Experimental and numerical hygrothermal analysis of a refurbished double-skin flat roof
Dóra Szagri, Balázs Nagy
Abstract
In order to mitigate the consequences of climate change, and in the view of increasingly stringent energy performance requirements, energy-efficient refurbishment of building constructions is extremely important. Double-skin roof constructions have been analysed in the case of pitched roofs or flat roofs without refurbishment in the past; thus, we examined a refurbished structure of a panel building. The ventilated air layer of the flat roof was partially loose-filled with glass wool thermal insulation, and the layer boundaries were equipped with temperature and relative humidity sensors at four measurement places. The monitoring measurement was conducted for more than a year. Laboratory tests analysed the density-dependent thermal conductivity and moisture storage function of the applied thermal insulation, and the refurbishment was modelled with dynamic hygrothermal simulation. As a result, we found that the ventilation continued to work, and no condensation occurred in the measured layers, and the external concrete skin can reduce solar radiation by up to 85%. Respectively, we determined the thermal transmittance of the structure under dynamic hygrothermal conditions, which was 35% higher in the heating season than the dry steady-state design value.