When the climate grows warmer, the need to cool down homes grows stronger – energy efficiency to guide planning

As the climate grows warmer, long heatwaves will also become more common in Finland. As is typical to Nordic countries, our homes have usually been built to withstand cold and winter weather, in particular. How should cities prepare and adapt to the stronger heatwaves of the future? Read the ideas of Sweco’s energy expert about what kinds of solutions could help cool down homes efficiently.

We have had many hot days this summer: in June, the temperatures climbed to over 30 degrees several times. In the future, these heatwaves will only grow more intense, common and longer, and their impact can be felt in concrete ways, especially in our constantly growing and densely built cities. The heat conductivity of urban construction materials, such as asphalt and concrete, is high. During the day, urban structures store the sun’s heating energy and then release it at night, forming ‘urban heat islands’.The temperature difference between a city and a rural area can thereby be up to 5–10 degrees during the night. Sweco’s recent Urban Insight report studies heat in the cities and looks for solutions on how urban planning can help prevent the detrimental impacts of heat and long heatwaves on people. According to the report, cities should improve their resilience to heatwaves.

In Finland, building planning has been based on keeping the warmth in for a long time, and homes have not been built for a warming climate. In their work, building service systems’ energy expert Niina Laasonen and her colleagues at Sweco consider issues such as how energy-efficient cooling systems can be implemented for buildings. She has noticed that people have started to understand the necessity of cooling down homes in recent years.

“Only few homes in Finland have a cooling system for now, but the heatwave in 2018 made people more aware of the need, and I’m sure the demand will grow further in the 2020s.”

Safe and healthy indoor conditions through cooling

As the climate grows warmer, the European population grows older. The relative amount of people aged 65 or older is also growing rapidly in Finland. The most vulnerable residents – the elderly as well as e.g. young children – also suffer the most because of heatwaves and high indoor temperatures. Heat is a cause for many public health issues: more Europeans are dying from heatwaves than from all other natural hazards combined.

“We should not compromise on healthy and safe indoor climate during the construction stage. We designers definitely want to provide socially sustainable solutions. Temperatures in Finland rise faster than elsewhere in the world, on average. When we intervene with this issue now, heatwaves may not become as major a threat to public health as they already are in many European countries,” Laasonen says.

Laasonen also points out that heatwaves may also become a national financial issue, in addition to a public health problem. Research shows that a person’s work efficiency decreases an average of 2 per cent for every degree exceeding 25 Celsius degrees. This spring, many of us worked from home, and it has been predicted that remote work will become more popular in the future. This means that cooling down buildings is also necessary for urban citizens without any underlying health conditions.

Energy-efficient solutions are available for cooling down homes

The increasingly common heatwaves require that the placement of buildings, shading in the local environment and architectonic solutions are planned more carefully, and also new building technology is needed. Laasonen says that it is no longer enough to just passively shade a building from the sun.

“As designers, we recommend constructing a cooling system for new residential buildings. Current technologies offer cost- and energy-efficient solutions for cooling down buildings. When the same system is used for both heating and cooling a building, the investment is not that massive. Cooling solutions also help dry the indoor air, which makes even higher indoor temperature feel much more pleasant.”

Laasonen also brings up circular economy: Cooling down premises creates condensed heat, which can be recovered and used for floor heating in the bathroom, for example. No extra energy is needed.

“The largest Finnish cities now have district cooling networks, through which we can produce cooling in an energy-efficient way and recycle the heat back to the district heating network to be utilised. Single-family homes, on the other hand, use electricity for heating, which makes heat pumps a convenient way of cooling down the building while also significantly decreasing the consumption of purchased energy in the winter,” Laasonen summarises.

Building resilience: being young and getting old in a hotter Europe is Sweco’s third Urban Insight report related to climate actions in cities. In the report series, Sweco’s experts highlight the specific data, facts and science that are needed to plan and design safe and resilient future urban environments.