Increased cooling demands – Why look beyond ventilation? What are the sustainable ways forward?
With record-breaking outdoor temperatures and unprecedented heatwaves, cooling has become necessary for peoples' lives, health, productivity and comfort. As individual buildings become smarter, the built environment expands so quickly that sustainable ventilation and passive cooling are no longer just a nice-to-have or a green feature – they are a necessary must-have.
The two reports presented show that cooling demand is growing rapidly worldwide to meet rising demand for indoor thermal comfort. There are practical solutions for buildings and people that must be part of their design, construction, and operation. There is also a need to shift from a static indoor climate to a more adaptive, dynamic, and sustainable approach.
The Global Status Report – Buildings fast. Falling short.
In May 2026, the United Nations Environment Programme (UNEP) and the Global Alliance for Buildings and Construction (GlobalABC) released the Global Status Report for Buildings and Construction 2025–2026: Building Fast. Falling Short. The report shows that cooling demands are growing rapidly worldwide.
"Cooling now accounts for 4% of total building energy use, and cooling-related energy demand has increased by 70% since 2015. Rising temperatures, urbanisation and increasing demand for thermal comfort are expected to further accelerate this trend in the coming decades." — Global Status Report for Buildings and Construction 2025–2026: Building Fast. Falling Short
The situation today
- Roughly half of the buildings that will be standing in 2050 have yet to be built or renovated.
- Every day, the world builds an estimated 12.7 million square metres of floor area – roughly the equivalent of adding the entire city of Paris in new floor space every week.
- In 2024, the global building floor area expanded by 1.7%, reaching 273 billion square metres. This rapid growth was driven largely by construction in emerging economies, including India and Southeast Asia.
The message from the report is clear
There is a paradox in progress: we are building smart, in a save-energy way and providing comfortable indoor environments, yet the scale of building is jaw-dropping, about one Paris in floor space built every week.
With construction heavily concentrated to emerging economies such as India and Southeast Asia, there is an energy risk due to weak or lacking building energy codes. Further, because buildings expand faster than the electrical grid is cleaned up, absolute emissions are still rising.
The Global Cooling Watch 2025 – The free degrees
In November 2025, the United Nations Environment Programme released the report Global Cooling Watch 2025: The Free Degrees, outlining pathways to achieve sustainable and equitable access to cooling as extreme heat events become more frequent and intense.
What are 'free degrees'?
It is no longer affordable to ignore 'free degrees' – the natural reduction in indoor temperatures through passive design and sustainable cooling strategies. Integrating shading, reflective surfaces and sustainable ventilation, including passive cooling, etc, is the ultimate shortcut to climate comfort. Cutting cooling loads and emissions at the source without driving electricity costs.
The benefits are huge
- Sustainable Cooling Pathway would cut 64% of cooling emissions by 2050, protect 3 billion people from rising heat.
- There are more benefits: solutions to extreme-heat problems, fewer heat-related deaths, stronger economies, enhanced liveability in homes and productivity in workplaces and schools.
- We must reimagine cooling – not as a source of emissions, but as a cornerstone of heat resilience and sustainable development.
Bridging the gap – Practical solutions with passive and summer cooling
There is a need to address growing cooling demands and overheating risks, and to prioritise the implementation of passive cooling for delivering thermal comfort for limiting energy consumption and emissions. Before relying on mechanical cooling systems, the critical cooling strategies must be implemented in all buildings. Measures such as external shading, natural ventilation, reflective surfaces and climate-responsive design can significantly reduce indoor temperatures and cooling loads, particuarly during extreme weather conditions such as heatwaves.
Buildings and their consumption must be considered at peak levels, in summer, and actively consider climatic conditions and indoor climate requirements. In short, buildings have to be designed to not rely on the grid and active energy consumption to stay cool.
Research proves that it is more effective to stop the heat from coming in
Look at summer-mode ventilation and the need for managing the cooling load, i.e. the total amount of heat energy that must be removed from a building to remain comfortable. It demands alignment with physics rather than fighting it, that is, moving from the 20th-century‘s idea of a static indoor climate to an adaptive.
In short: seal and shade the building envelope, set a higher summer-mode temperature in the ventilation system, deploy air movement for adaptive thermal comfort, and monitor indoor climate parameters for optimisation.
Utilise passive-first architecture and combine material abilities with airflow
- Focus on building envelope – apply shading and cooling techniques such as building insulation, window-integrated shading or passive shading, architectural features such as reflective coatings and exterior awnings, cool the roof with greenery and planting. Use facade technology to reflect the heat.
- Utilise thermal mass – start with the building mass and utilise the high-performing internal thermal mass to reduce peak cooling loads by over 35% through night ventilation.
- Night ventilation and flushing out – research looks at the optimisation of internal thermal mass to absorb daytime heat, which is then flushed out by night ventilation.
Focus on the people inside and their activities
- Look at adaptive comfort – instead of cooling a room to a certain temperature, focus on the people inside. Increase indoor air velocity through passive ventilation, people actually prefer and tolerate higher indoor temperatures if there is perceptible air movement.
- Adjust ventilation schedules – based on the outdoor weather forecasts in tandem with changing occupants' activities, i.e. shifting high energy tasks to cooler parts of the day.
- Use real-time data for indoor air quality and for running a mechanical ventilation system – instead of using traditional HVAC methods with strict set-points for indoor temperatures and further parameters, use an adaptive approach – supply air when and where it is strictly needed.
What does research say about summer and indoor climate?
- Before turning on any mechanical cooling, stopping radiant heat from entering the building reduces the baseline cooling load by up to 30%.
- Increasing the cooling setpoint by just 1° (e.g. moving from 23°C to 24°C) reduces the system's seasonal energy consumption by up to 15%.
- Moving air creates a 'wind chill' effect on human skin via sweat evaporation, making the room feel roughly 2°C cooler than the actual temperature reading without changing the thermal load.
From over-air conditioning to more dynamic adaptive settings
Adaptive comfort shows that human thermal expectations are dynamic and very largely based on recent thermal experience and current outdoor weather. The human body can naturally acclimatise to 35°C outdoor temperatures, thus an indoor temperature of 25-26°C can actually feel very comfortable. Just using this approach can cut cooling energy use by more than half compared to energy consumed if static settings of 20-21°C.
It is needed to move away from active cooling to using passive strategies and towards climate resilience and smart adaptation. Passive cooling strategies implement a dynamic setting, not a static. Similarly, there should be a transition from static HVAC setups in buildings to smart ventilation and controls that enable real-time ventilation tied to outdoor conditions.
It must also be noted that passive cooling strategies, including materials and technologies, remain largely overlooked by building regulations worldwide. Many countries implement energy efficiency requirements, but fewer include indoor air quality guidelines. Passive cooling strategies adapted to local climates and building technologies remain underrepresented in building regulations, despite their strong potential to improve resilience, reduce overheating and lower energy demand.
References and more to read
The presented facts are based on the following reports.
The United Nations Environment Programme (UNEP) & Global Alliance for Buildings and Construction (GlobalABC). 2026. Global Status Report for Buildings and Construction 2025–2026: Building Fast. Falling Short.
The United Nations Environment Programme (UNEP). 2025. Global Cooling Watch 2025: The Free Degrees. How sustainable, passive-first cooling can save lives, money and food.
