What Is Passive Design?
Passive design uses a building's orientation, form, materials and openings — not mechanical systems — to naturally heat, cool, light and ventilate interior spaces. It relies on climate-responsive strategies like solar orientation, thermal mass, shading and cross-ventilation.
Passive design shapes a building to work with sun, wind and climate instead of against them, reducing the energy needed for heating, cooling and lighting through orientation, insulation, thermal mass, shading and natural ventilation.
- 1↓Site & OrientationOrient the building to capture winter sun and block summer sun (long axis east-west).
- 2↓Insulation & Thermal MassUse high-performance insulation and dense materials (concrete, stone) to store and release heat slowly.
- 3↓Shading ControlAdd overhangs, louvers or vegetation to block high summer sun while admitting low winter sun.
- 4↓Natural VentilationPosition openings for cross-ventilation and stack effect to cool spaces without mechanical air conditioning.
- 5Daylighting IntegrationSize and place windows to bring in daylight while managing glare and heat gain.
Try it: interactive calculator
Step-by-step worked examples
A south-facing window has SHGC = 0.3, area 5 m², and receives solar irradiance of 700 W/m². Find the solar heat gain.
Q = SHGC × A × I Q = 0.3 × 5 × 700 Q = 1,050 W
A clear (unshaded) window has SHGC = 0.6, area 3 m², irradiance 500 W/m². Find the heat gain.
Q = 0.6 × 3 × 500 Q = 900 W
Compare heat gain through a 5 m² window at I = 700 W/m²: unshaded glass (SHGC = 0.7) vs. shaded glass (SHGC = 0.2). Find the reduction from shading.
Unshaded: Q = 0.7 × 5 × 700 = 2,450 W Shaded: Q = 0.2 × 5 × 700 = 700 W Reduction = 2,450 − 700 = 1,750 W
Flashcards
Quick quiz
Q1.What does the formula Q = SHGC × A × I calculate?
Q2.A window has SHGC = 0.5, area 4 m², irradiance 800 W/m². What is the solar heat gain?
Q3.Which strategy uses dense materials to stabilize indoor temperature?
Q4.A LOWER SHGC value means a window:
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Common mistakes
Passive design means no mechanical systems at all. — Correct: It reduces the LOAD on mechanical systems by using climate first; some heating/cooling equipment is often still used.
More glazing always means more free heat, which is good. — Correct: Excess unshaded glazing causes overheating in summer — shading and SHGC selection matter as much as window size.
Thermal mass works the same in every climate. — Correct: Thermal mass is most effective where day-night temperature swings are large (e.g., desert climates); less useful in constantly humid climates.
Any window orientation is fine for passive design. — Correct: Orientation is critical — south-facing (N. hemisphere) windows with proper shading capture winter sun and reject summer sun.
FAQ
What is passive design in architecture?
Passive design uses a building's orientation, form, insulation, thermal mass, shading and openings to naturally heat, cool and light interior spaces, cutting reliance on mechanical systems.
What is the solar heat gain formula?
Q = SHGC × A × I, where SHGC is the Solar Heat Gain Coefficient, A is the glazing area in m², and I is solar irradiance in W/m².
What are examples of passive design strategies?
South-facing windows with overhangs, thermal mass walls, cross-ventilation, night-purge cooling, and deep eaves for shading.
How do you calculate solar heat gain through a window?
Multiply the window's Solar Heat Gain Coefficient by its area (m²) and the solar irradiance hitting it (W/m²): Q = SHGC × A × I.