Building Orientation Is One of the Most Powerful Passive Design Tools
Before any mechanical system is designed, building orientation can dramatically reduce energy loads. Orienting the long axis of a building east-west (so major glazed faces look north and south) is one of the simplest and most effective passive design strategies in the northern hemisphere. The ARE tests solar access and orientation knowledge because these are fundamental site-level decisions that the architect makes before structural or mechanical systems are even considered.
Solar Geometry: The Foundation of Orientation Analysis
The sun's path across the sky varies by latitude, season, and time of day. Understanding this variability is essential for designing effective solar strategies:
- Solar altitude: The angle of the sun above the horizon. Higher altitude = more overhead sun (summer); lower altitude = lower, more raking sun (winter).
- Solar azimuth: The compass direction of the sun (measured from north). At solar noon, the sun is due south in the northern hemisphere.
- Summer sun: High in the sky (high altitude), easily blocked by horizontal overhangs.
- Winter sun: Low in the sky (low altitude), penetrates deep into south-facing windows.
- East sun (morning) and West sun (afternoon): Low angle, harder to shade with overhangs - vertical fins are more effective.
Optimal Building Orientation
In the northern hemisphere, optimal passive solar orientation is to maximize south-facing glazing and minimize east- and west-facing glazing. South-facing glazing allows winter solar gain (when the sun is low and building heating is needed) while being easily shaded in summer with horizontal overhangs (when the sun is high). East- and west-facing glazing is problematic: it admits low-angle morning and afternoon sun that is difficult to shade and contributes to overheating and glare.
The optimal building orientation for daylighting and solar control in the northern hemisphere is with the long axis running east-west, allowing the north and south facades to be the primary faces. Within 20-30 degrees of due south is generally acceptable for passive solar benefit.
Passive Solar Strategies
| Strategy | Description | Best For |
|---|---|---|
| Direct gain | Solar radiation through south-facing glazing heats thermal mass inside | Heating-dominated climates |
| Trombe wall | Thermal mass wall adjacent to south glazing stores and slowly releases heat | Cold climates, stable temperatures |
| Solar chimney | Stack effect through glazed vertical shaft drives natural ventilation | Hot climates, mixed |
| Shading (overhangs) | Horizontal overhangs block summer sun on south facades | All climates with cooling load |
| Cross ventilation | Inlet and outlet openings on opposite sides capture prevailing winds | Hot-humid climates |
Solar Access and Neighboring Buildings
Solar access refers to the right of a building or solar installation to receive direct sunlight without being shaded by neighboring buildings or vegetation. Some jurisdictions have solar access ordinances or easements that protect solar rights. Shading analysis - often performed with software modeling solar paths and shadow projections throughout the year - is used to verify that a building design does not unduly shade neighboring properties or that the site itself has adequate solar access for PV installations or passive solar design.
Key Exam Points
- Optimal orientation in northern hemisphere: long axis east-west, primary glazing south-facing.
- South sun in summer: high angle, shade with horizontal overhangs.
- East/west sun: low angle, difficult to shade, minimize glazing on those faces.
- Winter sun is low in the sky - south-facing glazing admits it for passive heating.
- Cross ventilation requires openings on opposite building faces for prevailing wind capture.
Study PA on AREprep
AREprep’s PA flashcards cover every concept on this exam with spaced repetition, and the practice exams mirror the real question formats so the actual test feels familiar.