Danish homes are being designed for a climate that will soon no longer exist

Despite rising temperatures and more frequent heatwaves, buildings are still being designed based on climatic conditions from the 2000s.

The result is housing that is already difficult to inhabit today – and will become increasingly so as climate change intensifies.

“We design buildings based on outdated data. Instead, we should future-proof our homes so that they remain healthy and comfortable places to live,” says Kristine Strøm.

She is a PhD fellow at the Department of the Built Environment, where she researches how Danish housing can be better prepared for a warmer and more extreme climate.

“Using multi-storey residential buildings as a starting point, I investigate which housing typologies are most vulnerable to, for example, overheating, and therefore will become the most difficult to live in as the climate warms,” says Kristine Strøm.

Her research also examines how climate-resilient housing can be designed with minimal environmental impact, and how the most vulnerable dwellings – already experiencing problems today – can be retrofitted.

From warm summers to cold winters

Kristine Strøm is currently analysing building robustness under three different climate scenarios (RCPs) based on recent climate projections from the Intergovernmental Panel on Climate Change (IPCC).

One scenario assumes continued greenhouse gas emissions at current levels, one assumes reduced emissions, and one assumes increasing emissions.

“Some scenarios are more realistic than others,” she notes.

By simulating how different building types perform under future climate conditions, she gains insight into which constructions can best withstand rising temperatures.

“We simulate the heating and cooling demand of a dwelling over a typical future year. This depends, among other factors, on materials, insulation levels, and glazing ratios,” Kristine Strøm explains.

A brick apartment building from the early 1900s, for example, performs under entirely different conditions than a newly built concrete apartment building from 2020.

“There are strong indications that newer buildings experience the greatest problems with overheating, and therefore will be the most challenged in a future climate,” she says.

A frequent cause of overheating is large glazed areas, which have become increasingly common over time.

They allow solar heat gains to penetrate the building envelope, and in combination with insufficient ventilation, the dwelling can feel like an oven in summer because excess heat cannot be dissipated.

However, it is not only newly built housing that will face heat-related challenges.

“We can say with certainty that cooling demand will generally increase across the Nordic region, while heating demand will decrease quite significantly,” she says, adding:

“Cooling demand is also emerging in regions that historically have only required space heating, which is quite remarkable.”

Buildings designed for the past

Today, the Danish Building Regulations require buildings to be designed using average historical weather data observed at a single geographical location during the period 2001–2010.

Somewhat caricatured, it is as if we are all assumed to live on Zealand in the past. In reality, we do not – and our buildings are therefore already warmer than anticipated.

This is because the underlying data do not account for climate change, local climatic variations, or the urban heat island effect associated with urbanisation.

Although the Danish Building Regulations are about to update the mean weather data file to the Danish Reference Year 2025, Kristine Strøm does not consider this sufficient.

“The new weather file is based on observed data from 2011–2023. The climate has already changed since then, and it will change even more in the future. So the upcoming updates are already outdated,” she says.

In 2025, Denmark experienced its fourth warmest year since measurements by the Danish Meteorological Institute (DMI) began in 1874.

Denmark’s mean annual temperature reached approximately 9.7 °C, yet buildings are currently being designed for an average temperature of 8.1 °C.

“Our buildings will stand for many decades into the future. Designing for current conditions is not enough – we must look much further ahead,” she emphasises.

Denmark is not alone in facing this challenge. Many Nordic countries face similar issues, where buildings designed for colder climates must now withstand much warmer summers.

England has for many years used more extreme weather data in building design, and Norway is moving in a similar direction.

Overheating: an inevitable consequence

The challenges associated with overheating are particularly evident in densely populated areas, where the largest temperature increases are observed due to the urban heat island effect.

“Because of population density and anthropogenic heat emissions, temperatures are higher in cities, whereas they are lower in coastal areas, primarily due to cooling from the sea,” Kristine Strøm explains.

On average, temperatures are therefore lower in Hirtshals than in Copenhagen.

When population density is incorporated into the analysis, the greatest challenges appear in the southern and most urbanised parts of the Nordic region.

“This means that climate change must be integrated far more concretely into building design, renovation, and energy planning,” she concludes.

As temperatures rise, maintaining indoor thermal comfort without large amounts of cooling energy becomes increasingly difficult.

In the worst case, air conditioning could become necessary in most buildings. However, Kristine Strøm emphasises that this would be the wrong solution.

“Air conditioning would increase energy consumption and thereby the total CO₂ emissions from our buildings. That is the wrong direction. Instead, we should focus on passive solutions that minimise the need for active heating and cooling,” she says.

Solutions: climate-adapted design and retrofit

So what can be done to ensure that our homes remain habitable in a warmer climate?

According to Kristine Strøm, several measures can reduce overheating, both in new construction and in existing buildings.

Solar shading, solar-control glazing, and strategies for enhanced natural ventilation can, for example, reduce the risk of overheating.

The most appropriate solution depends largely on the individual building, and this is something Kristine Strøm will investigate further in her ongoing research.

However, future-proofing the built environment requires that the Danish Building Regulations keep pace with developments and that the underlying data reflect the future climate we are facing. Investment is needed in new sustainable solutions that ensure a comfortable and healthy indoor environment.

“We need updated data and more forward-looking climate models if we are to design buildings on a realistic basis,” she says.

“I hope our results can help promote the integration of future climate scenarios and site-specific data as a foundation for climate adaptation strategies.”