Watch sunlight enter a room and cast shadows as the sun moves across the sky. See how
window orientation, room depth, and time of year affect daylight levels.
The sun path diagram shows the sun's arc for your chosen latitude — the foundation of
passive solar design.
Exhibit A · The living room
Sunlight entering through a window
What you're seeing. A top-down cross-section of a room with a window on one wall.
The yellow wedge is direct sunlight entering through the window. The gradient
shows how light intensity falls off with distance from the window — this is the
daylight factor concept. UK Building Regulations require an average daylight factor
of at least 2% in habitable rooms. North-facing rooms get diffuse light only; south-facing
rooms get direct sun in winter (low sun) but may overheat in summer (high sun).
Exhibit B · The sun path
Sun arc across the sky
The sun path diagram shows the sun's arc for each month at latitude 52°N (UK average).
In June, the sun rises north of east, climbs to 61° altitude, and sets north of west —
nearly 17 hours of daylight. In December, it barely reaches 15° altitude and is up for
only 8 hours. The golden dot marks the current time position. South-facing windows
capture the most winter sun (passive heating) but need shading in summer.