Architects prioritize heat resilience in building designs

Mark Harris, sustainability lead at Sika, insists architects must prioritize heat resilience in their designs, emphasizing that roofing systems are key to mitigating overheating risks through intentional planning.

What was once viewed as a minor seasonal annoyance, extreme heat in the UK has now proven deadly. Research from the London School of Hygiene and Tropical Medicine estimates that record-breaking temperatures during May and June 2026 resulted in 2,877 fatalities across England and Wales alone. The threat has evolved into a full public health crisis, with the built environment playing a decisive role in how people endure—and are affected by—intense heat events.

The majority of the UK’s housing and commercial properties were constructed for a climate that no longer exists. Urban centers, characterized by dark, heat-absorbing roofing and pavement materials, capture solar energy during the day and release it gradually at night, eliminating the natural cooling that once made summer evenings tolerable. This urban heat island (UHI) effect worsens the situation, as city temperatures can exceed those in rural areas by multiple degrees. Vulnerable populations, particularly the elderly, residents of poorly ventilated social housing, and individuals with pre-existing medical conditions, suffer the most severe consequences.

Changing Regulations and Design Pressures

For architects, addressing heat resilience has shifted from an optional sustainability measure to a critical design requirement. While Part O of England’s Building Regulations already addresses overheating in new residential projects, the recent surge in heat-related deaths demands that designers exceed minimum compliance, especially for retrofit projects and non-residential buildings that fall outside these regulations.

The roof, as the building element most continuously exposed to sunlight, has an outsized impact on thermal performance. Its selection directly affects both indoor comfort and the surrounding microclimate. Two primary strategies are currently leading the discussion: cool roofs, which rely on reflective surfaces, and green roofs, which incorporate vegetation. An increasing number of projects are adopting hybrid systems that integrate both approaches.

Reflective Roofing: A Cooling Strategy for Flat Surfaces

Cool roofing functions by minimizing heat absorption through high reflectivity. Surfaces designed to bounce back solar radiation rather than absorb it reduce the transfer of heat into the building and limit the warmth released into the surrounding air. Lighter-colored, high-reflectivity materials can significantly cut heat gain compared to darker alternatives, easing cooling demands and lowering indoor temperature risks.

This solution is particularly advantageous for large flat-roof structures, such as warehouses, retail spaces, and schools. In urban settings where heat buildup is most pronounced, these systems provide tangible relief for occupants while reducing energy consumption for artificial cooling.

Vegetated Roofing: Natural Cooling Through Plant Life

Green roofs address overheating through a different mechanism, using plants to cool the environment via evapotranspiration and shading. Beyond their thermal benefits, they deliver additional advantages that are becoming harder to ignore.

By slowing stormwater runoff and alleviating drainage system pressures, green roofs can contribute to broader environmental goals. They also enhance biodiversity, making them valuable in urban areas where cities have declared climate or ecological emergencies. For architects handling planning requirements, a green roof can fulfill multiple objectives with a single design choice.

Selecting the Right System for the Structure

Neither cool nor green roofs are universally the best option; the ideal approach depends on factors like structural load capacity, budget constraints, maintenance plans, and the building’s purpose. A logistics facility with a lightweight roof might best suit a high solar reflectance index (SRI) membrane. Meanwhile, educational or residential projects with greater load-bearing potential, and clients prioritizing sustainability, may opt for green roofing to achieve biodiversity, recreational, or stormwater management goals.