Should insulation and thermal mass be constructed on seperate walls?

It is my hope to construct a house on my property 11,000ft near San Luis, CO that will also have an attached greenhouse on the south side. Would it be a good idea to construct the south facing house walls enclosed in the greenhouse sides with an emphasis on thermal mass, while the north facing sides are built for insulation? It seems like a good idea as far as heating the greenhouse, which is a big priority, but I do worry that it may leech too much heat from the house to outside through the greenhouse walls. Would it be possible to compensate by adding more thermal mass inside of the greenhouse? I'm guessing at that point, I might as well insulate the entire house exterior.

My goal is to try and integrate the greenhouse and house heating as closely as possible, so I can avoid having to manage 2 heating systems and run the greenhouse all year long. If anyone has any input or ideas, I'd be glad to hear them. Thanks!

Thomas, could you post a few more details?

The Rockies at 11000 feet is nearly above tree line, so you will need a different design than most in order to compensate for the house drifting over in snow. I have had to dig out cabins to stay in in winter at lower elevations than this where the only indication of a cabin was the little wind cap on top of the stove pipe making a mound in the snow.

So if you could give a little more info on the site like is it sheltered, on the lee side of a ridge or something? Are there trees? What are the average wind speeds? What direction does the slope face? etc.

Hey Thomas,

Bill's query is "spot on," as altitudes between 6000 and 11000 feet in the Rockies is extreme architecture in some form or fashion no matter how you look at it...as Bill has suggested.

I believe I have already shared my views with you on "frontal greenhouses" and the ensuing challenges of their lifespan that will take place in maintenance, weatherization and heating. I am not say don't do it...yet be fully conscious of the many challenges:

1. They are absolutely their own heat zone or you must embrace more fuel consumption overall if the greenhouse space and living space is fully integrated.

2. A thermal mass wall separating the greenhouse from the living space is a very good idea...it must be massive to work well (minimum of 0.5 m with 1 m being the beginning of optimal.)

3. Doors and windows to close off living space strongly suggested.

4. Window maintenance and weatherization is ever ongoing.

5. Condensation management and moisture issues must be monitored and rectified immediately as this can affect the living space quality, and promote other challenges as well (i.e. interstitial mold and insulation compromise, structure decomp, etc.)

Regards,

j

It's around 7.6 acres, with the north half sloping down pretty steep and full of trees, and the south side along a dirt road frontage that seems pretty flat with a sharp dropoff to the south of the road. To the east on the neighbor's property, there is an incline that curves north, but it's very close to the top of that ridge I believe. To the west it doesn't slope down for probably 1/8 mile or so, where the road loops around and follows the north side valley. I've only been out there once, and not for the entire day, but it looked like there was a lot of room for a stable building site and plenty of sun exposure. However, none of this was measured precisely.

Living in Florida, I've got zero experience with cold climate construction. I'm not sure how I would prepare for snow, other than anchoring the walls and building the roof to accommodate snow loading. The moisture issues I will likely have no problem dealing with. I've had to rebuild my entire house down here because it was metal siding on studs, with no moisture barrier or sheathing. After dealing with moldy drywall after that, it's made me appreciate moisture-proofing the living space and providing adequate drainage outside.

I do not plan on beginning this project for at least another year, might even be as many as 5 years, so now is the best time to gather as much insight as I can to make it feasible and optimal. I guess it makes sense to design the heating separately, though, since the plants won't complain too much if it's cold as long as I keep them above freezing. If it's not possible to keep both the house and greenhouse at 50-60 degrees at its lowest temperature, I may go that route. I can always add a room specifically for collecting solar heat independently, where the temperature getting too hot inside won't affect the plants or human comfort.

Hi Thomas,

Good to read what the timeline is for construction...I think it really is going to be needed.

First and foremost to start...what "exactly" is the altitude of the property?

What is the average snow depth and loads for that specific sight?

I have to be honest, I have seen many folks from the "East" buy property out west in the mountains and not really understand what that entails and means. There are some areas that are commonly buried under 10 feet of snow...or more!!...So Greenhouses and "flat land" architecture....well...it doesn't work, or doesn't work the same nor is it as easy to facilitate. I believe we need to get some "knowledge" first before moving into what and how to build...

Regards,

j

Here is the location:
https://www.google.com/maps/dir/37.2732501,-105.2599767//@37.2729982,-105.2595583,910m/data=!3m1!1e3
This is the elevation map:
https://www.google.com/maps/@37.2718755,-105.2567688,15z/data=!5m1!1e4

It looks to be mostly 11,360ft in the area I would like to build on. Much of the climate data I have seen is based around the city nearby, which is closer to 8,000ft. I try to adjust as scientifically as possible, but in the end it's all just estimates. http://www.usa.com/san-luis-co-weather.htm

It will be a while before I can get a trailer up there or build a cabin to stay, and even then the data might be different from one year to the next. From what I've gathered, the area is dry and there is not a large amount of snowfall. I did not see any signs of water retention, erosion, runoff, etc when I was there.

Wow, those irrigated circles to the northwest of you are dramatic!

Looks like a pretty dry place, but somebody's taking a swing at agriculture. Interesting.

Thomas, that is great news!...

I spent part of my childhood in the Cochise Stronghold and around the Spanish Peaks area of southern Colorado...a high and dry mountain area not the far removed from where you plan to build. You may even have to consider water storage as it can be costly to dig wells more so than putting in cisterns.

Now we have the snow and precipe levels better understood, this area is more conducive to your goals...

I think a thermal mass wall as planed will be more than applicable...

I was actually considering a farm in the valley to grow quinoa and hemp. The thing that bothers me, and maybe I misunderstand how it works, are water rights. I'd hate to put down money on 40 acres or so and have someone tell me that I can't irrigate because the guy growing a billion acres of alfalfa has priority.

As far as water goes for the mountain, I would probably focus on a combination of rain collection, melting snow, possibly even humidity from the air, and if it really gets that bad I haul the water up there. I will end up needing a well permit for rain collection, so it's not entirely out of the question to drill, but I doubt I will go that route. I also hope to use the stored water as thermal mass in the greenhouse area instead of a cistern underground.

You're a brave man Thomas! This is what my grand dad used to call "a tough row to hoe".

I know that area well and it is not an easy place to live. Although it is very dry in summer, winter snows can be severe and it can be weeks of below zero weather sometimes.

First, know the weather. Here is the Colorado avalanche service snotel site Weather Stations, this will give you up to date reports on weather around there, just find the appropriate snotel for San Juan south.

Second is water. You will not be allowed to drill a well and yes the guy who grows alfalfa on a billion acres has most of the water because his ancestors claimed it first. You will be collecting your own water. Hopefully there is a spring that you can develop. Many people end up with a large plastic tank in the back of their truck that gets filled when they run to town. I have never grown hemp, but Quinoa does not need irrigation and will tolerate extreme altitude and cold, so I think that's a great choice.

Third is food. You will be traveling by snowmobile in the winter, so going to the store is a real pain in the neck. A green house is not going to work in winter. Put it off separate from the house and have a food growing area inside your home for winter veg. I would look into a climate battery system where the greenhouse exhaust vents travel under the house, heating the soil in summer so the soil retains that warmth through the winter.

The thermal mass should be connected to the earth in a climate battery system and insulation on the exterior extending out into the surrounding soil.

If it were me, I would build a log cabin and then build light straw/woodchip clay walls on the inside with a double roof as well(inner roof insulated to R-60 and outer roof vented).

Bill wrote:If it were me, I would build a log cabin and then build light straw/woodchip clay walls on the inside with a double roof as well(inner roof insulated to R-60 and outer roof vented).

Well that is right along what I was going to suggest as "best practice" for that area short of stone and timber into a cliff edge if you had one. I wanted to sound as positive as I could about the site Thomas, yet as my memory serves in that area at that altitude all that was there was summer log cabins and a few timber frames, mixed with a spattering of vernacular log and cobb structures...all seasonal accepte for a Kiowa/Cheyenne Woman named "Redsquirrel" that dated my Uncle until his passing. They lived in a trappers tent in summer and a Hogan in winter of log and earth with walls almost two feet thick...often getting stuck either there or in Walsenburg.

I also have to admit that few that I knew owned there water rights and this was a biggy to look into before ever buying land out there. My Uncle wouldn't touch a piece of property unless he had a spring, running water, or the water rights...otherwise it made living and build...well in his worlds..."impossible and not worth the efforts if you plan to live there year round..." Things have changed since then with water storage, yet it is still a major burden...especially if doing any farming instead of "off the land," living...

It seemed like the Sangre stations were closer than the San Juan stations, but I couldn't find any weather stations close to the property in that link.

If anything ever got too bad out there, I could always pack up and stay with family near the Denver area and reevaluate the situation. The original plan was to set up a solar array and wind turbine, supplemented by wood fuel or an emergency gas generator. I thought I'd just start with a cabin, and expand or add on every summer and spend the winters somewhere else until I felt like my energy production and storage were able to handle winters. I can also get a feel for how the local resources will work for construction materials. Passive solar seems like a good way to mitigate energy use, so it might be better to plan around this style of building instead of altering and adding on a piece at a time. It's definitely better than just adding batteries to a battery bank just to heat the place. The extra energy can be put to use meeting other needs.

As for construction, I am aiming for r65 exterior walls, r60 floor, and r90 roof. I may not be able to get those ratings using log and cob, or other natural building materials. I definitely want to use as much material from the property as I can, since it will be easier to make any repairs quickly and cheaply with minimal impact on the environment. If I am going to use an isolated gain system, maybe I can still go this route. It would be nice to find a passive way for the house and greenhouse to work together, though.

Hey Thomas, et al...Happy New Year!

I believe you shared this already yet I have forgotten...how much land do you have on this parcel?

As for construction, I am aiming for r65 exterior walls, r60 floor, and r90 roof. I may not be able to get those ratings using log and cob, or other natural building materials.

First, I am not sure why anyone ever believes they can't achieve the same or even better R and thermal mass ratings with natural materials? That always surprises me!

I am not sure the floor needs that much R factor...not even if a "raised floor" was used. Heat does not go down, and the average range of loss ratios are:

Floor: 10% to 15%

Walls: 20% to 50% (fenestration dependent anct)

Ceilings/Roof: 50% to 80%

A mixed modality log, timber, cobb structure could easily achieve your goals, and even easier if augmented with a wee bit of modernity if that seems more familiar with a material like rock wool.

...it would be nice to find a passive way for the house and greenhouse to work together, though...

Achievable...yet perhaps not as easy as good old wood heat and super insulation on a small foot print of architecture...

Regards,

j

Hey Thomas, you said that you have family in the Denver area. Have they ever been to your land?
I was thinking that if they had time and a good vehicle that they could drive over there and take some pictures so you could see what it was like this winter.
Maybe tell you how the snow drifts and how it melts in the spring.

It almost looks like the neighbor to the north of you has a yurt? Might be a good person to get to know!

Have you played around with the county assessor website? You can find a parcel map of your property and then find the names and adresses of your neighbors.

http://www.co.pueblo.co.us/cgi-bin/webatrallbroker.wsc/ackatrcos.p

You actually have a couple of neighbors from Florida!

Thanks, and happy New Year to you as well as everyone else! I also will look into climate batteries, thanks for that Bill.

The size is 7.6 acres. I would like to insulate the floor as best as I can, and that was one of the recommended ratings to use. I will definitely look into using less if I can. I've only dealt with cold earth once while camping and it wasn't a pleasant experience. I think for building it's less about being natural materials than it is the availability of it on site. If I need to source something from off site, then I will have to consider all of the combined factors- durability, cost, ease of use, etc. Maybe I can use logs, cob, and pine needles on my first structure to get a feel for things. I'm not sure if I can make a decent enough cob without hauling up more ingredients. I might toy around with making adobe blocks or rammed earth.

And if you have not seen this, here is Colorado's water rights page.

http://water.state.co.us/DWRIPub/DWR%20General%20Documents/SynopsisOfCOWaterLaw.pdf

Miles Flansburg wrote:Hey Thomas, you said that you have family in the Denver area. Have they ever been to your land?
I was thinking that if they had time and a good vehicle that they could drive over there and take some pictures so you could see what it was like this winter.
Maybe tell you how the snow drifts and how it melts in the spring.

It almost looks like the neighbor to the north of you has a yurt? Might be a good person to get to know!

Have you played around with the county assessor website? You can find a parcel map of your property and then find the names and adresses of your neighbors.

http://www.co.pueblo.co.us/cgi-bin/webatrallbroker.wsc/atrpropertysearchall.html

You actually have a couple of neighbors from Florida!

We all went out to the property once a few years ago. It was like a 4 hour drive one way, and I wouldn't want to burden them with that task unless they were going that way. I might find a way out there this year, but being in the planning stages and all it's not a huge priority. The knowledge I gain from here is valuable even if I decided to scrap the project for whatever reason.

I'll have to look into the neighbors, because that mountain was pretty much empty aside from the abandoned gold mine and a few houses near the base. I kind of liked the fact that it was solitary, but it's nice to see other people build out there.

Thomas here are a couple of photos of the area in winter. Not sure what month.

http://sdcro.com/ranch-photos/?album=all&gallery=8

Have you seen this thread at the city data forum?

http://www.city-data.com/forum/colorado/530530-fort-garland-sangre-de-cristo-ranches.html

Here is one of your neighbors who writes for mother earth news and has a blog about the area.

http://www.motherearthnews.com/biographies/bruce-and-carol-mcelmurray.aspx#axzz3NmGOvPKO

Thanks for those links. Hopefully I can take things further with proper design. I'd like to extend the growing season as far as I can, and if successful maybe even try to get chickens and a sheep. It will be hard, though, with few or no places to graze for part of the year. The other thing will be using less than 11 cords of wood a year. I'm trying to practice more of a low impact forestry approach, plus it will be dangerous trying to get wood on the northern slope of my property. I'm convinced that proper planning can overcome the climate out there, and I know it's not going to be sitting back and relaxing all day. Right now is the best time to plan while I hurry up and wait.

Has anyone built a heat recovery ventilator, or is it better to just buy from the manufacturers? I saw a build with corrugated plastic, but that's probably pretty inefficient for heat transfer.

Hey Thomas,

I have been thinking a fare amount about this project, and can't help but compare it to others...Like my Uncle and how he lived, as well as Elders I knew/know and their lifestyles. I have to suggest again, from experience, that the harsher the climates seem to get (i.e. weather, altitude, extreme biome) the more vernacular the architecture (that works) seems to become. So unless someone is going to build ultra modern...with all modern materials...the only alternative seems to be...proven vernacular systems...

I'm not writing this to discourage or dissuade you...I want you to do it the way "you want,"...yet and the same time keep as close to vernacular as possible. This brings me to the next point...architecture as if reflects life style...

There is 24 hours in a day...and our bodies need to have "x" calories to facilitate "y" exertion. Now what does the biome one lives in best facilitate for the most efficient and self reliant modalities. For me I look to not only the vernacular architecture that humans have evolved with for a given biome as my foundational guide...but also the indigenous culture. Are they agronomy based of hunter gatherer.

Like I tell folks all the time that say..."but...I want to build it this way..." or "I want to live this way..." My response is...you can...However, one is living in balance the other is forcing something to work. Modern architecture (or modern life) is a symphony of "reinvented wheels" and "making things work." There is very little homeostasis or ease in the flow of most modern lives. Humans think they have it easier, and is some ways they may, yet if mental and physical health is the barometer of this...well we are by far missing the mark.

This brings us back to your land and plans for living on it. My Uncle and his companion live as her ancestors did. Meat came from the surrounding forest and there was never a meal I shared with them that didn't have more meat than you could ever want...Deer, Elk, Antelope, Range Cattle, and even Horse a few times a year. This meat was "jerked," smoked, and often just hung in the meat barn to age. There were wooden bins of corn for corn meal, and baskets of pine nuts, dried mushrooms of all types, and the list goes on...They became "hunter-gatherers" as this was the most "efficient" way to live and not have to exert as much energy as trying to "make" other system "work."

Architecture...small, indigenous, superinsulated built from 95% of the materials on the land...Food, from the surrounding forest augmented with "bartter goods," from town.

So again, keep thinking, yet I would suggest anchoring my foundation of thinking to the "knowns" of what works and have "efficiency" of living the guiding light...

Regards,

j

Paul;
As you're chewing over options regarding a greenhouse, consider this. The 'chinese' greenhouses that get a bit of play on the internet now have an insulated and massy north wall and roof, and over the glazing of the south side, they also install a deployable EXTERIOR insulation cover that can go far (as far as you can make it thick) towards conserving that precious heat through the nights and storms. In a high altitude setting like you are considering, I wouldn't think twice about including such a feature, which would also be able to serve as a variable shade-system against overheating, and as a protective shield for preserving the glazing against extreme elements.

Sharing a wall with the house seems extremely prudent, provided you remain constantly aware of the different humidity needs of those spaces, and design barriers and air/humidity handling tools with that in mind.

I suspect we will see many more people working out variants on the HRV and ERV systems, as we continue to get better educated on tight houses, indoor air quality, ventilation, oxygen levels, humidity, etc.. I've got a stockpile of aluminum sheeting awaiting some experimentation on homebuilt heat/exchangers and 'condensers'.. but other items are higher on the list today.

Hey Thomas,
It's pretty awesome back up there. No county codes, but I believe modest covenants. Anyways you are 60 miles from
Mountains of graded Scoria $13/yd, 120 from pumice $25/yd, and 60 from super high quality bales $5 delivered. There are adobes in Antonito. Few hours from a warehouse of $10-20 pdr's. If you are low on cash, heed. Doubtful you'd find any clay close to home besides San Luis road base. Personally, I'd be anxious to live in a log cabin in a high desert forest, each year drier than the last, but that's cause I've worked wild fires. Strawbale has great fire rating once plastered, quick, cheap. Scoria is close as far as r value, don't rot, burn, mold, more flexibility... Adobes are cool but $$ for what you get. Depends on you.
Insulate all around, removable insulation on windows, thermal mass wall between house and sunroom as long as you insulate the exterior well. If you throw up a half hoop, then obviously don't thermal mass it up and expect comfort. Maybe a combination of direct, indirect, isolated gain. Pex in yo floor is cheap insurance. as i see it, beetle kill logs are for post/beam/ timber framing--not stacking-- when there is great sustainable local insulative choices that don't burn and rot or cause you to build multiple walls or burn cord wood all day. But I have never heard of a passive solar log cabin. I know the strawbalers keep their logs inside of their bales so that there is no thermal breaks... Food for thought.
Sitting in a sunroom or attached greenhouse is great in the winter (cause it's mostly sunny, less so on a mountain tho, some woodstove action during cloudy spells like this whole month). A more frugal (sustainable?) Approach would be direct gain with planter beds in your house, and cold frames off the front. Not nearly as fun though. Thermal mass interior walls are ideal, and it ain't hard to run plumbing through them. Cold frames often do better than greenhouses on the south wall out here btw; Although not as romantic, they really are more fruitful.
Or earthberm.
If you throw a ferro cement cistern in their, constantly draining and replenishing, don't expect that to heat up to much of anything. Likewise, 5000 gallons of untouched water would take all dang winter to warm up.
Chris

I also live at almost 11,000 feet high, and we heat our houses at our school only with greenhouses. We roll them down and fix them tight in October, and remove them in April or May. If we kept them on in summer it would be harmfully hot -- already some days in early May are uncomfortably hot. We have thick earth walls on three sides including the south, and then the north is either insulated or bermed into the earth. (I think insulated thick earth is better). The thick walls on the south mean that when the greenhouse is too hot in the shoulder season of fall and spring, the rooms are not too hot, and on winter nights when we close the doors and windows between the rooms and greenhouse, the house doesn't cool down too much. If it were my private house I'd probably use backup heat on January nights, but since we don't have backup heat on principle, it's not that bad, I mean, I wear a hat and three sweaters indoors in January, but december and February are just fine with a sweater or two. Normal winter indoors temperatures.

Absolutely right, it's a lot of fun having an attached greenhouse all winter when there's nothing green outdoors!

If half hoop is chosen, Some operable insulation on a half hoop would be killer: insulated curtains, pool cover, etc. Especially Thomas' site being the windward cloudier side of a mountain. On the hoophouses I've done (usually sunken), I like to bend schedule 20 tubing and throw a 1" hex end on the roller bar so that an impact driver can easily roll up any film, insulation, shade screen. Maybe A climate battery too.
Btw, aa radon system would be wise where you're at Thomas.
Build it solar has diy hrv plans.

But the real kicker is your snowfall. If you end up finding out that your spot gets 5,10, or 20' because of the way winds funnel, then that's a big determiner for a year round place.
Chris

I live not-so-far from your land. I've hunted elk in your neighborhood.

Yours is a beautiful summer cabin location. Could you live year 'round there? Yeah… and I could have, too, when I was in my thirties!

We are having a wintery blast right now in our area. It's snowing and blowing and below 25* and dropping. And we live in a sheltered spot at between 6k and 7k elevation on the warm side of those mountains. My point being that wintertime access to your land would be tough for a thirty year old.

Alamosa, the nearest "main" town is known as a sort of icebox by Colorado standards. The San Luis Valley floor is around 7k ft. The "SLV" as it's locally called, is bounded on the west by the San Juan mountains and on the east by the Sangre de Cristos, as you know. In winter the cold air flows into the valley and sits there since the Rio Grande gorge is the only low spot for water or cold air to flow out. Despite the cold winter in the valley, the summers are wonderfully cool and it's sunny all year. Lots of stuff (potato, lettuce, carrots, barley, hay, and more) are grown commercially. Alamosa has a great farmer's market and a long history of community working to assimilate people from south of the border that had once come up to work in the fields. No, I don't live around Alamosa, but I go there often.

As for the comment that you can't drill a well there, I'd have to challenge that. I believe the Colorado "35 acre" (Colorado SB 35) law was enacted in May of 1972. Land platted via the Clerk and Recorder's office before that is exempt… sort of. You can usually get what is known as a "hardship" permit or sometimes referred to as an "inside use only" permit. My understanding is that it remains a gray area in Colorado law as to whether or not an attached green house is household use or not. I looked at the topo for your land. Very unlikely to have a spring, IMO. And in a bizarre throw back to Winnin' The West, it remains technically illegal to collect all but a tiny amount of the meager rainfall that lands on your own roof!

I wish you the best and I hope you understand that as the reason I wrote this.

Well, I tried driving out to the property in February.  Apparently, they only plow halfway up the mountain, and it was about 2-3 feet deep after that.  I guess the good thing is that I can make a ski slope or half pipe going down the north side of the property.  Between building igloos, snowboarding, and making anatomically correct snowpeople, maybe this project is just what I need to make me stop liking winters.

So next month I'll drop my data logger onto the property to monitor the temperatures over the next winter.  I'll also be seeing how far down I can dig, as well as trying to determine how much clay and rock is in the soil.  Hopefully this will give me a more complete picture and I can start narrowing down the most efficient design.

Has anyone ever thought to build a donut shaped home with a geodesic dome over the hole in the center?  The living area could be the outside ring, with the greenhouse being in the center.  I was thinking double layer earthbag walls with the outside and greenhouse facing sides filled with scoria.  Maybe I could even add a strawbale layer to the exterior for extra insulation.  The dome could be built insulated on the north side, with polycarbonate on the south side.  The growing area could be raised a bit and mylar could be used to help reflect light around.  The roof underneath the outside of the dome could be a sloped metal roof with an insulated crawlspace.  If size is a question, let's start with a 22' total radius- 8 greenhouse, 2 inner wall, 10 living space, 2 outer wall.  I would think that this style of building would offer the greenhouse more protection from the cold than if it were placed independent of the structure or along the south side.

A greenhouse at the center of the house with a dome could be a beautiful layout for a warm climate, but it would make for several issues in a cold snowy climate.

The dome would necessarily be the highest point of the structure and thus where heat would want to rise to, while a dome shape would be tricky to fit with movable insulation. You would have to go up on the roof to adjust it (unless you made an automated system of some sort) and also to clear snow off when it drifts. The house on the southern sides would block a lot of low winter sun from directly hitting the greenhouse beds, while the dome would gather all possible high summer sun. You would need to completely isolate the greenhouse from the rooms to avoid major heat loss during cloudy cold weather, so moving directly from room to room would have to be in the plan.

If you don't have money to burn, I think you would be best off building a simple well-insulated house and a greenhouse with mostly south exposure. Check out the walipini concept for a possibility there.

I would split the dome into north and south halves.  The north half would be framed to hold insulation, likely perlite, inside of it.  I would probably try to insulate the south wall at night from the inside, by hanging quilts or something or possibly even building a shutter that would slide around to the north half when not being used.  Elevating the beds and using reflective surfaces would definitely be involved.  A climate battery to draw the rising heat back into the earth would probably be used as well.  There would only be one entrance to the greenhouse, so it's not a high traffic area.  I'm ok with having to walk around the house instead of cutting through the shortest path.  I would hope that adequately isolating the house would be achieved by a layer of scoria bags, and the earth filled bags would be on the interior of the house.  Do you think a vapor/moisture barrier would be needed?  It could be placed between the bags if so, with ventilation for the living area and greenhouse separated.  Snow accumulating on the southern roof did cross my mind, but I just figured I would manually remove it, unless I came across an easier or more efficient way.  Wouldn't the shape of the dome shed most of the snow down to the lower, outer roof?  I also need to consider how to seal the seams with something capable of withstanding low temperatures.

I've considered the walipini, but I'm waiting to see how far down I can dig.  I'm also planning on multiple structures, whether they're guest houses, sheds, or a garage.  Money isn't really a factor to me for this property, because it's more like a hobby or experiment.  A large part is just finding out what works, and being as hands on and diy as possible with it.  After that, I can evaluate where costs could be cut or what could be done differently to help other people interested in building in similar climates.