Why an earthship, you ask?
It all started in an ecology class that Bridgette was taking. She was learning about niches. A poignant paragraph gnawed at her naive yet earnest desire to find her individual niche.
"For a species to maintain its population, its individuals must survive and reproduce. Certain combinations of environmental conditions are necessary for individuals of each species to tolerate the physical environment, obtain energy and nutrients, and avoid predators. The total requirements of a species for all resources and physical conditions determine where it can live and how abundant it can be at any one place within its range. These requirements are termed abstractly the ecological niche."
Michael J. Pidwirny, Ph.D., Department of Geography, Okanagan University College"
Bridgette's intense desire to live as holistically earth-friendly a lifestyle as possible while fulfilling financial and societal obligations forced her to reevaluate the DC suburban culture she had always known. Throughout college, the luxury of summer and winter breaks to pursue her dreams of working with medicinal plants, living close to nature on a houseboat on the Chesapeake and meeting like-minded individuals at conferences, seminars and hostels, created an obsession of finding a niche she could be happy with, to the forefront of her mind her last year of college. She started with the basics; food, water and shelter. Perusing the net, she found http://www.earthship.org, Solar Survival Architecture's website, which she later realized yielded an answer to all three.
The earthship is a structure which utilizes the concepts of thermal mass (a very dense material which can hold heat or the lack of it for long periods of time), passive solar gain (which is the acquiring of heat from the sun without using any outside inputs) and heat ventilation (the process of eliminating heated air from an environment using skylights). The thermal mass is derived from automobile tires laid on their sides, not on the tread, pounded with approximately 300 lbs of dirt, accomplishing a 3 foot thick wall, 10-12 feet high with large amounts of thermal mass. The tires are stacked like bricks, prior to being pounded, and formed into a large single U-shaped structure or several smaller connected U's. The exposed side, or upper side of the U, faces south in the northern hemisphere and vice versa in the southern. It becomes a wall of vertical glass thus achieving passive solar gain. Operable windows and angles can be incorporated within this 'greenhouse' structure.
Within each room or U, an operable skylight is installed to aid in heat release. Shades are also used to block out unwanted sun and insulate from heat loss at light. The roof is also well insulated with a typical R-factor of 60; three times the industry standard. The tires are insulated on the outside of the U and earth is either piled up around the outside of the U extending at least 8 feet around, creating a berm. In drier climates, the bottom half of the U is an excavated earth cliff and the top half is the tire U bermed with soil as described above.
The tires on the interior are sealed via adobe plaster to prevent off- gassing due to oxygen and sunlight. The water to the earthship can be harvested from the propanel roof and stored in a cistern for pressurization and filtration. All water except toilet water is then fed to plants grown within permanent rubber-lined planters along the glass face of the house. The end result is odorless and clear water pumped to the toilet. It is then drained to a solar-assisted septic tank with outdoor planter similar to the indoor ones. These evaporate and digest the sewage. Some earthshippers grow copious amounts of food in the planters, as all the conditions, light, warmth, water and nutrients are plentiful.
There are many more details and nice pictures at Solar Survival's website:
http://www.earthship.org. Enjoy your findings and maybe one day we'll be fellow earthshippers ;-).