International Scientific Journal


In this study, the optimum insulation thickness was calculated for the heating season for external walls in the different directions of a building. For this reason, a building used for housing in Istanbul, Turkey was taken as model. The indoor and outdoor temperatures, along with the interior and exterior surface temperatures of the building’s external walls, were continuously measured using thermocouples and recorded in four different directions throughout the year. The effects of solar radiation, which vary based on the direction, were assessed for the heat transfer through the external walls. The results of this study indicate that the optimum insulation thickness for the north, south, west, and east facing walls should be 6.47, 2.87, 6.97, and 6.98 cm, respectively, based on the differences in the amount of solar radiation exposure of the walls in the different directions. The optimum insulation thickness of the building’s external wall was calculated as 5.25 cm, regardless of its direction. An economic analysis of the thermal insulation cost was conducted using the P1-P2 method, and then the payback periods were calculated. The heating energy consumption of the building designed using the optimum insulation thicknesses, as identified separately based on the direction, decreased by 17%, compared to the present building with 3 cm of thermal insulation.
PAPER REVISED: 2018-10-27
PAPER ACCEPTED: 2018-10-31
CITATION EXPORT: view in browser or download as text file
  1. Özkan, D.B., Onan, C., Optimization of Insulation Thickness for Different Glazing Areas in Buildings for Various Climatic Regions in Turkey, Applied Energy, 88 (2011), 4, pp.1331-1342
  2. Al-Sanea, S.A., Zedan, M.F., Improving Thermal Performance of Building Walls by Optimizing Insulation Layer Distribution and Thickness for Same Thermal Mass, Applied Energy, 88 (2011), 9, pp. 3113-3124
  3. Daouas, N., A Study on Optimum Insulation Thickness in Walls and Energy Savings in Tunisian Buildings Based on Analytical Calculation of Cooling and Heating Transmission Loads, Applied Energy, 88 (2011), 1, pp. 156-164
  4. Özel M., Determination of Optimum Insulation Thickness Based on Cooling Transmission Load for Building Walls in Hot Climate, Energy Conversion and Management, 66 (2013), pp. 106-114
  5. Axaopoulos, I., et. al., Optimum Insulation Thickness for External Walls on Different Orientations Considering the Speed and Direction of the Wind, Applied Energy, 117 (2014), pp. 167-175
  6. Özkan, D.B., et. al., Yalıtım Malzemesi Kalınlığının Isı Yalıtımına Etkisi, Sigma Mühendislik ve Fen Bilimleri Dergisi, 27 (2009), pp. 190-196
  7. Özel, M., Pıhtılı, K., Isıtma ve Soğutma Derece Gün Değerlerini Kullanarak Optimum Yalıtım Kalınlığının Belirlenmesi, Sigma Mühendislik ve Fen Bilimleri Dergisi, 26 (2008), 3, pp. 191-198
  8. Kürekçi, A., et. al., Türkiye'nin Tüm İlleri için Optimum Yalıtım Kalınlığının Belirlenmesi, Tesisat Mühendisliği Dergisi, 131 (2012), pp. 5-21
  9. Bolattürk, A., Determination of Optimum Insulation Thickness for Building Walls with respect to Various Fuels and Climate Zones in Turkey, Applied Thermal Engineering, 26 (2006), pp. 1301-1309
  10. Bolattürk, A., Optimum Insulation Thickness for Building Walls with Respect to Cooling and Heating Degree-Hours in the Warmest Zone of Turkey, Building and Environment, 43 (2008), pp. 1055-1064
  11. Gürel, A., Daşdemir, A., Türkiye'nin Dört Farklı İklim Bölgesinde Isıtma ve Soğutma Yükleri için Optimum Yalıtım Kalınlıklarının Belirlenmesi, Erciyes Üniversitesi Fen Bilimleri Enstitüsü Dergisi, 27 (2011), pp. 346-352
  12. Dombaycı, Ö.A., et. al., Optimization of Insulation Thickness for External Walls Using Different Energy Sources, Applied Energy, 83 (2006), 9, pp. 921-928
  13. Kaynaklı, O., A Study on Residential Heating Energy Requirement and Optimum Insulation Thickness, Renewable Energy, 33 (2008), pp. 1164-1172
  14. Kaynaklı, O., et. al., Isıtma ve Soğutma Süreci İçin Dış Duvar Optimum Yalıtım Kalınlığı Hesabı, Isıtma, Soğutma, Havalandırma, Klima, Yangın ve Sıhhi Tesisat Dergisi, 65 (2010), pp. 39-45
  15. Onan, C., Determination of the Thermal Insulation for the Model Building Approach and the Global Effects in Turkey, Advances in Mechanical Engineering, 1 (2014), pp. 1-12
  16. Turkish Standard 825 (TS 825): Thermal insulation requirements for buildings, Turkish Standarts Institution, Ankara, TURKEY, 2008
  17. ***, Central Bank of the Republic of Turkey,
  18. Uçar, A., Balo, F., Effect of Fuel Type on the Optimum Thickness of Selected Insulation Materials for the Four Different Climatic Regions of Turkey, Applied Energy, 86 (2009), 5, pp. 730-736
  19. Sisman, N., et. al., Determination of Optimum Insulation Thicknesses of The External Walls and Roof (Ceiling) for Turkey's Different Degree-Day Regions, Energy Policy, 35 (2007), pp. 5151-5155
  20. Bektas, B., et. al.,. A Study on the Optimum Insulation Thicknesses of Various Types of External Walls with Respect to Different Materials, Fuels and Climate Zones in Turkey, Applied Energy, 92 (2012), pp. 211-217
  21. Kücüktopcu, E., Cemek, B., A Study on Environmental Impact of Insulation Thickness of Poultry Building Walls, Energy, 150 (2018), pp. 583-590
  22. Ashrafian, T., et. al., Methodology to Define Cost-Optimal Level of Architectural Measures for Energy Efficient Retrofits of Existing Detached Residential Buildings in Turkey, Energy and Buildings, 120 (2016), pp. 58-77

© 2020 Society of Thermal Engineers of Serbia. Published by the Vinča Institute of Nuclear Sciences, Belgrade, Serbia. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International licence