Performance of a novel structural insulated panel in tropical climates: Experimental and numerical studies

This article investigates experimentally and numerically the thermal performance of a new type of structural insulated panel (SIP) termed 'UWall'. The panel core consists of an ad-hoc waffle skeleton of Expanded Polystyrene (EPS), EPS beads mixed with cement mortar (Portland cement type I and recycled concrete aggregate), and two external water-proof cement boards. The experimental programme examined the panels in three Phases. In Phase 1, 200x200x100 mm block specimens were exposed to a temperature of 70 degrees C for 12 hrs. It was found that the new UWall specimens had a better thermal performance (by up to 20%) over other types of walls typically used in house construction in Southeast Asia such as Mon block wall. In Phase 2, five scaled-down house units (1.5x1.5x2.8 m) were built in Thailand. Temperature and relative humidity outside/inside the units were continuously monitored for 7 days during the summer season. It was found that the new UWall has a good thermal resistance, reducing temperatures by up to 4 degrees C compared to mon-block wall material. The house units were subsequently modelled in Abaqus (R) software, and the modelling approach proved accurate (within 10%) at simulating the thermal performance of the house units. UWall panels were also tested in bending to determine their structural capacity. It was found that the panels can be safely used as load-bearing walls for single-storey houses. Design charts are then proposed and used to design and build a full-scale house in Phase 3. In Phase 3, a 10x7 m full-scale single-storey house was built using the new UWall panels. Based on results from bioclimatic charts, it was found that daytime temperature and humidity in the full-scale house were deemed as uncomfortable. However, if air movement was provided, the house remained within the comfortable zone at all times. New design charts for full-scale houses with UWall are proposed to meet a desired user-comfort level. This study is expected to promote the use of SIPs in house construction in tropical climates, which in turn is envisaged to save energy and make construction more sustainable.