Passive Solar Building Design — FarmPal

Harness the sun for heating and cooling without any mechanical systems. Proper orientation, thermal mass, insulation, and window placement can reduce heating needs by 50-80% the original renewable energy.

Principles

  • South-facing windows capture winter sun (low angle) while eaves shade summer sun (high angle)
  • Thermal mass (concrete, stone, water, cob) absorbs heat during the day and releases it at night
  • Insulation on the north, east, and west walls retains heat
  • Natural ventilation (stack effect, cross-ventilation) provides summer cooling
  • Earth-berming or earth-sheltering provides year-round temperature stability
  • Greenhouse/sunspace attached to south wall is a solar heat collector

Action steps

  1. Orient the building

    Long axis east-west. 60-80% of windows on south face. Minimal windows on north. Eave overhang sized to admit winter sun and block summer sun at your latitude.

  2. Add thermal mass

    Dark-colored masonry, concrete, stone, or water containers on the south interior absorb daytime heat. 4-6 inches of mass is optimal. Must be in direct sunlight path.

  3. Super-insulate the shell

    R-40+ ceiling, R-20+ walls, R-10+ foundation. Air-seal everything. The tighter and more insulated the shell, the more effective the solar gain.

  4. Design for summer cooling

    Operable windows placed low on north and high on south create stack-effect ventilation. Deciduous trees shade west windows. Earth tubes pre-cool incoming air.

Benefits

  • 50-80% reduction in heating costs
  • Zero operating cost no fuel or electricity
  • Increased comfort and stable indoor temperatures
  • Works for new construction or retrofits
  • Reduces or eliminates need for HVAC systems

Further reading

  • The Passive Solar Energy Book Edward Mazria
  • The Solar House Daniel Chiras
  • BuildingGreen.com