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How Resilient Are Slovenian Households to Summer Overheating?

A high-rise building with air conditioning units

Nathan Marcam/Pexels

Date of publication:

Tag:

  • UL FGG
  • Research achievements
  • University Office for Research
  • Research
  • SDG 7
  • SDG 11
  • SDG 13

A nationwide study shows that overheating already affects almost two-thirds of Slovenian households. Older multi-apartment buildings with inefficient ventilation are the most vulnerable, while the main barriers to adapting buildings are costs and technical limitations.

Responding to Climate Challenges

The study was designed by researchers from the Faculty of Civil and Geodetic Engineering at the University of Ljubljana, Assoc. Prof. Dr Mitja Košir and Assist. Prof. Dr Luka Pajek. The main motivation behind the study stems from more than a decade of research into the climate resilience of buildings, as well as a lack of key data on how people respond to overheating in practice and which measures they are willing to adopt.

The comprehensive study includes not only a public opinion survey, but also an analysis of climatic conditions in Slovenian municipalities and bioclimatic assessments of future changes. Combining these data will make it possible to identify key passive measures for sustainable heat mitigation.

The findings will provide an expert basis for strategic decisions by the national government and municipalities, ranging from better planning of new buildings and renovations to the development of new systemic policies. Residents’ willingness to make changes is already very high, as only 13 percent of respondents do not want or plan to take any measures to reduce building overheating. Appropriate financial support will therefore be crucial in turning these plans into action. “When it comes to improving the energy efficiency of buildings, especially in relation to winter conditions, subsidy mechanisms are already in place. Unfortunately, however, we currently do not yet have specific subsidies dedicated exclusively to preventing building overheating,” Košir points out.

Heat Is a Greater Problem in Urban Areas

The study is still ongoing, so only the preliminary results of the public opinion survey are currently available. Nevertheless, they already offer some interesting insights.

Responses from 2,681 participants show that 18 percent of Slovenian households consider their indoor thermal environment unacceptable during the summer. Households in multi-apartment buildings are particularly exposed.

In urban areas such as Ljubljana and Maribor, overheating is intensified by the urban heat island effect. The proportion of households living in multi-apartment buildings that consider their thermal environment unacceptable is significantly higher: 31 percent in Ljubljana and as much as 37 percent in Maribor.

At the same time, 55 percent of Slovenian households have at least one air-conditioning unit installed in their home. This proportion rises sharply in municipalities with warmer climates: 94 percent in Koper, 83 percent in Nova Gorica, 70 percent in Novo mesto and 67 percent in Celje.

A Considered Approach in Slovenia

Despite the high prevalence of air-conditioning systems, the study shows that people in Slovenia tend to respond to heat in a considered manner. External shading is installed on the buildings of 81 percent of households, while 57 percent regularly use night-time ventilation for cooling.

“Before switching on air-conditioning systems, people evidently tend to rely on passive measures first. This is in marked contrast to our study in Montenegro, where residents turn much more quickly to active cooling alone,” Pajek explains, adding: “This may give us an indication of what we can expect if passive measures are no longer sufficiently effective.”

All these findings clearly indicate that the resilience of residential buildings to overheating is already a significant issue and is expected to become even more pronounced in the future. However, with the knowledge gained through this research, together with appropriate systemic measures and financial incentives, it will be possible to improve the resilience of the built environment in good time and preserve a high quality of life in our homes over the long term.

Data sources: Statistični urad Republike Slovenije. (2026). STAGE II. https://gis.stat.si/ in Lehner, F., Maier, P., Klisho, T.& Formayer, H. (2025). FORSITE-Clim Europe: European-wide climate indicators for historical periods and climate projections at high resolution [Dataset]. Zenodo. https://doi.org/10.5281/zenodo.14843328