In the midst of a heatwave, many discover that their outdoor corner of the terrace has become impractical: the ground is scorching, the smell of hot plastic lingers, cushions are too hot to touch. We had imagined easy maintenance and a modern design, but not the surface temperature. Consequently, instead of a refuge, the garden turns into an oven as soon as late morning arrives. All of this stems from a few choices of garden materials that react very poorly to sunlight.
People often blame full-sun exposure and the lack of shade, piling on parasols, sails and misting devices. But if the floor, walls and furniture soak up heat all day long, the air remains suffocating until late in the evening, even when the weather cools down. Tests on certain surfaces have shown peaks well above 60 °C in the middle of the afternoon. The most surprising part is that these three mistakes are almost always the same.
Why do certain garden materials retain heat for hours after the sun
Experts talk about thermal inertia to describe a material’s ability to store heat and then release it slowly. The more substantial a coating, such as concrete, stone, brick, or tile, the more it behaves like a battery: it charges during the heatwave, then radiates again when the air has cooled. If this material is dark, it absorbs far more sunlight than a light shade, and the overheating is amplified.
A piece of terracotta tile laid under a watermelon illustrates this phenomenon: by day, terracotta stores the heat of the sun and gradually releases it at night. On a mineral terrace in midsummer, that same storage capacity makes the ground warm, then scorching, until late. When you add a plastic artificial lawn and a charcoal-grey upholstered sofa, you obtain the perfect trio for an outdoor space that is unliveable.
Artificial turf and dark floors: two choices that push the thermometer up
Often chosen to avoid the chore of watering, the artificial turf remains one of the worst materials in bright sun. It is made from plastic fibers that heat up quickly and intensively. “This plastic material literally cooks in the sun,” says Curtis Atkinson, founder of Sunline Landscapes. Tests on synthetic lawns in summer have recorded surface temperatures between 55 and 70 °C, compared with about 30 to 35 °C for a natural lawn that is well watered.
A natural lawn or a planted area, on the other hand, cools the air: the water that evaporates from the leaves carries away heat. Dark surfaces further amplify the furnace. “When your garden and rear walls are in full sun all day, they simply absorb heat continuously,” explains Tony Reynolds of Supreme Merchants. A terrace with anthracite slabs can then exceed 50 to 60 °C, whereas paving in sand, beige or light gray remains much more bearable to walk barefoot.
Dark furniture, light colors and greenery: rebalancing the garden’s freshness
The third trap is dark and heavily cushioned furniture. A large anthracite-gray sofa full of cushions looks stylish, but the thick fabric and foam quickly accumulate heat and become scorching to the touch. Experts recommend choosing furniture that is both aesthetically pleasing and able to withstand heat waves, with lighter fabrics and frames that allow air to circulate.
To limit overheating, it is better to favor airy structures in light wood or slim metal, breathable fabrics such as Textilene, cotton or linen, and colors like ecru, sand or pastels that stay tepid. The same logic applies to the entire exterior: the more greenery, shade and light tones, the less surfaces radiate. A good test to perform around 8 p.m. during a heatwave: touch the ground, walls and seating; those that burn the most should be reconsidered first.
