How to cool your house during a heat wave

Sizzling heat wave causes misery in Europe A heat wave broke temperature records in the U.K., sparked wildfires in France and Spain, and may have caused a glacier in Italy to crack.

Millions of Canadians are grappling with high temperatures reaching the high 30s and humidex values possibly hitting 40 or higher.

Staying cool can be a challenge, especially for seniors or those working from home who do not have an air conditioner or convenient access to public spaces like libraries and shopping malls. The heat wave sweeping across many parts of Europe has already killed more than a thousand people,  while last year’s record-breaking temperatures in B.C. are believed to have killed nearly 600 people, with the majority of deaths among those aged 70 and older.

Data from Statistics Canada published in October 2021 show that 61 per cent of Canadian households have some type of air conditioning unit and just 42 per cent have central A/C. While many Ontarians have A/C, data indicates that in Quebec, only 59 per cent have some type of A/C and just 27 per cent have central A/C.

CTVNews.ca spoke with Jennifer McArthur, an associate professor in architectural science at the Toronto Metropolitan University, for advice on immediate and long term solutions on keeping your home cool.

IMMEDIATE SOLUTIONS

Close your blinds and curtains. According to the U.S. Department of Energy, roughly 76 per cent of the sunlight that comes through standard windows turns into heat. This can be helpful in the winter, but in the summer, window coverings keep the heat out, especially in rooms that face the sun. Light coloured blinds and curtains in particular will help deflect more heat.

“Blinds will actually trap the heat between them and the window, so you want to pull the blinds down basically in the morning and keep them down all day,” said McArthur, who is also an Ontario Regional Advisory Board member of the Canada Green Building Council and a certified energy manager.

“You don’t want to be having them up and down because it does release some of the heat into the house. But if you have the ability to shade the window from outside, that will be 100 times more effective, because then the sunlight doesn’t even get into your house in the first place.”

You can open your windows if the temperature outside drops below 22 or 23 C and it is not overly humid.

If it cools down at night, have all the windows open, run your fans, bathroom and kitchen exhaust fans to try and drive as much fresh air through the house as possible. It also helps limit the pollutants that build up inside your home and keeps you healthier.

“You’re basically trying to purge all the heat that’s built up in the house out at night time. And then as soon as the temperatures start to increase, or as soon as it gets humid, you want to crank it shut because your body feels a lot hotter at say 23 degrees and humid than at 23 degrees and dry.”

How to use fans effectively. If you have a ceiling fan, make sure they are rotating in the right direction. In the winter, blowing up can help push the heat from the top of the room downwards. In the summer, it should be blowing down or rotating counter clockwise when you look up. You should be able to feel the fan when you stand under it, McArthur said.

If you do have A/C, using fans along with the air conditioner can also help reduce your energy bill, according to Natural Resources Canada.

McArthur recommends drinking hot liquids rather than cold ones and taking hot showers rather than cold ones to help maximize the effectiveness of the fan.

“This is going to sound really, really counterproductive, but the best way to cool yourself down is to sweat,” she said.

“What that does is it actually brings all of the blood flowing closer to the surface of your skin and it makes it easier for your body to actually reject that heat with the breeze.”

While bathroom and kitchen exhaust fans can help draw out air, don’t run them 24/7, especially on hot days. Instead, run them at night when the air is cooler, or after a rainfall when the air has temporarily cooled down.

“Nature abhors a vacuum, so any air that you push out of the house is going to be replaced with air from the outside, so if you don’t want that air coming into your house, don’t run those fans unless obviously you’re cooking or you need to,” McArthur said.

Some hacks have suggested placing a bowl of ice in front of a fan as another way to create cool air. Unless you picked up the ice from a gas station or grocery store, however, McArthur noted that the heat from making the ice cubes is released into the house out of the back of the fridge, which may ultimately be counterproductive.

A cold wet bed sheet. You can also drape a wet bed sheet or other light cotton fabric over a pop-up tent or a clothes drying rack. The evaporative cooling can really help cool you down, says McArthur, especially if it’s in front of a fan. It’s not something you want to do for too long, however, because the trade-off for the immediate heat relief is that it will add a bit of humidity to the air and could make your home feel a little muggy after, she cautioned.

Minimize the use of large appliances during the day. If you can, skip the stove and oven, and fire up the barbeque instead. Or if you are able, close off the kitchen while you are cooking and run the stove exhaust to get the heat out of the house. Microwaves, for those who use them, are another method that does not generate as much heat. Insulated electric kettles are faster and more efficient than boiling a pot on the stove as well. This is also the best time of year to skip the clothes dryer, which uses a lot of energy, and hang your clothes outside instead.

Using heavy duty gaming computers can also heat up a room.

“But that kind of escapism might also be better for your mental health to cope with the heat, so it’s really up to everyone to kind of decide on those trade-offs,” McArthur said.

LONG-TERM INVESTMENTS

Switch out your incandescent and halogen lights. If you haven’t already, change your old light bulbs to LEDs. Not only do LEDs last years longer, use dramatically less energy, they also do not generate enormous amounts of heat the way halogens and incandescent lights do.

Block the sun from the outside. As mentioned earlier, covering the windows from the outside is more effective than closing your curtains or blinds. Awnings and shutters, for example, can help keep out the sunlight. According to the U.S. Department of Energy, awnings over the window can reduce solar heat by as much as 65 per cent on windows that face south and as much as 77 per cent on windows facing west.

But the best long-term solution is actually using nature, says McArthur.

“The gold standard for passive design is actually to have deciduous trees outside so that they don’t block the sun in the wintertime and they do block the sun in the summertime,” she said.

“They also add local cooling because the trees actually evaporate a lot of water into the air, and that process actually cools the air around them. So trees are actually actively cooling.”

An example would be walking into a forest from a field on a hot day – the temperature difference is not just from the shading, McArthur explained. In addition to deciduous trees, hedges, climbing plants onto a trellis can all help. She cautions using ivy, however, which can cause structural damage to bricks, and recommends talking to a botanist for advice.

Install weather stripping and reseal your windows. This is a “no brainer” that will pay for itself year round, says McArthur, because it will stop the cold air from entering your home in the winter and hot air from coming in during the summer. Door sweeps can also help keep cool air in.

Updating your windows. If you are planning on replacing your aging, leaky windows, consider getting them with a special coating or tinted. Even a slightly tinted window will dramatically decrease the amount of heat that comes through without impacting the ability to see through them, McArthur said.

Updating your roof. If you are planning to reshingle your roof, choose a light colour. A silvery gray shingle will reflect a lot more heat and light than one that is black. You can ask about the shingle’s surface reflectance index, which indicates how hot they will get under the sun. Installing solar panels is another way of using the sunlight, but also reducing the amount of heat that is absorbed through the roof itself.

Consider installing an energy recovery ventilator. These systems help replace stale indoor air with fresh outdoor air, getting rid of pollutants. It transfers the heat from one air stream to another, McArthur explained, so in the summer, the air exchange results in the hot air from the outside losing heat to the stale but cooler indoor air. If you do have an A/C, the system also reduces the amount energy your A/C has to expend to cool your house.

Check your insulation. The easiest way to check if you have enough insulation is to look at your roof from the street in the winter. If there are patches of snow that have melted or if you have less snow and ice than your neighbours, then you may have an insulation problem. You can also hire someone to conduct an energy audit.

“But above a certain point it just gets overkill and it’s not really all that helpful,” McArthur said, adding that some types of insulation take a lot of energy to make and are worse for the environment.