Characterising thermal behaviour of buildings and its effect on urban heat island in tropical areas

Abstract

The heat island phenomenon in major cities is partly due to the excessive use of concrete and brick, which causes many problems regarding thermal comfort and energy expenditure. The thermal behaviour of the envelope wall material depends on its density, heat capacity, and thermal conductivity, and its effect on the heat island intensity (HII) is reported in this paper. Experiments and simulations were carried out on the four most popular building materials: brick, aerated concrete, wood with glass-wool insulation, and glass fibre-reinforced concrete with glass-wool insulation, with each material having a dimension of 1 m × 1 m. Experiments to analyse the thermal behaviour of the wall materials were performed by exposing each material to heat radiation from 2 × 1000 W halogen lamps for 4 h, followed by 4 h of cooling. The HII simulations were carried out in a simple urban kampong in a tropical area using Energy2D software. Heat flow analyses confirmed the thermal behaviour of the four walls, which can be categorised into two types: heat storage of block wall (BW) type and heat flow inhibition of insulated sandwich wall (ISW) type. The BW type showed 0.32 °C higher indoor air temperature than the ISW type, while the HII simulation showed ISW to be 0.74 °C higher than BW; however, both types increase the intensity and need mitigation treatment. The results of this study are important for the technological approach for dealing with local warming to lower the energy expenditure of poor people in an urban area. Keywords Urban heat island • Thermal behaviour • Block wall type • Insulated sandwich wall • Urban kampong List of symbols ρ Density c Specific heat κ Thermal conductivity avg Average density c avg Average specific heat avg Average thermal conductivity T so Outer surface temperature T si Inner surface temperature T m1 Temperature of the core wall at a depth of 2.5 cm T m2 Temperature of the core wall at a depth of 7.5 cm T m3 Temperature of the core wall at a depth of 12.5 cm P so Heat flow at outer surface P m1 Heat flow at a depth of 2.5 cm P m2 Heat flow at a depth of 7.5 cm P m3 Heat flow at a depth of 12.5 cm P si Heat flow at inner surface T ao Outdoor air temperature T ai Indoor air temperature T ac Outdoor air temperature above the canopy layer

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