MultiTX® Solar Earns BBA Certification for Integrated Solar Roofs

Don & Low’s MultiTX® Solar membrane has achieved BBA certification, confirming its suitability for use beneath airtight in-line solar PV roof systems and supporting compliance with the Future Homes Standard.

As in-line solar PV becomes more widespread, roof design has to balance energy efficiency with effective moisture control. Conventional underlays that perform well on standard pitched roofs can struggle beneath solar panels, where airflow is limited.

MultiTX® Solar addresses this challenge. Developed as a high vapour-resistance air and liquid barrier membrane, it provides an airtight layer without requiring counter-battens to ventilate the batten space — reducing installation time, materials, and condensation risk while maintaining compliance with Part L and BS 5250.

“Installers told us they needed a membrane that performs reliably under in-line solar PV without the cost and complexity of counter-battens,”

explains Mark Gray, Technical Manager at Don & Low. “MultiTX® Solar was developed in response, and its BBA certification confirms the consistency and reliability of its performance.”

Manufactured entirely in the UK, MultiTX® Solar is produced at Don & Low’s vertically integrated site in Forfar, Scotland. Controlling the whole production process — from polymer to finished roll — allows the company to maintain consistent quality, shorter lead times, and full traceability.

MultiTX® Solar joins Don & Low’s wider MultiTX® line, part of our roofing membrane range, which includes vapour-breathable and airtight, air-permeable variants for both roof and wall applications. Together, these membranes form part of the company’s broader strategy to support energy-efficient, regulation-compliant building envelopes in the run-up to the forthcoming 2025 Future Homes Standard.

For more information, contact membranes@donlow.co.uk.