Photovoltaic Glazing (BIPV): Can You Apply Solar Control Film to It?

Building-integrated photovoltaic glazing—known as BIPV, or Building-Integrated Photovoltaics—is becoming increasingly common in positive-energy building projects. A question often arises: can solar control film be added to this type of glazing to improve indoor thermal comfort? The answer is not a simple yes or no. It requires a precise technical assessment of the interactions between the film and the photovoltaic system.

What is BIPV glazing?

Photovoltaic glazing is an active component integrated into the building envelope that generates electricity from solar radiation. Unlike rooftop solar panels, it forms part of the architecture: it acts as a translucent or opaque wall while serving both a structural and an energy-production function.

Several technologies are available, each with different characteristics and sensitivities:

• Monocrystalline or polycrystalline cells encapsulated between two sheets of glass in a laminated structure, for opaque or semi-transparent modules
• Thin-film cells (CIGS, CdTe and a-Si) deposited as a film on the glass substrate, allowing semi-transparent glazing with variable visible light transmission—their spectral behaviour varies between manufacturers and formulations, so general data published for these technologies must be checked against the specific module
• Perovskite cells and other emerging technologies, whose commercial deployment remains limited and whose field data is still scarce

Each technology responds differently to heat, light and shading, so the manufacturer must be consulted before any modification is made.

Why solar control film can be a problem

Solar control film is designed to reduce solar radiation transmission—particularly near-infrared radiation, which is responsible for heat—while preserving good visible light transmission. On conventional glazing, this reduction is beneficial. On BIPV glazing, it directly interferes with the electricity-generation process.

The following interactions must be anticipated:

• Reduced instantaneous efficiency: photovoltaic cells convert solar radiation into electricity. Any film that reduces solar transmission—characterised by its total solar transmittance (Tts)—reduces the energy available for conversion and therefore the power generated at any given time. The cumulative effect on annual production depends on the building's exposure, orientation and the film's solar transmittance (Tts).
• Changes to the light spectrum: some photovoltaic technologies respond to specific spectral ranges. A film that filters certain wavelengths may affect production disproportionately, depending on the technology involved.
• Partial shading: if the film has variations in opacity or is not installed uniformly, partial shading may occur. This can cause a localised reduction in output through a hotspot effect—a mechanism in which a cell receiving insufficient light behaves like a resistor and dissipates heat, degrading the circuit as a whole.
• Higher surface temperature: some reflective films can send energy back towards the glazing surface and raise its temperature. For silicon-based cells, instantaneous efficiency decreases as temperature rises—the reduction is generally estimated at between 0.4% and 0.5% per degree Celsius above 25°C, based on commonly accepted data for this technology family. This coefficient nevertheless varies by manufacturer and module specifications.
• Impact on the production warranty: BIPV module manufacturers generally make their warranties conditional on use in accordance with their technical specifications. Adding a film that the manufacturer has not previously approved may affect this compliance. Conditions vary by contract and manufacturer, and only written confirmation from the module manufacturer can clarify the issue with certainty.

When compatibility may be possible

There is no universal rule prohibiting every film on every type of BIPV glazing. Some scenarios deserve closer analysis:

• Film applied to the inside of a BIPV module with an exterior active face: if the inner face is ordinary glass with no electronic components, a decorative or lightly tinted film applied on the inside may not significantly affect instantaneous efficiency or annual production. The thermal effect must nevertheless be assessed.
• BIPV modules with a low cell density: on some semi-transparent glazing with space between the cells, the areas of bare glass may provide a potential installation surface for a film with high solar transmission (high Tts).
• Factory-integrated film: some manufacturers offer BIPV modules with a surface treatment integrated during production and optimised to avoid reducing annual output.

Procedure to follow before making a decision

For any project considering film installation on BIPV glazing, we recommend the following process:

1. Identify the module's PV technology (cell type, layout and active face).
2. Obtain the complete BIPV manufacturer's technical documentation.
3. Contact the manufacturer to request a written opinion on compatibility with solar control film.
4. If possible, simulate production losses using the solar transmittance (Tts) of the proposed film.
5. Carry out an instrumented test on a limited area, measuring output before and after installation.
6. Do not install the film without written approval from the BIPV manufacturer in accordance with its technical requirements. This approval may be a condition for maintaining the production warranty.

For more information about solar control film, read Does Window Film Block Heat?. As an example of high-performance solar control film for standard glazing—not BIPV applications—the Solar 80 C solar control film illustrates the transmission and solar factor levels that can be achieved on conventional glazing.