Rigid foam insulation against lathe / canvas

[willothenorth]

Hi y'all,

I'm located outside of Fairbanks, AK.

I inherited (bought) a 30' pacific yurt when the owner, who had set it up on our property, moved away. They had purchased it used. They tried to live in it the first winter they had it but it was not tenable, despite the "full insulation" package-- that business cannot stand up against -40 and -50. Didn't even really hold up against -15. There were other problems they dealt with-- their woodstove install had some tight bends in the stovepipe and it didn't draw well, the oil drip stove they set up had the same. Trying to heat whatever cubic footage a 30' yurt is was just not happening.

I bought the yurt from them last summer with the intention of revamping it and making it livable. Either by setting up a smaller interior space to heat, by adding

insulation

to the walls, or all of the above.

I'm at the point of adding

insulation

. I'm also framing the walls on the inside (adding support 2x4's to each rafter at the walls) out of necessity, to protect the structure against heavy snowfall. My insulation plan was to utilize a combo of rigid foam + fiberglass insulation between the support 2x4's, and then add vapor barrier + either drywall or plywood wall panels. I decided this after seeing a couple threads on here about insulation practices for various yurts.

I left a 1.5" gap behind each 2x4, which means I can run the rigid foam behind them continuously and hopefully avoid thermal whatsit, conduction? I had left the gap originally just to provide the same depth for insulation as you'd have with 2x6's, but having learned about thermal conduction after installing half the posts, seems I (maybe) lucked out to be able to run rigid foam continuously behind them!

Except, here's my query: since the way I am doing this has the rigid foam butting up against the lathe, that means there will be an air gap between the outer layers of canvas (and included "space" insulation) and the rigid foam. FWIW I am using R-Tech foam with R-9.6. It's doublesided with reflective... stuff. (Can you tell I'm on the learning curve here??)

I'm concerned that I'm going to create a

moisture

trap between the canvas and the rigid foam, particularly since it sounds like this style of rigid foam IS a vapor barrier. I just paid a lottttttt of $ for this foam so I'd really like to make it work. Will the canvas layers breathe enough to not make this a worry? Should I take out the lathe to reduce the gap? Should I use the fiberglass first and keep the rigid foam on the interior to act as my vapor barrier?

Any thoughts on this would be really appreciated! Fairbanks is pretty dry, so I'm hopeful that will work in my favor. Thanks in advance for any advice folks may have.

-Will

[Bob Rowlands]

Beats the heck out of me. My suggestion is to just build it. You will learn what works, and what doesn't work, from your experience. Good luck

[Bob Rowlands]

Not directly on topic, but have you considered erecting a wall tent inside the yurt during subzero temps? The 30' yurt would be taking the wind and snow load, the two biggest drawbacks to a wall tent. I would think that a small wall tent surrounded by a yurt should hold the heat quite well. I have seen a small wall tent erected inside a larger one on youtube.

I have watched video of the nomadic Sami people of northern Europe. They live in hide covered tipis even when it is subzero. Tipis are heated with wood stove.

Good luck.

[willothenorth]

Hey Bob! Thanks for the replies. I think I will just go ahead and build it and see if the baseball team arrives / if things work.

I definitely considered a wall tent inside the yurt! I'm excited to see how the added insulation helps this winter. I'm also thinking of doing a barrel stove with a second barrel as a radiant heat thingy. But I've read mixed things about if that might be too much or not. Fun to mess around and find out.

Regarding the snow load, the posts I'm putting in are already halfway done so that at least will be amended no matter what other steps I take. Had to happen for safety!

[Bob Rowlands]

yeah getting studs under the rafters is a GOOD idea. My wife and I lived in Jackson Wyoming. The winter of 1978 1979 was -50. It was below freezing for one month straight. I can't imagine surviving those temps in a yurt that wasn't super insulated. At any rate, go for it, and as always with everything in life, give it everything you got.

[Jafo]

I think you are going to get some

moisture

issues with this. The roof and walls do not breathe at all. That is why the center

dome

opens. I myself would have paid for a larger wood stove with a better install. I use my Yurt up in the Adirondacks and the lowest temp I had was -32 and I was walking around with shorts inside because I oversized the stove.

If you are going to leave that gap, I might suggest you leave it all the way, from the walls on through the rafters so it can vent out of the

dome

. At this point you can decide whether you want to leave the dome uncovered on the inside? I think if you just cracked it slightly that would probably remove a lot of moisture, but maybe too much heat too.

So if you say, covered the dome on the INSIDE with some clear plastic, that could alleviate that issue? You might need the electric dome opener that

Pacific Yurts

sells to accomplish this.

Sounds like a fun experiment though. I would suggest you install some of the panels in a way that it will be easy to remove so you can inspect that there for moisture from time to time.

[trihartsfield]

What you haven’t discussed is what will be in the inside, bathroom, kitchen ect. That is where the vast majority of potential moisture will come from.

Is the cover already up and I am assuming it is vinyl?

[Bob Rowlands]

Good point about oversized stove, Jafo.

[Ivan]

I agree with Jafo, regarding largest wood stove. I believe the frost line will move inside the yurt to the lattice on cold cold days, So it seems that you need to be able to ventilate that space . How about a air to air heat exchanger, or install a few louvres low on one side with a couple high on the other side of the yurt, with a fan so you can power ventilate on occasion. I would use plywood on the interior, and put in a small removable section , so you check on mold status? We are mid New Hampshire in the mountains, where the temps get down to -20f occasionally , and are able to be comfortable with shorts and tee shirt. Good luck and keep us appraised of your results

[willothenorth]

Hey folks,

Thanks so much for the replies.

@Jafo, unfortunately I don't have the opening dome-- Or, at least not the kind that has some sort of mechanism to do so other than climbing up there and manually opening it if needed? I'll have to look. I need to get / build a scaffold to get up there, I have not been able to look closely at the dome myself since it was already up when we inherited it. I have definitely been planning to install a larger woodstove, and I do think that was a major problem with things. The yurt now has a toyo (oil) stove and that was able to beat back the cold a bit when the original tenant was there. So hopefully the combo can make things work.

@trihartsfield, great question about the plan for things. Currently I'm going to utilize the space as an office / shop. I will probably have a sink setup but dry (with hauled water that likely goes into a bucket to be emptied). Down the line we're interested in getting it more fancified, but that's not in the stars soon. So I think that will give me time to see about how the moisture/ insulation thing ends up going. I also have a dehumidifier running in there, which doesn't show a ton of moisture but maybe can aid down the line as well. The cover is up. The roof is vinyl and the walls are canvas. Currently I'm only working on insulating the walls, though I do know I'll be putting effort into the roof as well at some point of course.

@Ivan, I had to look up what a louvre was, I thought it was just a museum in France I'll have to see how folks use those up here. I had been considering an air exchanger but I don't know a ton about them. I am installing real windows that I can open, so potentially I could crack windows and utilize those as a form of ventilation too?

Back @Jafo, that's an interesting point about leaving the gap all the way up. My predecessor covered the dome on the inside for the winter. So leaving it uncovered on the inside might be a good idea if it doesn't kick my ass temp-wise. Even if the dome doesn't mechanically open, I do think there are cracks between it and the roof (maybe wasn't installed properly- I just know bugs get in there), so maybe it would already be kind of set for that. The canvas wall is undone around the bottom because of a repair I am doing, so I think it's currently breathing a bit at the moment.

Interesting thoughts from all, I really appreciate it. Sounds like a very good idea to leave an area where I can check on the moisture factor and make decisions from there. It's all a learning experience so that's not a bad thing!

Thanks,
Will