In order to realize energy-efficient renovation and new construction in 2050, the main focus is on insulation, replacement of joinery, airtight construction and energy-efficient heating. “Quite right, but oddly enough there is much less sense of urgency when it comes to keeping the heat out. However, preventing overheating in buildings becomes just as important as limiting heat loss if we want to achieve the energy targets,” says Ann Van Eycken, general secretary of Verozo.
It is expected that more frequent heat waves will occur in the future, which will also last longer and with increasingly higher temperatures. The increasing heat naturally leads to an increasing need for cooling. Many then choose the relatively cheap mobile air conditioning system, a bit like creating temporary comfort in the car. The downside is equally predictable: significantly higher energy consumption and emission of greenhouse gases.
“Tackling global warming with only active cooling, such as air conditioning, is a disaster for the environment and our energy bill. Prevention is better than cure. Limiting direct solar radiation is a first measure to cut off the heat. To this end, the orientation of the building and spaces is particularly important. A second step is mobile sun shading or, to a lesser extent, solar shading glazing. The mobile or dynamic exterior sun shading provides a double benefit. It blocks the sun if it is not wanted, but lets in daylight and solar heat in winter, which reduces the heating requirement,’ says Ann Van Eycken.
To disperse the heat, opening the windows at night is the most logical and natural third step. Mechanical ventilation of homes is also an option, although it has a rather limited effect. Cooling is a final step and can be done in several ways. There are passive methods that use cold in the environment and active systems such as air conditioning.
In the Netherlands there is a dynamic simulation program ‘Weighted Temperature Exceedance’ (GTO) that can specifically predict the risk of temperature exceedance. The program clearly shows that sun protection greatly reduces the risk of overheating. The Netherlands now even goes a step further by setting an upper limit for GTO (450 hours). With this, the government wants to promote that homes are also comfortable in the summer.
Also in the Netherlands, the Consultation Standards Climate Adaptation (OSKA) strives to ensure that standards for the design of buildings take into account warmer summers and the growing need for cooling. The ‘ladder for cooling’ was recently introduced with a preferential order of the measures. This model is currently being adopted internationally as a basic principle in the fight against overheating in buildings.
In the UK, new legal requirements were introduced at the end of last year to limit the risk of overheating. The focus is mainly on outdoor solar shading as a first step. The same rules prescribe that there must always be some form of passive cooling before active or mechanical cooling is used.
The RE 2020 rules apply in the French new construction, which imposes various requirements such as ‘conception bioclimatique’ (BBIO), primary energy consumption (CEP), summer comfort (DH), etc. Automated solar shading is one of the measures that enable ‘light’ to meet the requirements without having too much of an impact on the budget. In certain regions in the south, it has even become impossible to meet the requirements without automatic blinds. For existing buildings, the roller shutters or sun blinds must be retained or replaced during renovation.