Passive solar design is a key element of biotecture. This concept is ancient and is observable in nature.
In the Northern Hemisphere, the sun appears in the southern sky. In the summer, its path is quite high, almost directly overhead. In the winter however, it passes quite low in the sky. By orienting your windows to the South and surrounding the rest of the building with dense thermal mass, you can encounter and store the sun’s warmth in the colder months. Mass is actually the opposite of insulation. Unlike insulation which slows the transfer of thermal energy, mass rapidly conducts thermal energy. When you have a large block of mass, energy will fill it like a barrel of water and can be stored for later.
This thermal mass is achieved by filling tires full of dirt and staggering them like bricks. The dirt is packed in with a sledge hammer until they begin to feel solid and conform to one another. This creates an extremely strong wall that is its own foundation, and has the capacity to store an enormous amount of thermal energy.
This same concept helps to keep the building cool in the summer. The well insulated roof shades the home from the high summer sun, while the greenhouse still receives light.
An operable skylight in the greenhouse allows the heating air to escape, which draws air through cooling tubes on the North side. These horizontal cooling tubes are buried for up to 35 feet allowing the air to cool as it passes through and enters the building.
These techniques were proven in one of the most extreme climates in the country. With temperatures ranging from -30°F to nearly 100°F, Earthships in Taos maintain a constant indoor temperature year round.