Study on building surface and indoor temperature reducing effect of the natural meso-porous material to moderate the indoor thermal environment

Abstract

Abstract This paper aims to investigate the performance of several reflective and evaporative wall coatings, to determine the most effective one to moderate the indoor thermal environment. Eight reflective coatings with different colours and characteristics were selected. For the evaporative coating, three different samples with Wakkanai siliceous shale (WSS) particle; small, medium, large and silica gel type B were produced in the laboratory and another WSS mortar previously developed in the laboratory were selected. At first, an uncoated concrete, reflective coatings and WSS mortar, as a representative of evaporative group, coated blocks were experimented in the chamber under simple boundary conditions. The minimum value of outdoor and indoor surface temperature was recorded for the white uneven coating and white dirt resistant coating that can reduce the outdoor and indoor surface temperature by 6.9 °C and 1.9 °C respectively. The result of steady state experiment reveals that in constant relative humidity, evaporative coatings are not effective. Next, periodic experimentation was conducted with variations of temperature; relative humidity and solar radiation. From the results the minimum value for outdoor surface was found for white uneven thermal barrier coating (SR4), which can reduce the temperature up to 7.9 °C and the minimum inner surface temperature was recorded for WSS particle (L) that can reduce 5.8 °C. The better performance of porous particles was possibly caused by the moisture adsorption at night time and latent heat release at daytime. This study supports that the meso‑porous coatings for building envelopes can significantly contribute to moderate the indoor thermal environment.