Experiences in the airtightness of renovated tertiary exemplary buildings in the Brussels capital region

In the “Exemplary Buildings” program of the Brussels Capital Region, building owners and designers are challenged to realise building projects of both high architectural quality and superior environmental performance. After a project competition phase in which the Exemplary Buildings are selected, winning projects are supported by grants and expert guidance throughout further design development and construction. Building envelope airtightness is an important aspect during the follow-up, given its influence on the net energy demand.

This article describes through cases and general trends, the airtightness of renovated non-residential buildings. Several cases studies demonstrate that the resulting airtightness for renovated non-residential buildings, can be as low as the current standards for new-built buildings. The case studies are supported by photographs and technical information, showing the design approach and construction methods which were applied to obtain good airtightness. Airtightness testing will be discussed for the studied cases. This is particularly interesting as intermediate testing has been undertaken in order to enable airtightness improvement works well before final building acceptance. These tests also allow to determine the importance of some of the imperfections before they were mitigated.

General trends can be made by analysing the dataset of renovated tertiary buildings, realised within the Exemplary Buildings program. Keeping in mind that these projects aimed – and were supported – to reach superior environmental performance, the results show that it is possible to obtain excellent airtightness levels when renovating tertiary buildings. Although the dataset for this particular type of buildings is small, overall results of the Exemplary Buildings program indicate a learning effect throughout the years.

The cases and general trends demonstrate that excellent building airtightness can be realised when renovating non-residential buildings, when a coherent design approach, building methods and follow-up during construction are maintained. These results are important, given the necessity of renovating existing building stock in Brussels and the energy performance legislation evolutions, proving feasibility of gradually moving towards airtightness performance requirements similar to passivehouse criteria.