What type of shading system is effective for reducing solar heat gain?

The effectiveness of horizontal overhangs on southern exposures for reducing solar heat gain is attributed to their design and orientation. South-facing windows receive direct sunlight throughout most of the day, especially during the summer months when the sun is high in the sky. Horizontal overhangs are specifically angled to block the sun's rays during this time while still allowing sunlight to enter during the cooler months when the sun is lower on the horizon. This selective shading helps maintain comfortable indoor temperatures by minimizing solar heat gain, ultimately leading to reduced cooling loads and energy costs.

In contrast, other shading systems may not provide the same level of effectiveness depending on their orientation and operation. Vertical blinds on western exposures can block afternoon sun but may not be as efficient in terms of overall heat gain reduction throughout the day. Retractable awnings offer versatility but may not be fully effective if not deployed during peak sunlight hours. Fixed screens on eastern exposures could provide some relief from morning sunlight but would not address the more intense solar gain that typically occurs later in the day.