Humidity makes a sweltering apartment that much harder to live in

On a hot summer day, the air in Sridharan Vankeepuram's room can be nearly unbearable.

"It feels like a furnace inside," he said.

His small bedroom crammed with a single bed and a desktop computer doesn't get much cooler at night, especially when it's humid, as is often the case during a Montreal heat wave.

"It becomes really uncomfortable. When you close your eyes, you just start sweating."

Vankeepuram has spent the past two years in an aging brick building on the western edge of Montreal's downtown, while completing his MBA at Concordia University. The three-storey walkup faces the old Montreal Forum, which reflects the sun back through his window.

A few sparse trees along the block do little to counter the sun, and he has only a small oscillating fan to keep cool.

One day in July, Vankeepuram's room felt like it was 39 Cwhen taking the humidity into account,the highest heat index of any home measured as part of CBC's country-wide urban heat project.

(For this project, CBCusedheat indexto measure the combination of air temperature and humidity, rather than the humidex, a similar index developed in Canada.)

Hot and humid

To better understand the challenges of living in extreme heat as the climate changes,this summerCBC News installed sensors in 50 homes that were either wholly or partly without air conditioningacross five Canadian cities, including Montreal.

The sensors took temperature and humidity readings every 10 minutes. In some places, particularly in apartments in Toronto, Windsor and Montreal, the humidity made the residences feel much hotter.Winnipeg and Vancouver, which tend to have drier heat, were the other two cities featured in the project.

For half of the 56 days measured, Vankeepuram's room didn't drop below 26 C,the threshold considered dangerous for seniors and those with pre-existing conditions if they are exposed to it for a prolonged period.

And Vankeepuram's room consistently felt even warmer because of the humidity.

Knowing he would move out after graduating,Vankeepuramdidn't invest in an air conditioner. On the worst days, he took multiple showersor brought a bucket of ice water into his room.

For others, the consequences can be more dire. Humans cool down by sweating, but when the air is saturated with moisture, that doesn't work as well.

"The more humid it is in the air, the harder it is for that process to occur," said Prof. Daniel Gagnon, a researcher at the Montreal Heart Institute. "We might still produce sweat, but instead of it evaporating, it will drip off onto the floor and then we lose all of its cooling power."

Gagnon, an associate professor at the school of kinesiology and exercise science atUniversit de Montral, reviewed CBC's data and found it striking that although Montreal escaped this summer's record-breaking heat, the temperatures inside often felt like more than 30 C with the humidity factored in.

"It really emphasizes that maybe we should not only focus on outdoor temperatures, but we need to start thinking of indoor temperatures, especially knowing that most heat-related mortality occurs in homes," Gagnon said.

Research isn't conclusive on whether humidity increases the likelihood of mortalityin cases of extreme heat, but it nevertheless puts strain on the body.

During a historic 2018 heat wave, 66 people died in Montreal and 80 per cent of those people died in their homes.

"We need to factor in humidity as wellbecause a given temperature might be comfortable if it's very dry, but become very uncomfortable if it's very humid, and the body's response to those environments will also be different," Gagnon said.

'I worry about her getting heat stroke'

Another participant in the project, Bernadette Mamo, shares an apartment with her son and 86-year-old mother in Scarborough, Ont., a Toronto suburb.

Mamo had an air conditioner but it kept shorting out, so she gave up. She relies instead on fans to keep cool.

"It's difficult," she said, especially for her mother. "I worry about her getting heat stroke even though she's not outside."

Gregory Walton, a 51-year-old who lives in an apartment in Windsor, Ont., said the nights are especially difficult. With walls made of plaster and a ceiling of cinder blocks, the conditions are ripe for heat retention.

In his apartment, the temperature almost never dropped below 26C during the period CBC monitoredand, with the humidity, it felt like nearly 32 C on one particularly muggy day.

In a video diary Walton shared with CBC, he said he took a shower, dried off, then immediately started sweating.

"It is sweltering in here," he said.

Overall, in Montreal, Toronto and Windsor, high rates of relative humidity sometimes added as much as five to sevendegrees tohow hot a residence felt.

Here are the highest heat index measures our sensors recorded, by city:

• Windsor: 39.
• Montreal: 39.
• Toronto: 38.
• Winnipeg: 37.
• Vancouver: 34.

AC and beyond

Climate scientists say hotter, more humid summers are likely in the coming years, as the planet warms due largely to the burning of fossil fuels.

According to Environment and Climate Change Canada, a humidex in the mid- to high-30s is when the average healthy person should be more careful. Over 40 is considered extremely high and all unnecessary physical activity should be avoided.

The federal government's $2-billion climate change adaptation plan includes measures aimed at countering extreme heat such as funding for tree canopy projects and improved heat response plans to make sure vulnerable populations get the care they need.

Dr. David Kaiser, associate medical director at Montreal Public Health, said his own city's response has improved in recent years, but he said more remains to be done especially in helping those most at risk.

WATCH | How extreme heat affects the body:

How extreme heat affects your body

10 months ago

Duration 1:28

CBCs senior health and medical reporter Lauren Pelley ran for 20 minutes in a heat chamber set at 40 C while researchers measured the strain that the heat put on her heart, weight and core and skin temperatures. This is what the results showed.

Over the long term, Kaiser said better urban planning and changes to housing will help bring down the heat and humidity indoors.

In the more immediate term, Kaiser said the most at-risk would benefit from having an air conditioner. British Columbia recently announced a $10-million program for free air conditionersfor those most vulnerable to the heat.

"I think it's important from a health perspective, that if you have an air conditioner at home and it works, you're not going to die in a heat wave," Kaiser said.