Wool insulation questions

[cassandralee]

Hello there - I'm new here and I'm sure this topic has already been covered many times before, I have read a few old posts about it, but I'm wondering if any of you who have tried this in the past have any current advice for insulating your yurt with wool.

I have a new 24' Pacific Yurt under construction that is replacing a 30+ year old canvas-lined Keyman Jim 20 footer that my husband and I have been living in (in addition to a 16' Pacific Yurt as our bedroom) for the past several years. In an effort to solve mildew problems and the issue of things freezing over during the night in the winter when the fire went out (drawback to having two yurts to tend), our new yurt will have thermostat controlled air-to-water radiant floor

heating

and a high-quality woodstove as well (we are thinking a Jotul).

The yurt has an acrylic coated polyester fabric side cover, and reflectix

insulation

with a polyester liner (it's one piece). The radiant floor & platform is well insulated. My husband purchased loose natural wool

insulation

as well as 2 inch thick wool blankets (not felted), and the idea is to do blown-in insulation in the roof between the rafters (covered with a white polyester mesh) and the blankets for the walls. The wall insulation is the most confusing, because our yurt is already constructed and we were also worried about it being exposed to outside

moisture

if it was put behind the reflectix/liner and compression if it was behind the lattice - so the plan is to create very thin plywood-framed (to keep it from stretching/slumping) wool blanket panels along the *inside* of the lattice, and probably cover that with wooden paneling. The wool is white and beautiful and I don't mind the look of it exposed, but I worry about it being hard to clean if it weren't covered with something. And I also wonder if we need a vapor barrier underneath the paneling? It's confusing trying to figure out the layers and what order they should go, and how to make sure it can breathe. The idea has also come up to just do the roof insulation and forget the walls, since the R-value wouldn't be that big of a gain anyway for the amount of work it would involve.

Honestly the lack of insulation is one of my biggest complaints with yurt life, so if we could fix that issue it would be amazing, but I am worried about this wool becoming a mold disaster. We have a separate bathhouse so won't be bathing/showering in the yurt, but we do have a little dishwasher and will be cooking in it. We are considering installing a kitchen vent in addition to the open-able

dome

. We are in Northern California, in the Sierra foothills, and we get rain and some snow in the winter but overall our climate is pretty dry and it rarely gets below freezing.

Thank you for any pearls of wisdom you might have!

[Jafo]

If you can do a through-the-wall vent, that would probably help a lot! Of course get the openable

dome

. In fact, that shouldn't even be optional.

When you say "Northern California" that is a big area.. Are you in the part that gets a lot of snow or?

[cassandralee]

Hi Jafo! We are in the Sierra Nevada foothills, in Nevada City. Elevation is about 2500 ft. We are just on the snow line, and while just a half hour drive up hwy 20 there's lots of snow, we typically get only a handful of snow days each winter, usually around a foot or less. We did however just have a big (to us) snowstorm with 2-3 feet that caused havoc with downed trees and power lines, folks around here were not prepared for it!

Glad you think the kitchen vent would help avoid mold issues. Yes, we have the openable dome too!

[Yurts_latvia]

Hi,


I'm also asking similar sorts of questions just now so hope it's helpful to add mine to the mix to get some discussion flowing here!


I have a thermal mass rocket stove with at least 6 meters of pipe running through a stone / cob double bed inside my 15ft yurt. It's a massive heat source for the small space but I haven't insulated yet (just have a 12oz cotton canvas cover)


I'm wondering how much insulation I'd need, and what's the best source. I also would like to go with sheep wool if possible.



I have access to 5mm thick wool felt @ around 4 euros per m2 - very cheap compared to most felt in Europe!


I'm wondering, if I add two layers of this, with an inch air gap in between - surely the air gap would also act as a free insulation layer in itself, saving me on adding extra layers of felt.


It also occurred to me that even thin cotton sheets (e.g. 2nd hand bed sheets) in layers with air gaps in between would add to this effect, and may look quite attractive if done in the right way.



If anyone knows about this concept of using 'layers' rather than just one thick insulation sheet, ( in the same way we do with our clothing), it may be very helpful not just to me, but also to the original author of this thread.


Many Thanks, and Happy New Year All,



Charlie

[Bob Rowlands]

I haven't done it. I know zip about air gaps in yurt felt. I do have an opinion about felt as insulation though.

Felt is the traditional insulation on Mongolian yurts, and other nomadic tipi dwellings used by northern People. In general an internal liner cover is (sometimes) placed over the frame, and then heavy felt, then the exterior cover. Never seen any air gap that was deliberately placed.

Seeing as how thick felt has been 'the' nomadic tent insulation for untold generations, I'd give two layers a go. That will get you near a half inch, which I would think would be plenty in a 15' yurt. I had a 16' yurt with no insulation, just a canvas cover. Two layers of felt would have been very nice this time of year.

Since you have a mass heater instead of a typical wood stove, you could try one layer. Experience would tell you whether a second is needed?

Trying to gap between the layers? Never seen that on any video. My guess it would be a hassle when erecting the yurt, but that's just a guess. A second light 1/4" thick layer would be easier to place by yourself. Getting the second layer on might be easy. Or not. Beats me.

If I had the money and that yurt was my home, I'd go for two layers. Good luck.

[Yurts_latvia]

Thanks as always Bob for your insightful input!


My idea for two layers would be to put one layer each side of the yurt frame. The inner layer wouldn't immediately have anything to hold it up - that would have to be done with additional wooden bats, string, or even some invisible ties within the air gap between the two layers. But yes, I might start with one layer, then see how it goes.


I'm quite pleased with how much heat the rocket heater holds and provides the yurt without any insulation already - if fired up for a few consecutive days that is!

[Bob Rowlands]

Heat radiating off thermal mass is very cozy in a yurt on a bitter cold day.

[UKadventurer]

Traditional Mongolian gers use 1 to 3 layers of felts. Nomads move several times a year based on seasons. 1 layer of felt is about 2cm but varies. Up to 3 are added depending on the season. I’m guessing there’s some extra trapped air between layers. It’s not a pain to deal with because these gers can be raised and lowered in a few hours depending on how many hands are available. Adding or subtracting felts would be much quicker.

I have a couple of modern gers with 2 layers of wool felt but thicker than normal. I’d guess 8-10cm total thickness. It’s not a nomadic type so changing the felt layers is not trivial.

We also have a traditional ger but it’s just a backup for guests. It has the same number of layers but thinner felts.

I suppose felt is cheap here in Mongolia because it’s locally sourced. I believe there are 40+ million sheep in Mongolia. Traditional gers aren’t particularly well insulated but have a small volume and a wood/coal stove in the middle so they heat up quickly. However they lose it quickly so, unless somebody is willing to get up frequently in the night (not likely), it can be extremely cold in the morning. We’ve had -10C in the morning but you get used to it.

In the modern gers, we’ll have underfloor electric

heating

, thermostat controlled. It’s great for the night. In the day, we can burn local wood. We have several backups: diesel generator, diesel heater, propane heater. We have an electric grid connection but it can be flakey so we need backups.

Our climate is extreme. Below freezing nights 7 months of the year. January lows average -30C and can go below -40C/F on the coldest nights. It’s too cold for much snow but we get it in the warmer months but not much. Maybe 5-10cm in a big snowfall. At least it’s sunny and not windy in winter.

[TSRalex]

For me makes the insulation of an traditional Yurt (Ger) with sheep wool absolutely sense, because the inner and outer shell are made from natural fabrics too.

After some years probably it will be necessary to change the liner and that´s surely a good time for new insulation too.

On modern Yurts with industrial liners and long durability I would suggest modern insulation.

[UKadventurer]

Originally Posted by TSRalex

For me makes the insulation of an traditional Yurt (Ger) with sheep wool absolutely sense, because the inner and outer shell are made from natural fabrics too.

After some years probably it will be necessary to change the liner and that´s surely a good time for new insulation too.

On modern Yurts with industrial liners and long durability I would suggest modern insulation.

That sounds reasonable for insulation. However, the outer cover is the one that gets replaced most often in Mongolia. This is a decorative, sacrificial and low cost element. It protects the waterproof/breathable canvas below from dirt and UV damage. I was told it probably needs replacement every 3 years at a cost of about US$160 each (7.2m ger).