Phase change material cement-lime mortars for thermal retrofitting of facades

Abstract

The poor thermal performance of many dwelling units built from 1940 to 1980 produces a low energy efficiency under the present thermal standards. In order to fulfil comfort and energy efficiency requirements, these facades need to be retrofitted. In many cases, External Thermal Insulation Composite System (ETICS) are used to increase thermal insulation, although this solution does not consider the thermal inertia. New mortars with improved thermal insulation and inertia are investigated as an innovative solution. Twelve cement-lime mortars were designed, using: white cement, air lime, siliceous aggregate (0-4 mm), lightweight aggregate (LWA) (expanded perlite), short cellulose fibres and 10 and 20% of a Phase Change Material (PCM) - microencapsulated paraffin wax. PCM’s nominal melting temperature was 23 ± 1 °C. An experimental program was carried out to assess the effect of PCM on the physical and thermal performance of the mortars. Two different scenarios were considered to evaluate the temperature effect on the PCM-mortar performance. Bulk density, open porosity, capillary absorption, vapour permeability, thermal conductivity and compressive strength were characterized. PCM produced significant changes on the mortar thermal properties and a synergetic effect of PCM and LWA was identified.