IEA PVPS is pleased to share new findings on the Solar Heat Gain Coefficient (SHGC) of Building-Integrated Photovoltaic (BIPV) glazing units. The research presents methodologies for assessing the SHGC of BIPV modules used as architectural glazing and proposes modifications to international standards, now in the public enquiry phase.
The SHGC is a key indicator of how much solar radiation is transmitted through building envelope components and converted into heat. Unlike conventional architectural glazing, BIPV modules generate electricity, reducing the amount of absorbed solar energy that is transferred as heat into indoor spaces. Understanding this effect is essential for optimising energy efficiency in buildings, reducing cooling demand, and supporting the broader adoption of BIPV solutions.
The studies, conducted under IEA PVPS Task 15 – Enabling Framework for the Development of BIPV, focused on two complementary approaches:
- Calorimetric measurements – Researchers conducted an international inter-laboratory comparison to refine calorimetric methodologies for SHGC determination in BIPV glazing. The study confirmed that the SHGC decreases when electricity is generated and extracted, with the reduction depending on the PV cell coverage ratio and the thermal properties of the glazing.
- Component-based calculation methods – Existing international standards for conventional glazing were adapted to account for typical characteristics of BIPV, such as optical inhomogeneity and electricity generation. These modifications allow improved comparability and accuracy in SHGC assessment of BIPV glazing units.
Key Takeaways
- Existing calorimetric and component-based methodologies to determine the Solar Heat Gain Coefficient SHGC of conventional architectural glazing have been successfully modified for application to BIPV modules.
- Typical features of BIPV glazing units such as electricity generation and optical inhomogeneity are taken into account by these methodologies.
- The SHGC of a BIPV glazing unit is lower when electricity is generated and extracted; the magnitude of the reduction depends primarily on the PV cell coverage ratio and the thermal resistance of the BIPV glazing unit.
- Modifications to international standards based on these results have been proposed and are currently in the public enquiry phase.
“Removing PV-generated electricity from a BIPV glazing unit will lower its solar heat gain coefficient, but the size of this effect depends strongly on the area covered with solar cells and the thermal resistance of the glazing unit.” – Hisashi Ishii – Task 15 expert.
The findings from these publications aim to provide architects, engineers, and policymakers with reliable methodologies for integrating BIPV into energy-efficient building designs.
