ZEMCH 2015 - International Conference Proceedings | Page 853

can attain good indoor environments as the occupants adapt to a temperature band that is relative to the ambient thermal conditions outside. These studies show that occupants in air conditioned buildings can be more critical of the indoor thermal environment as their expectations are
higher, compared to those in naturally ventilated spaces (Wagner et al. 2007; Kim & de Dear 2012;).
A number of studies list the adverse effects of background noise on work performance and efficiency (Pejtersen et al. 2006; Haapakangas 2014; Jahncke et al. 2013, Li Huang et al. 2012; Schlittmeier and Liebl 2015; Jensen & Arens 2005). Noise is often defined as levels of undesirable sound
experienced by occupants within a space (Huang et al. 2012). Depending on the tasks at hand and
the levels of noise this could result in reduced job satisfaction, health and performance. According to C. Huizenga et al (2006), among the indoor environmental factors, the acoustic quality of
the office spaces scored the lowest at -0.2. Ringing telephones and background conversations
are the most disruptive noises in open plan offices. Occupants disturbed by noise within close
proximity are less affected by external noise sources. 60% of the occupants in this study complained about the noise disturbance in open plan offices compared to only 6% in cellular offices
(Pejtersen et al. 2006). Jahncke (2013) looks at the effects of background speech on cognitive performance. Based on the STI (Speech Transmission Index), the study showed that tasks requiring
short-term memory were more susceptible to speech disturbance than tasks requiring mathematical input. Greater legibility of background speech resulted in increased levels of disruption
in short-term memory tasks. Similarly, Schlittmeier and Liebl (2015) talks about the contradictory
nature of work environments: the need for easy communication among employees, and the need
for silence to accomplish tasks involving focus and concentration. As per standards such as the
ISO 3382-3:2012-2015 (2012) that define acoustical requirements in work environments, designers
are faced with the prospect of improving speech legibility within the immediate proximity of the
occupant workspace, while drastically reducing it beyond the radius of the immediate workspace
so as to allow concentrated work. This requires attention to two specific factors; a spatial layout
that facilitates the nature of work within the organisation and a good acoustic balance between
communication and concentration.
Jensen & Arens (2005) states that more than 50% of occupants surveyed express a lack of work
efficiency due to ambient speech. 80% of the respondents were also affected more by the lack of
speech privacy and with the information content in background speech, as supported by findings
in similar studies (Jensen & Arens 2005). Results show that there is a tendency for respondents
to get (unintentionally) ‘involved’ with background conversations thereby causing distraction in
their work. Distraction levels were higher with greater task loads for the same noise levels, resulting in elevated stress levels. Smith- Jackson and Klein (2009) discusses the impacts of irrelevant
speech on the level of work performance, tension, anxiety and exhaustion of the employees. 79%
of respondents in cubicles with high partitions expressed dissatisfaction compared to 77% in cubicles with low height partitions (Jensen & Arens 2005). This shows that increasing cubicle heights
will not drastically improve acoustic comfort.

Discussion
Research shows that better ventilation rate can substantially improve the indoor air quality and
subsequently the occupant health and comfort. A study of the US commercial building stock
shows that approximately 6.2% of end use energy is used to mechanically heat or cool outdoor air
(this includes the conditioning of infiltration air) (Griffith et al., 2009). Thus, it may seem viable to
reduce the ventilation rates in buildings so as to reduce costs and energy consumption. However,
studies also showed that an increase in ventilation rates helps reduce sick building syndrome

A review of indoor environmental quality in office environments

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