Fire proofing smoke stack

[tonka]

18282
How would some of you go about fire proofing the 2x4s near the smoke stack? Stack diameter is 20" with about 3" between the 2x4s and stack. I have 8 oc trusses/just over 3 ft between truss and stack.

My plan is to make a box out of stainless that will go around the stack and will get anchored to the 2x4s and will fit some blanket inside between the stack and the box.

[Potters3]

Yep, I would (and did in our sugarhouse) make a double wall pipe. Wrap stack in 1" ceramic blanket with a wrap made of stainless to go around and hold in place. Being that close 3" might want to put a layer of sheetrock on trusses to give more protection before running pipe up thru.

[Michael Greer]

A length of 6"diameter duct pipe installed around the 2x4 will work nicely. The basic rule of thumb I've heard is that every layer you put between the hot pipe and flammable materials cuts the temperature in half. My chimney has two layers of bigger duct pipe around it with 1" of air space between it. These shields run right up through the roof and into the flashing cone, which is vented below the storm collar. It keeps the weather out, and the outside layer never goes above about 80 degrees. The adjacent timbers are wrapped with a loose fitting section of duct pipe and they don't even get warm.

[maple flats]

I did that too on my latest improvement about 3-4 years ago. Before that I made my own triple wall pipe, but my trusses were 9" away. When I built the sugarhouse I set that one truss at 32" O.C. for a 30" space. the 12" stack goes up dead center. I have a 1.5" ceramic insulation with the SS stack inside and a second SS outside, I then cut 1.5" deep slits at the bottom of the outer layer and bent them inward to cover the bottom edge of the insulation.

[tonka]

18290
So here is my sleeve. I will take off the roof jack and slide it down so the stack comes through the center. There will be an inch gap between the purlins and the sleeve(let's call it) and will have a 1.5 inch gap between the stack and the sleeve. I will also install blanket between the sleeve and stack. What do you all think?

[tonka]

182911829218293
Here it is installed. About an inch gap between purlins and sleeve, with about a 1.5inch between stack and sleeve and blanket shoved inside firmly. Will it work?

[Michael Greer]

Well let's hope so. There's nothing more distracting than trying to put out a fire while trying to draw off.

[Daveg]

@Michael Greer: "The basic rule of thumb I've heard is that every layer you put between the hot pipe and flammable materials cuts the temperature in half...."
If you wrap that hot pipe with a layer of metal, the temperature will NOT be cut in half. I think what you heard was "every inch of layered AIR SPACE" cuts the temperature in half.

[Daveg]

Double wall chimney pipe made by Simpson (DuraVent) calls for a 8" air space between the pipe and ceiling combustibles (purlins, sheetrock, trusses, rafters, spider webs, grandma's portrait, etc). Any less, and you're playing with fire. Also, NO INSULATION CAN CONTACT THE PIPE. It's proper function relies on air freely moving over its' surface.

[tonka]

Daveg: aren't some of the insulated stove pipe out there have a layer of ceramic blanket between the inner and outer wall of the stack? I've had my fire box insulated with the same blanket as I have in my sleeve and I've been able to hold my hand on the firebox wall for a decent amount of time before it gets to warm for my hand. Not trying to be difficult on the subject, the last thing I want to do is burn down my sugar shack.

[Ghs57]

I used Simpson Class A SS chimney pipe to go though the roof. They make a single wall to insulated pipe adapter, which makes the connection easy. They also make several kinds of thimbles for wall/roof penetrations. Even with insulated pipe, there is still a required air gap of 2 inches to combustibles, and the insulated pipe must extend inside the space by 3 inches. I also used used the same pipe to meet code on a wood stove in another building.

As said above, fire on the outside of the chimney is very distracting, and can ruin your whole day.

[Daveg]

Daveg: aren't some of the insulated stove pipe out there have a layer of ceramic blanket between the inner and outer wall of the stack? I've had my fire box insulated with the same blanket as I have in my sleeve and I've been able to hold my hand on the firebox wall for a decent amount of time before it gets to warm for my hand. Not trying to be difficult on the subject, the last thing I want to do is burn down my sugar shack.
If my code inspector saw my chimney was in contact with combustibles and he told me to fix it before he would issue a Certificate of Occupancy, I would thank him and then I would fix it and give him a free quart for saving me from a non-covered insurance loss.

[tonka]

Ok, so I took your guys advise (which I greatly appreciate) and improved it. I have my sleeve around the stack but left the blanket out to allow adiquite air flow. I also installed a coupe pieces of tin on top and bottom with a 4 inch gap between the tin and 2x6 purlins on edge. The closest combustible is 15inches away from my sleeve (first layer of steel to the stack and 4inches away from the second layer of steel from the stack.1836918370

[Ghs57]

That looks so much better. You've got heat shielding and clearance. Now we don't have to worry about your chimney.

I know the codes are geared toward the "worst case scenarios", but you ready don't want to fall into that category for any avoidable reason.

[tonka]

I did a test boil today, didn't push the cooker by no leans, had a decent boil going in the front pans and a light boil going in my tube pan and the thermometer didn't get no hotter then 350 degrees.
I really do appreciate all the advise others share on my threads and others as well. First time in a sugar house and the last thing I want to do is burn the place down because of something that could have been avoided. Something like this is better to be over killed then under killed, simple as that.