Numerical modeling of the impacts of high albedo materials on building energy savings

• Main Author: R.E.W.M.R.K Nisansala Ratnadiwakara
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::General; DRNTU::Engineering::Mechanical engineering::Energy conservation
• Online Access: http://hdl.handle.net/10356/53971
• Institution: Nanyang Technological University

The use of high albedo materials (cool coatings) on buildings is an emerging passive building cooling strategy to mitigate the consequences of urban heat island effect. This study was carried out by developing a numerical model of high-rise residential buildings located in Singapore. Energy simulations were conducted using Integrated Environmental Solutions (IES) <virtual environment> software to investigate the impact of increasing solar reflectance (cool coating) of external walls and roof on the conduction heat gain and air- conditioning energy savings. It was found that the increasing solar reflectance of external surfaces of the building materials is linearly correlated with the conduction heat gain into the building. By increasing solar reflectance from 0.4 to 0.8 of the insulated building materials; the conduction heat flux through wall and roof could be reduced in the range 0.708 – 1.195 W/m2 for air conditioned building. And indoor air temperature could be reduced up to 1⁰C in naturally ventilated (NV) building. The impact of increasing solar reflectance of roof surface has a much higher impact compared to walls. This is due to the higher amount of incident solar flux that roof receives and reflected throughout the day. The impact of increasing solar reflectance from 0.4 to 0.8 for non insulated reinforced concrete is equivalent to the impact achieved by including 20~22 mm of insulation material with 0.03 W/mK thermal conductivity and it was further verified, increasing solar reflectance in both non-insulated and insulated roofs are more effective in reducing conduction heat gain compared to the double skin roof. The conduction heat gain contribution to the annual energy consumption is reduced in the range of 4 - 4.5 kWh/m2 due to the impact of increasing solar reflectance from 0.4 to 0.8 in a lower floor which has no effect from roof conduction. For the top most floors, which has the impact of roof conduction; 13 – 17 kWh/m2 of annual energy consumption could be reduced. However these reductions of energy consumption due to building envelope heat gain depends on wall to roof (W/R) ratio as well as roof to floor area (R/F) ratios of a building. Much higher energy savings could be achieved with a smaller W/R ratio and higher R/F ratio.