Dome Vent

[gastagg]

I have completed the stucco layers on top of 3" insulation. The dome has been completed for several weeks. I'm going to wait a few more days for the stucco to cure before starting the curing fires. But it has been noted that I do not have a dome vent. Didn't even know what that was until the last day or so, but as I have not yet completely sealed up the stucco layer, I set about installing a dome vent that would allow the steam formed in the curing process to vacate the insulation cavity, which would keep stress off the stucco layer.

I purchased some 3/8 brass fittings and will plan to affix the brass fabricated vent to the rear of the chimney arch. It will sit on the steel mesh layer. I've attached a drawing. Anyone see any problems with this plan or recommend a better option?

[david s]

That should work ok

[Gulf]

I would like to add this. I may should have went back to your thread to mention it, but it is relevant in both. The joint between the stucco and the chimney appears to be about 5/8" to 3/4". Any joint 1/4" and above will take backer rods to caulk. If my "guesstimations" are right, that would be three runs of backer rod to scale that gap. I'm assuming that you will use a ceramic or glass fiber rope against the chimney for the first run. Make sure that the brass is separated from the chimney with the first fiber/backer run. And, carefully seal around the vent pipe as you will the gap between the stucco and the chimney with the flexible high temp caulk. In a deluge, that is an area where fast water (coming down your chimney and rolling off of your dome) will meet slow water. That is a good place for water to enter your oven, if you are not careful.

[gastagg]

I just realized that the insulation layer of the dome is against the thermal break space of the flu arch, which is open into the flu. I could seal off the stucco completely and the gases could travel through the insulation layer into the flu. It would have to travel through a thermal rope, but would that work?

[Gulf]

I'll let David weigh in on that. But, I would remove the pex piping spacer that you have, seal the heat break joint with rutland and then continue venting the insulation/stucco separately.

[gastagg]

Here's a diagram of current state. Pex has been removed. Have a large thermal rope to fill gap.

[Gulf]

Since it is too deep to reach, I would pack another rope from inside the entry and use a heat sealant caulk from inside the entry. Russell found some good stuff for that area. Uni-Extreme High Heat Caulk. Maybe he will weigh in on this.

[gastagg]

OK, my last post was misleading. I currently do not have the large rope or the caulk in place. The gap is there, and yes, it is about 5/8" to 3/4" thick and deep. I have the right size of thermal rope to fill that gap. I've got moldable high temp caulk (2300degrees) to cover over that. So, it seems like the thing to do is still vent the dome separately.

[gastagg]

Here is a pic. big gap. no rope. no caulk. no vent. just a desire to avoid cracks

[gastagg]

Gentlemen, I really appreciate the encouragement and advice you've all been giving me. I'm confident that this oven will be far more reliable and enjoyable because of all this help. Thank you!

Here is the caulk I'm using. Can be used to fill large voids if surface layer across deep void is no more than 1/2" thick. Are to fill with thermal rope to within that 1/2". Up to 2300degree F. Only problem is that it's white and I don't think it's paintable .

[UtahBeehiver]

This area was a big concern for me since I my build was an exposed igloo and Utah winters. I am not sure if you will have a cover over your igloo or not but as Gulf says, this area could be a major point of water migration. Since my final covering was copper, I built up flashing around this area. So do all you can to keep this area waterproof. As far as color, the Fiberfrax caulk is what it is. The uni-extreme I used was gray in color and I found at a surplus store. On the open market it is really expensive and hard to find. Make sure you vent get an unobstructed path to the CF blanket.