New research reveals poor indoor climate in European schools


The German research institute, Fraunhofer Institute for Building Physics IBP, has published its latest report which shows that despite improvements to school buildings in recent years, we are yet to provide school children with an optimum indoor environment for learning. The VELUX Group believes that a greater focus needs to be placed on a healthy indoor climate when designing and renovating schools across Europe.

The new research, which is a systematic review of over 200 scientific studies, reports that a large number of the 95 million school children in Europe are working in classrooms with excessive levels of CO2 and an inadequate supply of daylight.

Although some schools have CO2 levels between the recommended rates of 1,000 to 2,000 ppm, this study shows that many schools have levels which are in excess of 2,000 ppm, and in some tests, scientists have recorded readings of up to 6,000 ppm. Furthermore, a number of schools did not achieve a daylight factor of 3-5%, the recommended the level of daylight in classrooms.

Improved indoor climate = improved performance

The study also reports the impact of an optimum indoor environment on the learning capabilities of school children. The researchers found that improving ventilation rates, reducing the CO2 concentration and increasing access to daylight in classrooms improves pupils’ performance in the sense of speed, higher levels of attention and concentration and lower rates of absenteeism. For example, the researchers came to the conclusion that the speed at which pupils work can be increased by up to 15% by simply increasing the amount of fresh air into the room.

"Our study shows that the quality of the indoor climate in schools, in terms of access to daylight and fresh air, has a significant effect on the learning capabilities of the children. As we have found that many schools in Europe do not have an optimum indoor environment, we hope that this report will encourage public authorities to take action,"
Prof. Dr. Gunnar Grün, a lead researcher at Fraunhofer IBP

However, the benefits of higher levels of achievement in education are not confined to the individuals. When comparing the educational levels between European countries, using a conditional test score based on PISA tests, the study shows that a correlation to the conditional growth within those countries exists. The researchers report that an increase of school childrens’ performance by 2.8% would lead to a 6.7% - 9.5% increase in the conditional economic growth of the country (based on GDP per capita).

“These results prove that ensuring a healthy indoor environment in schools must become a main priority for public authorities across Europe. Better buildings not only leads to brighter students, they are also good for the economy in terms of increased productivity. I am sure that this study will be the centre of much debate and act as a catalyst of change for the better in European schools,” 
Ulrich Bang, Director of Global Public Affairs and Corporate Responsibility in the VELUX Group

How to improve the indoor environment in schools

The report concludes with a number of ways to improve the indoor climate in schools. Firstly, as most schools in Europe have been designed for natural ventilation, more time should be set aside for airing during lessons. However, mechanical ventilation systems, such as motorized windows, can also ensure an optimum level of air quality without changing the behaviour of teachers in lessons. By monitoring relative humidity, CO2 concentrations and temperature, the system simply switches itself on when fresh air is needed. Lastly, hybrid ventilation systems, such as fan assisted natural ventilation, have now been developed which combine the advantages of both natural and mechanical ventilation. The report also notes that when it comes to daylight, skylights can increase the incidence of natural light by up to 50%.

“A healthy indoor climate is crucial if we want to ensure that children get the best chance of success at school. Alongside academic studies which have proven this to be true, our work at Langebjerg School and Endrup School have drastically improved the lives of both school children and teachers alike,” 
Peter Foldbjerg, head of the VELUX Group’s Knowledge Centre

The VELUX Group’s renovation projects at Langebjerg School and Endrup School are perfect examples of how more access to daylight and fresh air can transform the learning environment. For example, at Langebjerg School, the teachers greatly appreciated the installation of VELUX INTEGRA® Roof Windows, as ventilation to the upper part of the classrooms now prevents the uncomfortable drafts that occur when façade windows are opened to air out the rooms. 

The Fraunhofer IBP white paper, ‘Impact of the indoor environment on learning in schools in Europe,’ is now available for download. 

About the VELUX Group

About the VELUX Group

For more than 80 years, the VELUX Group has created better living environments for people around the world; making the most of daylight and fresh air through the roof. Our product programme includes roof windows and modular skylights, decorative blinds, sun screening products and roller shutters, as well as installation and smart home solutions. These products help to ensure a healthy and sustainable indoor climate, for work and learning, for play and pleasure. We work globally – with sales and manufacturing operations in more than 36 countries and around 11,000 employees worldwide. The VELUX Group is owned by VKR Holding A/S, a limited company wholly owned by non-profit, charitable foundations (THE VELUX FOUNDATIONS) and family. In 2022, the VELUX Group had total revenue of EUR 2.99 billion, VKR Holding had total revenue of EUR 4.29 billion, and THE VELUX FOUNDATIONS donated EUR 181 million in charitable grants.

For more information about VELUX Group, visit