![\"\"](\"https:\/\/images.newscientist.com\/wp-content\/uploads\/2024\/08\/09121439\/SEI_216519527.jpg\")
<\/div>A building\u2019s design can influence its temperature<\/p>\n
Alistair Scott\/Getty Images<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n
Walls with a protruding zigzag pattern could stay up to 3\u00b0C (5.4\u00b0F) cooler than regular walls, without using any energy. This approach could reduce the energy used by cooling systems and thus help limit global warming<\/a>.<\/p>\n \u201cWith this kind of design, we can have a cooler building,\u201d says Qilong Cheng at Columbia University in New York. \u201cSo we can cut down energy consumption for cooling.\u201d<\/p>\n The use of air conditioning is surging as the world heats up and the number of people who can afford it increases. Greenhouse gas emissions from cooling could more than triple<\/a> by 2050. As a result, many teams are trying to develop passive cooling solutions that don\u2019t require any energy.<\/p>\n For instance, simply making roofs white<\/a> so they reflect more sunlight<\/a> can keep buildings and cities cooler.<\/p>\n This approach is even more effective if roofs are coated with materials that reflect most sunlight but emit infrared radiation within the atmospheric transparency window<\/a>. This is the range of wavelengths that isn\u2019t absorbed by molecules in the atmosphere such as carbon dioxide.<\/p>\n \u201cInfrared radiation within this band can pass through the atmosphere and reach outer space,\u201d says Cheng.<\/p>\n <\/p>\n While materials with these properties have a significant cooling effect on roofs facing upwards, they aren\u2019t as effective on walls. The issue is that materials that are good at emitting infrared are also good at absorbing it, and surfaces near walls, such as concrete pavements, can radiate lots of infrared.<\/p>\n Cheng and his team\u2019s solution is to have walls with a series of protrusions running parallel to the ground with a zigzag shape when viewed from the side. To visualise this, imagine a flight of stairs tilted up from a 45 to a 90 degree angle.<\/p>\n Crucially, the upwards-facing zigs \u2013\u00a0the treads in the staircase analogy \u2013 have a surface that emits lots of heat in the atmospheric transparency window, while the downwards-and-outwards facing zags \u2013 the risers \u2013 have a surface that reflects infrared heat rather than absorbing it.<\/p>\n To test the idea, the team built a 1-metre-high model with both zigzag and flat surfaces. When put outside in New Jersey during the summer, the zigzag surface was 2\u00b0C cooler, on average, over 24 hours than the flat surface, and 3\u00b0C cooler between 1pm and 2pm.<\/p>\n There are a number of cheap materials available with the necessary properties, says Cheng. Existing buildings could be retrofitted by adding corrugated panels. The interior cooling effect will vary depending on other factors, such as the size of the building\u2019s windows, but simulations suggest it could be up to 2\u00b0C, reducing the energy needed for cooling by up to a quarter.<\/p>\n The zigzag cooling walls would only be suitable for hotter climes as they would increase the need for heating in winter in colder regions. But Cheng and his colleagues have also proposed a design with hinged \u201cfins\u201d<\/a> that can be raised in winter to increase heat absorption and lowered in summer to minimise this.<\/p>\n Topics:<\/p>\n<\/section><\/div>\n