Aalto University: Hot weather can turn homes into perilous infernos – researchers are now examining future needs for cooling

A hot summer can cause the deaths of up to 400 people in Finland, and climate change will make the heat more severe and more frequent. A new research project examines the temperatures of buildings and how they affect the comfort level of people – and seeks effective means of cooling that are also easy to employ.

Finnish building regulations require that new apartment buildings in Finland must be designed in such a way that the temperature dies not exceed 27 degrees for more than 150 degree hours during summer time. A degree hour refers to the product of temperature and time. For example, exceeding the temperature by two degrees for five hours equals 10 degree hours.

On the drawing board everything can look good, but things can still get hot for residents, says Risto Kosonen, Professor of HVAC technology at Aalto University.

‘Nowadays planning is based on average summer temperatures over a period of the last 30 years – not the temperatures of an unusually hot summer. Consequently, indoor temperatures in the hot summers that we are having will be reaching uncomfortable, and sometimes even a dangerous levels’, he predicts.

Kosonen and his group are engaged in a project funded by the Academy of Finland aimed at finding out how climate change is affecting the indoor temperatures of buildings and the temperature-related comfort levels that people have. Also taking part are THL, the University of Eastern Finland, and the Finnish Meteorological Institute.

For example, researchers at Aalto University are conducting field studies to analyse the actual room air temperatures of 8,500 apartments in Helsinki. Data both from last summer and the summer of 2018, which were exceptionally warm, are also being used. In addition, the researchers are using scenarios put forward by the Finnish Meteorological Institute to calculate how hot residential buildings and care facilities that lack air conditioning can become in the climate of the future.

According to the Finnish Decree on Health-related Conditions of Housing and Other Residential Buildings and Qualification Requirements for Third-party Experts, the temperature of a home should never exceed 32 degrees. For the elderly and vulnerable, the limit is 30 degrees. According to Kosonen, present limits are too high – and even they have been exceeded in recent hot summers.

. A retrofitted air-source heat pump is not very expensive, and the cost of the electricity that it uses is between 50 and 150 euros a year.

Risto Kosonen
Excess heat does not make indoor spaces merely uncomfortable; it also renders them hazardous to health. Statistics show that 350-400 Finns die premature deaths in hot summers, which is more than the number of people who lose their lives in fires each year.

Advanced age and underlying diseases add to the dangers posed by heat. For this reason, the project is studying, under laboratory conditions, how rising temperatures affect the physiology and comfort of elderly test subjects.

The test subjects are also testing easy-to-use and inexpensive local cooling solutions, such as table fans and fan jackets. According to Kosonen, these seem to work well in the daytime, but their use is not as effective and convenient when sleeping at night.

‘That is when mechanical cooling is really the only solution for controlling indoor temperature. A retrofitted air-source heat pump is not very expensive, and the cost of the electricity that it uses is between 50 and 150 euros a year’, he says.

The project ends at the end of this year. One of its most important goals is to offer reliable information to support decision-making. Kosonen firmly believes that temperature comfort will be considered more when the warming climate causes heat waves to significantly increase.

‘People nevertheless spend 90 percent of their time indoors.’

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