Glass for Europe launches a series exploring how the solar factor is integrated in national legislations

As a follow-up to the informative paper “The role of solar control glazing in passive cooling of buildings” published earlier this year, Glass for Europe has launched a communications campaign to explore how the solar factor is considered in various EU and international legislations.

As Europe experiences increasingly frequent and intense heatwaves, ensuring buildings remain habitable and comfortable has become a growing priority. Buildings that are not designed or retrofitted to cope with these conditions face significant decline in thermal comfort and increased public health risks for their occupants which also suffer from reduced productivity.

While insulation has long been at the heart of building energy performance, managing solar gains is now equally important to reduce overheating and properly size solutions such as mechanical cooling. To highlight how countries are addressing this challenge, we have launched a new series exploring how solar factor is integrated into national building regulations across Europe and beyond.

The solar factor is commonly measured by the g-value, which indicates the proportion of solar energy transmitted through the glazing. Selecting the appropriate solar factor can significantly improve summer thermal comfort, reduce cooling demand and contribute to more resilient, energy-efficient buildings. A high g-value means the glazing will capture more free solar heat gains, while a lower g value indicates most solar heat gains will be repealed to avoid over-heating.

Our series examines the approaches taken by England, Germany, Greece, Italy, Portugal, Romania, Spain and Turkey illustrating the diversity of regulatory frameworks. Some countries set maximum solar factor values based on climate or façade orientation, while others rely on performance-based assessments to demonstrate that overheating risks have been addressed.

By comparing these national examples, the series aims to showcase existing good practices and contribute to the discussion on how building regulations can better support summer comfort, energy efficiency and climate resilience across Europe.

You can find all the information about the various legislations here.