Quick Answer
Earth-sheltering can enhance passive solar effectiveness by reducing heat loss, increasing thermal mass, and minimizing north-facing wall exposure, thus allowing the structure to absorb and store more solar radiation.
Building Orientation and Earth-Sheltering
Earth-sheltered homes can be designed to maximize passive solar gain by orienting the south-facing glazing to face the equator, typically between 15° and 45° east or west of south. This orientation allows the building to capture the low-angle winter sun and reduce summer overheating. A well-designed overhang can also be used to control summer solar gain by blocking direct sunlight during peak sun hours.
Thermal Mass and Insulation
Earth-sheltering provides a unique opportunity to integrate thermal mass into the building design. By using materials like concrete, brick, or stone in the walls, floors, and ceilings, the building can absorb and release heat slowly, reducing temperature fluctuations. The thermal mass can be enhanced by incorporating insulation into the walls, such as foam board or spray foam, to minimize heat loss and gain. A 4-inch thick concrete wall, for example, can store up to 12,000 BTUs of heat per degree of temperature change, making it an effective thermal mass component.
Design Considerations
When designing an earth-sheltered home for passive solar effectiveness, it’s essential to consider the building’s geometry, insulation, and glazing. The building should be designed to maximize the ratio of glazing to wall area, while minimizing north-facing wall exposure. A well-designed earth-sheltered home can achieve high levels of passive solar performance, reducing the need for mechanical heating and cooling systems and minimizing the building’s carbon footprint.
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