Improving indoor climate and comfort with wooden structures

In this report, the moisture performance of a bedroom in a wooden apartment building is studied numerically using hourly weather data from 4 different cities (Helsinki, Finland, Saint Hubert, Belgium, Holzkirchen, Germany and Trapani, Italy). The bedroom is occupied for 9 hours by two adults during the night (22:00 to 7:00), the volume is 32.4 m3 and the wall surface area is 60 m2. With the basic input parameters (moisture production of 60g/h, ventilation rate of 0.5 ach and a permeable internal coating on the ceiling and walls) the moisture transfer between indoor air and the building structure is very active. With these parameters, the moisture transfer between indoor air and structures can significantly improve the indoor climate and air quality compared to the case where the internal coating is vapour tight. Moisture storage in wood based materials can reduce the peak humidity during the night and this moisture can then be removed by ventilation air during the following day. In general (at a ventilation rate of 0.5 ach), the indoor humidity is close to the outdoor humidity when the occupants enter the room (22:00) for all structures and materials. The increase in absolute humidity during the night is quite independent of the climate, but the amount of time when the indoor climate and air quality are unsatisfactory is very dependent on the climate. Passive methods of controlling the indoor climate are naturally more successful in moderate climates than in hot and humid climates, even though they provide benefits in all climates.