Laboratory characterization of brick walls rendered with a pervious lime-cement mortar

A laboratory study investigating important thermal retrofitting solutions for simple and double (cavity) brick walls is presented. Test walls were modified using materials of current interest including an external pervious lime-cement mortar render and insulation board prior to evaluation. Laboratory simulations of steady-state winter and summer scenarios were performed using apparatus comprising two opposing climate chambers. Temperature, relative humidity and heat flux rate were monitored with surface sensors every 10 min until stabilization on each wall type, retrofitting solution and climate scenario. The temperature and relative humidity profiles, heat flux, surface temperature difference, thermal conductance, condensation risk and stabilization times were assessed. Comparisons between simple and double (cavity) brick walls showed significant differences and a high condensation risk in the non-ventilated air cavity of the double wall. The pervious lime-cement mortar render enhanced substantially the thermal performance of the single wall although increased the condensation risk of the double (cavity) wall. As expected, the insulation layer reduced the thermal conductance of the wall, although the improvement in a summer scenario was considerably lower than in winter. The different performance observed between winter and summer steady-state conditions emphasized the importance of the heat and mass transfer coupling effect. Therefore, this work proves that effective retrofitting depends on materials, wall layouts and climate conditions. These experimental results provide essential knowledge about assessing the effects of common retrofitting solutions especially under hot-dry summer scenarios.