Airtightness of multifunctional tapes

For several years, multifunctional tapes have increasingly been used for the airtight installation of windows in new buildings or renovation projects. The adhesive tapes are wrapped around the window on three or four sides. After the installation of the window, the tape expands and closes the joints between window and reveal. Their manufacturers sing the praises of these self-expanding joint-sealing tapes made of foam plastic. However, BlowerDoor tests frequently reveal faults. Accordingly, experts vary in their evaluation and discussion of the products.

To bring clarity and objectivity into the discussion, the Passive House Institute (PHI) in cooperation with the FLiB working group on multifunctional tapes, conducted airtightness tests of multifunctional tapes of different manufacturers under lab conditions. Among other things, they analyzed the influence of the joint width in relation to the manufacturer’s specifications and the impact of the time passed since the installation on the airtightness. The test set-up and the measurement were conducted in line with German Industrial Standard DIN 18542. The test measured the material properties of the tapes if optimally installed between smooth and parallel aluminum profiles without corners. The installation at the construction site will always deviate from this set-up and airtightness will consequently decline.

The measuring results show predominantly positive results for the airtightness of the multifunctional tapes. They clearly indicate using the tapes in the lower range of their installation limits. At least for the exemplarily tested tape its use at the upper installation limit led to a significantly higher leakage rate. Installing tapes in a joint exceeding the installation limits results in considerably higher leakages. It can be observed, that in construction practice this is unfortunately frequently the case. When installing tapes at the construction site, the tape ends or junction points as well as the corners are critical areas regarding airtightness. Manipulation, installation, and sealing must all be performed with the utmost care. Significant deviations from the lab values presented here are to be expected.

The analysis with the lab set-up is complemented by measurements of wood and plastic windows (1x1m) in wood and solid walls. Here, the measurement includes the realistic installation with the critical corners. Some first experience to this effect overall gives positive results for the product tested.

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For more information, please contact the reference author at: soeren.peper@passiv.de