English
Русский A field comparison of the thermal performance of ventilated and plastered façades in hot conditions using the climate of Southern Kazakhstan as an example: internal surface temperature and air conditioning energy efficiency
Abstract
This paper presents a field (full-scale) study comparing the thermal performance of a ventilated rainscreen façade (VRF) and a traditional plastered (“wet”) façade on the eastern façade of a nine-story reinforced concrete frame residential building in Southern Kazakhstan during a hot summer period. Sensor-equipped sections of the multilayer wall structure from the 1st to the 9th floors were monitored simultaneously using DS18B20 multichannel contact temperature sensors, an unmanned thermal imaging system (DJI Mavic 3 Thermal), and a handheld thermal imager (Testo 875), providing double, independent validation of surface temperature data. Measurements were taken at 9:00, 12:00, 15:00, and 18:00 on a typical hot day. Although the temperature of the VRF exterior cladding during peak insolation hours exceeded the temperature of the wet façade by up to 2.2°C (reaching 60.1°C on the ninth floor at midday), the temperature of the VRF internal surface was consistently lower than the temperature of the wet façade internal surface on virtually all floors and at all times, the decrease reached 1.55°C, and averaged 1.0-1.3°C during the hottest hours. This apparent paradox, a hotter exterior cladding with a cooler internal surface, is explained by convective decoupling, which is provided by the ventilated air gap: it removes solar-heated air before it has a chance to transfer heat to the load-bearing wall via conduction. Based on the measured temperature difference of the internal surface and its standard heat transfer coefficient, it was shown that the conductive-convective component of the air-conditioning load for rooms behind the VRF is reduced by approximately 7-10% compared to a wet façade during typical hot daytime hours. These results, which relate to the relatively little-studied hot arid/continental climate of Central Asia, expand the evidence base, formed primarily from Mediterranean and Western European studies, and create a natural experimental basis for further thermal and aerodynamic modeling of the ventilated air gap.