The Liberty House
Earth Formed - Earth Sheltered Construction

How is it Constructed?

So far, my only real-world venture has been hand-digging a 20' earthen dome form for a room which would be the size of most of the rooms shown in the above model.  This dome form (pictured below) is 10' tall, rising 5' above ground level, and 5' below. The only tools used were a garden spade, a 30' piece of string, and a stick used as a pivot for scribing the circumference lines.  Most of the basic principles for the construction of the house in the slide show are illustrated in this simple animation. A multi-roomed structure can be designed and formed using intersecting earthen domes and earth-formed doorways. They can be dug at different grade depths and heights for varying purposes and levels of security ... from totally above ground to partially below grade, and completely below grade. The animation illustrates one half the dome above grade, the lower half below, with the entire structure then bermed with earth.

For one room module

-  Set stake, scribe one lime-powder circle the desired diameter of the base of the structure, then another circle at least at least 5' beyond the first. Now you are ready to begin digging out a 5' deep V shaped trench in the area between the circles.

-  Begin throwing one shovel full of dirt at a time into the center of the innermost circle.  Notice (with satisfaction) how with each shovel full deeper you make the trench, the mound in the center increases in height the same amount. This 2-for-1 action allowed me to dig and smooth the twenty-foot earthen dome in only 3, 4 hour shifts (12 total hrs.) at my then age of 57, unassisted, and out of shape. Obviously, with one or two helpers this could be achieved in less than a day, or with earth moving equipment, the better part of an entire house. Consider please.  This method results in a finished form for all foundations, walls, ceiling, doorways, and various openings and windows. This is accomplished without the use of a single nail, requiring no carpentry skills, building experience or lumber.  There is no tailor-made, expensive inflatable membrane to sew, and no muscle or back-straining and dangerous over-head work as required for 'monolithic domes'.   'Earth-formed' for real, and truly dirt-cheap.

- Shape and smooth the dome. This is much easier and faster than might be imagined. The bottom, below-grade half of the dome is comprised of firm, undisturbed earth, easily scraped and shaped, once the trench is dug. The top half of the hemisphere is of smaller volume and easily tamped firm and smooth upon the solid base below.  Here are three views of my twelve hour labor.  This dome form is 20' in diameter and 10' in height with an entrance and rear exit tunnel forms included.


- Place cement wire or rebar reinforcement, or use fiber-reinforced cement, or the yet to be released, hard-as-clamshell, carbon-sequestering cement made from passing CO2 ladened air through sea water. (Taking the climate change issues very seriously, and knowing the large part that the manufacture and use of Portland cement and iron reinforcement bar has played in causing them, my enthusiasm for using Portland cement and iron reinforcement has dampened my interest in the method the last few years. Even factoring in the long-life and low-maintenance standard concrete offers, making it over time ecologically more sound than other present state-of-the-art building materials and methods, still, I think it must be replaced, and soon.) 

- Form any desired openings for plumbing and electrical conduit pipes. Set culvert pipes as forms for later installation of 'sun-tube' windows and skylights. Dig out foundation area at base of the trench and reinforce with rebar, tying together the walls, footing and floor to be poured after the soil is removed from the interior of the shell. 

- Spray (shotcrete or gunite) or pour 2-4 inches of concrete mix, let set for proper time, cover with moisture proofing polyethylene sheeting, scoop out dirt from underneath the dome, re-filling the trench ring and adding:

- A couple foot of dirt over entire structure.

- Install insulating umbrella over this dirt and structure, extending 20' beyond perimeter to keep earth mass dry and btu's from escaping into the atmosphere.  DO NOT INSULATE THE DOME WALLS DIRECTLY. The idea is to allow free passage of the heat through the walls in the summer, and store it in the massive surrounding earth bank ... and then return spontaneously into the living space in cooler months ... NO air-conditioning or further energy use for heating or cooling required!  It serendipitously takes six months to warm the 20' deep bank surrounding the structure, and six months for the heat to move back into the living space when ambient temperatures become lower than the surrounding soil.  The result, an ambient temperature the same all year 'round!  Soil must remain dry however for this to work and insulated from the atmosphere above the structure.  Also, water table must remain below twenty foot deep, unless extraordinary measures are taken. 

- Add another two to four feet of earth over the insulating umbrella structure, and then plant ground cover. 

- sculpt interior earth reverse forms for any desired decorations or cubby holes, furniture sinks etc  forms. 

- pour floor or prepare earth floor

 Forming, Footing details 


Passive Annual Heat Storage ( PAHS)

This Liberty House model uses a novel insulating/water-shedding blanket or umbrella that covers the entire structure and the surrounding soil.  I first heard of this method introduced by John Hait in a Popular science magazine in 1986. This creates a huge subterranean thermal bank that absorbs the sun’s energy during the summertime and stores it for winter heating.  In many cases, if done properly, this method supplants a major heating system or air conditioning. 

  • Umbrella Homes ... from Popular Science, August 1986, pages 64-66.

    This simple underground house design uses a novel insulating/water-shedding blanket that covers the structure and surrounding soil.  The umbrella creates a huge subterranean thermal reservoir that soaks up the sun’s energy during summertime and stores it for winter heating.  In many cases, the clever design makes a heating system unnecessary.   The reverse can also be done for hotter climates.  

    By JOHN HAIT        My first earth-sheltered house, an underground geodesic dome was partially complete when the truckload of insulation my colleagues and I had ordered arrived. Right away, we knew we had a problem: How do you put flat, rigid polystyrene insulation on a round house?

    We called housing experts all over the country, but no one had any ideas. Finally, Ray Sterling at the University of Minnesota's Underground Space Center suggested that we place a flat, insulating "umbrella" in the earth above the building. This, he said, would keep the domelike house warm by insulating the soil around it.

    Figure 1 Geodome, the first umbrella home (in idealized form), maintains a 66°to 74°temperature year-round without heating equipment in western Montana’s cold climate.  In summer, solar hat radiates in, falls on internal surfaces, and is absorbed into the surrounding soil.  The umbrella traps heat in the dry soil until winter, when it migrates back into the house.  Convection-driven earth tubes provides ventilating air.

    "What a marvelous idea!" I thought when I heard his advice. After two weeks of rigorous examination, I realized that the concept was even more promising than I'd supposed. By then I was convinced that the dry earth under an insulating/water-shedding umbrella could store enough free solar heat from the summertime to warm the house through the entire winter (see diagrams above). This meant that a house could actually be constructed with an unchanging built-in temperature, which would make heating and cooling equipment unnecessary. Now, five years later, I still think it's a marvelous idea. The Geodome, the house we built in the cold and cloudy climate of western Montana, remains at 66 to 68 degrees F, even through the coldest winters.

    The success of the Geodome led to the establishment of the Rocky Mountain Research Center, a nonprofit organization dedicated to the development of what is now called the passive annual heat storage (PAHS) approach to free year-round passive-solar heating. Four basic points make PAHS different from techniques used in conventional solar-heated earth-sheltered houses:

    ·     The house's window shades are opened to collect solar heat in summer.

    ·     The umbrella's laminated sandwich of polystyrene insulation and polyethylene sheeting (about R-20) insulates a huge mass of surrounding dirt instead of just the house.

    ·     The umbrella sheds water to keep the soil around the house dry.

    ·     The natural-convection-driven ventilation tubes (see below) provide very high heat retention efficiency by acting as counter-flow heat exchangers.

    Conventional passive-solar theory tells us to exclude the abundant summer sunshine by blocking it out with large window shades because the typical (relatively small) thermal mass in a solar house can store only a night's worth of heat. Yet we're also told to make the windows large enough to capture what little solar heat we can in winter. PAHS, on the other hand, uses the summer's abundant sunshine to heat up a large body of earth around the house to a comfortable 72 degrees F or so. That warm thermal mass keeps the house and its occupants cozy all winter. Simple thermal conduction transfers heat through the walls, into the soil, and back.  

    Twenty feet underground, the natural soiltemperatureis nearly constant (see diagram), and is equal to an average of the entire year's worth of temperature changes on the surface. The Geodome's inexpensive umbrella isolates the soil beneath it from fluctuating outdoor air temperatures above. By controlling the heat flow in and out,the blanket raises the constant soil temperature around thestructure to reflect the newly established average annualair temperature inside the house. The result is a comfortable indoortemperature that varies only six or eight degrees during an entire year, whileoutdoor air temperatures may vary from minus 40 to more than 100 degrees F.

    Although the Geodome's window area amounts to about six percent of its floor area—less than most solar homes —the summer sunshine lasts much longer, and so more solar heat is collected and stored away than is available from any passive winter thermal-collection system.

    We've learned several lessons from the Geodome that have advanced our understanding of integral year-round thermal systems. First, the design temperature of 66 to 74 degrees is built in and is difficult to change. This became apparent during its first winter. The Geodome's tenant at that time, a salesman who was constantly on the road, found that the house temperature was still at 66 degrees F in March—even with a few warm bodies or appliances to add heat. We realized then that if you would like it a little warmer or a little cooler in such a house, you would have to enlarge the window area and install adjustable shades. That way, the annual solar input could be altered to modify the internal temperature as desired.

    Second, thermometers indicated that the umbrella altered the ground temperature much farther out from the walls than we expected. I located some National Bureau of Standards studies that showed that air-temperature changes affect the soil temperature more than 20 feet down into the earth, so we concluded that the umbrella should be extended to at least that distance beyond the walls.

    Third, an examination confirmed that the earth underneath the umbrella was bone-dry, even though the soil on top was moist. The dry dirt below makes waterproofing the structure easier, while the moist soil above helps alleviate the desert-like conditions that often occur on top of many earth-sheltered houses. Note that the water table must not moisten the thermal mass.

    PAHS seemed to offer a way to build energy-efficient homes that require no commercial energy supply for heating or cooling, but we realized that to become truly practical, we needed to provide for ventilation, heat retrieval, and moisture control.

    No good solution presented itself until one day when I was teaching a class of students at the center about convective heat flow. After a time, the discussion turned to-ward the use of earth tubes—pipes in the ground that bring in outside air for ventilation. Then one of the students asked about convective heat flow in earth tubes. Before I knew it, the solution to our problem was sketched on the chalkboard: an open-loop, convection-driven earth-tube system (see diagram) that draws outdoor air into the house to be heated by the summer sun, transfers it to the buried earth tubes where it passes some of its warmth to the relatively cool soil, and finally exhausts it outside. In winter, the cycle would reverse itself.

    Essentially, the earth tubes act as heat exchangers: If the air in the tubes is warmer than the earth, the earth soaks up and stores the heat. If the soil is warmer than the air, it gives up heat to the air flowing through the tubes (see diagram). In this way, the temperature of the outside air can be altered to provide the house with warm fresh air in winter and cool fresh air in summer.

    The tubes themselves must be very long (between 150 and 200 feet) so they can snake their way back and forth> through the soil under the umbrella. (For clarity, the tubes in the diagrams are shown straight rather than bent.)  Typically, we use earth tubes that are between four and eight inches in diameter. We lay each pair out under the umbrella so that they slant downhill from the house to permit water runoff and so they both exit the ground at the same elevation.

    This type of earth-tube arrangement differs considerably from the earlier "cool-tube" installations, which have been in use for some time. A single cool tube allows air to flow only one way—into the house. The house can inhale, but it cannot exhale. To exhaust stale air in winter, a window or vent must be opened, which would dump large quantities of heat outside. Also, lacking the insulating/ water-shedding umbrella, cool tubes do not have the warm earth environment that allows the air in the tubes to be heated as well as cooled. Properly coupled, the open-loop, convective-heat-flow earth-tube system and the PAHS sys-tem can provide free, year-round heating, cooling, and ventilation for the earth-sheltered home.

    Figure 24  Second generation umbrella home in Missoula, Montana was constructed by Tom Beaudette, the engineer of Geodome.

    This still-experimental housing technology is already being used to satisfy at least a portion of the heating needs for several recently constructed earth-sheltered homes. It is also being built into a number of full-fledged PAHS earth shelters, such as the house depicted above, which was constructed by Tom Beaudette, the engineer of the Geodome.

    Detailed explanations of these concepts are provided in my 152-page book: Passive Annual Heat Storage, Improving the Design of Earth Shelters. It's available directly from the Rocky Mountain Research Center

     The Rocky Mountain Research Center has a current web address of:
  John Hait's  book, PASSIVE ANNUAL HEAT STORAGE, Improving the Design of Earth Shelters  can be purchased here. An easily read and understood book with invaluable information about  earth-sheltered construction and energy needs and savings.

Dr. Arnold Wilson and the Ream's Turtle

A good building

“It was a very good building for a very long time – but that’s progress, I guess,” said Dr. Arnold Wilson about the February 11, 2006 razing of a historic, thin shell concrete dome in Provo, Utah.

Because of its shape, locals had dubbed the structure the Ream’s Turtle in 1967, when owner Paul Ream turned it into a giant general store that sold everything from groceries to Tony Lama cowboy boots.

But its history predates that 1967 conversion. It goes back to 1961, when Dr. Wilson, now Senior Consulting Engineer for the Monolithic Dome Institute and Professor Emeritus of Civil Engineering at Brigham Young University (BYU), was just working on his master’s degree.

The history of that dome

Young Wilson befriended Harry Hodson, an engineering professor at BYU who gave him articles about and sparked his interest in thin shell domes. As a result, Wilson asked Hodson if he could do his master’s thesis on thin shells. Professor Hodson not only agreed but invited his eager protege to join him in the engineering of a giant ice skating rink – the dome that eventually became the Ream’s Turtle.

Originally named Winter Garden Ice Rink when it debuted at BYU’s 1963 Winter Carnival, the Ream’s Turtle was a triaxial elliptical dome, 240’ long, 160’ wide and 40’ high at its center.

Flamed interest

Asked if it further flamed his interest in thin shells, Dr. Wilson said, “Oh, very much so! Boy, did it ever!” He recalled that Architect Lee Knell wanted a giant ice rink with an open interior, uninterrupted by posts or poles. So Knell, Hodson and Wilson got to work.

“We came up with a three-dimensional elliptical structure,” Dr. Wilson said. "But in those days, we didn’t have computers to analyze the engineering, so we decided to build and test a model in Lee Knell’s yard. And in the middle of that project, Professor Hodson accepted a new job and moved to Ohio.

“So, using a mound of earth to form its shape, I built the model – a one-twelfth scale model made of reinforced concrete that looked like a giant dollhouse,” Dr. Wilson added. “I load tested it to failure and went back and made changes in the original design that matched the test results.”

Cost-effective construction

At a cost of about $75,000, Dr. Wilson said that he thinks the Ream’s Turtle was the most economical building of that size ever built. He described its cost-effective construction. "The site for the Ream’s Turtle was an old clay bed – actually a giant hole – created by Provo Brick and Tile, a company that excavated clay and made bricks for many years. When BYU began building its campus on a hill, they began filling that hole with material they excavated. After filling that hole, they hauled over an additional 40,000 cubic yards.

“We molded that mound into the earth-form we used to shape the dome,” Dr. Wilson said. “It was free and it really produced a very, very economical building. But it wasn’t easy. Today, of course, we use Airforms and that makes it much easier.”

The article, “Provo preps to say goodbye to oddly shaped landmark” in the Daily Herald of Feb. 5 says, “…contractors heaped 40,000 cubic yards of dirt fill and sculpted it into a smoothly rounded dome with smaller mounds rippled around the perimeter. They braced it with a grid of steel bars that, if placed end-to-end, would stretch 21 miles. Then they sprayed on about four inches of concrete. Sprinklers moistened the roof for a month to prevent curling, and after the concrete shell dried, contractors spent three weeks scooping out and hauling away the dirt.”

The demolition

So with all that history very much in mind, on a windy Saturday morning in February, Dr. Wilson watched the demolition of the Ream’s Turtle: "They scheduled a public affair, with the mayor and city council present for about noon. We got there at about 10 a.m. They were already working on the building as about 100 people watched.

“They used two track-hoes. One had a 5000-pound, steel, wrecking ball hanging from it. That ball had been going all around the dome, pounding its concrete, but avoiding the area around its five entrances. Nevertheless, it had knocked the concrete off in a strip four to five feet wide along most of the structure.

“As they continued preparing for the ceremony, someone hollered, ‘One last look. Come and take a look.’ About twenty onlookers ran over to one of the back entrances. At about the same instant, the second track-hoe, working on the dome’s other side, reached up and yanked down one of those entrances. That triggered it – zip – the beloved Ream’s Turtle collapsed in about 30 seconds.”

According to the Daily Herald, that demolition cost more than the Turtle’s construction.

“It was a very interesting structure,” Dr. Wilson concluded. “I’m glad I was there at its beginning. I not only helped design it, but I helped build it. One day, as I just stood watching, the contractor said, ‘Well, if you’re going to be over here all the time, watching, you might as well tie steel.’ So I got a pair of pliers and began tying rebar.”

Since that memorable building of the Ream’s Turtle, Dr. Wilson became a Civil Engineering Professor at BYU – a forty-year career during which he inspired interest in thin shell domes among his students. Then in the 1970s, he met David B. South and began working with Monolithic. More recently, Dr. Wilson authored Practical Design of Concrete Shells, a text specifically written for engineers, architects, builders and students of civil engineering. With that book completed, Dr. Wilson retired.

What David said about Reams

While working on this article, I asked David B. South, Monolithic’s president about the Ream’s Turtle’s collapse. Specifically, I wanted to know if David was surprised by what many described as the structure’s near-instantaneous fall.

“But it wasn’t,” David said. "I wouldn’t describe it as anywhere near instantaneous. That was a huge dome that took a huge amount of continuous battering. A very large section of it had to be systematically and significantly weakened before those track-hoes could bring it down. And then it only came down when one of those track-hoes began yanking on one of the entrances – a structure’s most vulnerable area.

“Notice the very large areas along the side of the dome that have had all of the concrete knocked out. Only the reinforcing bar is left. More than 50% of the support has been removed.

“Also consider that it was a 5000-pound wrecking ball that was swung against the dome. Think of the impact that has on a structure. Just the vibration created by such an impact is horrendous.

“And how many centuries do you think the Turtle would have survived if some ole meanies hadn’t beat the devil out of it with a wrecking ball?

“No, that demolition wasn’t quick at all. It took a lot to get it down,” he concluded.

Note: We first published this article on April 21, 2006.


Originally named Winter Garden Ice Rink when it debuted at BYU’s 1963 Winter Carnival, the Ream’s Turtle was a triaxial elliptical dome, 240’ long, 160’ wide and 40’ high at its center

Image: Economical






Image: Demolition






Image: Steel bars

Steel bars





Image: Ream's Turtle collapses

Ream's Turtle collapses