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Performance criteria of wall-building materials under influence of climate change

A technical requirement profile for plasters was developed that actively intervenes in indoor climate by moisture storage and transport capacity.

Many criteria influence the behavior of a wall. Therefore, it is crucial to consider the overall system, i.e. weather and climate, indoor climate and user acceptance as well as building shell and material behavior. This unique holistic approach is unique and was carried out within the here presented interdisciplinary project RoomClimatePlaster (Figure 1).

Figure 1: Schematic representation of the influences on the indoor climate (Graph: Michael Kleber)

 

Sustainable criteria for room air humidity ranges for non-air-conditioned residential buildings were categorized within three different disciplines: user acceptance (ROOM), climate change (CLIMATE), and material characteristics (PLASTER). This categorization enabled a fundamental consideration of the different disciplines as well as their interaction, which in the end could be quantified by the close cooperation. Within the scope of the imminent climate change, it was possible to develop requirement profiles for the inner plaster layer that are ready for the future.

ROOM – A special feature of the summer indoor climate is that uncomfortable conditions can arise not only due to high temperatures, but in particular due to the interaction of high temperatures with high indoor humidity. By means of sample tests in the KIT-LOBSTER as well as building simulations an extension of the existing sultriness criteria could be achieved. Instead of a fixed limit, a dynamic limit dependent on temperature and humidity was determined. (Kleber et al. 2017).

CLIMATE – High-resolution regional climate simulations with COSMO-CLM provided the boundary conditions for the building simulations for both the past and the future. They not only showed changes in temperature over the last decades, but also in other meteorological parameters such as humidity and precipitation. The analyses carried out at IMK-TRO quantified an increase in the number of days with humid conditions and thus showed the necessity and potential of new sustainable wall building materials (Brecht et al. 2020).

PLASTER – Materials must be developed in such a way that at a given temperature and air humidity, rapid moisture absorption or release is guaranteed as permanently as possible. In extensive laboratory tests supplemented by simulations, the reaction of various plaster systems to a wide range of climatic conditions was determined. This provided additional knowledge about the moisture transport and storage capacity of the uppermost wall layers in order to influence the room climate in a targeted manner (Umminger et al. 2016).

RESULTS – The main result of the project was a requirement profile for restoration plasters that takes into account both comfort criteria in the interior and factors influencing the outdoor climate. It could be shown that the project results on the material level lie within selected criteria (water vapour diffusion resistance factor, dry bulk density and thermal conductivity) of already existing plaster systems and thus show the feasibility of an actual implementation (Figure 2). A further central result was that, on the basis of the detailed user studies, far more realistic criteria regarding the feeling of sultriness for user comfort in residential and commercial premises could be derived and, on the basis of these criteria, spatially quantified statements about the required properties of interior plaster systems in Baden-Württemberg and beyond could now be made.

 

Figure 2: Single criteria of the newly developed technical requirement profile for plasters compared with existing profiles

 

The investigations presented here have shown that by equipping living spaces with plaster systems specifically adjusted to the location and the user profile, a considerable improvement in user comfort in the rooms can be achieved - also taking into account significantly aggravating boundary conditions because of climate change.

The project was funded under the "Sustainable Building" programme of the Baden-Württemberg Foundation and carried out under the leadership of the South German Climate Office (https://www.bwstiftung.de/forschung/programme/umwelt-nachhaltigkeit/nachhaltiges-bauen).

Brecht, B., Schädler, G. and Schipper, J.W., 2020: UTCI climatology and its future change in Germany – an RCM ensemble approach, Meteorologische Zeitschrift. Akzeptiert.

Kleber, M., Umminger, M., Brecht, B., Vogel, M., Haist, M., Müller, H.S., Schipper, J.W. and Wagner, A., 2017: Leistungskriterien für Innenraumputze vor dem Hintergrund des Klimawandels und des Nutzerkomforts. Bauphysik, 39: 234-244. DOI: 10.1002/bapi.201710026

Umminger, M., Kleber, M., Schipper, H., Haist, M., Vogel, M., Brecht, B., Wagner, A. and Müller, H.S., 2016: Leistungskriterien für wohnkomfortgerechte Wandbaustoffe unter Einfluss des Klimawandels in Baden-Württemberg. Mauerwerk-Kalender 2016 (Hrsg.: Wolfram Jäger), 547-551, Ernst & Sohn GmbH & Co, ISBN: 978-3-433-03131-5