Impact of Indoor Environmental Quality on Occupant Satisfaction, Perceived Health, and Work Performance in “Green” Office Buildings in the Middle East
: (Alternative Format Thesis)

Student thesis: Doctoral ThesisDoctor of Engineering (EngD)

Abstract

Globally, green-certified buildings (GBs) are promoted as an effective solution to mitigate climate change challenges, saving energy, and delivering better Indoor Environment Quality (IEQ). However, the actual role of green certification in improving the quality of indoor environment and improving occupant satisfaction is much debated. There is a concern that GBs may succeed in achieving energy efficiency targets but may exhibit unintended consequences that reduce the quality of indoor environment and curtail occupant satisfaction, health, and work performance.

In the Middle East (ME), the number of green-certified buildings is increasing rapidly and associated with an increase in the number of localised Green Building Codes (GBCs). However, to date, no systematic research has evaluated the actual performance of IEQ in green buildings in this region. Hence, this thesis is designed to examine whether the IEQ of green office buildings in the ME meets the standards-recommended ranges of thermal comfort and indoor air quality (IAQ) that identified by GBCs, and if so, to what extent they are perceived satisfied by their occupants.

This thesis starts with examining the role of localised GBCs in improving the performance of IEQ. This is achieved through a longitudinal field study, we follow 120 occupants who transitioned from four conventional office buildings (CBs) to the first GB, designed to the local Jordanian Green Building Guide (JGBG). The repeated-measures protocol (pre- and post-move) is used. Measures cover physical parameters (i.e., air temperature, relative humidity, and indoor CO2 levels), subjective parameters (i.e., occupants’ satisfaction, self-reported Sick Building Syndrome symptoms (SBS)), and occupant thermal comfort. Alongside this, instantaneous measures for temperature, mean radiant temperature, air speed, and relative humidity were conducted for compliance. Results show that moving from CBs to the JGBG-certified building does not improve the occupant satisfaction of IAQ, lighting and acoustic comfort and associated with an increase in the prevalence of SBS symptoms. Further, both building types fail the ASHRAE 62.1 threshold of 20%, so can be labelled as “sick” buildings.

Next, this thesis expands the evaluation to include the green-certified office buildings designed to the international LEED standard. It compares CBs and LEED-certified buildings in terms of the performance of IEQ, occupant satisfaction and work performance. A cross-sectional study design with between-subjects comparison is followed. Further, continuous measures for temperature, relative humidity and CO2 are adopted, covering 13 office buildings and 502 occupants. In addition, semi-structured interviews are conducted to gain in-depth information about green design motivation and features. Data were collected between summer 2017 and winter 2019 in Jordan. Results show that although LEED buildings comply with recommended ranges of thermal comfort and CO2 levels, occupant satisfaction with IEQ aspects was significantly lower compared to occupants in CBs, while no significant difference in absenteeism and presenteeism was reported between building types. Over half of those surveyed in LEED buildings and CBs reported IAQ, ventilation and thermal comfort as important issues that need to be improved.

Finally, this thesis investigates the suitability of the applied thermal comfort standards in predicting occupant thermal sensation in air-conditioned buildings in the ME. This is achieved using three approaches. A meta-analysis is used to aggregate outcomes of existing thermal comfort research in the ME to identify challenges faced by occupants in air-conditioned buildings. This is followed by seven thermal comfort field surveys covering 31 air-conditioned buildings and 1,101 occupants in four countries in the ME. Finally, energy model simulations are carried to estimate any potential energy saving in the building energy demand for space cooling in air-conditioned buildings in the surveyed countries. Results demonstrate a clear gap between thermal comfort models and observed thermal sensation of occupants in air-conditioned buildings (i.e., CBs and GBs) in the ME. During the cooling season, the PMV model fails to predict the thermal sensation of 94% of occupants. The monitored thermal conditions in surveyed buildings complied with standards recommended ranges for 58% of the time, and only 40% of occupants find these conditions comfortable. This thesis provides the empirical evidence of overcooling in summer, as 39% of surveyed occupants expressing cold discomfort, which is associated with an increased energy demand for space cooling up to 20% compared to non-overcooled conditions.
Date of Award8 Sep 2021
Original languageEnglish
Awarding Institution
  • University of Bath
SupervisorSukumar Natarajan (Supervisor), Nick McCullen (Supervisor) & Ian Walker (Supervisor)

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