is not met and someone burns the fireplace for lets say a week straight (can we say 2 week power outage from an ice storm?) that brick could get so hot it starts something on fire. Also if there is a massive chimney fire it could also start the walls on fire.

 

[oconnor]

Slightly expanding the topic, but here it goes....

The key in the liner insulation issue is that nothing ever meets code unless you follow the instructions - doesn't matter what part of the stove system you are talking about, you only meet code if you follow the instructions. If you don't meet the stove clearances to walls and mantels that are combustible, then you have a non-compliant install.

Your liner has clearances too - they are in the instructions. Sometimes, they say nothing more than "install in a code compliant chimney", and sometimes they do a better job and spell it out. Even better, sometimes they tell you what the clearances are with and without insulation.

In the end, you have to follow the instructions - don't follow the instructions, then you won't meet code, and you may have a latent safety hazard on your hands that rears it's ugly head in 5, 10, 15 years.

Not sure why some folks go nuts over an inch on a hearth extension, and spend extra time and effort on getting the R value they need for the floor around the stove, and then choose to ignore the clearances for the liner. But many do, and it seems illogical to me.

I actually had a certified installer in my house yesterday who was willing to admit that not installing an insulated liner when we know that the chimney doesn't have the clearances was a clear code violation. When I asked him if he would start insulating them, he said in 15 years he has only done 2, and doesn't plan on starting now.

I hold the same sentiment for folks who want to shove various insulation types around liners as block off plates - they wouldn't think of not meeting clearances around the stove, but then they shove fibreglass up the flue to keep hot air from passing around the liner - using that stuff around a liner is not in anyone's instructions, and is a bad idea.

So, in the end, buy a liner that comes with good instructions, and follow them. If they say to insulate, then do what they say. Don't do what your buddy says, unless it is the same as what the instructions say.

But, once you insulate the liner, you don't need clearances around the brick, so you can wrap it in whatever you want then.

 

[jtp10181]

Amen

 

[vwboomer]

If I end up getting a new add on furnace - if Menards puts em on sale - I will probably install a liner. Sadly with the flue being 7x12 at best, I'm not sure I could use a full 6" with the insulation so may have to go 5.5"
I'd rather do it right the first time in instances like this. Just can't believe the insulation is so freakin expensive.

 

[jtp10181]

For an oval clay flue if its fairly straight down you can also use either pre-ovalized liner or the rigid simpson duraliner which is double wall and pre-insulated. We have used the simpson stuff and it works awesome.

 

[jtp10181]

Vermiculite does not melt at under 2100 deg. Also thats not why Class A has a 2" clearance. No point in arguing with people who dont know or care. I've said enough.

 

[oconnor]

If I end up getting a new add on furnace - if Menards puts em on sale - I will probably install a liner. Sadly with the flue being 7x12 at best, I'm not sure I could use a full 6" with the insulation so may have to go 5.5"
I'd rather do it right the first time in instances like this. Just can't believe the insulation is so freakin expensive.

I don't recall insulation being expensive, considering the benefits. I recall around $300 for the ceramic blanket wrap and required accessories for enough to do a 25 foot flue.

 

[vwboomer]

Yup that's about the range I was seeing it. Add that onto the 450 for the pipe kit, the 900ish for the furnace, 250 for misc wiring and duct work....it's getting expensive considering I'm on natural gas for my FA furnace. Well, it wouldn't be if I had a sure source of wood instead of hoping I can scrounge enough to keep the gas off

I've got my $7500 homebuyer 'credit' coming, which is why I'm even considering this. Waiting on the list of requirements from my insurance company, too, in case they have some odd requirements.

 

[jtp10181]

You did see that $7500 is like a loan from the government, right? Just making sure. I did not qualify for it but I read the info about it. You have to pay it back over the next 10 years.

 

[vwboomer]

Yup, as referenced in my post
Of course now the new stimulus had the 15k for a house added on, with no payback! argh. Not that I can argue with a 0% loan for 17 years, but still.

 

[jnthuskers]

I have been wondering if I should insulate my chase, which will be on the outside of my home, when i finally get my fireplace installed.

 

[jtp10181]

If its a normal studded chase with a prefab fireplace then you need to include the fireplace inside the envelope of the home and insulate and drywall the chase behind the fireplace just like every other wall of the house.

BTW This thread has nothing to do with that. We are talking about masonry fireplaces.