Beyond Passive Cooling: Hybrid Cooling for Climate-Resilient Care Homes

Keywords: Climate resilience, overheating, thermal comfort, epilepsy care homes, hybrid cooling strategies, human-centred design

Indoor overheating is already compromising the health and well-being of vulnerable residents in care homes and is projected to intensify under future climate change. This study demonstrates that while passive measures remain essential, hybrid cooling strategies, combined with targeted training, are necessary to deliver resilient, low-carbon thermal comfort in specialised care environments.

Epilepsy and Thermal Stress

Overheating is emerging as one of the most pressing challenges for building services engineers. In temperate climates like the UK, residential buildings have historically been designed to retain heat in winter, often at the expense of summer performance [1]. As a result, these buildings are increasingly ill-equipped to cope with rising temperatures and more frequent heatwaves.

For vulnerable populations, overheating is not simply a matter of discomfort. It represents a significant health risk. Residents in care homes typically have limited mobility and reduced capacity to physiologically or behaviourally adapt their environment [2]. In epilepsy care settings, this risk is intensified, as elevated temperatures are associated with increased seizure activity, sleep disruption, and fatigue [3, 4]. Ensuring safe indoor conditions is therefore critical (Figure 1).

Figure 1. Intersection of hazards, vulnerabilities and exposures in determining overheating risks and systemic impacts within epilepsy care homes.

Meanwhile, the built environment is facing mounting pressure to reduce energy consumption and carbon emissions. Global cooling demand is expected to rise substantially under climate change, creating trade-offs between thermal comfort and global decarbonisation goals [5]. This makes the identification of effective, low-carbon cooling strategies an urgent priority for practitioners.

This study builds on the UK-based ClimaCare research programme, investigating overheating risks in care settings [6]. While previous work focused primarily on passive strategies and aged care home typologies, this research advances the field in three distinct ways. First, it examines epilepsy care homes, an under-researched but highly vulnerable building typology. Second, it evaluates hybrid cooling strategies, combining passive and active systems. Third, it integrates human-centred design approaches, incorporating staff insights to better understand the lived realities within the care home.

The aim is to provide evidence that is directly applicable to industry, particularly in retrofit contexts, while reinforcing the importance of good passive design in new buildings, which remains the first line of defence against overheating.

Case Study and Methodology

Collaborating with the Epilepsy Society, the case study was conducted in a single-storey care home in Buckinghamshire, South-East England, accommodating eight adults with severe epilepsy and additional comorbidities (Figure 2). Residents spend most of their time in communal lounges and have limited ability to adapt to their environment. The building relies primarily on natural ventilation, supplemented by fans in bedrooms and ad hoc use of portable air conditioning units in lounges. Although this is a single case study, the building typology is considered representative of newer low-rise care homes commonly found across the UK and temperate European climates. As such, the findings are broadly transferable to comparable settings.

The research adopted a mixed-methods approach, combining empirical data, dynamic thermal modelling, and stakeholder insights. Indoor and outdoor hygrothermal conditions were monitored over a summer period to capture the existing baseline performance. A calibrated dynamic thermal model was then developed using IES-VE to simulate current and future overheating risks.

Weather files from the UK Climate Projections (UKCP09) were utilised. Current conditions were modelled using Design Summer Year 1 (DSY1) 2030 (RCP 8.5, 50^th percentile), with future performance assessed using DSY1 2050 and 2080 (RCP 8.5, 90^th percentile) to represent severe but plausible warming scenarios. This approach remains compatible with wider European climate projections and relative performance trends are unaffected by dataset choice.

Figure 2. Ground floor plan of the case study care home.

In parallel, a staff focus group was conducted to understand how overheating is experienced and managed in practice. This provided valuable insights into operational challenges, system usability, and priorities for cooling interventions. The integration of these qualitative insights with quantitative modelling distinguishes this study from purely technical analyses and ensures that the findings are grounded in real-world operation.

Baseline Risk Assessment

Monitoring data confirmed that overheating is already a persistent issue. During the 10-day measurement period in July 2025, indoor temperatures exceeded 26°C for approximately one-third of the time, aligning with staff reports of thermal discomfort. The calibrated model showed strong agreement with measured data, providing confidence in its use for future projections (Figure 3).

Baseline simulations indicate that overheating will worsen substantially under climate change. Under current conditions, between 9% and 14% of occupied hours exceed 26°C, with bedrooms, particularly those facing East, being the most affected; By the 2050s, overheating more than doubles, and by the 2080s, up to 38% of occupied hours exceed 26°C, with peak temperatures surpassing 40°C.

Night-time conditions in bedrooms emerge as a critical concern. These spaces consistently failed comfort criteria across, highlighting the importance of targeting sleeping environments in overheating mitigation strategies. The findings reinforce a growing consensus that night-time overheating poses one of the most significant risks in residential and care settings, where recovery and rest are essential for health.

Figure 3. Boxplots comparing monitored and modelled results during the monitoring period (30th June to 9th July 2025).

Passive Cooling Performance

A range of combined passive measures were tested, including enhanced natural ventilation, external shading, and increased thermal mass (Table 1). Under current conditions, these strategies provide meaningful improvements. External shutters combined with night ventilation were particularly effective, reducing overheating to approximately 2% of occupied hours (Figure 4).

However, their effectiveness declines rapidly under future climate extremes. As night-time outdoor temperatures rise, the cooling potential of night ventilation is reduced. Additional thermal mass provided little benefit, beyond what is achieved through shading, in the already thermally heavyweight structure. By the 2080s, passive strategies alone failed to maintain acceptable thermal conditions.

Figure 4. Percentage of annual occupied hours exceeding 26°C implementing passive cooling strategies under all climate scenarios.

Table 1. Tested passive and active cooling strategies.

These findings demonstrate a performance ceiling for passive-only approaches in retrofit contexts. While they remain essential under current conditions and contribute to reducing cooling loads, they cannot provide sufficient thermal resilience on their own in a warming climate.

Hybrid Cooling Performance

Hybrid strategies, combining the most effective passive measures with active systems, altered this performance trajectory. Most hybrid configurations successfully maintain thermal comfort across all climate scenarios. However, system performance varies significantly.

Portable air conditioning units, often used as short-term solutions, are shown to be highly inefficient, increasing energy use by up to 85%

compared to the baseline with no adaptation. Mechanical ventilation with cooling coils reduces energy consumption but fail to maintain thermal comfort under extreme future conditions. In contrast, systems based on reversible air-source heat pumps (ASHPs) deliver the most balanced performance. These systems consistently achieve comfort while significantly reducing both energy use and carbon emissions compared to the baseline. Energy savings of up to 66% are observed under current conditions, alongside substantial reductions in emissions, even under future climate scenarios (Figure 5). The results indicate that electrified, heat pump-based systems offer a robust future-proof solution for care environments, particularly when integrated with passive-first strategies.

Figure 5. Total annual systems energy consumption and carbon emissions implementing hybrid cooling strategies under all climate scenarios.

Operational Insights and Implications for Practice

A key contribution of this study is the identification of real operational challenges. Staff reported that managing indoor temperatures is complicated by inconsistent use of systems, driven by conflicting thermal preferences and limited technical understandings, undermining the performance of cooling strategies.

The focus group revealed a strong preference for automated, low-intervention systems that reduce operational burdens. This has important implications for design. Systems must not only be technically efficient but also intuitive, reliable, and aligned with the capabilities of users. Automated controls, sensor-driven operation, and simplified interfaces can help to ensure consistent performance while reducing operational burden.

At the same time, retrofit solutions must consider cost and feasibility. While ASHP-based systems offer long-term benefits, they require higher upfront investment and may increase electricity demand. This raises broader questions around affordability and highlights the need for supportive policy frameworks, including funding mechanisms and guidance for care providers.

Conclusion

This study demonstrates that overheating is already a significant and escalating risk in care homes. For vulnerable populations, including people with epilepsy, maintaining safe indoor temperatures is essential to health, well-being, and care delivery.

While passive strategies remain a critical component of building design, their limitations in a warming climate are clear, particularly in retrofit contexts. Hybrid cooling is essential to ensure long-term thermal resilience. Among the systems evaluated, reversible air-source heat pumps offer the most effective balance between thermal comfort, energy efficiency, and decarbonisation goals.

Importantly, effective climate adaptation must be human-centred. The results show that system performance is strongly influenced not only by technical specification, but by usability, control strategies, and stakeholder interaction, reinforcing the need for simplified, well-integrated solutions. This work advances a transferable methodological framework for assessing overheating mitigation strategies in care facilities facing climate-related health risks.

The findings may be applicable to similar care home typologies across the UK and similar European climates. They provide a clear direction for practitioners: adopt passive-first strategies, integrate efficient hybrid systems, and design with users in mind. As climate change accelerates, addressing overheating in care homes must be a priority for practitioners to deliver safe, sustainable, and future-ready care environments.

References

[1]     Gupta, R. et al.(2016) Care provision fit for a future climate, ClimateJust. Available at:  https://climatejust.org.uk/sites/default/files/19.%202016_gupta_et_al_report_3208_final_0_0.pdf

[2]     Arbuthnott, K.G. and Hajat, S. (2017) ‘The health effects of hotter summers and heat waves in the population of the United Kingdom: A review of the evidence’, Environmental Health, 16(S1). doi:10.1186/s12940-017-0322-5.

[3]     Swanborough, N. (2024). Seizures and hot summers - Epilepsy Society. Available at: https://epilepsysociety.org.uk/news/seizures-and-hot-summers

[4]     Bartolini, E. and Sander, J.W. (2019) ‘Dealing with the storm: An overview of seizure precipitants and spontaneous seizure worsening in drug-resistant epilepsy’, Epilepsy & Behavior, 97, pp. 212–218. doi:10.1016/ j.yebeh.2019.05.036.

[5]     Ciancio, V. et al.(2020) ‘Energy demands of buildings in the framework of climate change: An investigation across Europe’, Sustainable Cities and Society, 60, p. 102213. doi:10.1016/j.scs.2020.102213.

[6]     ClimaCare (2021) ClimaCare: Climate Resilience of Care Settings, UK Climate Resilience Programme. Available at: https:// www.ukclimateresilience.org/projects/climacare-climate-resilience-of-caresettings/