Modified lime-cement plasters with enhanced thermal and hygric storage capacity for moderation of interior climate

Abstract

The absorption or release of heat and moisture by interior surface layers of building envelopes under specific conditions can set effective limits to the extreme levels of indoor air parameters. Moderation of interior climate achieved in this way can contribute to a reduction of energy demands for building conditioning and overall operation cost using a straightforward material solution. In this paper, lime-cement plasters modified by two types of PCM based admixtures are designed specifically for the moderation of relative humidity and temperature fluctuations of the interior environment. The plasters are subjected to a detailed characterization procedure including the assessment of a complex set of basic physical, hygric, thermal and mechanical properties. Experimental results show that the application of small encapsulated PCM particles leads to an up to 10% increase of open porosity, as compared with the reference plaster. Contrary to this fact, the water vapor transport is slightly decelerated, what is attributed to the encapsulating polymer shell which creates impermeable barrier for water vapor transmission. Two contradictory factors affect the liquid water transport, namely the higher porosity of PCM modified plasters and increasing content of not-wettable polymer shells. The moisture storage capacity increases with the increasing amount of PCM in the mix. The moisture buffer value is improved due to the utilization of both PCM admixtures, the developed plasters can be classified as good moisture buffering materials. The thermal conductivity of modified plasters is greatly improved, as well as the heat storage capacity, the additional phase change enthalpy being up to 13J/g. Although the inclusion of PCM into the lime-cement matrix decreases the mechanical strength, the achieved values of tested mechanical parameters are still satisfactory for the application of the designed plasters in building practice. In summary, PCM modified plasters can be considered a prospective solution for the moderation of interior climate in contemporary buildings.