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Title: Thermal operating practice in mixed-mode buildings : higher education case study in a hot-humid climate
Author: Mongkolsawat, D.
Awarding Body: University College London (University of London)
Current Institution: University College London (University of London)
Date of Award: 2013
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The rapidly increasing demand for cooling in buildings and the growing evidence of ‘air-conditioning addiction’ concern energy policy makers in hot-humid countries. Despite this concern, many existing mixed-mode non-residential buildings in hot-humid climates are operated as fully air-conditioned. This research applies adaptive thermal comfort theory to address the potential reasons for this design-use mismatch and evaluate how to optimise the use of fan assisted natural ventilation in existing mixed-mode non-residential buildings in hot-humid countries in order to limit impending global climate change, focusing on the interrelationships between: individual thermal adaptability, organisational thermal adaptability and the role of facilities managers, pro-environmental attitudes, and user performance. This thesis hypothesises that Acceptance of fan assisted natural ventilation in existing mixed-mode non-residential buildings in hot-humid climates is affected by users’ perceived behavioural adaptive opportunities and psycho-physiological adaptation, as well as by facilities management practice. Higher education buildings in Thailand were utilised as a case study, and a series of student questionnaires were conducted involving a total 2,825 students in 11 Thai universities across six regions and observing 39 classes, 14 of which were instrumented and monitored during the survey. The study also included semi-structured interviews with 25 facilities managers in four universities. The findings generally supported the hypothesis and identify not only the criteria for students’ acceptance of assisted natural ventilation, but also the reasons behind the current facilities management operating practice in HE sector. Approximately 76% of students reported a willingness to accept (rather than not) the use of assisted natural ventilation in existing mixed-mode classrooms during the cool season if they perceived moderate-high opportunities (i.e. effective and probable) for using fans (3.3 times more willing than with perceived low opportunities) and windows (2.8 times more willing than with perceived low opportunities). The perceived opportunity to use fans increased when there was at least one fan per 20 students. During the hot season, 37% of students reported a willingness to accept (rather than not) the use of assisted natural ventilation if they perceived moderate-high opportunities to use fans (2.8 times more willing than with perceived low opportunities), had a high daily exposure to naturally ventilated environments (1.8 times more willing than with full air-conditioning exposure), and a low income (1.5 times more willing than with a high income). Students with high exposure to naturally ventilated environments also tended to have a high level of pro-environmental attitudes, but the direction of causality is not certain. The high level of pro-environmental attitudes could be a new driver of adaptive behaviours and the willingness to reduce air-conditioning use. Interviews with facilities managers revealed that their preference for a certain thermal operation mode appeared to be dominated by preferences for cool comfort of users with high organisational status and/or students on a high income. Universities participated in this study so far had no explicit targets of monitoring and reporting of energy use. Fans, the most effective adaptive device, had been gradually removed from many mixed-mode buildings, and facilities managers tended to rely on full air-conditioning to avoid user complaints and possible user performance drop. However, the study found that students in assisted naturally ventilated classrooms did not perceive their learning performance to be lower than those in air-conditioned classrooms, as long as they felt thermally comfortable. The risk of performance drop appeared to increase when the room air temperatures reached 31C, the upper limit of comfort boundary for fan-assisted naturally ventilated spaces. The findings highlight the gradual obsolescence of mixed-mode operation in the non-residential sector in a hot-humid climate. Air-conditioning reduction policy should target high-ranking people within organisations as their commitment is considered to be a key driver of changes in organisational thermal comfort practice. In this regard, monetary incentives alone for high-ranking and high-income users to reduce energy consumption may not be effective. Organisations should maintain the variability of thermal environments indoors and engage more with end-users to reduce air-conditioning use through practical adaptive behaviours. The key performance indicators of facilities management should not only focus on user satisfaction but also energy reduction achievement in order to encourage and empower the facilities managers to implement the more effective energy policies. Regarding the adaptive behaviours, organisations and building designers should be made aware that not specifying or removing fans could potentially shift mixed-mode buildings to fully air-conditioned operation because window opening alone could not always guarantee thermal comfort for the majority of users even in the cool season. Further research is needed to evaluate the thermal and energy performance of the existing mixed-mode non-residential building stock and the potential energy saving associated with applying assisted natural ventilation based on climate change scenarios. Practical guidelines in terms of effectiveness and practicality for mixed-mode building design and operation for hot-humid climates could then be developed. The links between pro-environmental attitudes and thermal experience needs further investigation in order to clarify the direction of the relationship. More studies using intervention approaches should be conducted to estimate the potential for user performance risks if using mixed-mode operations.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available