Literature Review: Thermal Comfort and Air-Conditioning

Abstract

The cost of supplying energy to the office space has historically been insignificant compared to the cost of labour. A study on a typical American office (Holz et al. 1997) found the cost of salaries to be 100 times more than that of energy. In Singapore, the electrical consumption of offices accounts for 12 % of the overall non-manufacturing sector's usage, with an average annual energy efficiency of 231 kWh/m 2 (Lee 2001). In an ongoing study by the Energy Sustainability Unit in Singapore (esu.com.sg) the median office building uses 49 % of its energy on air-conditioning and a further 14 % on mechanical ventilation. The common modern day office is predicated on an uninterrupted supply of affordable electrical energy. Ubiquitous deep-plan buildings with fixed windows and heat producing office equipment demand air-conditioning, artificial lighting and power. However, in a resource-constrained world where there is an increasing need to reduce our energy footprint, what levels of comfort could we forgo without sacrificing productivity? It appears that thermal comfort is not a phenomenon that can be adequately defined in the science of temperatures, humidity, airflow, metabolism and clothing. It does not, for example, explain why in the tropics like Singapore, office workers do not adopt the climatically appropriate dress code. Winter clothes sometimes carry labels to indicate which conditions they are suited for. Most of the business clothes worn in tropical offices are hardly suited to prolonged wear within the 30–35 °C temperature range. The need to go out for lunch in the hot afternoons, gives some respite to excessive air-conditioning in offices (see Figs. 3.1 and 3.2). During a poll in Singapore by the World Wide Fund For Nature (WWF 2011) it was found that 40 % of respondents found offices and schools too cold, stating: Almost half of them also compared the temperature in their office/school to ''Autumn in Seoul'', while one in four likened it to ''Winter in Siberia''. T. Law, The Future of Thermal Comfort in an Energy-Constrained World, Springer Theses, DOI: 10.1007/978-3-319-00149-4_3, Ó Springer International Publishing Switzerland 2013 17 Whilst clearly tongue-in-cheek, the comparisons show a general dissatisfaction with indoor temperatures amongst the office workers, with a strong dissatisfaction from a significant minority. The situation of the excessively cold office is partly a result of routine over-sizing of air-conditioning plant equipment which will be discussed in detail later. The other contributor is the problem of overheated executives after walking under the blazing sun and dining in a warm and humid eatery, the whole time garbed in office clothing that is ill-suited for a tropical afternoon. This phenomenon illustrates the complexity of the problem. The problem of overdependency on air-conditioning is intertwined with comfort, acclimatisation, marketing, social norms, workplace stress and personal preferences. Consequently, any resolution for the over-reliance on air-conditioning, and over-conditioning on top of that, needs to harmonise these disparate fields—a harmonisation that pre-sents itself as a gap in our knowledge, and the most vital one in order to advance thermal comfort research. Fig. 3.1 Office workers going for lunch in Singapore. Executives typically leave the air-conditioned offices for nearby eateries during the hour long lunch break. Image credit: Wolfgang Kaehler Ó 2008 (used with permission)