Exterior Horizontal Insulation on an earthship

I had been planning on doing a whole concrete foundation to get insulation under the whole living space including the tire walls. After playing with the EnergyPlus Ground Temperature Calculator I discovered that even here with permafrost down around 5-15m, that with no insulation under the center a living space a slab or floor directly on the ground (mass) is always warmer than an insulated floor in a house with a room temperature around +20C. Wow. The insulation under the floor really functions to protect the floor around the edges. Most of the heat loss is not straight down, but out the edges of the slab or floor on the ground. Even just 1 meter around the edge was fairly good performance.

I realized that I was planning on a slab, but now only 1-2 m of the slab edge really needs insulation, not the center. I discovered that exterior horizontal insulation will do the trick. All we have to do is put insulation down to the first course of the ground of the first tire course and go out horizontally about 1 ft. underground. Here 2m is probably enough. It doesn't even have to be that thick. This is also called frost-protected shallow foundation. This way we can make an earthship in the coldest city in the world and use standard procedures to build o the ground, like doing tire walls directly on dirt. The external insulation acts like the slab or floor is larger, so the heat has much further to travel outside of the house. The house itself has insulation on the walls.

This would drastically save costs unnecessarily. The mortgage bankers won't like this if people can build decent houses even in cold places without the need to do expensive insulated slabs, and news will not be allowed to get out about this fabulous technique. We don't have to dig deep 2m deep trenches around the perimeter of the house, which would disturb earth to lay tires on.

Energy Modeling, Energy Plus software

I'm using EnergyPlus software to model the thermal situation of our earthship. After reading all kinds of posts in Facebook groups and web pages, I thought I needed various things: heat exchangers, insulation under the whole floor. Ulaanbaatar, Mongolia is under spotty permafrost. It's just below freezing 5-15m down all the time. However, even 2m down on open exposed soil, the winter soil temp is only about -4C. Today I was running the Ground Temperature Calculator again. Several things were quite obvious. With a slab and no insulation, the center of the slab is actually warmer than with insulation, because even with a regular house the house can access the mass under the center of the house. However, the perimeter areas of the slab are much colder. 2m Vertical insulation is the default setting on that program, and that works quite well, because it contains a lot of mass for the living space. The downside of that is you need a backhoe to dig out a 2m deep trench and manage the edge of the slab. Possible, but more expensive. Surprisingly covering the entire floor with an insulated slab did not perform the best. Then 2m of horizontal insulation in from the edges was OK for having a warm temp near the perimeter, but the living space was a little colder (less than 1C). I tried to model just 1m of horizontal insulation under the 3rd greenhouse, but extending 2m horizontally out to the south and sides. That worked great, because it maximized the mass under the living space and 2nd greenhouse. I thought for our climate that it's too cold to go without floor insulation, but the tire U's with living space glass are collecting a lot of heat like solar ovens with thermal buffer zones around them and lots of mass in the floor. The 3rd greenhouse will go below freezing here, but the 2nd greenhouse low temp is about +17C. This is a fabulous tool. I found some researchers who modeled a vol. 2/3 south facing earthship with south facing roof and one thermal zone. I modified their file for the current v.7.2. They confirmed that the tool modeled reality. 

We're still waiting to sell our old apartment. Hopefully the sale comes soon so we can start building this summer. 

Future Plans

Our plan is to start building probably next year, probably in the spring or early summer.

Neighbor's large stash of jars and bottles

A neighbor showed me his stash of bottles and jars like Urbanek pickle jars and various jam jars and fruit jars. At first I was only interested in the bottles, including many dark green bottles. I eventually decided to just take them all, even though the jars are shorter and stubbier and wider diameter. I tried to calculate about how many there were. Maybe 1,200 - 1,500. 30,40 bags ... hauling them out. The whole thing was about the size of a small dumpster.

How do you keep a cistern from freezing in Mongolia 3

I didn't update much lately. We are simply waiting for developers to swallow up our very old apartment and buy us out. It could happen any day. Until then, I'm just in material collection mode. This spring I was very busy teaching. I've wanted to learn EnergyPlus in more detail. This will help us to understand the energy situation and what we can expect and how big we need to make the heat storage.

Last winter, at least the first half we lived in an old house and better understood the energy situation. The building is so old that the only insulation is logs with mud plaster on both sides. The building does not have a water line coming into the house, so I made a bottle shower stall with hanging tanks, which drains into the yard. That worked until late November. One night we were not home and did not stay home and the water in the cold water tank froze and that was it for the whole winter. Coal/wood stoves are powerful at a low price, but they are a burden to maintain everyday, when you have to collect/buy coal/wood/paper/cardboard and watch the fire as it starts out. The wall couldn't be more than R-7 or R-10 at best. The ceiling is concrete with lots of dirt up there. It felt like most of the heat loss was through a side wall that had mud knocked off on the outside and under the floor. The house has a pseudo-foundation of raised stones and a wooden floor, so heat just seemed to escape under the floor.

It took me a while to understand the ground situation. Nobody really publishes max frost depth on the web around here. Some mining .pdf literature suggested a max frost depth of 2 meters. Later I found other research on permafrost in Mongolia. Basically in the southern half of Mongolia there is no permafrost and a max frost depth of 1,2 or 3 meters. Then as you go north there is permafrost. Around Ulaanbaatar as best I could tell the permafrost is 5-15 meters deep, except where influenced by human development and perhaps topography. The permafrost is -0.4 to -0.1C or close to that. Roughly speaking that means that from a depth of 15 meters and deeper that it is above freezing as warmer as you approach the center of the earth. Unfortunately, the earth temperature is not +58F as earthship vol. 1 suggests. That is the true max frost depth: 15 meters. Above 5 meters it may get above freezing and be influenced by the seasonal weather.

This has several implications. If a thermal wrap of insulation is made around the perimeter of the house, that's an improvement, but 5 meters down (below the thermal wrap) it will always be freezing or close to it. Heat will always transfer in winter from the warmer living space to permafrost area below. Therefore floor insulation is absolutely necessary (unless the thermal wrap was about 15 meters deep or possibly more).

It also means that a cistern cannot be placed below a frost line, but it and all its components must be enclosed in excessive insulation in a freezing environment that can get below -40F. They do sell cisterns in Mongolia and my wife knew somebody that had one in the ground and it worked. Water just has to be +1C or above and you're OK. Here 80% of the precipitation falls during June-September, so the cistern has to be so big to hold an entire year's worth of water, so I am planning to do multiple chamber connected tire cisterns with lots of insulation so the water will never freeze, even if that means an insulated cap after November.

Almost no one owns a snow shovel in Mongolia, because it doesn't snow enough in winter. It does snow. Somebody was suggesting to melt the snow on the roof like the global model to maximize water collection. The problem is even if I melt it on the roof, it will freeze in the gutter. Even if I melted that, it would freeze in the silt catch. In Mongolia ice sublimates directly into the air it is so dry, so it is better to make a large(r) roof and collect a little more of the summer precipitation and just cap the cistern from about late October. Another issue is letting pressure relieve in winter, since even a tiny hole might lead to freezing. I'll just have to deal with that as we go. We can always open it periodically or experiment with tiny holes.

I learned one thing from the bottle wall shower stall. That shower stall has an opening from the shower drain to the hose to outdoors. I expected that water would make it outside, but freeze as it sat outside in the hose. What happened in real life was that cold air from outside entered through the hose and cooled the metal drain to below freezing. When any water touched the drain, the water froze in the drain. That water stayed freezing until probably late March. I disconnected the hose from outside; I poured in hot water in the drain, but the concrete shower stall remained pretty cold with its thermal mass and being fairly close to a cold wall. In the same wall the problem could be metal components in the water line, not the actual cistern.

Another thing I learned from that experience is: What if we had to leave the house for a week or a month in winter and didn't want to make somebody live there for us? The water system has to remain frost-free. We need to have assurance through energy modeling that the house inside would somehow stay above freezing (even +1C might be enough) even without running artificial heating. OK, we perhaps have to insulate most if not all the piping. The cistern and the incoming line must be frost free on their own. OK, maybe if we knew we were leaving for days we could perhaps drain the water system.

Another thing is that we are planning to implement the ZED style multiple layers of insulated curtains (or shutters) on computer control to open around sunrise and close around sunset. (Here, it's so dry and consistently sunny that we don't need to be concerned about cloudy days. Even in winter 33% of avg. solar gain in January was like an minimum value over a long period, unlike NYC which was 3% of avg. one day.) If we have the "third greenhouse" buffer zone on front as well as the 1st greenhouse glass in front of the living space, then there is a good chance it will never be below freezing in the house. All the plumbing will be in the center living space area.

The bottom line is insulation and lots of it. Then with enough insulation around the cistern, we can keep its bottom well above the floor level in the berm. This means that we need to use high density floor insulation under the living space and the cistern. In Mongolia the cost of rigid insulation is 1/6 of the price in the US. Insulation works. Without it here one would have to rely on a pan of water to wash yourself. If we have adequate insulation, then things may not freeze if everything is properly managed.

How do you keep a cistern from freezing in Mongolia? 2

The general wisdom about water is: it must be below the frost depth for your location, then any water at that depth, even during the coldest periods won't freeze. Usually we're talking about water coming in from a water line, and the pipe is sealed. In the case of earthship cisterns they're open air in some sense, though covered with pebbles at the riser. Dan Richfield showed his cisterns and how: 1) the top of the cisterns were below the frost line (18" in Taos, NM); 2) the cistern was insulated. So even though the cistern was open air with air holes going down into the cistern, the water in the cistern would theoretically have enough mass to resist freezing. I'm taking that one on faith that it's going to work. Mongolia has a frost depth of about 2 meters (almost 7 feet). As long as the surrounding soil isn't frozen and the cistern(s) is insulated, then I guess that's enough. Temps drop below freezing everyday around early November (almost now), rivers freeze into solid blocks until the end of March. During those 5 months or so, I don't plan on collecting any precip. Maybe if I'm worried about it, I could put some insulated cover over the cistern catch on top. 

I was considering having something like the equivalent of 2 stacked garbage cans full of pebbles as a catch. That may be so many pebbles to drip through that some may be lost to evaporation. Maybe like many earthships I could do the small amount of pebbles (about 12"?) in a plastic drain thing (on top of a pipe?) and just put an insulated cover over that during winter. Maybe just the depth alone would protect the water from freezing.

Largest pieces of slate yet

Today I hauled in a piece of slate that was 80% in the ground that was 77cm long on the flat surface and about 50cm wide. Although slate is very hard, some of it in that area had a tendency to crumble a little bit on the sides. Another piece was over 60cm long. I just collect this when I have time. Many of the pieces are 10-20cm. I'll worry about chiseling them later to make them useful. We are nowhere near having enough slate to do a whole building and garage, but definitely the garage if the slate doesn't crumble into little pieces. If we could successfully split layers, some of the big thick pieces will go a long way.

Overall I have about a shed full of bottles, which is something like 4,000-5,000. Only about 5-7% are cans, since no soft drink sodas are canned in Mongolia, though I started seeing more beer cans. I feel the amount is enough to do the whole main building easily, but I plan to make a bottle / dirt / cement wall around the property, so that wall could demand quite a lot of bottles. In our small micro ger district we must have a large amount of alcoholics. I walked only about 200 meters in an alley this afternoon and picked up maybe 40 bottles, not to mention what I got in the morning.

I am debating about what third greenhouse design to do. I want to do the solar toilet. That typically needs to be on the south face, but on the 2nd greenhouse glass.