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A new approach to measure liquid transport in capillary active interior insulation

: Binder, Andrea; Künzel, Hartwig M.; Zirkelbach, Daniel

Mahdavi, A. ; TU Wien:
Contributions to building physics : Proceedings of the 2nd Central European Symposium on Building Physics, 9 - 11 September 2013, Vienna, Austria; CESBP 2013
Wien: Technische Universität Wien, 2013
ISBN: 978-3-85437-321-6
Central European Symposium on Building Physics (CESBP) <2, 2013, Vienna>
Conference Paper
Fraunhofer IBP ()

The application of an interior insulation is not seen without reservations even by specialists. While it is a fact that interior insulation confronts installers as well as planners with a challenging moisture control task, it is, nonetheless, a task that can be resolved. This applies in particular to insulation systems that feature liquid transport in the hygroscopic region, the so-called "capillary-active" systems. Such systems utilize the materials' ability to transport liquid moisture under non-isothermal conditions against the water vapor diffusion flux, in this way naturally limiting the moisture content inside a construction. The serviceability of the system and prevention of damages is ideally assessed beforehand via hygrothermal simulation. For this, it is vital to know the materials specific liquid transport characteristics. The description of liquid transport inside building materials is challenging because of many influencing -and partially counteracting- parameters. Conventional test methods are dominated by isothermal conditions and the transport in larger capillaries and therefore are not fully appropriate to quantify the liquid transport in interior insulation materials. The Fraunhofer Institute for Building Physics has lately developed a new laboratory method, the "capillary return flux test". In imitation of the specific boundary conditions of interior insulations, this test works with non-isothermal conditions and opposing liquid moisture and water vapor flows, with humidification only by vapor diffusion. By closely monitoring the materials moisture content and distribution, its specific liquid transport properties in the hygroscopic region are determined. For materials destined only to be used on the interior surface of constructions, the respective properties illustrate the materials behavior with good reliability. However, some materials, such as mineral foam, are intended to be used both interiorly and exteriorly. To represent both the materials liquid transport in the hygroscopic region (due to vapor diffusion etc.), as well as near capillary saturation (due to driving rain etc.), new findings call for a special approach, possibly with combined parameters.