Are Europe's Heatwaves Rewriting the Rules of Building Performance?

Why building owners must rethink HVAC performance to stay efficient, resilient and comfortable in a warming climate

Since the beginning of summer, Europe has already experienced three major heatwaves, with temperatures exceeding 40°C across several countries.¹ According to the Copernicus Climate Change Service, the rapid succession of heatwaves since May signals a clear shift: extreme heat is no longer an isolated event, but an increasingly persistent feature of European summers.²

For the HVAC industry, this represents more than a changing weather pattern. It marks a fundamental shift in how buildings must be designed, operated and upgraded. Managing extreme heat is no longer a future challenge - it is a present-day requirement for building owners, engineers and consultants across residential and commercial buildings, from single-family homes to hospitals and office complexes.

As temperatures rise, delivering occupant comfort, energy efficiency and operational resilience is becoming significantly more complex. HVAC systems must now perform reliably under longer periods of extreme heat while adapting to evolving building use, stricter sustainability targets and growing pressure to reduce both energy consumption and carbon emissions.

Yet Europe's building stock remains largely unprepared. According to the World Resources Institute, only around 20% of European buildings are equipped with cooling.³ As heatwaves become longer, more frequent and more intense, retrofitting existing buildings with efficient, resilient HVAC solutions is rapidly becoming one of the sector's most pressing challenges.

While extreme heat is affecting every type of building, the operational implications vary significantly across residential buildings and commercial properties. Each faces different performance pressures, investment priorities and operational constraints, making a one-size-fits-all HVAC strategy increasingly ineffective.

Residential buildings: redefining year-round comfort

For decades, most European homes were designed with one priority in mind: keeping occupants warm during winter. Today, that assumption is changing.

Homeowners increasingly expect their properties to deliver comfortable indoor temperatures throughout the year while keeping energy consumption and operating costs under control. As summers become hotter and longer, demand for efficient cooling is growing rapidly alongside the need for reliable heating.

However, improving thermal comfort is not always straightforward. Major envelope upgrades, such as replacing windows or adding insulation, can significantly improve building performance but often require substantial investment and are not always feasible, particularly in existing or historic buildings.

Installing air conditioning is not always a practical or even legal solution, as planning restrictions and building regulations often limit the options available.

As a result, many homeowners are looking for solutions that maximise the performance of their existing HVAC infrastructure. Reversible heat pumps that leverage the existing hydronic pipework and terminal units offer an attractive way to add efficient cooling while continuing to provide heating. When combined with rooftop solar PV, these systems can further reduce operating costs and improve overall energy performance.

Introducing cooling into an existing hydronic system, however, also changes the demands placed on the installation. Lower operating temperatures and seasonal changeovers increase the importance of maintaining water quality. Effective air and gas removal therefore becomes essential to protect water quality, minimise corrosion and preserve system efficiency, helping ensure reliable long-term performance and extending the lifespan of the installation.

Commercial buildings: getting more from existing assets

Commercial buildings account for around 42% of final energy consumption in the European Union, making them one of the greatest opportunities to improve energy performance and reduce emissions.⁴ At the same time, owners face a growing dilemma. Rising cooling demand, ageing HVAC infrastructure, changing occupancy patterns and ambitious decarbonisation targets are all increasing pressure on existing buildings.

Recent events have demonstrated how quickly this challenge can become critical. During the July 2026 heatwave in Switzerland, the Geneva University Hospitals (HUG), announced their patient rooms reached temperatures of up to 34°C.5 The hospital has announced emergency measures and investments needed to improve cooling resilience across its estate.6

For many organisations, replacing entire HVAC systems is neither economically nor operationally feasible. Instead, attention is shifting towards renovation strategies that improve the performance of existing systems, extending asset life while enhancing occupant comfort, operational resilience and energy efficiency.

This approach is already delivering measurable results. During the renovation of the Royal Court of Appeal in Gothenburg, persistent HVAC performance issues were resolved by analysing the behaviour of the complete hydronic system rather than individual components. By optimising the system as a whole, the project achieved a more stable indoor climate, improved energy performance and extended the lifespan of the existing installation.

Different buildings. One engineering challenge.

While the impact of extreme heat varies across building types, the underlying engineering challenge is increasingly the same: ensuring HVAC systems continue to deliver reliable, efficient performance under more demanding operating conditions.

As customer requirements become more complex, success depends on looking beyond individual HVAC components to understand how the entire hydronic system performs. From balancing and pressure control to water quality management, intelligent monitoring and optimisation, every element contributes to the efficiency, resilience and longevity of the overall system.

At IMI, we believe improving building performance requires this system-level approach. By combining engineering expertise with close collaboration across the building lifecycle, we help building owners, consultants and engineers optimise hydronic systems, improve energy performance and extend the life of existing HVAC infrastructure.