Constancy of Air Tightness in Buildings: Fid-Bau Portal

Constancy of Air Tightness in Buildings

P. Metiaeinen / J. Saarimaa / P. Saarnio / H. Salomaa / K. Tulla

In order to reduce consumption of energy, more air tight buildings have been built. There were many doubts, that too air tight construction can cause some harm to indoor climate and structures. It was also unclear whether the building would remain air tight with time. In the study, pressure measurements have been carried out to discover whether the air tightness of mainly detached houses changes with time. The study consists of 34 new buildings and 9 old improved buildings. The air tightness of the building envelope decreased significantly in energy two buildings during the two first years. The change occurred mainly in timber framed buildings In many cases it was very difficult to detect any specified causes to reduced air tightness. In timber framed buildings drying of wood is one notable reason. It causes small cracks all over the building envelope and reduces thus the air tightness evenly. The study of the inconveniences caused by too air tight constructions was carried out by sending inquiries to the holders of real estate. Some buildings were then thoroughly inspected and measured. The study showed that too air tight as well as too leaky constructions cause much harm. Draught and bad smell of indoor air seemed to be quite common in flats. The window pane became misty in several buildings, whereas moisture defects inside the constructions were rare. The radon content was measured in several buildings, and very low concentrations were found. The problems of indoor climate were significantly connected with poor ventilation. The main problem was the insufficient use of mechanical ventilation devices and the incompatibility between the ventilation system and air tightness, in other words, the air change rate was out of control. (ERA citation 13:014896)