As the UK solar market continues to expand, in-roof photovoltaic systems, also known as building-integrated photovoltaics (BIPV), are becoming a more common choice for residential and new-build projects.
Earlier in-roof systems often came with practical challenges, including more complex installation, concerns around long-term waterproofing, and limited compatibility with different solar panel sizes.
S4 Mounting Systems has been developed to address these challenges through a simplified, universal, and performance-focused design.
A Smarter Way to Fit In-Roof Solar
S4 represents a new generation of in-roof mounting systems designed for both full and partial roof integration. The system is built around a patented universal base plate and a simplified component architecture, enabling consistent installation and long-term reliability.
The system integrates directly with the roof structure, supporting efficient load distribution and consistent structural performance over time.
The design is based on three key principles:
- Structural reliability
- Simplified installation
- Long-term compatibility
A key innovation is the separation of waterproofing from the photovoltaic module. Unlike earlier systems, S4 does not rely on the panel itself to maintain roof integrity. This helps ensure that the roof remains weatherproof during maintenance, replacement, or system upgrades.
Waterproofing and System Integrity
One of the defining features of S4 is its integrated waterproofing system, designed to protect the roof independently of the solar module.
This approach provides:
- Continuous roof protection independent of the solar module
- Reduced risk during maintenance or panel replacement
- Improved long-term system reliability
- A clean, integrated architectural finish
The system uses compact EPDM rubber seals (70 Shore A) designed for direct mechanical clamping, maintaining compression over time and ensuring durable watertightness. By eliminating the need for additional top flashings, S4 provides a consistent, sealed interface with the roof covering.
EPDM Seal Performance:
- Temperature range: –40°C to +120°C
- Resistant to UV exposure, ozone, and environmental conditions
- Maintains compression under mechanical load
- Service life exceeding 20 years
No routine maintenance required
S4 RooFit: Universal, Flexible
At the core of the system is the S4 RooFit platform, engineered to support a wide range of configurations and applications.
Key Features:
- Universal compatibility with all panel sizes and orientationsÂ
- Five-component system reducing installation complexityÂ
- No battens required in portrait configurationsÂ
- Reduced battens in landscape layoutsÂ
- Integrated waterproofing with no additional flashingsÂ
- Temperature tolerance: –20°C to 85°CÂ
- Suitable for roof pitches between 12° and 70°Â
- 10-year product warrantyÂ
The system incorporates honeycomb-structured components within its design to provide high stiffness and strength while minimising weight.
Compatibility with Solar Panels
A defining characteristic of S4 is its universal compatibility. The system supports a wide range of photovoltaic modules, including modules from leading manufacturers such as LONGi Solar, Trina Solar and Tongwei Solar.
Key Benefits:
- Compatibility with current and future panel formatsÂ
- Reduced dependency on specific manufacturersÂ
- Access to a database of over 2,000 validated modulesÂ
- Flexibility across multiple project typesÂ
This broad compatibility supports long-term adaptability as solar panel technologies continue to evolve. When combined with modules from leading manufacturers, S4 provides a scalable and flexible solution for UK solar installations, supporting consistent system design and long-term operational reliability.
To support S4 installations, Alternergy supply a selected range of high-efficiency solar panels that are compatible with S4 mounting systems and suitable for residential and new-build applications.
Available Panel Options from Our Stock:
From LONGi Solar
- LR7-54HVB-480MÂ
- LR7-54HVD-480MÂ
- LR7-60HVD-530MÂ
From Trina Solar
- TSM-NEG9R.28 – 450WÂ
- TSM-NEG9R.28 – 455WÂ
From Tongwei Solar
- 48HD – 455WÂ
- 54HD – 500W to 520WÂ
These modules are selected based on standardised dimensions, frame design and performance characteristics aligned with S4 system requirements.
This list is not exhaustive. S4 mounting systems are designed as a universal platform and support a wide range of photovoltaic modules. For project-specific validation, compatibility should always be confirmed using:
- The latest official S4 compatible panel listÂ
- The S4 configurator, which includes an extensive database of validated modulesÂ
This helps ensure compliance with certification requirements and optimal system performance across different project types.
Materials, Durability and Compliance
S4 systems are manufactured using high-performance materials selected for durability in external environments.
Key Materials:
- EPDM rubber seals (70 Shore A)
- High-grade aluminium and stainless steel
- Recycled technical polymers
Quality Control:
- Tested in accordance with ISO and ASTM standards
- Full batch traceability
- Designed for long-term outdoor exposure
The system also supports sustainability principles through the use of recyclable materials.
S4 mounting systems are designed to meet recognised UK and international standards, including:
- MCS Certification
- BBA Certification
- IEC 61215 and IEC 61730
- Fire testing to BROOF standards (with approved panels)
How S4 Compares with Conventional Mounting Systems
Compared to conventional rail- or bracket-based mounting systems, S4 provides a more integrated and efficient solution for in-roof solar installations.
Key differences:
- Integrated roof design reducing reliance on external support structures
- Improved load distribution through the roof structure
- Reduced system complexity with fewer components
- Simplified installation with lower risk of errors
- Optimised material usage through lightweight design
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Improved long-term performance through independent waterproofing
Frequently Asked Questions About S4Â Mounting Systems
S4 is an in-roof solar mounting system that integrates photovoltaic panels directly into the roof structure, replacing traditional tiles for a clean, fully integrated finish.
S4 mounting systems offer simplified installation, integrated waterproofing, and universal compatibility, helping reduce complexity while improving long-term performance.
The S4 system provides better visual integration and can be more cost-effective for new-build and re-roofing projects, while on-roof systems may be quicker to install on existing roofs.
The S4 mounting system supports a wide range of photovoltaic modules, including panels from LONGi Solar, Trina Solar, and Tongwei Solar.
The S4 system is particularly cost-effective for new-build and re-roofing projects, where integrating solar panels into the roof can reduce overall material and installation costs.
No, the S4 mounting system includes integrated waterproofing using EPDM seals, eliminating the need for additional flashings.
Conclusion
S4 Mounting Systems offers a reliable and cost-effective solution for modern in-roof solar installations in the UK. By combining simplified installation, integrated waterproofing, and broad panel compatibility, the system supports efficient project delivery and long-term performance.
As in-roof solar continues to grow in residential and new-build applications, S4 provides a practical approach to achieving both technical performance and architectural integration.
If you would like to learn more about S4 mounting systems or discuss a specific project, feel free to get in touch with our team.