Illustration of summer and winter passive solar sun angles. Solares project: Black Bank Hill
Passive solar design is a sustainable design approach that uses natural site elements, sun orientation and building materials for space heating and cooling. The principle is simple and has been used by humans and animals for thousands of years: capture the sun's heat in winter, keep it out in summer, and ventilate. Common building components of the passive solar approach are roof overhangs, thermal massing and operable windows.
Local Climate: The first element to consider for any passive solar project is the site and local climate. If the building is on a hill, are there prevailing winds that can be harnessed? Are summer temperatures constant and humid, or do they rise during the day and grow cooler at night? Are there many trees next to the building, and do they lose or keep their leaves in the winter? These questions help to inform design decisions around sun angles and ventilation techniques.
Sun Angles: Roof overhangs and deciduous trees help to keep the hot sun out in summer when sun angles are high, and inversely maximize sun penetration in winter when the sun stays lower on the horizon. Thermal mass effect uses heavy building materials like stone or concrete to collect the sun's heat during the day and release it at night when temperatures are lower. Thermal mass helps keep a building warm in the winter and cool in the summer.
Ventilation: Natural cross ventilation is very important to residential passive solar design. Essentially, it's about strategically placing operable windows so fresh outside air flows through the house, moving cool and warm air as needed for each time of year. Locating windows requires in-depth study of site conditions and prevailing winds so the airflow happens naturally without mechanical intervention.