Assessing the indoor air quality of natural-ventilated bedrooms in renovated Norwegian houses using detailed field measurements

Abstract

The objective of this work is to investigate the indoor environment in bedrooms ventilated by window opening during night-time. How window opening behaviour affects indoor air quality (IAQ), and how window opening behaviour and IAQ is influenced by external factors, are central questions. The context is renovation of detached wooden houses in Norway. To motivate building owners to renovate their ventilation system, it is important to know the typical indoor environment in bedrooms of existing buildings with natural ventilation. 37 bedrooms in 17 case houses were investigated by measuring temperature, relative humidity, CO2 and TVOC. The window opening and door opening was also logged. Each house was measured for a two-week period, during the winter of 2021. The dwellings were renovated single-family houses, situated in an area with unpolluted air and little outside noise, outside Trondheim. The bedrooms had natural ventilation, and the occupants stated they used to open bedroom windows at night. Participants answered a questionnaire about motivations and habits regarding window opening. The most common motivation given for opening windows was to supply fresh air. The window opening behaviour was both predictable and persistent. Windows were open every night in most of the bedrooms, and most of the windows were opened to the same position every night. High CO2 levels during night were found in some bedrooms. In most of the bedrooms, the CO2 concentration was satisfying during night-time, although high concentrations were found in several bedrooms when occupied during daytime. Finally, indoor temperature measurements confirmed that many occupants prefer a low bedroom temperature.