Thursday, November 16, 2017

Boxing in the Stovepipe

When my stovepipe collar was first installed properly by Dan VanLenthe's crew, I was really surprised to find that the stovepipe itself was not in any way fastened, let alone sealed, to the collar itself!  That explained the purpose of the storm collar - it was to actually keep rain and such out of that gap betwixt the pipe and the rim of the collar.

My issue with that situation was that with a cathedral ceiling (essentially - the floor of the attic is not vapour sealed from the rest of the cabin), I essentially had a hole in my roof where the stovepipe stuck through!

Thinking myself somewhat clever, I packed the upper roof cone full of stone wool insulation and then sealed it all up with loads of foil tape.


The next time I was talking with the good fellows at Thunder Bay Fireplaces though, I was warned that this was not appropriate, and it was suggested to even be a fire hazard.  I'm not certain how though; I'd love to have someone enlighten me...

In any case, they suggested all sorts of schemes for dealing with this situation, but the one that made the most sense was to simply build a small "room" around the stovepipe in the attic and seal it off from the rest of the cabin.

I began this project last spring, but as the weather warmed up, it moved from a priority to a "maƱana" situation.

Of course, it hung over my head all summer, and with nothing particularly planned for a recent day, I steeled myself with a warm mug of tea, and slipped into my overalls.  I promised myself to just cut "one board" and then I could quit if it was too annoying or discouraging.  Of course, one board led to another and I pretty much would have finished the entire deal if I hadn't run out of expanding spray foam.

I put in sheets of closed cell foam on the floor and walls of the attic "room" around the stovepipe, and then sealed it with spray foam.  Then I piled more stone wool insulation on top of the floors until it was about four to six inches below the "no insulation above this line" mark on the stovepipe thimble.


Once more into the breech after six months of avoidance.
Hard to make out - this is a small crevice packed solid with a mass of dead flies.  Not the way I'd want to go!
Here's the final wall with most of the plywood installed.  I opted not to bother with a stud for extra support in the centre, as it's simply a barrier, and not at all structural.
The final wall in position.
I packed the outside top edge of the walls with stone wool to support the spray foam on the inside.  Note the transition to the latex foam at the top edge of the wall - it allowed me to install it with the can held upright in this tight space.
A view through the peephole.  Things look messy but functional.  I removed all the stone wool from the cavity above just before sealing in the stovepipe.
And on the floor, a deep covering of stone wool.  Just beneath the collar, you can see the red tape marking the maxium height of insulation.
Heading back downstairs.  The top piece of foam is just pressure-fit to allow me to reopen and inspect for the next month or two before I seal it up.  You can see the latex foam is looking even more sad that usual.  I will return soon with a fresh can to see if it works any better.
I was impressed that the fireproof spray foam still worked as if it was newly purchased.  The latex DAP foam seemed to have degraded significantly over the summer on the other hand, and at first simply ran out of the nozzle as a liquid.  I gave it a very vigorous shaking, and then it came out more like melted marshmallow.  I put it where I could, but as I was finishing up, several large areas "glooped" out of where they were suppose to be.  I will purchase more and see if I can't convince it to stay in place a bit better for me.


Ugh, the latex foam is clearly past its best before date.
Sadly, it was still 14 degrees Celsius inside the cabin when we woke up the next morning, after being 24 degrees around 3 p.m. when we put on the fire.  I'm not sure if dropping 10 degrees in 12 hours is considered good or bad in a conventional home - I don't know anyone who would let it get that cold.  I'd love to hear some comments about the struggles of other people in keeping their family warm in a cold environment.  I suspect that many of my readers are in the enviable position of only being a dial or button (or app?) away from quickly and efficiently warming their home.

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