Abstract
Condensation in a building encourages microbial growth, which can have an adverse effect on the health of occupants. Furthermore, it induces the deterioration of the building. To prevent problems caused by condensation, from the design step of a building, predictions of the spatial, temporal and causation for condensation occurrences are necessary. By using TRNSYS simulation coupled with TRNFLOW, condensation assessment of an entire office building in Tokyo, Japan, was conducted throughout the year, including when the air-conditioning system was not operated, by considering the absorption-desorption properties of the building materials and papers in the office and the airflow within the entire building. It was found that most of the condensation occurred during winter and was observed mainly in the non-air-conditioned core parts, especially the topmost floor. Additional analyses, which identified the effect of variations in the thermal insulation of the external walls, roof and windows and the airtightness of the windows on condensation, showed that the lower airtightness of windows resulted in decreased condensation risks, and condensation within the building was suppressed completely when the thermal insulation material thickness of the external walls was greater than 75 mm, that of the roof was greater than 105 mm and the windows had triple float glass.
Highlights
Moisture in a building directly affects an occupant’s thermal comfort and health and induces corrosion of the building
Expresses the ratio of wall area where condensation has occurred to The condensation ratio (CRt) periods intermediate
It is clear from these figures that for lower airtightness grades, the amount of outdoor air (OA) entering through the gaps of the window is greater, causing the relative humidity of the staircase to decrease
Summary
Moisture in a building directly affects an occupant’s thermal comfort and health and induces corrosion of the building. To consider the movements of airflow in the entire building and the effect of outdoor conditions, such as wind velocity, wind direction, wind pressure due to the height from the ground surface, infiltration and exfiltration, the airflow network should be coupled with a simulation to estimate condensation. By using TRNSYS simulation, condensation conditions for all wall surfaces in an office building were investigated to identify the location(s) where condensation occurred. The effect of the airtightness of the window and variations in the thermal insulation properties of the external walls, roofs and windows, which are considered to affect the occurrence of condensation, on the CR were examined, and measures to restrain building condensation were discussed.
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