Field measurement testing of air tightness - example from a hospital project in Sweden

Over the recent years more effort has been given to air tightness of public buildings such as hospitals. The demand for well insulated buildings increases the importance for low infiltration air rates and thus the air tightness becomes more important. Besides, air infiltration is a quantitative way to put into requirements for the tenders to fulfill.  In this work we describe field measurement of air-tightness on site in early stage of production, as well as field measurement of a whole floor in a hospital building. Hospital buildings are large enclosures that sometimes are difficult to test. We describe some outcomes from evaluating the testing method and how qualitative results as well as quantitative results can be used to improve the building process. Early measurements are important to give input to the builders how to build correct and to give an understanding about the importance of the air-tightness of a building. The different techniques to measure air tightness and to find leaks in the building envelope has been part of a learning process, both for the builders as well as the design team. The results show, after that the air-tight measurements was started, that the building process has improved. However, another finding from the project is that information should be given continuously and to all builders, as various work teams, has their own way of working with air-tightness. Measuring building parts should be the first test to evaluate different constructions and how the construction has been sealed. In the work described in this paper the building was divided by a temporary construction made by plastic film, adhesive tape everywhere where the plastic film meets another material and where the plastic film is overlapping. Butyl-based adhesive strip was used under the floor joist, at the corners and under the ceiling joist. The measurements showed that there was an air-leakage between ceiling and outer walls. This air-leakage was evaluated by a small box for only that part. By this test a suitable method involving air-tight foam was used and the results from measurements after the action shows air-leakage close to zero. The result from the whole floor measurement shows higher air-infiltration than the requirement. The contractor will take action to improve the air-permeability. From the experience of the measurements one last conclusion is that a design that emphasise air-tightness is the first step to achieve an air-thigh building.