Tightness of the thermal envelope of recent office buildings and educational institutions

In 2006 tightening of the energy regulations in the Building Regulatons were introduced including requirements regarding the tightness of the building envelope. The requirements are, with minor changes, continued in the current Building Regulations, BR10. During the past few years experience has been gained regarding both the actual execution of air tightness measurements and solutions that will lead to more air tight building envelopes. Experience, however, are primarily with respect to single family houses. Knowledge on the tightness of the envelope in large buildings is more sparse, partly because it poses special challenges regarding practical and economical aspects to carry out measurements in large buildings. The challenges are different depending on whether it comes to large new buildings or existing buildings. The project team strived for arranging measurements in existing buildings. However, because of difficulties assoicated with persuading decision-makers to make a building available together with limited financial resources, the project team assessed that it scientifically and economically was most appropriate to establish close contact with kwy individuals and companies being in charge of air tightness measurements and thereby obtain access to relevant measurements in large buildings. In addition, the project team has gained access to relevant tests and measurements through own networks. The report presents results of measurements in large builidngs and discusses reasons for lack of knowledge and experience on the tightness of the building envelope in large buildings. Apparently there is a need for dissemination of knowledge on the importance of a tight building envelope both in terms of energy consumption and indoor climate and in terms of the difficulties and costs associated with repairing leaks in a completed envelope. Air tightness must be brought into focus at an early stage in the planning process, and during the construction phase air tightness measurements should be performed, e.g. on facade sections or in parts of the building. The project team has attended a number of measurements in large buildings and further gained access to results of a large number of measurements. In summary, the results show that it is possible to achieve the required tightness, and in most buildings the results are better than the requirement of a maximum of 1.5 l/s per m2.