Thermal performance of envelope wall/roofs of intermittent air-conditioned rooms

The thermal performance of six wall/roof configurations in an intermittent air-conditioned room, in a climate where the outdoor temperature or the sol–air temperature swing crosses the thermal comfort zone, was numerically evaluated. The intermittent air-conditioning system operates heating or cooling. When operating for cooling it is turned on when the indoor temperature is greater than the upper comfort temperature and when operating for heating it is turned on if the indoor temperature is smaller than the lower comfort temperature; otherwise it remains off. A one dimensional heat transfer model with periodic outdoor conditions was considered. The parameters used to evaluate the configurations are the energy for the on-periods and a thermal index during the off-periods. For comparison purposes, the wall/roof configurations were also evaluated in an air-conditioned room where the temperature was kept constant full time. The results show that the thermal evaluation of a wall/roof must be done taking into account the operation condition of the air-conditioning system.

► The thermal effect of wall/roof configurations is studied.
► 6 roofs are studied with two conditions, full time and intermittent air-conditioning.
► In a hot climate where temperature swings cross the thermal comfort zone.
► The best roof is the one that uses less energy and produces small thermal discomfort.
► The best roof depends on climate and operating conditions.