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Seigan 03-20-2015 11:13 AM

Yurt in northen Scandinavia: Tips?
 
Hi guys.

I've started to build a 8 meter (~27 foot) yurt on a mobile trailer that hold some of the utilities such as fire place, bathroom, kitchen and sleep-loft. The goal is to have something that is a mix between cabin, trailer and tent tha can work of grid and part time home year round.

Now this wierd hybrid is thought to be placed in northern Sweden. That means long cold (down to -40 c) and dark winters, short and sometimes cold summers (0 to +35 c) with midnight sun. The spring and the falls are is usually very wet, either by rain or snowmelting. The winters have up to 6 foot of snow but usually 2-3 foot but the air is often very dry as long as it is below 0 c. In the summernights thick fog is very common. There is wind but it rarely catches very high speed as the landscape is quite uneven and clad by (mostly) pine or spuce forests. I guess the cilmate is pretty similar to north east US or parts of Canada or Alaska.

So now to my questions:
1) Any ideas on how to manage the moister? Any special materials for the canvas and isolation? Any special demoisterise systems? We are also giong to cook and shower inside, and also our breaths etc creates moister from the inside in addition to the weather from the outside.

2) Any ideas about angles of the roof to manage heavy snow? I know that tradtional mongol gers are rarely above 25 degrees. On ordinary villas here they are often above 40, sometimes 60. I thought of around 40 degrees as it also are a round building sloping in many angles at once. Do you think it will be enough?

3) I have seen reinforsments done to the roofs to manage snow. Like 2 by 4 beams, bridges and vires between the beams however the beams often do not lay on the walls and only sometimes on a pillar. There also seems to be fewer beams when thicker beams are used. Any one that know how much one would gain with this types of solutions compared to a tradtional solution with many thinner rounded beams that lay directly on the walls (in the top X)? Pros and cons?

4) As we will not be in the yurt all the time (it is thought to be a year round vacationhouse) we are worried about deteration while we are not there because of stale air, damp, mold etc. We have thoughts about put in a passive solar pannel that heats up the air and a fan on solarcells tha push it in when the weather is dry and sunny. We have also ideas about compost heating system (give up to 60 c for up to 18 months) used to passivly heat a floorheating system to keep the temprature while we are not around keeping the fireplace going. Any more ideas to prevent damp and stale air while not living in the yurt?


This is our first time building our own yurt so any tip from you more experinced builders that have tackled the same problems in the past is very welcome!!

Thanks

Jafo 03-20-2015 01:18 PM

Re: Yurt in northen Scandinavia: Tips?
 
If you are not going to insulate it, I wouldn't worry too much about the dampness. I would use a wood stove over a fireplace though. My yurt is actually heated with an old Swedish wood stove (my yurt is a 30 footer). The wood heat will keep things dry enough when you are there. When you are not there, there should be no moisture issues if the heat is off.

hierony 03-20-2015 03:22 PM

Re: Yurt in northen Scandinavia: Tips?
 
Roof poles: If all you have is small saplings, you use many small (2x2) roof poles. If you have engineering and high-quality graded lumber, you use fewer large roof poles (2x4 to 2x6). Small poles are usually individually cheaper & easier to work with but you'd need more of them--just basic tradeoffs in material availability, design, construction, and portability.

Snow loads: Slippery surface is better (think slides). Wind exposure is good (blows snow away); sheltered in the trees is worse. 'Hot roof' is better--helps melt off the snow. Steeper slope is better--some Kyrgyz/bentwood yurts have steeper roofs if it can be made it strong enough for your snow loads. Baghana/crown ring support poles would really help in heavy snow loads--or you could use bigger roof poles, stronger tension cable, and roof pole pillar supports. Also, is your 2-3 ft/6 ft of snow all in one storm or typical ground accumulation?

Moisture: The winter you describe would have very dry, cold outside air--bringing this air inside and heating it while venting the moist air to the outside would prevent moisture issues. In fact, it might be too dry! During the warmer spring/fall months you wouldn't have the dry outside air though--you might want to use a dessicant such as zeolite, calcium chloride, drierite (calcium sulphate) while you're away or a dehumidifier (if you have electricity). Warm moist air contacting a cold surface (such as the outer cover) will cause condensation leading to mold/mildew. Monitoring the humidity and temp levels once constructed would tell you better what is needed...

Cotton canvas is breathable but not slippery and will mold/mildew/rot if not taken care of in a moist environment (frequent drying via wind/sun or warm/hot dry air). Vinyl/acrylic canvas won't mold nearly as easily but wouldn't have breathability to allow moisture to dissipate, so intentional venting (fans?) would be important.

There's a few yurt forum members with their location set to Sweden (Stephanwik, I suspect a few others too). You might try messaging them and ask for their experiences. Also, searching the forums for 'insulation' will get you lots of posts.

Bob Rowlands 03-20-2015 05:57 PM

Re: Yurt in northen Scandinavia: Tips?
 
Regarding potential snow load on your 27' yurt, especially with global warming causing changes in the 'typical' winter, the most important issue IMO is this. Let's say for sake of arguement there was a massive spring storm that dumped two to three feet of very wet snow atop your 27' yurt. If nobody is around to clear the snow off the roof you'd have at least 5 tons of weight atop that roof system, possibly a couple tons more depending on the depth.

I'm into heavy duty overkill as a rule. With that in mind, consider installing a super heavy duty 5/16ths or even 3/8ths cable atop the wall lattice. Consider installing three 4x4 baganas under the roof ring. Use 2x6 rafters, not 2x4. Install a 2x6 stud under every rafter at the wall. Tie the rafter to the support stud with construction hardware on each side, and anchor the stud to the deck with hardware on each side as well. If you really have potential for massive snow load, forget dinky little Mongolian round rafters. The design is great, but consider it is for arid climate. Not for massive snow load.

My cover is 100% cotton canvas. Our climate is sunny and arid. Five years out of my cover maybe? I'm at about two years and going strong, so five is an educated guess based on what I'm seeing now. A long term professionally made fifteen year cover is the way to go IMO. Canvas is fine in a dry climate. Canvas degrades VERY fast if continuously damp.

As for dampness, install operable windows on your yurt, just as you have in your house, and moist air can be vented after cooking bathing etc. Consider an electric fan to help vent the tent.

Good luck.

Knecht 03-20-2015 06:08 PM

Re: Yurt in northen Scandinavia: Tips?
 
Welcome.
You may find some usable ideas or answers in my CZ yurt thread here, I'm just about to finish my build.
The place where I live rarely has -30C or below, but -20C in winter isn't uncommon. We also get lots of snow. I used PVC coated canvas for my roof and the snow is easily sliding off it - either lightly touched with a pole, or when it gets slightly warmer for a day or two. I think once I live there and fire the stove, the warmth should deal with the snow easily. My roof angle isn't any steeper than what usual Mongolian yurts have.

Jafo 03-20-2015 07:40 PM

Re: Yurt in northen Scandinavia: Tips?
 
If you can heat the place from time to time, the snow will just fall off btw. (providing pitch is right)

stephanwik 03-20-2015 07:55 PM

Re: Yurt in northen Scandinavia: Tips?
 
Quote:

Originally Posted by hierony (Post 5007)
There's a few yurt forum members with their location set to Sweden.

Indeed. However we are on the west coast where the climate is pretty similar to say Portland, Oregon. We very rarely get more than about 20cm of snow.

The very north of Sweden is 1500 km from here and a very different climate!

I suspect people in Alaska will be of more use in this discussion :)

MT Rod 03-23-2015 12:13 PM

Re: Yurt in northen Scandinavia: Tips?
 
A couple winters ago I was in the north of Xinjiang, China when it was snowy and -28c. They have steep pitches on their yurts and they cover them with a plastic sheet if they won't be around, and told me it was to help the snow slide off.

You can look at my website: Home Page. and check out the pictures section.

Good luck on your adventure,

Rod

Seigan 03-23-2015 01:49 PM

Re: Yurt in northen Scandinavia: Tips?
 
Thanks for the ideas! The helps alot.

I was thinking about silicon prepared cotton canvas for cover. But it might be better as you say to use a acrylic cover instead... Had not thought about that.

My goal is to set ut the yurt in a sunny slope faceing southwards to get the most sun. I was hopeing to have some trees in the north but not in the other directions to break some wind but not be in the shadow.

Stephanwik: if you are on the westcoast and have your yurts up all year round then you will probably have much more damp, fog and rain then in the north. The westcoast do not have as cold as up north but when the westcoast get snow it is often very wet and heavy. So if you have any lessons, experinces or tips I would be eager to hear it!

Knecht: Where did you buy your PVC cover? What isulation do you use, and how thick?

Bob Rowlands: Thanks for the ideas. I have no real clue on how much the fallen snow weight. We do not usually get very heavy snow fall at once - not like Buffalo this year. Because of that lack of knowledge it is kind of hard to get the correct dimensions... You might be rigth: I'd better build to contain bears :)

Hierony: the 2-6 feet of snow is accumelated and not in one storm. However it very much depends on the temperature. If it is cold the it is very fluffy (so fluffy I can die) snow and it adds to the height but is light weight. But if it is just a bit warmer the it is much denser, heavier but do not add so much height... Damn I never thought it would be so hard to describe snow... :)

I have both sapplings and sawn planks avaible to me. I do however both need to keep the weight down a bit (as it is a trailer) but I need it to be strong to manage to hold the snow. So the big question is how can I both have it light weight and strong at the same time?

MT Rod: Thanks! I'll look in to it! Thanks for the link!

Knecht 03-23-2015 05:24 PM

Re: Yurt in northen Scandinavia: Tips?
 
Quote:

Originally Posted by Seigan (Post 5015)
Knecht: Where did you buy your PVC cover? What isulation do you use, and how thick?

I had my cover custom-made by a local company that makes all kinds of big fabric works...from tents to truck tarps. They do sell the coated fabric by meter, but it's not easy to put it together by yourself, while they have means to weld it easily. It was made quickly and very accurately to the plan, but as you can read in my thread, they didn't do very good job stitching the attachment straps to the cover, making several unnecessary needle holes around each stitching. I had to glue patches over each of these spots. Ironic enough that in the end, I have no need for the straps at all. Lesson learned.
As for insulation, I'm using sort of hemp-fiber construction insulating stuff, 30mm thick as my main layer, plus some carpets and blankets.

hierony 03-24-2015 12:03 AM

Re: Yurt in northen Scandinavia: Tips?
 
You'll probably be alright for snow loads--I like MTRod's link with the yurts that look to have 45+ deg slope. A 45 deg roof coupled with a warm, slippery surface gives a slope factor of 0.38 (ie, your roof will see 38% of the ground snow load, excluding other factors; can vary). Heavy wet spring snow can be 50% water by volume, delectably light & fluffy snow is probably <5%.

As for roof pole/rafter size, it isn't just the dimension of the poles that determines the total roof strength but also the total number of poles. Parallel force/compression works a bit differently from perpindicular bending and I need to think how best to describe it here... Also, I think there is an advantage to using whole saplings over sawn lumber, but I need to look that up. Baganas significantly reduce the unsupported span of the roof poles/crown ring, greatly increasing the allowable load on each pole.

My yurt was built just outside Budapest, Hungary--the maker used local companies for cotton/jute canvas and a synthetic geotextile felt insulation but also had options for architectural fabric from Sioen Industries in Belgium.

Any particular reason you're building on a trailer instead of a platform? What kind of wood stove you plan on using?

Groovyyurts 03-31-2015 10:29 AM

Re: Yurt in northen Scandinavia: Tips?
 
Tjena!

- For snow resistance, Hierony's comment to add central poles under the dome (even if only temporary) is a good idea (add them when you leave for a long time in winter).
- 30' is a BIG yurt in such climate. You will indeed have to use heavy duty engineering to resist snow loads if you are not there to remove the snow. Have you thought of smaller diameters, even if you connect two yurts?
- for the damp period, vents in the platform and small solar ventilators somewhere in the dome or roof can be a great help, at least to avoid condensation which is the best start for mold.

Har det bra!

Seigan 09-07-2015 05:16 AM

Re: Yurt in northen Scandinavia: Tips?
 
Thanks guys for all your help.

Now the wooden fram is nearly finnished. I use 22x45mm for the wall (sturdy as hell yet flexible) and are put at 70 degrees instead of 90 which make it even sturdier. The distance between them standing upright are 30cm.

The roof beams are 45x145 mm (c24m/c24+standard) and will sit 60 cm apart (so I get 40 beams) at the bottom. They will be at 40 degree angle. Where it is placed the building standard is to calculate for 200 kg per square meter in snowload. Usually the roof beams are 45x170mm (c24 standard) and sit at 120 cm apart or more. On half my roof they will be less then 30 cm apart. I have consulted local carpenters an engineers and all of then have said the dimentions should be enough. I will also have space to have 40 more beams in the crown, total of 80 beams 30 cm apart at the bottom an 15 cm in the middle, if nessecerly but all carpenters I have talked to deam that way more the I need so...

In addition I am planning to set a 10 mm harden steel wire around the roof beams, vertical support poles to take the pressure of the walls and a small wire to hold all beams together as as safety line if some beam would break. Temporaly vertical support poles for the crown while away sounds like a very good idea that I will surely implement.

Furtermore I've found a windprotection cloth called "Bison 100 windprotection" that protects against wind and water 100% from the outside but let steam out from the inside. It breath very well and acts a bite like gortex. My plan is to put this between the canvas and the insulation layer. The hope is that it will protect the wooden construction and insulation from condence and if the canvas leak a bit.

I am also wondering about put up a heat barrier (bubblewrap clad in aluminiumfoil) between the windprotection and the canvas. It certainly entraps the heat but the question is what type of bi-effects I will get as the heat barrier also acts kind of as a moister barrier as well though it do not breath at all. I am wondering if I am not shoting my self in the foot by adding it and entrap the moister in the construction instead of letting it out through the canvas.

For the floor I have 170 mm tree-fiber insulation (Hunton Flex) which has the same or even a bit better value then ordinary rockwool but not at all bad for the health. It is also capable of buffer moister when it is wet and letting it out when it is dry (which rockwool do not do) witout attracting mold which helps keeping the construction healthy. I will also add a water floor heating system to even out the spread of the heat (and it enables me to multiple heatsources).

I hope this will be sufficent to withstand the winter :)

Bob Rowlands 09-07-2015 02:02 PM

Re: Yurt in northen Scandinavia: Tips?
 
I'd install no material I thought woyld trap moisture inside the yurt UNLESS the yurt was very drafty. Thanks for the deets on your build.

Jafo 09-08-2015 09:16 AM

Re: Yurt in northen Scandinavia: Tips?
 
If you will be living in the yurt full time, the snow will just slide off most of the time I think you will find. Very interesting build. Please post pics when you can. :)


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