Can rammed earth structures incorporate passive solar design features?

Designing for Solar Gain

Rammed earth walls can be designed to maximize solar gain by carefully selecting the orientation and shape of the structure. In arid and desert climates, a south-facing wall with a slight overhang can capture direct sunlight during the winter months while minimizing heat gain during the summer. A 30-degree overhang can reduce summer heat gain by 75%. To further enhance the wall’s thermal mass, a mixture of 10% clay, 40% sand, and 50% silt can be used, which provides a high thermal mass capacity.

Building Formwork for Optimal Insulation

To optimize insulation and reduce heat transfer, the formwork used for rammed earth construction should be carefully designed. A 2-inch (5 cm) air gap between the formwork and the earth wall can reduce heat transfer by 50%. Additionally, using a combination of insulation materials such as recycled denim and expanded polystyrene can provide an R-value of 30, significantly reducing heat loss during the winter months.

Thermal Mass and Energy Storage

Rammed earth walls can be used as a thermal mass to store heat energy during the day and release it at night, reducing the need for artificial lighting and heating. By strategically placing thermal mass elements such as concrete or brick within the rammed earth wall, the building can take advantage of the natural temperature fluctuations, creating a more stable and comfortable indoor environment. A minimum of 4 inches (10 cm) of thermal mass is recommended to achieve optimal energy storage.