PTJ Event 2022 - Solar Yurt Design

Oh I'm so excited for this design!

Welp, now I've done it. I opened my big mouth so now I actually have to think about how this thing would work.

Here is a proof of concept. The actual design will depend largely on the yurt that is purchased, how the walls are made, if there are any windows, insulation, etc.

But basically, the southern end of the yurt needs be opened up to the sun for solar gain. This should include at least one high transom for air draw for the cooling tubes. Cutting through that space on the interior will be another added wall to create a 'greenhouse effect'. The interior will contain as much stable earth as thermal mass as is prudent, including walls and floor. There ought to be a rubble trench foundation for the earth walls and as drainage. The space will be cooled in summer by geothermal cooling tubes buried 4+ feet down, and at least 30 feet long. These should be brought up the interior and dump out near the top, for more even cooling of the space. And finally the interior should be as well insulated as it can be on all but the south side (double greenhouse walls handle that) and especially the ceiling.

Michael, is there a canvas/solid roof over the greenhouse part or is that somehow transparent?

Mike Haasl wrote:Michael, is there a canvas/solid roof over the greenhouse part or is that somehow transparent?

Ideally that would also be as transparent as possible for maximum solar gain. However the trick would be in making it so it lasts and doesn't develop leaks...

Perhaps a skylight is installed over the framing, cut through the canvas and then sealed around with some bad ass roof sealant.

With the mostly sunny summer days at WL, I was thinking sun through the roof would be a hindrance to keeping it cool in the summer.  In the winter, I'd assume that most of the sun would come through the walls and very little through the roof (additionally some is reflected due to the glancing angle).

Mike Haasl wrote:With the mostly sunny summer days at WL, I was thinking sun through the roof would be a hindrance to keeping it cool in the summer.  In the winter, I'd assume that most of the sun would come through the walls and very little through the roof (additionally some is reflected due to the glancing angle).

That's a good point. You could simply cover the skylight in the summer if you had to, however it probably wouldn't be getting much direct sun in the winter anyway. I've become accustomed to building much farther south where the sun doesn't get as low.

Michael (and Mike), maybe there's some ideas to borrow from Pacific Domes since their dome covers are both fabric/transparent combinations, and have to be both roof and wall.

Any thoughts on what the insulation will be? There will be an instructor on site for doing wool insulation at the PTJ

Ashley Cottonwood wrote:Any thoughts on what the insulation will be? There will be an instructor on site for doing wool insulation at the PTJ

Well, if the yurt was ordered with insulation, then, we don't have to worry about the walls or ceiling.

If not, the space between the yurt walls and the earth wall can be filled with any manner of lightweight insulation. The ceiling will be more tricky.

Under the earth floor should be insulated, and that will need to be something kind of solid like rigid foam insulation.

For the floor, what about siting the yurt so that it is upon a mound, surrounded by a "donut-shaped umbrella" to keep that mound dry. The yurt would act as the center of the umbrella. Basically a John Hait PAHS style, or wofati, but above ground.
Maybe then there's no need for foam insulation?

Is the earthen wall rammed earth? cob? or earth bags with plaster? Also, the earthen wall could be an opportunity for a not-a-circle space within the yurt. A private nook for a bed, or an indoor "facility", whatever...

I see some discussion related to insulation both underneath the floor and in the walls.  Has any thought been directed at natural insulation such as hemp?  Hemp is a great insulator whether in brick form or poured or as hempcrete.  Basically it provides a better insulation than equal thickness fiberglass, about on a par with mineral wool, but with the advantage that it can get wet and dry out whereas mineral wool basically loses its insulation value on wetting and cannot recover as hemp does.  In addition, hemp is a natural insect and rodent repellent and continues to sequester additional CO2 as it ages.  In addition, non-treated hemp does not burn until it hits around 900 degrees F.  Hempcrete is made of the central hemp core, or hurd, lime and water.  It can provide some structural support, especially in a floor situation while being far more healthy than Portland Cement.  I believe it would provide a really decent leveling material beneath such a structure and act as a vermin retarder as well as carbon sink.  

For the earth cooling tubes, I remember an inventor friend who raised that concept about 50 years ago.  The main concern I had then and still would, relates to the fact that ambient air being drawn through cooler soil will tend to create "rain-out" or condensation in the tube.  If the tube is closed, then mold will rapidly follow and the system becomes an increasing risk factor for healthy air.  My modification was to use a perforated (on the bottom) pipe wrapped in geotextile (could be hemp cloth) to keep soil and small beasties from entering while allowing condensate to seep downward and out with some porous material underneath, hopefully directed to a french drain or other area to sequester the condensate from the incoming air.  In a more arid environment, perhaps one could direct such condensate to holding tanks to create an Arrakis-style water source.  For non-sci-fi readers, this came from Frank Herbert's novel, Dune.  More work, but potentially rewarding, especially if melded with a rain collection system.

Kenneth Elwell wrote:For the floor, what about siting the yurt so that it is upon a mound, surrounded by a "donut-shaped umbrella" to keep that mound dry. The yurt would act as the center of the umbrella. Basically a John Hait PAHS style, or wofati, but above ground.
Maybe then there's no need for foam insulation?

Is the earthen wall rammed earth? cob? or earth bags with plaster? Also, the earthen wall could be an opportunity for a not-a-circle space within the yurt. A private nook for a bed, or an indoor "facility", whatever...

It would be good for the yurt to be elevated. I haven't seen the site but once it's leveled and the trenches are dug I'd probably spread the dirt out inside under the subfloor and pile some outside the trench so it kind of does that.

I was picturing the earth walls as cob since that's simplest but if they had earth bags that would make it easy to keep the walls the same width all around. The more mass inside the better, I haven't seen the yurt that was ordered yet but it could be a pretty tight space.

Richard Henry wrote:I see some discussion related to insulation both underneath the floor and in the walls.  Has any thought been directed at natural insulation such as hemp?  Hemp is a great insulator whether in brick form or poured or as hempcrete.  Basically it provides a better insulation than equal thickness fiberglass, about on a par with mineral wool, but with the advantage that it can get wet and dry out whereas mineral wool basically loses its insulation value on wetting and cannot recover as hemp does.  In addition, hemp is a natural insect and rodent repellent and continues to sequester additional CO2 as it ages.  In addition, non-treated hemp does not burn until it hits around 900 degrees F.  Hempcrete is made of the central hemp core, or hurd, lime and water.  It can provide some structural support, especially in a floor situation while being far more healthy than Portland Cement.  I believe it would provide a really decent leveling material beneath such a structure and act as a vermin retarder as well as carbon sink.  

For the earth cooling tubes, I remember an inventor friend who raised that concept about 50 years ago.  The main concern I had then and still would, relates to the fact that ambient air being drawn through cooler soil will tend to create "rain-out" or condensation in the tube.  If the tube is closed, then mold will rapidly follow and the system becomes an increasing risk factor for healthy air.  My modification was to use a perforated (on the bottom) pipe wrapped in geotextile (could be hemp cloth) to keep soil and small beasties from entering while allowing condensate to seep downward and out with some porous material underneath, hopefully directed to a french drain or other area to sequester the condensate from the incoming air.  In a more arid environment, perhaps one could direct such condensate to holding tanks to create an Arrakis-style water source.  For non-sci-fi readers, this came from Frank Herbert's novel, Dune.  More work, but potentially rewarding, especially if melded with a rain collection system.

The insulation will depend on what is easily available. If Wheaton labs has access to hempcrete I think that would make a great subfloor material. Apparently someone is doing wool insulation, if that is produced in great enough quantity then it could perhaps be used for the walls and ceiling.

Cooling tubes are a pet topic of mine, they will have weep holes and probably some gravel underneath to keep them dry.

I understand that readily available local materials are best to use if possible.  Has there been any thought to use of cattail for insulation?  A German institute has developed a way to cut cattail stems into specific lengths and then mix them with mineral adhesives and then subject to heat and pressure to create an insulating board.  Since the natural spongy constituency of the cattail stem is the base for the insulating value, it would seem logical that laying cattail stems along a sub-floor would provide pure insulation.  As a natural swamp plant, the stems are resistant to mold and naturally water resistant while allowing water vapor to pass.  Not sure if any local ponds are around the site, but just for mental gymnastics.

I am very glad to hear that weeps and drainage are to be incorporated into the cooling tubes.  If kept below the frost line, one would wonder if small barrels of water could be placed next to the tubes to allow even greater cooling in summer months with geothermal assistance in fall months by heating the incoming air.  Another thought would be to build an ice house that at least some of the tubes could be routed through to take advantage of cooling along the base of that structure as well as using it for refrigeration for foods.  Some tubes could run along the floor of the ice house.

Looking at the opening illustrations 2 points can be make from the original transportable design. (1)  the roof angle can be steeper or shallower. the steeper angle would shed snow more easily and give a better sun angle for the winter entrance through the roof.  (2) Traditional assembly shown shows the insulation being rolled out over the inner covering which could be transparent.  With the outer water shedding layer able to open like the teepee flaps, a selected area of outer and insulation layers could be opened to the desired amount of solar gain during the desired part of the day.[ only morning for example during spring and fall ]
Third point: earth tube heat and cooling storage experiments for greenhouses has shown that much of the heat transfer happens through condensation and evaporation with the moisture being  stored  in and supplied by the surrounding sand.  The corrugated flexible tubing allowing the best exchange of both liquid and vapor so surface of the tube can dry.   The intake for the tube could be down hill from the mound and then coiled in the floor exiting in the center.  Center rocket mass cook stove mass could incorporate the final tempering of the air.
Forth point: The traditional expanding lattice used in yurts is a natural matrix for cob but could be woven on site with coppiced saplings for reduced expense but additional labor.  A second layer of woven saplings over insulation could be added later if heat loss is too great during the first winter.

1) Is this to be a permanent installation similar to the tipi on the lab?

2) Any guidance given so far on materials to be used? The "bad-ass roof sealant" reads kinda un-ecoish at first glance. I looked at the Pacific Domes site and almost everything they use for the cover and windows there are vinyl. I talked with a yurt maker at length on design and he contended a PVC outer is the only way to deal with snow load outside of manual removal, even with a 45* slope as pictured in the frame of the opening post above.

3)Do you have any information to share on the yurt that was ordered; diameter, wall height, roof slope?

What if you extended the roof poles on the south side and made a walipini in that space?   They could share a thermal mass wall. To keep the yurt cooler in the summer the wall could be insulated and covered with something white.

Coydon Wallham wrote:1) Is this to be a permanent installation similar to the tipi on the lab?

2) Any guidance given so far on materials to be used? The "bad-ass roof sealant" reads kinda un-ecoish at first glance. I looked at the Pacific Domes site and almost everything they use for the cover and windows there are vinyl. I talked with a yurt maker at length on design and he contended a PVC outer is the only way to deal with snow load outside of manual removal, even with a 45* slope as pictured in the frame of the opening post above.

3)Do you have any information to share on the yurt that was ordered; diameter, wall height, roof slope?

As far as I'm aware this will be a permanent structure, that's certainly how I'm designing it. I haven't gotten the specs for the yurt yet, I am hoping since they're in Montana that they purchased a yurt that can take snow load and is insulated. The skylight was just speculative I highly doubt we'll actually put any windows in the roof.

randy nottellin wrote:What if you extended the roof poles on the south side and made a walipini in that space?   They could share a thermal mass wall. To keep the yurt cooler in the summer the wall could be insulated and covered with something white.

That would definitely work better than the design as shown but it's more logistics than we will have time and resources for on this project probably.

As I look at the current provided plans, I am curious as to how large this yurt will be.  For one thing, any air change for a residence is recommended to be at least 0.35 to 1 air changes per hour (ACH).  There seems to be far more air flow restriction through the walls and ceiling than a regular yurt.  This will determine how large and how many cooling tubes will be needed.  For example, if the interior is 300 cubic feet, a rough calculation would be that the tubes should provide 100 to 300 cubic feet per hour of air change.  If the interior is to be a classroom, a minimum of 6 ACH up to 20 ACH would be required.  That is quite a bit of air flow.  Seems that estimated 4" PVC might require a number of tubes.  If larger tubes are used to obtain greater air flow, calculations of volume to surface area will be needed to determine cooling capacity as a larger tube does not provide as much cooling per cubic foot of air flow.

I did not see any suggestions to provide the southern exterior or interior glass walls.  I have always considered using recycled patio sliding doors.  One reason would be that such glazing would allow opening with screens to increase cooling on a very hot day.  Another is that it would be easy to install interior curtain rods with shade cloth and heavy insulating curtains, depending on the time of year and heating/insulation needs.

For a short time, there was an experiment constructing homes with two walls.  It was called "envelope construction" This allowed hot air to be taken from the ceiling and pulled down the north wall to heat the interior walls and then route the cooled air back to the southern glass walls.  In this case, tubes could be installed along the outside of the interior divider wall off the greenhouse area to carry warmer air along the ceiling and down between the outer wall of the yurt and the earth wall.  They would then run under the floor (probably below the insulation) and back up at the front of the south exterior wall.  The envelope construction method had a weakness in that in a stick-built structure, it added significant cost and also was considered a fire threat by allowing a fire to chimney through the walls.  If tubes are used, that negative vulnerability would be minimized.  In this design, the primary added cost/effort would be to add the tubing, but the design using an earth wall on the north sides allows leveraging heat transport methods with low added cost.

Just as a thought, instead of considering skylights for interior light and solar gain, what about using a higher front wall like a clerestory with a peak pole carried from top of wall to center pole?  Running canvas in a form similar to a cabin tent roof would modify the traditional yurt roof line, but interior light would expand greatly.  I would anticipate only one peak window assembly would be needed to substantially open light to the interior.  This design solves much of the water infiltration issues created by skylight installation.

What is a ger?

A handmade Mongolian yurt!

This one has 6 walls.   It sets up with a 21' diameter.
The walls are 6' tall.  
Two lovely floor to ceiling windows and a beautiful weather tight door.
350 sq. ft of cozy indoor space!


The Mongolian ger has two key components: the wooden frame and the felt and covers.  A ger is essentially a sturdy, portable well-insulated felt tent. Gers are designed to be easily dismantled and moved on the backs of camels and yaks. Mongolians will move their camp 4-10 times a year and can break down and set back up their entire home in a few hours.

Our authentic Mongolian gers are hand-painted with traditional designs and constructed of renewable materials. They are fair trade, bought directly from a local Mongolian manufacturer whom FIRE has been working with since 2006. Each ger is unique and made to order.

The base price includes the wood frame; all natural, thick, felt insulation cover; two canvas covers; two layered door; window frame inserts for the crown; and delivery to Flagstaff, AZ. Color, height, window and alternative delivery options are available.

   All of the wood parts are made from locally sourced and renewable larch, birch or pine woods.
   The door, roof poles, and roof crown are hand-painted with beautiful traditional Mongolian design using lead-free paint.
   The ropes are made from yak hair.
   The lattice walls are tied together with camel sinew.
   The felt is 5/8 of an inch thick, all natural sheep wool that has been cleaned and processed in a factory. Factory processing makes the felt an even thickness, very clean, with no sheep smell and more bug resistant.
   The door, roof poles, and roof crown are hand-painted with beautiful traditional Mongolian design using lead-free paint.
   The ropes are made from yak hair.
   The lattice walls are tied together with camel sinew.
   The felt is 5/8 of an inch thick, all natural sheep wool that has been cleaned and processed in a factory. Factory processing makes the felt an even thickness, very clean, with no sheep smell and more bug resistant.

The list below is the parts a typical ger comes with. The number of each part depends on the size ger you choose. These gers consist of:

       Roof poles
       Expandable, wood lattice wall sections
       Roof crown with a smoke hole and window frame inserts
       Two center support poles
       Double layer wooden door with the outside being a full door and the inside split into a double door
       All ties and ropes
       Durable factory-processed natural felt covering
       Two water repellent canvas covers, one decorative
       Cotton liner

So beautiful!  

These are from the Mongolian FIRE project
Real handmade art, preserving tradition and culture.

Here is their website:
https://fireprojects.org/

Here is one being built

Thank you so much!  This is what I envisioned as a yurt, however the thread seemed to be considering a hybridized version that raised some questions.  I have seen yurts taken down and reset in the snow above the arctic circle and this most certainly fits that memory.  If this remains what will be constructed, many of my questions become unnecessary.  This is a wonderful example of indigenous engineering.  Like a tepee, it fits the environment because it has withstood the test of time.

Richard Henry wrote:Thank you so much!  This is what I envisioned as a yurt, however the thread seemed to be considering a hybridized version that raised some questions.  I have seen yurts taken down and reset in the snow above the arctic circle and this most certainly fits that memory.  If this remains what will be constructed, many of my questions become unnecessary.  This is a wonderful example of indigenous engineering.  Like a tepee, it fits the environment because it has withstood the test of time.

I love that they are preserving their cultural heritage.  

They use natural materials just like in the old days.  They make camel hair rope and wool felt.   It is really a piece of art they are making for us, not just a neat shelter!    

This is a very cool and beautiful traditional yurt that we're getting, definitely not what I expected. Fortunately I don't think we'll have to alter the original components in any way to make the design work.

This will need modification to bear a Montana snow load. Or snow will need to be diligently removed by hand, as they suggest on their website. Otherwise it could collapse. 2x6 boards or equivalently strong timbers are recommended, perhaps every 4th or 5th roof pole. And those would need to be mounted on posts... I will include this as a recommended option in the next iteration of the design.

It's important to remember that designs like teepees and yurts are optimal dwellings for nomadic peoples on the move. They are relatively quick and easy to set up, take down and transport with horses. But the people that perfected them understood that these were not the most appropriate option for long term stationary use. So we also see more permanent ancient dwellings like longhouses, or the pueblos built with earth.

What we will do is take this traditional nomadic design, and combine it with principles of a permanent earth structure, thermal mass to store and radiate heat, and a layout which optimizes annual solar gain to reduce fuel needed for heating. Possibly there will be a passive cooling system as well.

I have also thought more about the suggestion above where a whole greenhouse is attached to the south side of the Yurt. There is a simple way to accomplish this, and it would drastically improve the performance of the build. You would use plain old metal greenhouse hoops. Buy them straight and find or rent a hoop bender. Then you construct a wood frame, or use greenhouse hoop joints to wrap a metal greenhouse around the building. Use wiggle wire track to attach plastic in the winter and shade cloth in the summer or nothing at all. It would be about as east to take apart as the yurt if you ever wanted to build something more permanent.

J. Rubins chimed in over on my mycelium insulation thread - he is growing mycelium insulation in a manner similar to what I am doing, but in a form that will make panels sized perfectly for his yurt.  

https://permies.com/t/177485/Homegrown-Mushroom-Mycelium-Insulation-Panels#1396005

Just a bit of PTJ synergy for good measure . . .

Beau Davidson wrote:J. Rubins chimed in over on my mycelium insulation thread - he is growing mycelium insulation in a manner similar to what I am doing, but in a form that will make panels sized perfectly for his yurt.  

permies.com/t/177485/Homegrown-Mushroom-Mycelium-Insulation-Panels#1396005

Just a bit of PTJ synergy for good measure . . .

This yurt comes with a felt cover apparently but the more insulation the better. Mycelium panels could be attached to the interior of the lattice and the cob wall could be built up to them.

Perhaps they could be pizza sliced and placed over the roof poles to insulate the roof. They could also be fixed under or in between any snow reinforcement framing but it would be a shame to completely hide the beautiful roof poles.

Michael Ot wrote:This is a very cool and beautiful traditional yurt that we're getting, definitely not what I expected. Fortunately I don't think we'll have to alter the original components in any way to make the design work.

This will need modification to bear a Montana snow load. Or snow will need to be diligently removed by hand, as they suggest on their website. Otherwise it could collapse. 2x6 boards or equivalently strong timbers are recommended, perhaps every 4th or 5th roof pole. And those would need to be mounted on posts... I will include this as a recommended option in the next iteration of the design.

It's important to remember that designs like teepees and yurts are optimal dwellings for nomadic peoples on the move. They are relatively quick and easy to set up, take down and transport with horses. But the people that perfected them understood that these were not the most appropriate option for long term stationary use. So we also see more permanent ancient dwellings like longhouses, or the pueblos built with earth.

My thought on snow load was to sort of hybridize with a teepee, bumping the roof slope up to 45*. I'm taking advantage of the additional space with a light framed loft toward the center for sleeping space or storage. A consultant seemed to think that a PVC cover would shed snow on it's own, but canvas wouldn't (we didn't discuss felt). I'm sticking to natural materials, so not counting on the canvas to shed the snow, but on the roof angle to support the weight better. I'm curious if the limiting factor would be along the length of the uni or at the connection of the uni to the tono. Is there data out there about weight loads in a form that would be relevant to this?

Also, I'm not sure what they are called, but what about poles that support the tono? Are they included, wouldn't they be enough to deal with an extra weight load?

My thought on snow load was to sort of hybridize with a teepee, bumping the roof slope up to 45*. I'm taking advantage of the additional space with a light framed loft toward the center for sleeping space or storage. A consultant seemed to think that a PVC cover would shed snow on it's own, but canvas wouldn't (we didn't discuss felt). I'm sticking to natural materials, so not counting on the canvas to shed the snow, but on the roof angle to support the weight better. I'm curious if the limiting factor would be along the length of the uni or at the connection of the uni to the tono. Is there data out there about weight loads in a form that would be relevant to this?

Also, I'm not sure what they are called, but what about poles that support the tono? Are they included, wouldn't they be enough to deal with an extra weight load?

Has anyone considered running a pulley system with curved poles along the center top so that canvass or other water resistant fabric could be pulled down the slope to the side where the snow could be dumped off the roof and then pulled back into place?  This might require 4 to 5 pulleys, but that would be better than taking a chance on collapsing the roof under load.

Richard Henry wrote:Has anyone considered running a pulley system with curved poles along the center top so that canvass or other water resistant fabric could be pulled down the slope to the side where the snow could be dumped off the roof and then pulled back into place?  This might require 4 to 5 pulleys, but that would be better than taking a chance on collapsing the roof under load.

Might want to provide some sort of diagram of this idea? The way I'm familiar with a yurt/ger, you sew together a covering that is water tight and it is either on or off as a whole, there wouldn't be anything retractable about sections of it...

Just go around inside and bump the roof between each rafter pole with s broom to shake the snow off.

This past week in the northeastern US, we had a record spring snow/blizzard.  In Central NY, I received around a foot of very wet, heavy snow.  The snow took down tons of trees and power lines even though greenup has yet to get going.  Even though I have a metal roof, the snow did not like to slide off.  I am afraid in those conditions bumping the roof of a yurt would have less than favorable results.  It would require a way to lift the snow off some of the roof at a minimum, which a pulley system could accomplish.

My 200 year old farmhouse came through with flying colors and my generator rose to the occasion, however a great many people went cold and ate cold meals.  I have a generator to serve an adult child and cancer-impacted wife.  In the last couple of years, I have joined the walking wounded when I was diagnosed with an apparent genetic issue where my throat collapses when I go to sleep.  No wonder I used to rattle the rafters.  So, cue up the CPAP to keep me breathing instead of choking.  I am researching how to install a solar system to use non-fossil fuel energy in the future.  The moral of this digression is - sometimes we need technology to accomplish needful tasks.  The real challenge is to use that technology in the best and most efficient way so we do not add to the destruction.

Really love this design!

Michael Ot wrote:

Beau Davidson wrote:J. Rubins chimed in over on my mycelium insulation thread - he is growing mycelium insulation in a manner similar to what I am doing, but in a form that will make panels sized perfectly for his yurt.  

permies.com/t/177485/Homegrown-Mushroom-Mycelium-Insulation-Panels#1396005

Just a bit of PTJ synergy for good measure . . .

This yurt comes with a felt cover apparently but the more insulation the better. Mycelium panels could be attached to the interior of the lattice and the cob wall could be built up to them.

Perhaps they could be pizza sliced and placed over the roof poles to insulate the roof. They could also be fixed under or in between any snow reinforcement framing but it would be a shame to completely hide the beautiful roof poles.

Very cool project, Michael!  Thanks for the heads up on this, Beau.  I haven’t gotten very far on my mycelium insulation, but I am also planning on the pizza/pie wedge idea for the roof insulation.  I am molding the panels with a one inch half-lap to help reduce wind infiltration too which I also suggest if you go this route.  It may help to give some wiggle room and get a better seal since gers aren’t exactly precision structures when set up (which gives them a whole heap of charm).  But I’m not certain yet of the half lap’s durability.  Will know in a month or so once the panels are made and will post results on Beau’s mycelium insulation thread.

Michael Ot wrote:

Richard Henry wrote:I see some discussion related to insulation both underneath the floor and in the walls.  Has any thought been directed at natural insulation such as hemp?  Hemp is a great insulator whether in brick form or poured or as hempcrete.  Basically it provides a better insulation than equal thickness fiberglass, about on a par with mineral wool, but with the advantage that it can get wet and dry out whereas mineral wool basically loses its insulation value on wetting and cannot recover as hemp does.  In addition, hemp is a natural insect and rodent repellent and continues to sequester additional CO2 as it ages.  In addition, non-treated hemp does not burn until it hits around 900 degrees F.  Hempcrete is made of the central hemp core, or hurd, lime and water.  It can provide some structural support, especially in a floor situation while being far more healthy than Portland Cement.  I believe it would provide a really decent leveling material beneath such a structure and act as a vermin retarder as well as carbon sink.  

For the earth cooling tubes, I remember an inventor friend who raised that concept about 50 years ago.  The main concern I had then and still would, relates to the fact that ambient air being drawn through cooler soil will tend to create "rain-out" or condensation in the tube.  If the tube is closed, then mold will rapidly follow and the system becomes an increasing risk factor for healthy air.  My modification was to use a perforated (on the bottom) pipe wrapped in geotextile (could be hemp cloth) to keep soil and small beasties from entering while allowing condensate to seep downward and out with some porous material underneath, hopefully directed to a french drain or other area to sequester the condensate from the incoming air.  In a more arid environment, perhaps one could direct such condensate to holding tanks to create an Arrakis-style water source.  For non-sci-fi readers, this came from Frank Herbert's novel, Dune.  More work, but potentially rewarding, especially if melded with a rain collection system.

The insulation will depend on what is easily available. If Wheaton labs has access to hempcrete I think that would make a great subfloor material. Apparently someone is doing wool insulation, if that is produced in great enough quantity then it could perhaps be used for the walls and ceiling.

Cooling tubes are a pet topic of mine, they will have weep holes and probably some gravel underneath to keep them dry.

Neat ! Sounds like an awesome project . Are cooling tubes be something that I should be worrying about with putting in earth floor for climate controlled quanset hut (in mountain plains of SW Colorado ) ? I was mainly thinking more about how to install in-floor heating for winter.  

How much snow load can the yurt deal with?

paul wheaton wrote:How much snow load can the yurt deal with?

This is all I found on their website:

"These gers are made for a harsh climate and can withstand wind, temporary snowpack (remove snowpack daily), "

No data about snow loads, just a recommendation to remove snow daily. Perhaps they could answer this if called or emailed. This is why I suggest adding our own 2x6 or timber reinforcement frame.

Looking at the slope of the roof poles, and their size, I think it definitely will not support any significant load and would require diligent snow removal otherwise. I am not familiar with the property's winter staffing and if that would be possible.

It seems that 2 contradictory goals are trying to be achieved at the same time. (1) Set up quickly a prefabricated structure during the jamboree. (2) Have a structure that is designed to be disassembled and stored  when not in use stand as a permanent structure.  Not that the structure can not be built as a permanent structure but that it needs to be built with materials that will meet the requirements of a permanent structure.  For example octagon buildings have been built in this locality in just a few weeks and have stood securely for decades with little degradation.