This service provides in-situ measurement of the Solar Heat Gain Coefficient (g-value) of transparent building components, such as windows, balcony doors, or glazing systems. The g-value is a key metric for determining how much solar energy is transmitted through glazing into the interior of a building, and is crucial for evaluating the thermal and energy performance of building envelopes.
Measurements are conducted in the NTUA LivingLab, a specially designed pilot building featuring interchangeable glazing systems and precise environmental control. The facility allows for the testing of windows in real operating conditions, including exposure to actual solar radiation, ambient temperature fluctuations, and natural daylight.
The g-value is calculated as the total solar energy transmittance, which includes both directly transmitted solar radiation and the fraction of absorbed radiation that is subsequently released inward. In practice, this requires simultaneous monitoring of several parameters:
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Surface temperature and heat flux on the interior side of the glazing (for U-value context)
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Global incident solar radiation on the exterior surface (glazing plane)
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Global transmitted solar radiation reaching the indoor environment
These are measured using calibrated radiometers, pyranometers, and heat flux sensors. All measurements are conducted during daylight hours, as the presence of solar radiation is essential for meaningful results.
The testing method is aligned with international best practices and supports early-stage validation (TRL5) as well as advanced product performance verification. It is especially useful for manufacturers of solar control glazing, low-emissivity (Low-E) coatings, and dynamic or smart window technologies.
