Tomoko Uno

Field Survey of Air Conditioner Temperature Settings in Hot, Humid Climates, Part 1: Questionnaire Results on Use of Air Conditioners in Houses During Sleep

This paper presents the results of a questionnaire survey on the use of air conditioners in houses in Surabaya, Indonesia, and Kuala Lumpur, Malaysia. The objective of the survey was to clarify what temperature and humidity levels people in these regions prefer in order to feel comfortable, with special focus on their sleeping environment. This was determined through survey responses and by measuring the thermal environments in their bedrooms. The questionnaire file was distributed to 64 university students in Surabaya and 65 in Kuala Lumpur. The students interviewed their family members and described their own experiences in their daily lives at home. The survey results show that the respondents set their air conditioners at very low temperatures. They also show that more than half of the respondents reported a cold or cool thermal sensation while using the air conditioner. Many respondents also reported various health problems and feeling cold while they were sleeping.

Reduction of Energy Consumption by AC due to Air Tightness and Ventilation Strategy in Residences in Hot and Humid Climates

Abstract This paper proposes strategies for reducing energy consumption for cooling in residences in hot and humid climates. Based on the results of fieldwork measurements and questionnaire surveys, a simulation of indoor thermal environments in consideration of air conditioner operation was carried out, in order to evaluate energy consumption by air conditioners. This simulation program takes into account both heat and moisture transfer in building materials. In order to simplify the calculation and due to lack of measurement of ventilation volumes, the ventilation volumes are assumed as constant values depending on open or closed windows. The combined effects of building air-tightness and the opening time of windows for ventilation were examined. Making an entire building airtight results in a small reduction in energy consumption, as the air-conditioned area increases. Meanwhile, simply making an air-conditioned room airtight is more effective for reducing cooling energy consumption. Irrespective of this, nighttime ventilation of non-air-conditioned spaces is quite effective in reducing sensible cooling load. Thus, introduction of not only a high degree of insulation but also air-tightness along with well controlled ventilation is required to achieve energy savings in hot and humid climates.

Field survey of air conditioner temperature settings in a hot, dry climate (Oman)

In conventional air-conditioning design, the comfortable range of temperatures is between 25°C and 27°C with relative humidity levels of 40% to 60%; these numbers vary only slightly based on a persons race and country. Several studies in tropical climates show that the observed thermal comfort requirement often does not agree with those obtained based on experiments, which have mainly used North American subjects. However, there is no consistent rationale that explains why comfort requirements are different in hot climates, suggesting that more surveys on thermal comfort may be needed in the tropics. In Asia, there has recently been a rapid and widespread diffusion of air conditioners; therefore, a survey was conducted to clarify what temperature and humidity level people in Asian countries prefer in order to feel comfortable. Following that research, this article presents the results of a questionnaire survey on the use of air conditioners in houses in hot, dry climates. Nizwa and Rustak, Oman, characterized by the hot, arid climate of the Arabian Peninsula, were chosen as survey areas. The questionnaire survey was distributed to students of Nizwa University. Questions were asked about the duration of air-conditioner use and preferred air-conditioner temperature settings. To determine how respondents felt about their indoor environment, questions were also asked about the thermal sensations that were experienced while using the air conditioner. In both cities, the mean operating time of the air conditioner was very long. The respondents reported selecting a low temperature setting while sleeping, despite the fact that many of them reported that they were cold while sleeping. Ninety percent of respondents reported a cold, cool, or neutral thermal sensation while using the air conditioner without feeling discomfort.

Survey of Thermal Environment of Residences Using Air Conditioners in Surabaya, Indonesia

This chapter reports the results of a survey on the attitudes of residents towards the use of air conditioners in Indonesia. A questionnaire survey and measurements of the thermal environment were carried out. With increasing income, the percentage of residents who felt that air conditioning was necessary also increased. Once residents start to use air conditioners, they continue their use. When an air conditioner is used, the lowest room temperature ranges from 23 to 29 °C, which is lower than that observed in Japan. Air conditioners are typically used around 14:00 and during sleeping time; this is similar to the situation in Naha, a subtropical area of Japan. Also, the duration of air conditioner use is longer than that in Japan. As a result of these findings, the consumption of energy used for cooling is expected to increase in this area.

Passive Cooling Strategies to Reduce the Energy Consumption of Cooling in Hot and Humid Climates in Indonesia

This chapter proposes strategies for reducing the energy consumption of cooling in residences in hot and humid climates. Based on the results of field measurements and questionnaire surveys in Surabaya, Indonesia, a simulation of indoor thermal environments – with consideration of air conditioner operation – was conducted to evaluate energy consumption by air conditioners. This simulation program considers both heat and moisture transfers in building materials. The combined effects of building airtightness and the opening times of doors and windows for ventilation were examined. The simulation is conducted for the rainy season. Making the whole building airtight results in a small reduction in energy consumption, because the size of the air-conditioned area increases. Meanwhile, making only the air-conditioned room airtight is more effective for reducing cooling energy consumption. Regardless, nighttime ventilation of non-air-conditioned spaces is quite effective in reducing the sensible cooling load. In conjunction with economic growth and requirements for improving indoor environmental quality, energy consumption for cooling is expected to increase rapidly in hot and humid areas. Therefore, the introduction not only of high levels of insulation but also of airtightness, in addition to well-controlled ventilation, is required to achieve energy savings.

Indoor Thermal Environments in Apartments of Surabaya, Indonesia

This chapter presents the results of detailed field investigations of thermal conditions and occupants’ window-opening behaviour in several apartments located in the city of Surabaya, Indonesia. In the public apartments, almost all of the respondents did not use air-conditioning, and approximately 70–80% opened their windows/doors on both front and rear sides, while 20–40% of them kept the rear opening opened at night. Meanwhile, most of the respondents in the high-rise private apartments depended on air-conditioning, and about 20% of them opened the rear window only during daytime. The results of field measurement showed that under the naturally ventilated conditions, the old public apartment unit provided better thermal conditions compared to those in the other types of apartments. It was difficult to achieve the thermal comfort without relying on air-conditioning in the high-rise private apartments.

Thermal Sensation and Comfort in Hot and Humid Climate of Indonesia

In conventional air-conditioning design, the comfortable range is considered to be between temperatures of 25 and 27 °C and relative humidity of 40 and 60%; these numbers vary only slightly based on a person’s race and country. However, several studies conducted in regions with hot and humid climates show that the observed thermal comfort requirements often do not agree with those obtained from European-based studies. In this chapter, the results from the questionnaire surveys and measurements in residences in the hot and humid regions of Indonesia and Malaysia are shown. It was found that the residents use air conditioning at low temperatures for sleeping and that many people consider cold condition as “comfortable” and desire “cooler” conditions even if they feel “cold” in thermal sensation.