We’re facing it more and more often: heat. As the Earth warms up, extreme weather events such as heavy rain or heatwaves are becoming increasingly common. Prolonged heat can be very unpleasant, but fortunately there are a number of steps you can take to keep your home and yourself cool.
Here are some measures you can take to combat the heat
Plant a tree
The best way to combat the heat is to plant more trees. A tree helps to cool the air by providing shade and through evaporation. A single tree can actually cool the air just as effectively as ten air-conditioning units! Both the ambient temperature and the perceived temperature are lower under a tree than in direct sunlight. This difference can be as much as 10 to 15 degrees. If you have trees around your house, the shade they provide also ensures that walls, roofs and paving tiles heat up less. American research shows that walls in the shade of a tree heat up by as much as 20 degrees less. If you don’t have much space in your garden for a large tree, you could also opt for a roof-trained tree (such as a roof plane tree or roof sweetgum) above the patio.
Soften and green up
Stones absorb heat and slowly release it again in the evening. This so-called ’heat island’ effect is particularly prevalent in urban areas, resulting in temperatures here being around 7 degrees warmer in the evening than in the countryside. This is not conducive to a good night’s sleep. You can also notice the difference between having lots of tiles and just a few in the garden. On hot days, the temperature of patio tiles can easily reach 50 degrees. The darker the tile, the warmer it gets. Light-coloured tiles and gravel heat up less, but it is even better to minimise hard surfaces and plant as much greenery as possible. This is because evaporation and the shade provided by plants ensure that the immediate ambient temperature is 2 to 5 degrees lower. So make sure you have as much greenery as possible around your façade and around the patio.
You don’t have to limit yourself to borders or potted plants. By opting for a green boundary, a pergola or a green façade, you can increase the amount of greenery without taking up any of your garden space. A wall covered in climbing plants feels 10–15 degrees cooler. The insulating effect of green walls is beneficial for both indoor and outdoor temperatures. Good climbing plants with a cooling effect include, for example, Tuscan jasmine and clematis. You could, for example, let a grapevine grow over a pergola. This way, you can sit comfortably in the shade in summer, whilst still enjoying plenty of sunshine in winter and spring, as the leaves only start to form later in the spring.
Lay a green roof
On summer days, the indoor temperature under a green roof can be 3 to 5 degrees cooler. On a sunny summer’s day, the surface temperature of green roofs is around 27 degrees, compared with 70 degrees for a bitumen roof! The ambient temperature above a green roof is not significantly lower during the day, but it is in the evening when the heat island effect occurs. A prerequisite is that the green roof is well watered. It is best to use rainwater that you have collected in, for example, a rain barrel.
Read more about installing a green roof
Go for white
White roofs and façades heat up less because they reflect more sunlight. For example, the reflectivity of white concrete roof tiles is 15 times greater than that of black bitumen roofing (which can reach temperatures of up to 70 degrees). On hot days, the spaces beneath a white roof are around 4–10 degrees cooler than those beneath a black roof. In America, a paint has been developed that is even whiter than snow. This white paint reflects 98% of sunlight. Applying such paint to roofs and façades keeps the indoor temperature lower than the ambient temperature. In our climate, however, we only want this effect for a few months a year. It is therefore not yet entirely clear whether the benefits of a white roof or white façade outweigh the benefits of darker surfaces.