Passive solar is a design approach that utilizes natural sunlight to heat and light buildings without relying on mechanical systems. It involves strategic placement of windows, walls, and floors to capture and store solar energy. This method can reduce energy costs and improve comfort by maintaining a stable indoor temperature. Key elements of passive solar design include thermal mass, which absorbs heat during the day and releases it at night, and insulation to minimize heat loss. Proper orientation of the building towards the sun and the use of overhangs can also enhance energy efficiency by controlling sunlight exposure throughout the year.