Durable, Energy Efficient Dome Homes Chu c k Snyder What if thinking outside the box meant Chuck and Louise Snyder moved into their dome literally getting out of the rectangular boxes house, overlooking the Alaska Kasilof River in 1998. The house stayed warm for days even though they ran that most of us call home? out of oil and outside temperatures dropped to -30°F. by Carol Lanham spring. In addition to classroom time, ost people would agree variations. Like the building itself, attendees get hands-on experience that if you want a truly the insulation is monolithic, with no building a dome. Even when work- Menergy-efficient home, you gaps, cracks, or breaches except for the shops are not in session, there is plenty have to be willing to think outside the openings that are specifically designed of activity at MDI. Many of the build- box. Whether you explore alternative into the structure. ings are open daily for tours, both heating-and-cooling methods or inno- Introducing Bruco for curious passersby and for those vative building techniques, it pays to get who call ahead for an appointment. out of the mainstream and be willing Like many Texans, I had seen Bruco—the caterpillar—serves as a to consider unconventional approaches. Monolithic Domes while driving along manufacturing facility for the Airforms But what if thinking outside the box Interstate 35 between Dallas and Austin. used to build the domes. meant literally getting out of the rectan- Beside the freeway, about 30 minutes Dome Home Details gular boxes that most of us call home? south of Dallas, sits a giant caterpillar In fact, what if it meant living in a made up of seven interconnected domes, An Airform is a giant tarp made of round building instead? That’s exactly and affectionately nicknamed Bruco. superstrong single-ply roofing material. what a small but growing group of It serves as a landmark for the Italy, During the construction process, it homeowners has been doing for the last Texas-based Monolithic Dome Institute is attached to special hooks on the several decades. They have been moving (MDI), which is dedicated to raising circular foundation and inflated using into Monolithic Dome houses, giant fans to create the shape of and achieving extraordinary the dome. Work then moves to energy savings as a result. The monolithic nature of the structures the interior, where crews bring As their name implies, the plumbing and electrical Monolithic Domes are one- is one of the factors that account for wiring in through the floor and piece, round structures that their energy efficiency. frame in windows and doors by have no roof, no joints, and fastening treated wood to the no seams. Their surface is Airform. They then spray the smooth and unbroken like that of an awareness about these unusual struc- rest of the Airform with polyurethane egg, with the exception of windows, tures. MDI’s president, David B. South, foam, reinforce it with steel rebar, and doors, and vents, which are all carefully built the nation’s very first Monolithic coat it by spraying on several inches sealed to prevent unnecessary air flow. Dome home back in the 1970s in Idaho. of Shotcrete, a brand of concrete that The monolithic nature of the struc- Today, the unusual round structures can is sprayed in place. Once the Airform tures is one of the factors that account be found in 45 states and several foreign is solid, crews cut out the tarp for the for their energy efficiency. The mate- countries, with dozens of domes in the window and door frames along with the rials used in the homes’ construction small town that South now calls home. vents, and then seal them by foaming also help conserve energy. Specifically, The buildings are also used as schools, around openings and covering the Monolithic Domes are made out of churches, performing arts centers, edges with a fabric boot made out of the concrete, and are insulated with 3 storage facilities, and assorted other same material as the Airform. inches of polyurethane foam on the commercial structures. Interior walls are generally erected exterior of the building. This provides South and his team train would-be using steel studs and Sheetrock, but a thick layer of insulation that protects dome builders at the institute at other options include concrete blocks, the concrete from extreme temperature five-day workshops held each fall and brick, or sprayed-up concrete. Wood is

32 Home Energy | November/December 2008 dome homes Sunny Cu s hn i e

This Monolithic Dome home sits nestled in a forested area near Lake Huron in Southhampton, Ontario, Canada. another alternative, but it is considered the least desirable because of the fire hazard it introduces to these virtu- ally indestructible homes. The curved Shotcrete sides of the dome can be troweled to make them smooth or left in their rough and varied natural state. The exterior finishes of Monolithic Domes also vary. The Airform can remain in place for as long as five to ten years, but it eventually deteriorates. Coating options include exterior house paint, silicone, ceramic tile, rock, or 2 inches of concrete reinforced with chain link and coated with silicone. Modified stucco with colorant or silicone is currently the most popular choice. M D I (See Figure on p.35 for a schematic Designed by Larry Byrne, vice president of marketing and design for the Monolithic Dome showing typical dome home construc- Institute, this home graces the cover of Dome Living, a book of more than 115 Monolithic tion details.) Dome house plans. Paul Norton, senior engineer in the Center for Buildings and Thermal installing energy recovery ventilators giving domes the most favorable Systems at the National Renewable (ERVs), in every dome home. While air ratio of surface area to volume of any Energy Laboratory in Golden, exchange systems often result in higher structure. Because there is less surface Colorado, points out that there are clear utility bills, ERVs work a little differ- area, not as much heat escapes in the advantages to this unusual construc- ently. They recapture most of the heat winter or seeps in during the summer. tion method. “One of the benefits of from the fresh air that is brought into “If you reduce the surface area of a this construction style is that there are the home, so there is much less need to home and get the same living volume, no thermal shorts or thermal bypasses,” cool and heat the exchanged air. that’s an energy attribute,” Norton Norton says. “You don’t have all the At a more basic level, the shape of a says. Monolithic Domes, however, are joints that you find in a normal stick- dome building offers an energy effi- actually oblate ellipsoids, or flattened built home, and it’s the joints that cause ciency advantage. Spherical shapes spheres, which reduces the height of the the leakage.” In fact, the buildings cover the greatest amount of space ceilings and cuts down on the amount are so airtight that MDI recommends with the least amount of materials, of unusable space. While some argue

www.homeenergy.org 33 his 1,600 ft2 dome home in Colorado. He reports using 500 gallons of propane per year for cooking and space heating in his mobile home and 20 kWh per day of electricity for his water heater and lights. Once he moved into his dome home, he reduced his annual propane consumption by half to just 250 gallons, which he used for in-floor heating and hot water. His electricity usage dropped to 13 kWh per day. The savings are not limited to cold- weather locales. Air conditioning needs are also reduced in Monolithic Domes.

Sunny Cu s hn i e While HVAC needs for traditional homes are determined by consulting the ASHRAE standards, or by following the manufacturer’s specifications, the same rules do not apply for Monolithic This is the same home featured in the top photo on p. 33. It was built by The Great Lakes Dome Company. Domes. That’s because thermal mass must be taken into account. MDI that the round floor plan and sloping insulation on a building’s exterior are recommends using 1 ton of air condi- walls are space inefficient, proponents pronounced. For example, a 2.5-inch tioning per 1,000 square feet of living of domes argue that they are actually wood wall with 1 inch of interior insula- area in warm climates, generally south more efficient than traditional homes tion would result in a ratio of exterior of the Mason-Dixon line. Because the because they have much less hall space. to interior temperature of 1 to 0.7. In smallest and least expensive commer- Domes also lack attics, which can act as contrast, an 8-inch concrete wall with 1 cially made units are typically at 1.5 solar collectors. inch of interior insulation would reduce tons, any dome home up to 1,500 A dome’s passive-solar design is the ratio of exterior to interior tempera- square feet is usually equipped with a also an important factor in its energy ture to 1 to 0.5. By placing the insula- 1.5-ton unit. efficiency. Windows that face south and tion on the exterior of the concrete, the Fortunately, there is also empirical overhangs that allow sun to penetrate ratio would be reduced by a factor of 10, evidence that supports the anecdotal in the winter and provide shade in the resulting in a 1 to 0.05 ratio. “The ratio stories of energy savings reported by summer, and judicious use of porches, demonstrates the change from night dome owners. As the following two case are key considerations as well. For those to day or month to month, not specific studies show, owners who have sought who want to use solar energy, domes temperatures,” says South. Energy Star ratings, or the Canadian have an advantage because part of the Success Stories equivalent, for their dome homes have roof is always aimed at the sun. received very high ratings. The placement of the insulation in There is plenty of anecdotal evidence Moulton Dome Home in Monolithic Domes is another key factor for the energy savings associated with Ottawa, Ontario, Canada in their energy efficiency. According to Monolithic Domes, especially in harsh the California Energy Commission’s climates. Chuck and Louise Snyder, The Canadian government, which Passive Solar Handbook, placing insu- both natives of Alaska, tell how they has a reputation for high environ- lating material next to the external unknowingly ran out of heating oil mental standards, developed and environment allows significantly less for their boiler, which warmed the financially supports the Energuide heat into or out of the building. By water for the in-floor radiant heating for New Houses (EGNH), a rating combining this low heat conductivity system in their dome home. Two days system based on a scale of 0 to 100. with the high heat capacity of the passed before they became aware of it, According to EGNH standards, a 0 concrete, the little heat that does seep because their home remained comfort- represents “an uncomfortable house into or out of the building does not able even though the temperatures that has major air leakage, no insu- change the interior temperature very outside had plummeted to –30°F. lation and extremely high energy rapidly. “Simply stated, the concrete They finally realized they were out of consumption,” while a 100 represents acts as a heat sink, which slows the heating oil because they were using the a house that is “very well-insulated, passage of heat back and forth through same boiler to heat their water and ran airtight yet well ventilated, and the wall,” South says. out of hot water. heated by renewable energy sources, According to the California Then there’s Charles Brath, who lived such as wind or solar power.” After handbook, the benefits of placing the in a 700 ft2 mobile home while building moving into their triple-dome home

34 Home Energy | November/December 2008 dome homes in 2006, Ray and Rebecca Moulton, along with their builder, Great Lakes Dome Company, decided to put the new house to the test. (The Great Lakes Dome Company also built the Shotcrete Layers home shown in the top Airform on Interior of Dome photo on p.33 and the on p.34) The energy effi- Reinforcing Rebar ciency report they received Second Layer of Foam stated that new homes Rebar Hangers constructed to building First Layer of Foam code standards would Exterior Coating typically rate between 65 M D I Monolithic Footing and 70, while a signifi- cantly updated energy- efficient new home might Figure. Dome homes are built so rate between 75 and 79. airtight that the Monolithic Dome Ring Beam Footing Institute recommends the installa- At the top of the scale, tion of energy recovery ventilators in with a rating of 80 or every dome home. more, would be what the EGNH characterizes as a “highly energy-efficient house.” The Colorado (ERHC) in order to qualify Another factor that contributed to the Moulton’s dome rated 88 with no for a low-interest mortgage. Like EGNH low rating the first time was incom- special features other than a ground ratings, Energy Star ratings are based plete installation of the windows. “We source heat pump. on a scale of 0 to 100, with homes resolved those difficulties, re-rated the The report also estimated that the scoring 86 or above receiving the home when it was completely finished, home would consume approximately maximum five stars. and the home did pass with flying 6,100 kWh for space and water heating Convinced that her home would colors,” the official wrote. in an average year. An equivalent receive five stars, Cheryl was not at Since most homeowners do not go R-2000 home—considered at the time all worried as an inspector set out through the evaluation process asso- of the report, 2006, the most energy- to evaluate the home’s heating-and- ciated with the government rating efficient and environmentally respon- cooling system, insulation, windows systems, the anecdotal evidence on sible structure on the market—would and doors, hot water system, appli- dome homes continues to be more use nearly 3 times that much, or just ances, and air flow. To her surprise, plentiful than empirical data. But that’s short of 17,000 kWh, according to the however, the home only received a been enough to make a believer out of report. In their evaluation of the home’s rating of 80, or four stars. Certain that Ward Huffman, who recently retired emissions of greenhouse gas (GHG), the there had to be some mistake, she met as a financial specialist from DOE and inspectors determined that the dome with an official from ERHC. After is now a business professor at Mesa home would produce 13.7 tons per year some discussion, they concluded that State College. He became intrigued less GHGs than a similar house rated the software program used to evaluate by the energy savings associated with at 68. Considering that the government the home needed some adjustment. Monolithic Dome homes during his is challenging Canadians to reduce It seems the software was designed tenure at DOE and even traveled to the amount of their personal annual to evaluate conventional houses with Texas to speak at MDI’s annual confer- GHG emissions by 1 ton, the dome corners, not rounded edges. A home ence. Today he remains convinced home meets the challenge quite readily. with no roof and a ceiling area that that the round concrete homes are was different from the floor area threw extremely energy efficient. Roberts Dome in La Junta, Colorado everything for a loop. “There’s been a lot of contro- The Energy Star rating system used After the appropriate adjustments versy about the energy efficiency of to rate homes in United States also were made, a second evaluation of Monolithic Domes because they don’t gives dome homes high marks—once Roberts’s dome home resulted in a fit the standard building criteria, inspectors figure out how to adapt their score of 87, enough to qualify for the and inspectors sometimes won’t pass measurements to a round dwelling. maximum five stars. In a letter to MDI, them because they don’t meet code,” Cheryl Roberts discovered that when ERHC explained that there were tech- Huffman says. “The way I judge it is by she sought an evaluation for her dome nical difficulties associated with “getting the cost of the energy that’s used in the home from Energy Rated Homes of the round home to fit in a square box.” home’s operation. The average 2,500

www.homeenergy.org 35

dome homes significantly reduced need for HVAC equipment and daily energy usage.” ft2 existing home in Colorado will Considering that the superstrong cost you probably $200 to $300 per buildings also meet the Federal month to heat in the winter and at Emergency Management Agency’s stan- least that to cool it in the summer. dards for near-absolute protection from With a similar-size dome home, tornadoes and hurricanes, South thinks it will cost you $500 or $600 it’s only a matter of time before more per year.” people give up their aversion to change Skeptics also have questioned the and decide to go round. “We live in Ja

use of the materials used to build m e s a world of rectangles and squares, so

the dome homes. But Norton points Am o s we’re trailblazers on an uphill trail,” out that while the concrete used he says. “But even folks who say they to construct domes has a relatively Cheryl Roberts stands in front of her dome home in don’t like the way a Monolithic Dome high embodied energy, it is much La Junta, Colorado. The home earned a five-star rating looks—usually just because it’s so lower than the energy used over from Energy Rated Homes of Colorado. different—can’t deny that it has indis- the life span of the building. “Over putable advantages.”

the life of an average home the energy It’s that personal experience that efficiency is much more important than makes him a zealot in spreading the Carol Lenham has worked as a jour- embodied energy, by over a factor of 10.” energy-saving message to others. “The nalist for the Associated Press, Reuters, Furthermore, Norton points out that Monolithic Dome is the strongest, best- Newsweek, and Vatican Radio. In 1991, there is very little waste in the construc- insulated structure that can be built she co-founded Business Writers Group tion of the dome, which serves to reduce for conventional prices, and it’s also and writes frequently on the topic of the home’s embodied energy. the most airtight of all structures,” he Monolithic Domes. South and his extended family have says. “The concrete stores enormous experienced the energy savings first- amounts of heat and acts as a thermal For more information: hand over more than three decades of battery, and because most dome homes To learn more about the Monolithic Dome living in dome homes in such diverse are passive-solar structures, there’s a Institute, go to www.monolithic.com. locations as Idaho, Texas, and Utah.

36 Home Energy | November/December 2008