Subjective and Objective Measurement of Indoor Environmental Quality and Occupant Comfort in a Multinational Graduate Student Office

Abstract

In an air-conditioned multinational graduate students’ office in Japan during the winter season, we examined indoor environmental conditions, occupants’ perceptions, and their acceptance levels over five consecutive days. Indoor air quality (IAQ) acceptance peaked on the third day, coinciding with the most favourable thermal sensation vote, which was “neutral” at a geometric mean indoor temperature of 25.1 °C. Aural comfort received the lowest acceptance due to ongoing construction work, but did not significantly impact overall IEQ acceptance, thus suggesting that unacceptable aspects of indoor environmental quality (IEQ) can be offset by acceptable aspects. IAQ and thermal comfort compensated for its effects, offering insights into occupants’ environmental tolerance. IAQ sensation votes and visual comfort votes exhibit a strong relationship with overall comfort, as indicated by their respective R2 values. However, variations in overall comfort are primarily explained by IAQ, which has the highest R2 value of 0.50, suggesting that IAQ accounts for 50% of the changes in overall occupant comfort. Non-Japanese participants had lower IEQ acceptance and a significantly higher number of complaints than Japanese participants more so in visual comfort where acceptable luminance levels were higher in Japan than other participants’ countries of origin. Thermal comfort was mutually highly accepted by both groups. Nose and eye irritation were significantly experienced by the international participants due to low RH levels but experiencing loss of concentration and lethargy was comparable in both groups (p > 0.05, t-test). We recommend global coherence in indoor environmental quality standards as is the case with drinking water standards for public health protection and seamless transitions in new indoor environments.