The Overheating Time Bomb Is Ticking – Cooling Solutions Should Be Considered Already at the Building Design Stage

Historical Data Does Not Predict the Future – It’s Time to Stop Relying on It

urrently, heat-related deaths in buildings in Finland are estimated at around 100 people per year. This figure is expected to increase six- to sevenfold by 2080.

New buildings are being designed today with a technical lifespan of at least 50 years. However, in building services design—particularly when assessing cooling needs—there is still a tendency to rely on historical data. The future risks and impacts of climate change are generally not taken into account at all.

Yet future climate risks are now widely known. It is high time they are also considered at the design table.

Cooling in Residential Buildings Should Be a Standard Feature

Residential construction faces high cost pressures, often pushing the quality of solutions to the bare minimum required by regulations. As a result, current regulations allow indoor temperatures in residential spaces to remain at 27°C continuously and up to 32°C in summer.

This might come as an unpleasant surprise to a new homeowner during their first heatwave.

Cooling is already unavoidably needed, and this need will only grow. Cooling solutions should therefore be considered from the outset of planning and construction and clearly highlighted in property sales. This would help prepare buyers to invest in better thermal comfort.

Improved resident wellbeing and reduced health problems can also serve as compelling sales arguments.

At present, it looks like homeowners will soon have to install separate air-to-air heat pumps for cooling—after first navigating the often slow and complicated approval process of their housing association.

The result? New apartment blocks may start to resemble southern European “architecture”, where entire facades are covered with the outdoor units of air conditioners. It would be far more economical, simpler, and visually appealing for all parties if cooling were implemented centrally—through ventilation systems, for example—during the planning and construction stages.

Fortunately, building regulations are set to become stricter regarding the assessment of cooling needs in new residential buildings. A new decree by the Ministry of the Environment, currently under public consultation, would tighten the overheating threshold from 27°C to 26°C. Furthermore, weather data used in calculations would be based on 2050 climate scenarios. These changes would likely compel many residential developers to include cooling in their buildings.

Cooling Is Also Essential for the School Day

Current building regulations and the Indoor Climate Classification do not sufficiently guide the design of new or renovated school buildings. They are based on historical weather data, and the allowed maximum indoor temperatures are relatively high.

School projects often aim to meet the requirements of Indoor Climate Class S2. These allow operative temperatures—those perceived by humans—of 27°C briefly and 26°C continuously during occupied hours. These targets are usually met on paper without mechanical cooling.

In reality, on a warm spring or summer day, indoor temperatures can easily exceed 30°C—and there’s nothing that can be done about it during actual use.

At most, minor mitigation measures such as solar control window films can be applied afterwards. But the most cost-effective approach is to anticipate potential problem areas already in the design phase.

Technical Solutions Exist – Now Project Owners Must Show Willingness

There are already well-established and proven solutions for implementing cooling in various building types. For example, centralised supply air cooling through the ventilation system is usually sufficient in both residential and educational buildings.

In particular, geothermal systems can provide nearly free cooling from the ground loop via passive cooling. This also extends the lifespan of the geothermal field, as heat is transferred back into the boreholes during summer. It’s a win-win solution.

And when combined with solar power, the energy for summer cooling can even be produced entirely emission-free and self-sufficiently.

Change Begins with Design

As a solution, future climate scenario-based weather data should be consistently used in thermal comfort calculations and design, particularly when referencing target levels in the Indoor Climate Classification.

Since the Classification itself does not define which weather data must be used, it is up to project owners to demand this more stringent requirement.

Currently, Indoor Climate Class S1 is very similar to S2 and does not significantly raise requirements for cooling. The main difference in S1 is the ability to adjust cooling room by room.

As the need for cooling increases, its consideration during the design phase becomes ever more critical. Qualified energy and lifecycle planners should therefore be involved in projects as early as possible. This minimises the risk of unfavourable indoor conditions during use and avoids investing in under- or over-dimensioned systems.