Personally, I preferred the style of the earth sheltered “home” shown in the last post. I liked everything about it from the organic lines to the tropical color palette and location. But there is more than one way to go underground. Here is another option.
If you live in a cloudy, wet, windy maritime climate and want a very modern earth shelter with just a little bit of earth, a wide view and room to breath… Maybe the Malitor house is what your are looking for.
This is the “back” of the Malator house. The front has similar windows, so you can imagine the cross breezes…
This home was built in 1998 for a wealthy Welsh Member of Parliament There were strict rules in place against “visible construction, destruction of the landscape, or disruption of wildlife” on this site. Earth sheltering was really the only solution. Even the drive way and walking path are hidden just below the sod.
The structure is only one room deep and 3 rooms wide with a “pod” hiding the bathroom and other pluming. The roof is contoured to fit naturally into the hilly site, and like the surrounding hills, it is covered simply with grass. In fact, I suspect the roof is mowed by Welsh sheep. Looking thru these links, I noticed that they went with the same wood stove that I was initially considering; before I saw the price.
This is the front door of the home. This angle hints at the expansive view seen thru the back window wall…
With its small scale and other clues (such as no garage), I suspect this is more of an occasional weekend retreat rather than a full time home, but it is still very interesting and shows some of the flexibility of earth sheltered design.
Malator made it into Forbes magazine as “Incredible Fortress Home”, and Architectural Digest listed it as one of the “Most Innovative Homes of the Last Century“. But this link has the best slide show…
Understanding the earth and how it behaves, particularly thermally, is key to Earth Sheltered home design.
The earth is not some magical heat sink or constant temperature material that so many people believe it to be. It can conduct and store heat in a way that is very similar to other materials. It has a specific heat capacity less than 1/4th the specific heat capacity water, and its R value is about 1/12th of rigid insulation. So, pound for pound, it is not the best heat storage medium and is a relatively poor insulator. However, we have a lot of it and it is, as everyone knows, dirt cheap (or even free).
Soil temps moderate and lag behind air temps
It is well know that the temperature of the earth is relatively constant. In south eastern Michigan, it is about 54 degrees Fahrenheit 20ft below the surface. Further south, it can be even higher. This constant temperature is roughly the average of the air temperature over a period of time. The air exchanges heat with the earth, which stores it and slowly conducts it downward. In the winter, this reverses and the earth slowly gives up its heat to the cooler air and the earth cools as its energy is conducted toward the surface. In both directions, the earth has a somewhat moderating effect on the climate, which (in addition to the larger effect of water doing the same thing) is why the air temperatures lag behind the seasons. Some refer to this heat stored in the ground as “geothermal”, but really is just a form of stored solar energy. True geothermal energy is found near tectonic fault lines (due to friction between the plates of the earths crust) or deep (miles) within the earth, emanating from the earths core ( actually due radioactive decay and friction caused by gravitational forces as the massive core of the earth interacts with the moon )… but I digress…
This thermal exchange with the mass of the earth is slow enough that, increasing with depth, daily changes and even seasonal changes in the air are moderated (averaged out). At the 20ft depth, the soil temperature is stable, roughly averaging the whole year. Actually, there are a variety of other smaller influences including reflectivity and permeability of the ground cover, transpiration of plants, the water table, etc., The net effect of these influences tends to keep the temperature a little below the average air temperature.
At about 10ft below the surface, the temperature is said to be roughly the average of the past 6 months of air temperature ( not quite, see the results of my experiment). This convenient “thermal capacitance” means the earth temperature at this depth is at its warmest when the air temperature is the coldest. Over the next 6 months, it cools until it is at its coolest just before the air temperature is the hottest.
When we place a home in the ground and start to control the temperature in the home, the soil temperature profile starts to change. The soil temperatures near our home adjust to an average of the air temperature we prefer in the home (rather than averaging the extremes outdoors). If our means of heating or cooling the home is interrupted, the thermal inertia in the walls and earth can continue to moderate the environment within our homes.
So, at some point, I decided that I wanted to build myself an earth sheltered home. This is not like saying I would like to build a colonial or a bungalow or something that has some know design DNA, or that uses known systems and processes… This is a wide open endeavor with a wide range of possibilities and even more unknowns. I have always been an Architecture buff, so it would have to be nice looking and functional. The engineer in me wanted to build an “engineered house”, what ever that is… I wanted it to be light, but authentic, and a bunch of other vague ideas that would have left any architect scratching his head. Of course, this wouldn’t just be my vage want list, I had a wife and kids who were also giving vague input. My kids wanted tunnels that connected things impossibly (they were not worried about the engineering or cost). My wife’s wants were harder to nail down, but she knows when she doesn’t want something ;^). But everyone was pretty supportive of the overall idea, so I started trying to add specifics to the vision…
Of course, I started by searching the web for other examples (check out my links page). The range was quite wide, from free-form (curvy) shotcrete vaults without a straight line in sight to more “practical” homes with concrete block walls and simple flat roofs. Some basically just buried Quonset huts (maybe a nice cottage idea some day). I have a big folder full of pictures in my computer. I wish I could share them all here, but getting permissions would be too much pain. Instead, here is a google image search, and here is another. The variety is amazing.
Many of the photos came with detailed blogs about their construction. Many were home builders who kept their budget low and did all the work themselves. I did like that idea, but I am full time employed and too busy to build my own home by hand. I am willing to spend a little more (not mortgage phobic) and wanted something more architecturally interesting. You could also see that many had a lot more money than I did (Bill Gates lives in an earth sheltered home), so I won’t be on that end of the spectrum either. There was also a strong contrast between those that were built without any compromise on the scientific principles (no north windows, brown cement floors, insulating shutters, tromb walls, etc.) and those that were built as art, without any consideration for the scientific principles. I wanted to stay married, plus I am a little artsy myself, so I plan on compromising where I need to. For instance, I plan to have a number of windows on the north side to capture the view even though I know they will leak precious heat. I also plan to have rugs on my floor although they inhibit solar gain into my storage mass…
I shared these ideas and pictures with my wife in an “agile” way, trying to get as much input as possible. For instance, i found it interesting that my wife really liked the concrete block or “ICF” idea because she liked the simplicity of the Lego-like construction method. I also discovered that she thinks about thinks like curtains very early in the design process… ;^) So, we initially co-imagined a rather rectilinear cement home (but with fibonacci proportions) with an undefined roof type (research pending) covered in some unspecified thickness of earth…
We cut these standard room sizes out and arranged them on the dining room table
For the actual layout of the home, I got some plan books and looked at single story homes that were about 2400 square feet. I took the room sizes from those and made a bunch of scale room tiles. Sherri and I printed these out and shuffled them around endlessly as we talked about design concepts.
- How do we divide the public and private areas of the house?
- How do we keep the TV noise out of other areas?
- Where can Simon’s office go? (I work from home 80% of the time)
- Why do people put laundry rooms by the garage instead of next to the bedroom?
- Do we need somewhere for our guests?
- How can we keep it affordable and make it interesting?
Also, we didn’t like the idea of an entry that appeared to be leading to a bunker. We wanted the functional areas of house to be on one floor, but I liked the idea of a “storm room” like a gazebo/conservatory on the roof that would give me 360 degree views. I thought a zero flush urinal in the boys bathroom would be a good idea. I really wanted a courtyard, but that idea morphed into a more practical green house or sunroom.
We some how expected that we would be entering from the North side (the earth bermed side) and wanted to avoid the bunker look, so we came up with the idea of the entry cottage. It would look like a little house to disguise the entrance to the underground portion of the house. I liked the idea of a modest little cottage concealing the larger home inside it.
We worked out the look of these rooms with extensive notes (in ppt) for each room.
Layout from Nov 2007, featuring the entry cottage and a decent sized courtyard. It also had a lot of small sunrooms… Funny now to look back at this.
By Dec 2007, I had realized that the courtyard wouldn’t work well in our norther climate, and moved it to the south side
By July 2008, we shrunk the courtyard, tilted some rooms (solar angles) and added the start of the rotunda idea. The walls were still straight because I had not yet figured out a roofing plan. I was considering individual square shotcrete domes for each room.
I used my ppt “skills” to record/share our ideas and layouts for each room in a rudimentary, but useful way. We could edit these easily as we tweaked our design.
I really spent the most time thinking about the structure of the house. I was I going to safely hold up all that dirt without spending too much money or having a house that looked like a bunker? I ended up with this idea of a central tower (the rotunda), with site-cast concrete ribs radiating out from it. There would be shotcrete arched vaults between the ribs passing the load to the ribs, which passed the loads to the ground. It was this central “structural umbrella” concept that changed the design from angular concrete block to the more circular layout built with shotcrete. It was somewhat of a Eureka moment for me as I saw it all come together in my head.
From there, I spend few minutes here or there each day for a month researching shapes for the ribs. I ended up looking into the mathematics of natural shapes such as shells or eggs. These had been studied by ancient mathematicians and Renaissance men and there was a lot of information on the web and in books. Since the ribs would need to be cast on site and lifted into place, I was particularly interested in designs that could be drawn in the field with just a piece of wire (or a stick) and a pencil. I tried these shapes (such as the golden egg, a mathematically sacred shape based on the golden ratio) built into arched ribs at many different angles and simulated loading the ribs with an estimated 68000 lbs of load until I eventually settled on a particular orientation of a 2300 year old euclidean 5 point egg design that had the right proportions.
Golden Egg design
“Golden egg” on its side as part of a rib. However, the heights at the ends were not right, so I would need to tilt it up…
Golden egg, 19 degrees tilt, but still not the right proportions…
Golden Egg, 38 degrees, still not right…
I tried a lot of other eggs, the Euclidean 4 point, the Moss Egg, etc. But this Euclidean 5 point egg, tilted at 41 degrees, had the right clearances, proportions and strength…
I created computer simulations for most of the promising candidates and loaded them with the estimated 68000 lbs that I expected they would each need to carry…
Eventually, by the end of 2008, I got into Autodesk Revit where I could CAD up the model in 3D. Now it was getting interesting. We had spent a lot of time discussing each little detail and there was a reason for everything. All the rooms had purpose, even the angles of the windows were designed to line up views thru the house (and even functioned as a solar clock).
An early version in Autodesk Revit, windows are missing, furniture is still sitting outside, but you can get the idea.
At some point, I hit that little button that calculates the square footage. Ouch, 3917 sqft, plus another 1035 sqft for the garage. We could not afford that much house… How had this happened? We had started from the rooms of a 2400 sqft house, but then probably added a few feet with each alteration. We ended up making some drastic cuts to get it back under control.
Our original footprint was much too large, the house had to go on a diet. The purple outline is the original floor area, the white walls are the shrunk down version… At least for a few days… A lot has changed since then.
Then we went out to shop for some land… I will save that story for another day, but the punch line is that the lot we bought had primary access from the south and best views were to the north, so we had to scrap much of what we liked about these these early designs… More on that later.
