Two young inventors from Zurich have developed a 3D-printed terracotta brick called bloc°, designed to cool urban areas using evaporative cooling. The prototype uses water, sunlight, and clay to reduce the air temperature by up to 9 °C, according to the designers. The innovation was presented at the James Dyson Award 2025 and aims to provide relief in public spaces that become excessively hot during heatwaves, such as bus shelters and schoolyards. The bloc° brick works by using evaporative cooling, a process similar to how human sweat cools the body. The porous terracotta material absorbs water, and as hot air passes through the brick, some of the water evaporates, drawing heat from the air in the process. This method is not new—similar principles have been used in ancient structures like Persian wind towers and in the natural cooling systems of termite mounds. However, the use of 3D printing allows the creation of internal chambers that increase the surface area for water and air interaction, making the cooling process more efficient. The system is powered by solar panels, which run small fans and a pump to maintain the brick's humidity level. However, the device requires a significant amount of water—about 56 liters per day when temperatures exceed 30 °C. A funnel-shaped roof collects rainwater, providing around 24 liters per day, but additional water from the municipal supply might be necessary during dry periods. This raises concerns about water usage in areas where water scarcity is a challenge. The bloc° bricks are designed to be modular, allowing them to be stacked and assembled into various structures like benches, bus shelter backrests, and low walls. However, the inventors have not yet tested the device in real-world conditions, and the 9 °C cooling claim has not been independently verified. Additionally, the efficiency of evaporative cooling drops in high humidity environments, and the designers have not disclosed details on manufacturing costs or the durability of the bricks.