Numerical Investigation of Roofing Materials Effect on Solar Heat Gain in Different External Conditions

Document Type: Full Lenght Research Article


1 Department of Mechanical Engineering, University of Victoria, Victoria, Canada

2 Persian Gulf University


In this study, the thermal performance of three kinds of roofs with different heat capacity and thermal conductivity under different external conditions has been investigated using a numerical method. For this purpose, the combined solar radiation, conduction and convection heat transfer were calculated implicitly in terms of a one-dimensional finite difference method. Different high and low solar radiation conditions in two common climates in the Middle East, including hot-humid and hot-dry, were considered. The effect of roofing materials was investigated in terms of their thermal storage and overall heat transfer coefficient. Moreover, the time lags and decrement factors were evaluated to compare the performance of the roof. The numerical model has been validated using EnergyPlus. The results indicate that the roof with high thermal storage and low thermal conductivity has better performance in comparison to others. However, the total heat gains are not linearly proportional to the overall heat transfer coefficients, e.g. here, the ratios of a total load of roof 1 to roofs 2 and 3 are about 12 percent lower than the ratio of overall heat transfer coefficients. Furthermore, the solar radiation intensity had considerable effects on time lags. Finally, it can be concluded that the external conditions have no significant effect on the decrement factor.


Main Subjects

[1] B. Yesilata, H. Bulut, P. Turgut, “Experimental study on thermal behavior of a building structure using rubberized exterior-walls,” Energy and Buildings, 43(2-3), 393-399, (2011).

[2] C. Martins, P. Santos, L.S. da Silva, “Lightweight steel-framed thermal bridges mitigation strategies: A parametric study,” Journal of Building Physics, 39(4), 342-372, (2016).

[3] Z. Yılmaz, “Evaluation of energy efficient design strategies for different climatic zones: Comparison of thermal performance of buildings in temperate-humid and hot-dry climate,” Energy and buildings, 39(3), 306-316, (2007).

[4] C. Balaras, “The role of thermal mass on the cooling load of buildings. An overview of computational methods,” Energy and Buildings, 24(1), 1-10, (1996).

[5] S. Maneewan, J. Khedari, B. Zeghmati, J. Hirunlabh, J. Eakburanawat, “Investigation on generated power of thermoelectric roof solar collector,” Renewable Energy, 29 (5), 743-752, (2004).

[6] J. Han, L. Lu, H. Yang, “Investigation on the thermal performance of different lightweight roofing structures and its effect on space cooling load,” Applied Thermal Engineering, 29(11-12), 2491-2499, (2009).

[7] T. Runsheng, Y. Etzion, E. Erell, “Experimental studies on a novel roof pond configuration for the cooling of buildings,” Renewable Energy, 28(10), 1513-1522, (2003).

[8] K. Vijaykumar, P. Srinivasan, S. Dhandapani, “A performance of hollow clay tile (HCT) laid reinforced cement concrete (RCC) roof for tropical summer climates,” Energy and Buildings, 39(8), 886-892, (2007).

[9] A. Sharifi, Y. Yamagata, “Roof ponds as passive heating and cooling systems: A systematic review,” Applied energy, 160, 336-357, (2015).

[10] N. Daouas, “Impact of external longwave radiation on optimum insulation thickness in Tunisian building roofs based on a dynamic analytical model,” Applied Energy, 177, 136-148, (2016).

[11] J. Yu, L. Tian, C. Yang, X. Xu, J. Wang, “Optimum insulation thickness of residential roof with respect to solar-air degree-hours in hot summer and cold winter zone of china,” Energy and Buildings, 43(9), 2304-2313, (2011).

[12] S.M. Heibati, F. Atabi, M. Khalajiassadi, A. Emamzadeh, “Integrated dynamic modeling for energy optimization in the building: Part 1: The development of the model,” Journal of Building Physics, 37(1), 28-54, (2013).

[13] S. Mohammad, A. Shea, “Performance evaluation of modern building thermal envelope designs in the semi-arid continental climate of Tehran,” Buildings, 3(4), 674-688, (2013).

[14] Bureau for Compiling and Promoting National Regulations for Buildings; Code No. 19, Isfahan, Iran, (2010).

[15] R. Fayaz, B.M. Kari, “Comparison of energy conservation building codes of Iran, Turkey, Germany, China, ISO 9164 and EN 832,” Applied Energy, 86(10), 1949-1955, (2009).

[16] G. Barrios, G. Huelsz, J. Rojas, “Thermal performance of envelope wall/roofs of intermittent air-conditioned rooms,” Applied Thermal Engineering, 40, 1-7, (2012).

[17] C. Mackey, L. Wright, “Periodic heat flow—composite walls or roofs”, ASHVE Transactions, 52(283), 194-196, (1946).

[18] E. Al-Regib, S.M. Zubair, “Transient heat transfer through insulated walls,” Energy, 20(7), 687-694, (1995).

[19] S.A. Al-Sanea, “Thermal performance of building roof elements”, Building and Environment, 37(7), 665-675, (2002).

[20] H. Asan, “Numerical computation of time lags and decrement factors for different building materials,” Building and Environment, 41(5), 615-620, (2006).

[21] S.F. Larsen, C. Filippín, G. Lesino, “Thermal behavior of building walls in summer: Comparison of available analytical methods and experimental results for a case study,” Building Simulation, 2(1), 3-18, (2009).

[22] H. Asan, Y. Sancaktar, “Effects of wall's thermophysical properties on time lag and decrement factor,” Energy and Buildings, 28(2), 159-166, (1998).

[23] H. Asan, “Investigation of wall's optimum insulation position from maximum time lag and minimum decrement factor point of view,” Energy and Buildings, 32(2), 197-203, (2000).

[24] K. Kontoleon, E. Eumorfopoulou, “The influence of wall orientation and exterior surface solar absorptivity on time lag and decrement factor in the Greek region,” Renewable Energy, 33(7),1652-1664, (2008).

[25] L.E. Mavromatidis, M.E. Mankibi, P. Michel, M. Santamouris, “Numerical estimation of time lags and decrement factors for wall complexes including Multilayer Thermal Insulation, in two different climatic zones,” Applied Energy, 92, 480-491, (2012).

[26] L. Zhang, J. Zhang, F. Wang, Y. Wang, “Effects of wall masonry layer’s thermophysical properties and insulation position on time lag and decrement factor,” Indoor and Built Environment, 25(2), 371-377, (2016).

[27] G. Athanassouli, P. Massouros, “A model of the thermal restoration transient state of an opaque wall after the interruption of solar radiation,” Solar energy, 66(1), 21-31, (1999).

[28] S.F. Larsen, G. Lesino, “A new code for the hour-by-hour thermal behavior simulation of buildings,” Proceedings of VII International Building Simulation Congress (Brazil), 75-82, (2001).

[29] A. Al-Turki, G. Zaki, “Cooling load response for building walls comprising heat storing and thermal insulating layers”, Energy Conversion and Management, 32 (3), 235-247, (1991).

[30]Available from:

[31] G.N. Walton, Thermal analysis research program reference manual, National Bureau of Standards, (1983).

[32] H. Suehrcke, E.L. Peterson, N. Selby, “Effect of roof solar reflectance on the building heat gain in a hot climate”, Energy and Buildings, 40(12), 2224-2235, (2008).

[33] H. Shen, H. Tan, A. Tzempelikos, “The effect of reflective coatings on building surface temperatures, indoor environment and energy consumption—An experimental study”, Energy and Buildings, 43(2-3), 573-580, (2011).

[34] American Society of Heating, Air-Conditioning and Refrigeration Engineers, Inc, ASHRAE Handbook, Fundamentals, Atlanta, (2005).

[35] M. Ozel, K. Pihtili, “Optimum location and distribution of insulation layers on building walls with various orientations”, Building and Environment, 42(8), 3051-3059, (2007).

[36] Energyplus, EnergyPlus Engineering Reference, (2010).

[37] W. Hayt, Engineering circuit analysis, 8th Ed, New York, McGraw-Hill, (2012).


Volume 6, Issue 1
Winter and Spring 2019
Pages 41-53
  • Receive Date: 20 January 2017
  • Revise Date: 03 September 2018
  • Accept Date: 08 September 2018