Grand Designs presenter Kevin McCloud has shared a "simpler" and "much cheaper" alternative to air conditioning for keeping homes cool during UK heatwaves. In an Instagram post, he explained how water evaporation can act as "nature's air conditioning."
How water evaporation cools the air
McCloud demonstrated the principle using a modern house with a pond. He said: "This is a modern house... there are some very simple principles at work here. One of which is that it has skylights and it has windows on the far side of the building. And it has, most importantly of all, something we can all put in - a pond."
He described the process: "In the summer, the building gets shut up, on the far side, a window is opened, or the skylight is opened, warm air rises, and it sucks in cool air... the cool air coming into the building is sucked across the pond, it picks up moisture, it hydrates, and in so doing, it's picking up the moisture, turning the water into water vapour."
McCloud explained that the phase change from liquid to gas requires energy, which cools the air. "That water vapour through that phase change of liquid to gas requires energy. So what it does, when it turns into water vapour, is cool the air. Now that air coming into the building is already several degrees cooler than it otherwise would be. It's also hydrated, which means when the air touches your skin... that small amount of moisture in the air evaporates off your skin and for a second time, it cools you."
Simple alternatives for any home
McCloud noted that building a pond is not the only option. He suggested that putting a pot of water on a balcony or wetting stone steps can also allow water to evaporate and be carried into buildings as cooler, moist air. "It's brilliant, I don't know how to stop talking about it," he joked.
