The thesis was commissioned by Lammi Kivitalot Oy product development unit. The purpose of this study was to draw up quality control instructions for the company. The aim of the instructions is to enable the company to use the air leak value in residential buildings according to the principles set in RT 80-10974.

The tightening building regulations and energy-efficiency requirements have put a pressure to improve the air tightness of the building. The air tightness of the building plays a significant role in the living comfort of the building, the energy-efficiency and in the building physical functionality of the envelope of the building.

The regulations and instructions related to air tightness of buildings in Finland were studied. First, the standard SFS-EN 13829 directing air tightness measurements in Finland and the quality control instructions for residential buildings contained in RT 80-10974 were studied.

The company’s whole manufacturing process all the way from the planning phase to the finished residential building was examined according to the quality control instructions to find the weak spots of the process.

As a result of this thesis the structural details were improved to meet the present air tightness standards of residential buildings. The installation manuals were improved and the air tightness instructions were drawn up for the sites. A supervision document was compiled containing the most important stages related to the air tightness to help the supervision of the building site. The planning value for the house type manufactured by the company was calculated to be 1,0 m3/(h m2) based on the declaration method in RT 80-10974.