Passive cooling really does ease scary indoor heat
Passive cooling strategies can reduce the load on air conditioning by as much as 80 percent, report researchers.
In simulations using weather data from a 2021 severe heat wave, a combination of shading and natural ventilation kept apartment temperatures out of the danger zone during the entirety of the three-day event, even without air conditioning.
The findings could inform building codes to protect renters from the effects of severe heat. Cities could mandate that apartments have operable windows that can be safely left open overnight, as well as working shades.
“In the Pacific Northwest, where we get such cool night air, we have an amazing climate for passive cooling,” says Alexandra Rempel, a building scientist at the University of Oregon who led the study. “And we should take advantage of it.”
The findings appear in the journal Applied Energy.
In June 2021, an extreme heat wave roasted Oregon and Washington. Temperatures hit 116 degrees Fahrenheit in Portland and 111 degrees in Eugene, breaking previous records. The prolonged heat was deadly, and the impact was especially great on people living in apartments in dense urban areas.
Buildings in the Pacific Northwest, for example, are usually designed to keep heat in. Many homes don’t have air conditioning, given the typically mild summer weather, or only have window units.
While strategies like drawing the blinds and opening the windows are time-tested ways to cool down homes, there wasn’t much solid evidence showing whether they could make a meaningful difference in the face of triple-digit temperatures, Rempel says.
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 inside a hypothetical west-facing, two-bedroom apartment with different cooling strategies.
“Without any shades or ventilation, you’ll quickly be in danger zone,” says undergraduate student Jackson Danis, a coauthor of the study.
But even opening windows a little bit lessened the amount of time the apartment was dangerously hot. And strategically using a combination of passive cooling techniques could make the apartment surprisingly livable, even in the face of triple-digit outdoor temperatures.
Opening the windows made the biggest difference at night and in the early morning, when the outside air is the coolest, researchers found.
Meanwhile, using blinds or window shades helped the most during the late afternoon, when the sun was directly shining on the windows.
Thick outdoor shades were most effective, but standard indoor pull-down shades or blinds, which renters are more likely to have, still made a difference, especially if their edges were sealed with side tracks.
The impact was even greater with a fan in the window to help circulate air.
While the advice seems intuitive, “the magnitude of the improvement is something that we didn’t expect,” says Alan Rempel, an applied mathematician and a coauthor of the study.
Passive cooling strategies can be a lifeline for people without air conditioning. But even people with AC could use the techniques to lower their summer energy bills, adds Michael Fowler, a building scientist at the Seattle firm Mithun Inc. who co-directed the study.
Reducing air conditioning use relieves stress on the power grid, lowering the risk of power outages during heat waves. It’s good for the environment, too, Alexandra Rempel adds.
“It helps keep AC demand within the reach of renewable energy sources,” she says.
See more here: futurity.org
Header image: Caribbean Blinds
Editor’s note: Am I missing something here, or will having ‘thick outdoor shades’ make rooms darker, and require the lights to be switched on? That does not reduce the stress on the grid. If anything, it will increase it. Also, keeping demand ‘within the reach of renewable energy sources’ is a tacit admission ‘renewables’ cannot provide sufficient electricity for normal usage.
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Phil Inman
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I live in So Cal so hot is not unusual. I agree with the obvious findings that Opening windows, taking advantage of cool air to cool down house etc. is correct, cuz that is how I deal with heat. Doesn’t everybody know that?
But how about some numbers in the article? How hot was the inside of the apt if the windows weren’t opened? …if they were? and more.
Shocking to learn open windows and a fan would make a difference. Not! And that the reason anybody would make such dim witted observations is to save load on the renewable Grid. Nothing will save the renewable grid other than reduced population, a totally collapsed economy and government meddling.
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Hans
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Good advice, however, it does little for areas
which suffer high levels of humidity. You can
take the heat out of the country, but you can
not take the country out of the humidity.
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