Why were traditional buildings in Beijing commonly built facing south?

Traditional buildings in Beijing were commonly oriented to face south for a combination of climatic and cultural reasons.1

• Climatic Function: The southern orientation allowed rooms to receive the maximum amount of sunshine during the winter months, providing natural warmth. Conversely, the deep, overhanging eaves of the roofs provided essential shade during the summer when the sun was high, helping to keep the interior cool.2
• Cultural and Geomantic Significance: Beyond practical climate control, this orientation was conventionalized and sanctified as early as the Bronze Age in connection with the worship of heaven and earth and ancestral ceremonies. This practice was deeply integrated into fengshui (geomantic) systems, which emphasized the importance of proper siting to align with auspicious forces. In this tradition, the southern direction was considered benign and open, while the north was associated with dark forces, necessitating a layout that favored the south.13

This southern orientation was a standard feature of the city's urban planning, which was symmetrically arranged along a north-south axis.21