Field investigations of the indoor air quality regarding the potential health effects in energy efficient buildings during the heating season
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In the search for energy reduction in the building sector, the focus on energy efficient buildings is increasing. In addition, people spend up to 90% of their time indoors. Norwegian office buildings experience low levels of relative humidity (RH) indoors in the heating season, which may lead to developments of asthma, affect the skin or reduce productivity among occupants. Particulate matter (PM) in the atmosphere is associated with increased rates of mortality, cardiovascular disease and respiratory illness. The objective of this study is to investigate the health effects of indoor PM concentrations and RH in energy efficient office buildings in the heating season in Norway. The relationship between PM concentrations and RH in indoor office environments is also studied. This study is divided in two main parts, a literature study and a case study. In the literature study, the influences of indoor climate on human health are analysed and recommended guideline values are stated. Field measurements in three office buildings located in Trondheim have been performed. Two energy efficient buildings and one reference building were evaluated and a total of 21 rooms were assessed. PM concentration, RH, air temperature and carbon dioxide was measured in all rooms. A web-based questionnaire was distributed to a total of 317 office workers (Response rate=46%) in the three buildings. The objective of the questionnaire was to establish experienced health symptoms, experiences of dust and dirt and perceptions of dry air by the occupants in the three buildings. Mass concentrations of PM10 exceeded the recommended concentrations by the Norwegian Institute of Public Health in one room in the energy efficient buildings, however the other rooms remained below the recommendations. Notably lower concentrations of PM1 and PM3 were found in the energy efficient buildings compared to the reference building, indicating a lower risk of developing cardiovascular and respiratory illness among the occupants. A statistical significant (P<0.01) correlation was found between the experience of dust and dirt and cough in energy efficient buildings, which indicates that insufficient cleaning may lead to development of respiratory health symptoms. The measured indoor RH varied with outdoor conditions and ranged from 15 33%. Perceptions of dry air were lower in the energy efficient buildings than in the reference building. A significant (P<0.01) correlation between experiences of dry air in the work place and symptoms of dry/flushed facial skin, dry hands, hoarse/dry throat, cough, itching/irritation/burning of eyes and scaling/itching of scalp/ears were found from the responses to the questionnaire in the energy efficient buildings, indicating that occupants may experience problems with mucous membranes and dry skin in the heating season. A trend of decreasing PM concentrations with increasing RH was observed from the measurement results. Statistical significant (P<0.01) correlations between experiences of dust and dirt and experiences of dry air were found from the questionnaire results. This indicates a connection between RH and PM concentrations in indoor office environments, however a clear relationship was not recognised.