Many residents in Singapore may find that their homes do not provide an effective refuge from rising temperatures. A research project led by the Singapore University of Technology and Design (SUTD) has revealed that nearly half of more than 400 Housing Board (HDB) flats visited were warmer than the outdoors.
Indoor Heat and Ventilation Challenges
The study, titled Climate Resilient Citizenry, mapped 416 HDB flats across 10 neighborhoods and surveyed more than 1,000 residents. Researchers found that poor or impeded airflow was a primary cause of elevated indoor temperatures.
Data based on the heat index—which combines humidity and air temperature—showed that around one-third of households were up to 2 deg C warmer than their immediate void decks. Approximately 10 per cent of homes were up to 5 deg C hotter.
In some extreme cases, the difference was more pronounced. Dr Harvey Neo, a professorial research fellow at SUTD’s Lee Kuan Yew Centre for Innovative Cities, noted one home where the heat index was 35.9 deg C while it was 31.1 deg C outdoors. In 1 per cent of homes, the gap was even wider, with one residence recording 36.2 deg C against an outdoor temperature of 27.8 deg C.
Close to 60 per cent of the visited households experienced lower airflow than the outdoors. Researchers attributed this to building arrangements, home layouts, closed windows and indoor clutter.
Dr Neo explained that “higher levels of indoor clutter and keeping windows closed for long periods were associated with warmer homes and poorer ventilation.” He added that when airflow pathways are blocked, heat accumulates and is slow to dissipate.
Other contributing factors include heat emitted by cooktops and refrigerators, as well as concrete floors and walls that release stored heat hours after outdoor temperatures peak.
The Human Cost of Heat Normalization
The report indicates that seniors, low-income families, and those in rental units or smaller homes are the most vulnerable. These groups often have less access to air-conditioning and other cooling options.
A concerning trend identified in the surveys is the “normalisation of heat in everyday life,” where residents view extreme heat as a condition to be lived with rather than a problem to be solved.
Dr Samuel Chng, head of the Urban Psychology Lab at SUTD, warned that this mindset could be dangerous. He noted that residents often only respond during temperature spikes, potentially ignoring the effects of cumulative stress, health impacts, and sleep disruption.
Seniors are particularly at risk. Associate Professor Jason Lee of NUS Medicine explained that because many older adults grew up without air-conditioning, their baseline expectations of comfort differ.
Prof Lee noted that the body’s ability to regulate temperature is compromised with age, meaning seniors may not notice heat stress clearly and could delay necessary cooling measures.
Coping Mechanisms and Financial Barriers
Electric fans remain the most common cooling tool, used by around 76 per cent of respondents. Other common methods include adjusting attire and opening windows.
While more than half of the surveyed residents use air-conditioning at bedtime, only around 14 per cent use it regularly during the day.
The study also tracked the use of $300 climate vouchers provided to households in 2024 for energy-efficient appliances. Between April and October 2024, about 60 per cent of surveyed homes had not used their vouchers, despite being aware of the scheme.
Another 18 per cent had partly used them, and 18 per cent had fully claimed them. The most popular purchases were LED lights, washing machines, and energy-efficient fans.
The report suggested that the voucher amount may be insufficient to cover the high upfront costs of purchasing and installing air-conditioning units. Future policies may need to consider top-ups or more co-funding for effective cooling solutions.
Future Interventions and Infrastructure
The multi-institute team, which includes the Singapore-ETH Centre, Singapore Management University, and NUS Medicine, is now planning to trial indoor cooling solutions.
Possible next steps include the development of a renovation guide to prevent stuffy homes and a cooling toolkit for residents. Dr Zheng Kai from SUTD is also exploring modelling tools to support interior designers and housing planners virtually test ventilation improvements.
Dr Zheng noted that real-world factors—such as safety concerns, insects, rain, and air quality—often prevent residents from keeping windows fully open, contrary to what standard simulation guidelines assume.
Professor Petra Tschakert from the NUS geography department emphasized that infrastructure and housing design are more impactful than individual action. She suggested that housing retrofits in older flats could improve natural ventilation and comfort.
a project called Staying Cool may focus on specific interventions for rental unit residents and other vulnerable groups. Authorities have already begun analyzing wind flow in the planning of the Jurong Lake District to improve airflow in newer estates.
Frequently Asked Questions
What factors contribute to homes being warmer than the outdoors?
Heat accumulation is driven by poor airflow caused by indoor clutter, building arrangements, home layouts, and keeping windows closed. Concrete walls and floors release stored heat, and appliances like cooktops and refrigerators emit heat.
Why are seniors more vulnerable to indoor heat?
Seniors may have different baseline expectations of comfort because they grew up without air-conditioning. The body’s ability to regulate temperature decreases with age, which may lead them to notice heat stress less clearly and avoid cooling measures.
What happened to the $300 climate vouchers issued in 2024?
Between April and October 2024, about 60 per cent of surveyed homes had not used the vouchers. 18 per cent used them partially and 18 per cent used them fully. The vouchers expire at the finish of 2027.
Do you think housing design or individual habits play a larger role in managing urban heat?
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