What is the primary reason for south-facing windows in cold-weather climates?

The primary reason for south-facing windows in cold-weather climates is to maximize natural lighting throughout the year. South-facing windows allow for greater solar gain during the winter months, harnessing sunlight to naturally warm interiors and reduce heating costs. This orientation effectively utilizes the sun's path, as the sun is lower in the sky during winter, allowing rays to penetrate deeper into living spaces.

While avoiding cold northwest winds is a consideration in building orientation, it is not the main advantage provided by south-facing windows. Additionally, minimizing sun exposure during the summer can be a concern, but that is typically addressed with overhangs or shading devices rather than the window orientation itself. Enhancing the visual aesthetics of a building can be important but does not convey the primary functional advantages that south-facing windows offer in terms of energy efficiency and comfort in cold climates.