Mark Harris, Head of Marketing – Roofing at Sika, explored how green, blue, biosolar and photovoltaic roofing systems can help architects address biodiversity loss, urban overheating, flood risk and energy security, while navigating increasingly complex specification and fire safety requirements.

As climate change places growing pressure on the built environment, roofs have an increasingly important role to play beyond simply protecting buildings from the weather. In an Architecture Today CPD webinar, Mark Harris outlined how multifunctional roofing systems can contribute to more resilient, sustainable cities.

“We’ve been building a built environment that doesn’t work with nature,” Harris explained, arguing for an approach that integrates ecological benefits into building design.

Green roofs were central to this discussion. Harris outlined the differences between intensive landscaped roofs, lightweight sedum systems, wildflower roofs and biodiverse roofs designed with ecologists to recreate lost habitats. Beyond supporting wildlife, these systems can improve air quality, moderate urban temperatures through evapotranspiration, manage rainwater and provide valuable amenity space.

Biosolar roofs offer additional benefits by combining vegetation with photovoltaic panels. The cooling effect of plants and retained moisture can improve solar performance, while careful consideration of substrate depths, structural loading, panel orientation and maintenance is essential.

Turning to blue roofs, Harris explained how integrated water-retention systems can slow rainwater discharge during heavy rainfall, reducing pressure on drainage infrastructure. Flow-control devices, overflow outlets and carefully calculated attenuation capacities enable roofs to contribute to sustainable urban drainage strategies.

However, Harris repeatedly emphasised that environmental aspirations must not compromise fundamental performance. “The primary function of the roof is to keep the building and its occupants dry,” he said.

Fire safety was another major theme, particularly concerning rooftop solar installations. Harris discussed the limitations of existing guidance, including RC62, and the industry’s ongoing engagement with government over future regulatory requirements.

Drawing on emerging research into fire behaviour beneath photovoltaic panels, he highlighted the potential importance of panel clearance and inclination in mitigating heat accumulation and fire spread. He also stressed the importance of suitable waterproofing, appropriate fire protection measures and consultation with insurers.

Maintenance emerged as a consistent priority across every roofing typology, with safe access and regular inspections critical to long-term performance.

Harris concluded by encouraging architects to consider roof design holistically, balancing biodiversity, energy generation, rainwater management, structural implications and whole-life performance.

His overarching message was clear: roofs represent an opportunity to address multiple environmental challenges simultaneously, provided sustainability is supported by robust technical design, compliance and ongoing maintenance.