Thermal comfort and IAQ characteristics of naturally/mechanically ventilated and air-conditioned bedrooms in a hot and humid climate

The characteristics of thermal comfort and indoor air quality (IAQ) in bedrooms, occupants' perceptions and their impact on sleep quality are not often studied. It becomes even more interesting if climatic conditions allow Naturally/Mechanically Ventilated (NMV) concepts as opposed to Air-conditioning (AC) and this becomes very significant from an energy perspective. This paper reports our findings from such a study conducted in a hot and humid climate. Objective measurements of thermal comfort and IAQ were carried out during sleeping period in 12 NMV and 12 AC bedrooms over a period of 2 months. Questionnaire responses were sought from each subject at the end of the objective measurements to assess their perceptions on thermal comfort and indoor air quality of the bedrooms during sleep and their sleeping conditions. Although the "Historical" and "Immediate" responses for the NMV and AC bedrooms indicate that there was a good level of acceptability for both Thermal Comfort and Perceived Air Quality (PAQ), it was found that NMV bedroom was a better sleeping environment. The subjects' immediate perception of PAQ and thermal comfort were reasonably correlated with their historical perceptions. The subjects' perception of PAQ was fairly closely correlated to their perception of Thermal Comfort. There was a considerable increase in the carbon dioxide level in an AC bedroom relative to a NMV bedroom. However, there was no clear evidence to substantiate that sleeping duration decreased with increasing level of carbon dioxide, but the findings do suggest that high level of carbon dioxide may hinder the duration of sleep. (C) 2011 Elsevier Ltd. All rights reserved.