Insulation

Living in a climate with significant temperature extremes requires a high level of insulation. Earthbag homes only have an R-value of around 5 - 10. This is not really very good when it's 30 below outside. Earthbags do have a ton of mass however, meaning that once they get warm, it takes longer for the heat to leach off.

There are a number of approaches that would help insulate an earthbag dwelling better. One of the more popular approaches is to fill the bags with any combination of rice hulls, pumice, vermiculite, perlite or scoria (lava rock). All of these fillers would add to the overall R- value of the earthbag home.

The option that most interests me however is adding a layer of straw bale insulation on the outside of the earthbag wall. The R value for straw bale is between 45 - 50, much better. Combine that with the 5 - 10 of the earthbags and you could be up to an R value of 60, which is excellent. The chum roof design also lends itself to a much greater level of insulation.

A simple wood burning stove would be more than enough to successfully heat such a small space. The earthbags would warm up and be able to really retain the heat because of their mass and the insulation that the straw bale is providing.

My main concern with all of these insulating measures is the summer. What's it going to be like when it's 90 - 105 degrees for two weeks? At first I would imagine it would be excellent, much like a cave. Because of the huge mass of the earthbags they would be slow to take on the heat of the outside...but eventually they would...and worse yet, they would be holding on to it.

How would I go about cooling the hut down? I've looked into earthtubes . That seems like a definite possibility. Essentially it involves pulling cool air from a storage area below ground and circulating it throughout the hut. It seems like it may work; it also seems like a lot of work, and more resources. I'll have to keep thinking about it, but these are my thoughts thus far.

Building Process

Building an earthbag home is a straightforward process. There are certainly nuances involved, but the principle is pretty basic: stack up the dirtbags.

Artificial forms are made ahead of time to replicate the presence of windows and doors. By creating these you can lay the earthbags around the planned gap as needed. As you can see by the picture to the right an arch can be used to close off rounded windows and doors. I chose to show this process because I really like the looked of rounded off windows and doors. You can see from the picture up top that traditional flooring approaches can be used, merely placing the framing into the earthbag wall.

Between each course of earthbags is layed down two lines of 4-point barbed wire. This acts to hold the bags together so they don't slip at all during the laying process. As mentioned before the first few courses are made up of gravel (or in the case of the picture it looks like they are just using bags of cement). Stacked atop that would be bags of soil.

The secret to getting a perfect circle made is to use a compass. A tall pole is driven into the center of the roundhouse. From there a chain or rope is made that is the length of the desired diameter of the roundhouse. As each course is layed you check with the compass chain to ensure that each layer is exactly round and in line with the previous.

There are a number of ways to attach a traditional roof to an earthbag roundhouse. What seems the most secure (in my mind) is to affix a concrete bond beam to the top of the wall. A concrete form is made around the circumference of the earthbag wall. Large pieces of rebar are inserted through the form and into the earthbags (securing the form to the earthbags). Then the cement is poured. From there traditional roofing practices can be used.

Finally some kind of protective layer needs to put over the earthbags. You can use stucco, concrete, or any number of plasters. From what I've read a lime based plaster would be the best to use as it seems to hold up to the elements well.

Foundation

The foundation is one of the most important pieces of any home, an earthbag home is no different. In an environment like the northern midwest you will definitely need to have a foundation that is up to the major freezing and thawing cycles of the region.

Here is a really great write up on the Earthbag Building Blog. A trench is dug around the footprint of the roundhouse. I would opt to use a French drain to ensure proper water drainage. I think it's worth the extra work to get as much water away from the foundation as possible. That way there is less to freeze, and less heaving of the land that could crack the plaster finishing. Atop the French drain would be gravel until it is at the same grade as the surrounding land. At that point bags would be filled with more gravel to form the first few courses (layers of earthbags) to ensure that there is no water that is wicked up from the foundation.

Overall I feel like this would be the best foundation to use for an environment rich in weather extremes.

Earthbag Shelter in Haiti

Check out this awesome earthbag project in Haiti. Earthbag homes are being built all over Haiti to help resettle residents made homeless by the devastating earthquake. Earthbag homes are inherently resistant to earthquakes and other such natural disasters. Of course being so inexpensive to make helps as well, as it usually always seems to be the impoverished that suffer the most from these disasters.

I am impressed by the incredible detailing going into the doors and windows; that level of finishing really creates a "home".

Siberian Roundhouse Visioned Again

Here is my slightly revised layout of the Siberian Roundhouse. I used my retro graphing program to format the layout. The biggest change is the lack of an indoor bathroom. I'm not so sure I'm a big fan of composting toilets...at least not in such a small living space. By removing the bathroom much more room is opened up to use as needed.

I have also added a vestibule. I think it's really important for homes built in areas that experience intense climatic conditions to have a buffer that separates the inside of the home from the elements that are outside. Additionally all of the winter wear; giant parkas, snow covered boots etc...will stay outside of the house proper.

I'm kind of on the fence about not having a bathroom in the house itself. It is really only for conveniences sake to have one inside. Though it takes up a lot of space and can be quite pricey. In staying true to a minimalist design strategy; having one outhouse I think will help cut costs and keep us connected to the reality of our existence...by freezing our ass off to run to the bathroom.

Earthbags

One of the great draws that earthbag building has is its financial accessibility. It is simply polypropylene bags filled with compressed dirt stacked on top of one another. The building technique is very straight forward, though labor intensive.

Polypropylene bags are readily found. Farmers around the world use them to store feed, rice etc... So acquiring large quantities of them should be a fairly simple and inexpensive process. Simply fill it with dirt, tamp them solid and move on to the next one. I think even I could handle that.

Chum and Bones

Here's the Siberian Roundhouse with plans as found at the Earthbagplans blog. Here's the description from their page:

Specifications: 16' interior diameter with a 201 sq.ft. interior, sleeping loft, half bath.

Footprint: 19' x 19'

Here's a compact design ideal for cold climates. The basic concept comes from the Siberian Chum (tent). There are two chum roofs or conical shaped roofs made of poles with insulation between. Virtually all materials are made from small diameter wood poles, which are often abundant in northern forests - roof poles, bond beam, lintels, loft joists, wood shakes and woodchip insulation. Tilt - down stairs lead to a sleeping loft. Only a very small wood stove is needed for heating. It would be quite easy to build debt - free by gradually adding extra roundhouses as time and resources allow. A small cluster of these roundhouses would be real cozy.

This is a pretty straightforward layout. 201 sq.ft. definitely pushes the need for minimalism. I also like the chum roof idea as being in the North American equivalent of Siberia; it does get pretty fracking cold. Though I would feel more comfortable spending a little extra money ensuring the roof is completed using commercial grade materials. I like that it is an easy layout and that others can be readily made; with relatively little money and a butt load of manual labor.