Night Work on Construction Sites - Can It Solve the Daytime Heat Problem in Malaysia?

In June 2025, western Europe as a whole saw its warmest June on record, with an average temperature of 20.49°C, surpassing the previous record for the month from 2003 by only 0.06°C. Two major heatwaves led to ‘very strong heat stress’ in large parts of western and southern Europe, with ‘extreme heat stress’ and feels-like temperatures reaching 48°C in parts of Portugal. Spain experienced its warmest June in 64 years while England reported the highest temperatures for June since data records began in 1884.

Outside of Europe, warmer-than-average temperatures were observed in a large part of the United States, northern Canada and central Asia, while record-breaking warmth was reported in Japan, some regions of China and many Korean cities (Copernicus). Climate Impacts Tracker Asia reports that Indonesia and the Philippines began registering extended and unusual heat as early as December 2024, a trend that has continued into 2025. The same report also identified Myanmar, Thailand and Vietnam as experiencing mild to very dangerous heatwave conditions, in which humidity levels higher than 80% would make temperatures in the 40s feel as hot as 52°C. 

Predictably, India and Pakistan top the charts for temperature extremes, with temperatures reaching up to 8°C above seasonal norms as early as April this year. This brought power outages, stress on the health system and triggered deadly thunderstorms. Some climate experts note that, by 2050, India will be among the first places where temperatures will cross survivability limits. In fact, experts cited by Vox were quoted as saying that South Asia should brace for earlier, longer-lasting and hotter heatwaves going forward. But scientists also warn that the same patterns observed in the Southern Asian region are also starting to affect countries like Indonesia, Malaysia, Thailand and Vietnam, with profound implications for outdoor work, notably in the building construction industry.

One common strategy to avoid outdoor work during the most thermally hazardous times of the day is to work at night. In fact, most large airports and maritime ports operate 24 hours a day, seven days a week, though not all facilities or services will be open and available at all times. However, a primary consideration of night-work in particular, is the impact of construction and vehicular noise, as well as light pollution and vibration on the surrounding communities and ecosystems. Airports and Maritime ports, while known for operating at high decibel levels, are usually situated away from densely inhabited areas, and so have limited impact on surrounding communities. 

Within city limits, however, noise generating activities such as construction are strictly limited and regulated. The Guidelines for work hours on construction sites, issued by the Kuala Lumpur City Hall (DBKL) stipulate normal working hours as 7am until 5pm.

In this context, a 12-hour workday spanning 7am until 7pm is permitted on weekdays and Saturdays, with the additional two hours from 5pm until 7pm being in lieu of delays due to traffic jams that might obstruct and delay vehicles transporting building materials to the site. However, the same guidelines state that under special circumstances, construction projects may apply for approval to operate outside normal work hours, either extending the workday until 10pm, or so-called ‘critical work’ on a continuous (24 hour) basis. Approval is subject to proper management of noise and other potential disturbances and disruptions. No work is permitted on Sundays and public holidays. 

But do these regulations actually resolve the problem of high daytime temperatures? A 2020 study by Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia on the Urban Heat Island (UHI) effect measured insolation (solar radiation), wind, temperature and humidity at seven locations around Kuala Lumpur and found that at street level, the combined effect of building and tree shading actually imparted an urban cooling effect during the daytime hours. The temperature trace below (beginning at midnight and tracking temperature over 48 hours), adapted from Zambri et al. 2020, Urban heat island in the modern tropical Kuala Lumpur: Comparative weight of the different parameters, compared temperatures at six built up locations in Kuala Lumpur with the temperature on the grounds of the parliament (denoted as Parl in the legend), representing an undeveloped green space.

In effect, the UHI effect was most pronounced from sunset to dawn, during which built-up areas retained heat, and were approximately 3°C warmer than undeveloped green space, which cooled rapidly even before sunset. Clearly, the warmest part of the day is between 11am and 7pm, while temperatures are lowest between midnight and dawn, reaching a minimum of 29°C for the built up areas between 5am and 7am. Interestingly, note that without the UHI effect, temperatures begin decreasing at 3pm, dip below 29°C as early as 8pm, and reach a minimum of 26°C just before sunrise.

But importantly, the graph shows that, because of the UHI effect, working until 10pm, while sparing workers from the highest mid-day temperatures (ca. 34°C to 36°C) still exposes workers to temperatures of 32°C and higher. To take advantage of the lowest temperatures, work would need to be approved between midnight and dawn, which, while currently permitted under the regulations, needs to be justified as ‘critical work’ though justification criteria are not specified, and fulfil all noise management, lighting, safety and local community engagement requirements. But as daytime temperatures climb globally, we will need to balance worker safety with other environmental considerations.