Suffering from hot weather: Those who live under the rooftops, feel like baking in the oven
August of this year surpassed all previous records, to become the hottest August in the history. As temperatures rose, the World Green Organisation (WGO) recognised the exceptional and unprecedented nature of the phenomenon, taking the opportunity to conduct a survey, updating previous investigations which focused on household temperatures in old buildings. The study determined that in Hong Kong the highest rooftop surficial temperature, measured for an individual buildings, exceeded 70 degrees Celsius. While the underlying household’s temperature peaked at over 36.8 degrees Celsius.
When comparing empirical records of the outdoor temperatures against the indoor temperatures, a disparity of 4 degrees Celsius was discovered.
Thus it was determined that inhabitants of the tops floors were exposed, unnecessarily, to inhospitably high temperatures. In response to the above investigation, WGO has proposed a government scheme aimed at promoting healthy and environmentally sound strategies for combating excessive heating at the tops of old buildings. Simple, yet highly effective programs may include re-painting the roof surface or establishing rooftop gardens. Such implementations would ensure a lowering of the interior temperatures in top-floor apartments, as well as potentially promoting community spirit and adoption of sustainable lifestyles.
This August, the WGO conducted surveys in which 38 measurements were taken in structures spanning 7 districts dominated by old building designs. These included: Cheung Sha Wan, Mongkok, Yau Ma Tei, Shek Kip Mei, Sham Shui Po, Kwun Tong and Tusen Wan. The methodology for the investigation team comprised repeated visits to the rooftops and uppermost floors of the aged apartment blocks, during which time the temperatures of the roof and topmost floors were noted, and averaged across the area. Each time measured the rooftop floors’ temperature for at least 3 times. Based on the mean temperature deduced, they compared it with the top floors’ interior air temperature. The final calculations were determined through analysis of 570 records.
The findings of the study were quite alarming. On 26th August, at 12:55 noon, with the ‘Very Hot Weather Warning’ announced, by the Hong Kong Observatory, WGO’s investigation team arrived at the 5-storey flats under scrutiny, on Shanghai Street. They determined that the rooftop’s surficial temperature had reached 74.4 degrees Celsius – the highest temperature observed across all buildings examined. The mean temperature deduced for the rooftop surface was 70.33 degrees Celsius, whilst the air temperature atop the rooftop was 38.9 degree Celsius. Due the rooftop heat transfer effect, the air temperature of the topmost floor was 36.8 degrees Celsius. The investigators remarked that “When you were inside the flat, you could hardly breathe. It felt like baking in the oven.” While comparing the last floor’s temperature to the record of the Observatory’s Kings Park Meteorology Station at the same period – recorded as 32.4 degrees Celsius – the indoor temperature of the Shanghai St building was 4.4 degrees Celsius higher the temperature recorded by the Meteorology Station. [Table 1][Table 2]
Six family members live under the rooftop
The participant families, who lived under this baking rooftop, were subjected to these harsh temperatures throughout the summer, and had done for years. Mrs. Lee who lives at an old 6-storey building in Cheung Sha Wan, had six family members, including two grandchildren. They lived on the fifth floor – the top floor – of their building. The Lee family rented two subdivided flats, each of them being around 60 square foot, with a monthly rent of HK$2,500 per flat. Mrs. Lee said that as the Sun directly heated the rooftop, her family members experienced exceptionally high temperatures and, despite their residenctial footprint remaining small, the electricity fees raised around HK$1.4 per degree – approximately 27% higher than the market price. Therefore, the Lee family dared not turn on their air-conditioner despite to brutal heat of the summer. Not until mid-night, would they breakdown and turn on the air-conditioner. In addition, an electrical fan was purchased to help cool the apartment at night. In order to save on electricity, they had to switch off the air-conditioner as when dawn came. Mrs. Lee added that, her 15 months old granddaughter would be woken up by the heatwave. Moreover, the Lee family used the electric fan to substitute the air-conditioner, often relying on two electricity fans to help lower the indoor temperature, allowing Mrs. Lee’s exhausted husband, who had to night shifts, would be able to sleep soundly.
The Last floor of the old buildings is hotter than ever
Dr. William Yu, CEO of the World Green Organisation explains that rooftops exposed under the Sun, absorb heat throughout the morning, and subsequently release heat at dusk – explaining why the rooftops floors are hotter than ever. Compiling the problem of this absorption of incoming solar radiation, old buildings are densely built, and suffer from a lack of social amenities like greenery areas, such as parks, which otherwise may alleviate some of the heating effects. As a result, over-crowed districts are prone to the ‘Urban Heat Island Effect’, which intensifies hot weather. Dr. Yu expressed his concerns that, under the influence of climate change, the global temperature is rising, and will persist, unless serious actions are taken. Should this condition continue the lives of inhabitants, such as the Lees, of poorly designed buildings hang in the balance.
Dr. Yu said,
Many people had concerns that sub-divided flats were exposed to high temperatures. Our findings indicate the living conditions of residence of the top floors are also worrying. According to the investigation teams’ observations, if carpets or plants are applied to the rooftops, both may be effective in helping to lower the rooftop temperature. However, such methods can be quite expensive. In the old buildings, where central management is lacking, it is rather difficult to apply the measures which can alleviate temperature elevation. An alternative strategy for dealing with these issues is through coordinating and cooperating with different stakeholders, and to seek for the suitable partners to apply paint on the rooftops’ surfaces as an insulator.
Dr. Yu further said,
Another approach is is to leave the air-conditioners on all the time. However, this practice might lead to heavy electric expenses, and could easily result in underprivileged families being driven into poverty.
Dr. Yu suggests that the Hong Kong government can help to resolve the energy poverty problem via the Community Care Fund. With the support of various parties, WGO plans to supply hundreds of electrical appliances to reduce their energy bills.
Dr. Kirk Yip, a former president of Rotary Club, in Soho, Hong Kong, expressed his views on the matter. The Rotary Club of Soho Hong Kong cares for residents from all walks of life, paying particular attention to climatic change-related challenges faced by underprivileged residents. Dr Yip said that ‘The challenges presented by climate change should not be underestimated’. According to the latest monthly report issued by the National Oceanic and Atmospheric Administration (NOAA), this August was warmest August on the record at a global scale. The past summer also saw several ‘warmest’ records being set. Moreover, with reference to the Hong Kong Observatory, the general conditions in August 2014 were noted to have exceeded the usual conditions, due to prolonged spells of fine and sunny weather throughout the month. The monthly mean temperature of 29.0 degrees was 0.4 degree higher than the ‘normal’ mean of 28.6 degrees. Throughout the month, the ‘Very Hot Weather Warning’ was posted for 8 times. [Table 3]
http://www.weather.gov.hk/prtver/html/docs/wxinfo/pastwx/mws2014/mws201408c_uc.shtml
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