Opening windows at night, using shades can keep buildings cool during heatwaves: Study

According to a study in the US, opening the windows at night and pulling down the curtains during the sunniest part of the afternoon can prevent homes from becoming dangerously hot during extreme heat waves. Researchers at the University of Oregon in the US used simulations using weather data from a severe heat wave in 2021, especially in the Pacific Northwest. They found that a combination of shading and natural ventilation kept the temperature in the apartments out of harm’s way for the entire three-day event, even without air conditioning. It also reduced the load on the air conditioning to 80 percent.

The findings, published in the journal Applied Energy, may inform building codes to protect tenants from the effects of severe heat. Cities could require apartments to have operable windows that can be safely left open at night, as well as working shadows, the researchers said. “In the Pacific Northwest, where we get such cool night air, we have a great climate for passive cooling,” said Alexandra Rempel, a construction scientist at the University of Oregon who led the study. “And we should take advantage of that,” Rempel said.

In June 2021, an extreme heat wave devastated Oregon and Washington. Temperatures reached 46.7 degrees Celsius in Portland and 143.9 degrees in Eugene, breaking previous records. The prolonged heat was deadly, and the impact was especially large for people living in apartments in densely populated urban areas, the researchers said. Such extreme heat events are only expected to become more common thanks to climate change, they said. Buildings in the Pacific Northwest, however, are usually designed to keep the heat in. Many homes do not have air conditioning, given the typically mild summer weather, or have only window units. While strategies like drawing the blinds and opening the windows are tried and true ways to cool homes, there wasn’t much solid evidence showing whether they could make a meaningful difference in the face of triple-digit temperatures, Rempel said.

Armed with weather data collected from cities like Eugene, Portland and Seattle during the 2021 heat wave, the researchers used a computer program to simulate conditions in a hypothetical two-bedroom west-facing apartment with different cooling strategies. “Without shadows or ventilation, you’ll soon be in danger,” said student Jackson Danis, a co-author of the study. say researchers. Strategically using a combination of passive cooling techniques could make the apartment surprisingly livable even in three-digit outdoor temperatures, they said.

Opening the windows made the biggest difference at night and in the early morning, when the outside air is coolest, researchers found. Meanwhile, using blinds or blinds helped the most during the late afternoon, when the sun was shining directly on the windows, they said. Thick exterior blinds were most effective, but standard indoor flip-up blinds or blinds, which renters tend to have, still made a difference, especially if their edges were sealed with side rails.

According to the study, the impact was even greater with a fan in the window to help circulate the air. While the advice may seem intuitive, “the magnitude of the improvement is something we didn’t expect,” said Alan Rempel, an applied mathematician. and a co-author of the study.

Passive cooling strategies could be a lifeline for those without air conditioning, the researchers said. But even air-conditioned people could use the techniques to lower their energy bills in the summer, added Michael Fowler, a construction scientist with the firm Mithun Inc. in Seattle, please. – led the study.

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