The joint study by the Concerning Subdivided Units Alliance and CarbonCare InnoLab surveyed 78 households in inadequate housing and tracked temperatures inside their units for three straight weeks between late June and early July.
During the period, the maximum indoor temperature of a unit reached 44.4 degrees and the maximum “feels-like” temperature soared to 52 degrees during the day and remained as high as 51 degrees at night.
The survey also found that 74 percent of respondents experienced symptoms of heat exhaustion, while 70 percent reported poor sleep quality due to the hot conditions at night.
One man, in his 70s, lives with his wife in an 80-square-foot subdivided unit in Kwai Chung.
He said due to the intense heat, his wife suffered from dizziness, breathing difficulties, and chest tightness.
A woman and her family of three lives in a similarly sized unit and pays HK$4,000 a month in rent — roughly one-third of their total income.
To escape the suffocating conditions, she and her child spend almost their entire day at a local community living room.
“It’s summer break now and I’m taking care of my child full-time,” she said.
“The community living room is open from 11am to 10pm, so we head over as soon as it opens and only return home when it closes.”
“At home, we only run the air conditioner from 10pm until around 2am or 3am, turning it off once the room cools down.
Running it for just five to six hours a day adds around HK$400 a month to our electricity bill,” she added.
Ho Wai-fun, a policy analyst at CarbonCare InnoLab, noted that many households simply cannot afford to run air conditioning for a long time due to financial constraints, while poor ventilation worsens the problem.
“Most of the people we interviewed live in standard subdivided flats, which are generally quite cramped. Some have windows that cannot be opened. As a result, indoor temperatures consistently remained above the Observatory’s ‘warm night’ threshold of 28 degrees. Average night-time temperatures in these units reached 29.4 degrees,” she said.
Senior programme manager at CarbonCare InnoLab, Kwok Hiu-chung, urged authorities to incorporate “indoor high temperature” and “night-time heat risk” into the city’s soon-to-be-revised climate action plan — alongside long-term temperature monitoring in subdivided flats to issue timely warnings.
He added the government should mandate heat insulation and shading as minimum standards for “basic housing units”, while providing targeted energy subsidies during the summer months.