In-situ and laboratory airtightness tests of structural insulated panels (SIPs) assemblies

One of the main factors influencing building airtightness is the construction typology. As building environmental performance requirements raise so does the prevalence of less conventional envelope construction systems as modular structural insulated panels (SIPs) buildings.  
In this paper, the airtightness performance of a constructive solution based on SIPs was evaluated. Airtightness tests were performed on the laboratory according to the EN 12114-2000 methodology. One complete exterior wall assembly and another one with the inclusion of a window were tested to determine their performance as an effective air barrier. The impact of the window framing in the overall resistance to air leakage was also determined. Additionally, the airtightness of a dwelling using these SIPs was measured during the construction phase and after commissioning. The objective was not only the assessment of the n50 difference between the two stages, but also the comparison with previously tested conventional envelopes on the same climate.  
Laboratory and field test data resulted in mismatching values. Workmanship and unforeseen leakage paths were found to be the main contributors to these findings. Moreover, the case study displayed a superior airtightness performance when compared to heavy type construction solutions, common amongst the Portuguese building stock. Additional work is needed to identify and quantify envelope air paths in order to properly design lightweight buildings solutions.