Subjective indoor air quality and thermal comfort among adults in relation to inspected and measured indoor environment factors in single-family houses in Sweden-the BETSI study

Abstract

Totally 1160 adults living in single-family houses in Sweden participated in a questionnaire survey on subjective indoor air quality (SIAQ). Inspectors investigated the dwellings and performed home measurements (mean indoor temperature 21.4 °C, mean indoor air humidity 34.2%, mean indoor air exchange rate 0.36 ac/h and mean moisture load indoor 1.7 g/m3). Totally 15.5% perceived draught, 28.0% perceived too high room temperature, 42.4% unstable room temperature, 36.8% too low room temperature, 19.6% stuffy air, 19.8% dry air and 29.9% dust or dirt.Measured room temperature was related to perception of room temperature. Higher relative air humidity was related to perceived unstable room temperature (OR = 1.70) and too low room temperature (OR = 1.96). Higher absolute air humidity was related to too high room temperature (OR = 1.21), unstable room temperature (OR = 1.34) and too low room temperature (OR = 1.35). Higher measured relative humidity, absolute air humidity and moisture load were all associated with stuffy air and unpleasant odor (OR = 1.45–1.97). Higher air exchange rate was related to less perceived unstable room temperature (OR = 0.93). Higher U value was related to draught (OR = 1.17), too low room temperature (OR = 1.09), unpleasant odor (OR = 1.12) and dust and dirt (OR = 1.07). New concrete slab foundation was related to less stuffy air (OR = 0.39) (vs. basement). Damp foundation was associated with more stuffy air (OR = 1.44) and unpleasant odor (OR = 1.61). Window pane condensation was related to stuffy air (OR = 1.88). Moldy odor reported by inspector was related to stuffy air (OR = 1.73). Observed mold in the attic was associated with more stuffy air and unpleasant odor.In conclusion, complaints of room temperature can indicate poor thermal environment. Higher air exchange rate can create a more stable thermal sensation. Excess indoor humidity, lower degree of thermal insulation, presence of window pane condensation and indoor dampness/mold can impair SIAQ. Higher ventilation and concrete slab foundation with underlying thermal insulation can improve SIAQ.