Update, July 2017: After two summers of experimentation, I firmly believe in closing windows and blinds to keep the house cool when it’s hot outside. But many people will resist. You can’t tolerate closed windows and blinds when it’s a nice sunny day. There’s evidence of this when I ride the bus. The bus is air conditioned but people insist on opening the windows which actually makes the bus warmer. But I admit that it is a pleasure to experience a breeze on a sunny day, even when that breeze is warm.
The original post: This assumes that you want to keep your home as cool as possible in hot weather without resorting to air conditioning. I checked * a few dozen internet listings for positions on whether to open or close windows to get to a cooler house in hot weather. There were many entries to choose from; Lots of people have thought about it. The consensus is, it depends.
Generally, if your home is properly insulated, keep the windows and blinds closed when the sun is shining. Open the windows in the evening and at night. Keep the windows closed when the outside temperature is hotter than inside and open the windows when it is cooler outside than inside.
This will not work if your home is not well insulated and has been illustrated for me in a home in my past. We had a self-contained garage that wasn’t insulated and it got pretty hot in the summer with the doors and windows closed. Our house next door didn’t get nearly as hot.
Chad Skelton of the Vancouver Sun wrote my favorite open-close article. He bothered to use a thermometer and confirmed that it is indeed a good idea to keep windows and blinds closed on a hot day. But there is more to it than that. Here is an excerpt from his blog published in July 2012:
“However, it is important to differentiate between how hot the air feels and how hot the air actually is.
“If you open the window on a warm, windy day you may feel like you are cooling down your house, but it is an illusion. While the breeze feels nice, you are actually letting in much hotter air into your home.
“I think the better strategy is to keep the windows closed to trap the cool air and then, if necessary, use a fan to move the air and feel cooler.”
Chad Skelton’s article is here.
On the southern island of Vancouver, it almost always cools down at night. That’s not the case on the prairies, at least not when I lived there. It often stayed miserably hot all night. Same experience visiting relatives in Ontario.
We can take advantage of the island’s cool night air. Speed up the cooling of your home by blowing in the cooler air from a fan. I’ve tried and it works. I put a fan on the deck and it blows cool air through the patio umbrella.
Open windows can, of course, pose safety concerns. You need to assess which windows are safe to open in the evenings and at night, if at all.
Despite the logic, there are reasons to refuse the wisdom of closing windows and blinds during the day:
The cat likes to laze around in the sunshine.
The cat likes it when the windows are open.
Having a darkened house depresses you.
You have to see what’s going on outside.
You have a great view that you paid a lot of money for.
You long for a breeze in the open air; The artificial breeze from a fan is not good enough.
It’s summer you want to hug the warmth.
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Your basic, cool arsenal will need an indoor thermometer, a shaded outdoor thermometer, and a fan. Plus the discipline of keeping the windows and blinds closed, even if it makes your house feel like a dungeon. Check out the links below for more cooling suggestions, such as awnings, overhangs, lots of insulation, and strategically placed vegetation.
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* Academics are constantly writing articles based on literature research on a topic. They do minimal or no original research. Instead, they review the research that has already been done and then offer their conclusions. That’s how I do it here, but with far less accuracy than an academic journal could ask for. For example, a diary could look askew about how I found my literature. I have entered variations of the phrase “windows closed or open in hot weather” in the DuckDuckGo and Google search engines.
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Articles I noticed:
A discussion on reddit.com: Is it better to open or close windows on a hot day?
StarTribune.com: Summer comfort is an open and closed case
Fixit’s columnist answers this question: if a house is not air-conditioned, is it better to keep the windows open or closed? A friend said it was best to keep the windows closed to keep the heat out. I think the opposite. The windows should be open to allow the house to cool down. Which is correct?
Chad Skelton’s Curious Dad Blog: Should You Keep Your Windows Open or Closed on a Hot Day?
BC Hydro: Power Smart Tips to Help You Stay Cool and Save
An in-depth discussion at answers.yahoo.com where some people prefer to keep the windows open during the day.
theconversation.com: How to Keep Your Home Cool During a Heatwave
BuildingGreen.com: Simple Strategies to Stay Cool
University of Nebraska Extension: Staying Cool This Summer
Could traditional architecture provide relief from the rising temperatures in the Gulf?
ibpsa.org (PDF): A preliminary model of user behavior in relation to the manual control of windows in office buildings
Among the observations: people open more windows on summer days than in winter; Windows opening and closing usually occurs when a person arrives.
Warm House Cool House, a book summary
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You can find more of my contributions here.
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