Calculated Illumination: The Physics of Solar Heat Gain and Automated Curtain Control

Move beyond timers. We explore the science of using smart curtains for dynamic building management, calculating Solar Heat Gain Coefficient (SHGC) and automating for thermal comfort and energy savings.

: solar heat gain coefficient, dynamic shading automation, energy saving smart curtains

Smart curtains can be transformed from a convenience into a sophisticated building management tool by understanding the physics of solar heat gain. The primary metric here is the Solar Heat Gain Coefficient (SHGC), which measures the fraction of solar radiation admitted through a window, both directly transmitted and absorbed and re-radiated inward.

The energy flux entering a window is a product of the SHGC of the glazing and the Incident Solar Irradiance. While the SHGC is a fixed property of the window, a smart curtain system dynamically modulates the "Incident Solar Irradiance."

An Automated Control Strategy:
A primitive system uses a simple timer. An advanced system uses real-time data:

• Geolocation & Ephemeris Data: The system knows the sun's position relative to the building at any time of day and year.

• Weather Feed Integration: Cloud cover dramatically reduces solar irradiance.

• Thermostat Communication: The system can receive signals from the HVAC system.

An optimized algorithm would close the curtains only when two conditions are met:

1. Solar Irradiance is High: The sun is positioned to directly strike the window.

2. Cooling Demand Exists: The indoor temperature is at or above the thermostat's cooling setpoint.

By closing the curtains under these specific conditions, the system effectively reduces the window's instantaneous SHGC to near zero, blocking the primary source of heat gain and reducing the cooling load on the HVAC system. The energy savings can be quantified and are most significant in buildings with large south- and west-facing glazing.

Turn your windows into active energy-saving assets. Our advanced control platforms can integrate with building management systems (BMS) or use open APIs for custom automation rules. Schedule a consultation with our commercial solutions team to model potential energy savings for your property.