Highly Reflective Roofing Sheets Installed on a School Building to Mitigate the Urban Heat Island Effect in Osaka

Currently, strategies to mitigate urban heat island (UHI) effects and reduce building energy consumption are implemented worldwide. In Japan, as an effective means of mitigating UHI effects and saving energy of buildings, highly reflective (HR) roofs have increasingly been used. In this study, in order to evaluate the effect of HR roofs on building energy conservation, we investigated the solar reflectivity of a subject school roof in Osaka, Japan, in which HR roofing sheets were installed on the roof from 2010. Additionally, monthly and annual thermal loads, including the cooling load and heating load of the top floor of the school, were calculated using the thermal load calculation software New HASP/ACLD-β. Comparing the calculated thermal loads of the school after HR roofing sheet installation to before, the annual thermal load decreased about 25 MJ/m 2 /year, and the cooling load decreased about 112 MJ/m 2 /year. However, the heating load increased about 87 MJ/m 2 /year in winter. To minimize the annual thermal load, thermal insulation of the roof was also considered to be used together with HR roofing sheets. Thermal load calculations showed that the combination of HR roofing sheets and thermal insulation can be effective in further reducing the annual thermal load.

[1]  M. Santamouris.  Regulating the damaged thermostat of the cities—Status, impacts and mitigation challenges , 2015 .

[2]  Jihui Yuan,et al.  A method to measure retro-reflectance and durability of retro-reflective materials for building outer walls , 2015 .

[3]  M. Santamouris,et al.  Estimating the ecological footprint of the heat island effect over Athens, Greece , 2007 .

[4]  H. Takebayashi,et al.  Study to examine the potential for solar energy utilization based on the relationship between urban morphology and solar radiation gain on building rooftops and wall surfaces , 2015 .

[5]  H. Akbari,et al.  Cooling energy savings potential of reflective roofs for residential and commercial buildings in the United States , 1999 .

[6]  M. Santamouris.  Cooling the cities – A review of reflective and green roof mitigation technologies to fight heat island and improve comfort in urban environments , 2014 .

[7]  M. Santamouris,et al.  Using advanced cool materials in the urban built environment to mitigate heat islands and improve thermal comfort conditions , 2011 .

[8]  D. Asimakopoulos.  Energy and Climate in the Urban Built Environment , 2001 .

[9]  G. Mihalakakou,et al.  Determination of places in the great Athens area where the heat island effect is observed , 2002 .

[10]  Lena Vogler.  Energy And Climate In The Urban Built Environment , 2016 .

[11]  Jihui Yuan,et al.  Development of a retro-reflective material as building coating and evaluation on albedo of urban canyons and building heat loads , 2015 .

[12]  Helena A. Flocas,et al.  Application of Neural Networks to the Simulation of the Heat Island over Athens, Greece, Using Synoptic Types as a Predictor , 2002 .

[13]  Yinghong Qin,et al.  A side by side comparison of the cooling effect of building blocks with retro-reflective and diffuse-reflective walls , 2016 .

[14]  J. Taylor,et al.  Toward mitigating urban heat island effects: Investigating the thermal-energy impact of bio-inspired retro-reflective building envelopes in dense urban settings , 2015 .

[15]  N. Klitsikas,et al.  The effect of the Athens heat island on air conditioning load , 2000 .

[16]  Masatoshi Nishioka,et al.  RETROREFLECTIVE PROPERTIES CALCULATING METHOD BASED ON GEOMETRICAL-OPTICS ANALYSIS , 2008 .

[17]  Elena Morini,et al.  Beneficial effects of retroreflective materials in urban canyons: results from seasonal monitoring campaign , 2015 .

[18]  Luis Pérez-Lombard,et al.  A review on buildings energy consumption information , 2008 .

[19]  A. Pisello,et al.  Experimental Analysis of Natural Gravel Covering as Cool Roofing and Cool Pavement , 2014 .

[20]  H. Akbari,et al.  Local climate change and urban heat island mitigation techniques – the state of the art , 2015 .

[21]  Anna Laura Pisello,et al.  Experimental in-lab and in-field analysis of waterproof membranes for cool roof application and urban heat island mitigation , 2016 .

[22]  Andrea Presciutti,et al.  Retroreflective façades for urban heat island mitigation: Experimental investigation and energy evaluations , 2015 .

[23]  Marwa Dabaieh,et al.  Reducing cooling demands in a hot dry climate: A simulation study for non-insulated passive cool roof thermal performance in residential buildings , 2015 .

[24]  Mattheos Santamouris,et al.  Development and analysis of advanced inorganic coatings for buildings and urban structures , 2015 .

[25]  Norio Igawa,et al.  Reduction of Reflected Heat of the Sun by Retroreflective Materials , 2009 .