Optimization of insulation thickness of walls and roofs using energy, exergy, economic and environmental (4E) analyses


  • Aynur Uçar Department of Mechanical Engineering, Firat University, 23279 Elazığ, Turkey. Phone: +90 0424 2370000/5333; Fax.: +90 424 2415526




Optimum insulation thickness, 4E analysis, Optimization model, CO2 emissions, Exergy


Buildings play an important role in consumption of energy and carbon dioxide emissions all over the world.  The optimum thickness of each insulation material of wall and roof of residential buildings depending on energy, environment, economy and exergy was determined in this study. For this purpose, an optimization model was established based on four different criteria: energy, environment, economics, and exergy. A function was defined containing these four criteria. It has been seen from the results that the optimum insulation thickness of the wall and roof depends on the weight coefficients of the energy, environment, economic and exergy parameters and insulation material types. The results of the economic analysis indicate that the optimum insulation thickness of wall varies from 1.01 to 7.7 cm and the optimum thicknesses of roof varies from 3.25 to 6.7 cm for XPS, EPS and Glasswool insulation materials. According to the results of the enviromental analysis, the optimum thicknesses of wall for different insulation materials are 6.5, 8.6, 9.4, and 9.55 cm and optimum insulation thicknesses of roof are 7.55, 8.1 and 8.2 cm, respectively. The effect of economic and energy parameters on the optimum thickness of the wall and roof for the three insulation materials was investigated using the sensitivity analysis method. It was seen from the results that impacts of interest rate, inflation rate, electricity cost, fuel cost, insulation material cost, heating and cooling degree-days on the optimum insulation thickness of wall and roof and 4EF optimization function were different.


IEA, “A source of enormous untapped efficiency potential: Buildings,”The International Energy Agency [Online], Available: https://www.iea.org/topics/buildings.

Ö. A. Dombayci, Ö. Atalay, Ş.G. Acar, E.Y. Ulu, and H. K. Özturk, “Thermoeconomic method for determination of optimum insulation thickness of external walls for the houses: Case study for Turkey,” Sustainable Energy Technologies and Assessments, vol. 22 pp. 1–8, 2017.

G. Özel, E. Açıkkalp, B. Görgün, H. Yamık, and N. Caner, “Optimum insulation thickness determination using the environmental and life cycle cost analyses based entransy approach,” Sustainable Energy Technologies and Assessments, vol. 11, pp. 87-91, 2015.

P. Jie, F. Zhang, Z. Fang, H. Wang, and Y. Zhao, “Optimizing the insulation thickness of walls and roofs of existing buildings based on primary energy consumption, global cost and pollutant emissions,” Energy, vol. 159, pp. 1132–1147, 2018.

J. Yuan , C. Farnham, and K. Emur, “Optimum insulation thickness for building exterior walls in 32 regions of China to save energy and reduce CO2 emissions,” Sustainability, vol. 9, pp. 1-13, 2017.

I. Axaopoulos, P. Axaopoulos, J. Gelegenis, and E.D.Fylladitakis, “Optimum external wall insulation thickness considering the annual CO2 emissions,” Journal of Building Physics, vol. 42, pp. 527–544, 2019.

A.P. Akan, and A.E. Akan, “Modeling of CO2 emissions via optimum insulation thickness of residential buildings,” Clean Technologies and Environmental Policy, vol. 24, pp. 949–967, 2022

M. Braulio-Gonzalo, and M.D. Bovea, “Department Environmental and cost performance of building’s envelope insulation materials to reduce energy demand: Thickness optimization,” Energy and Buildings, vol. 150, pp. 527–545, 2017.

R.M. Lazzarin, F. Busato, and F. Castellotti, “Life cycle assessment and life cycle cost of buildings insulation materials in Italy,” International Journal of Low Carbon Technologies, vol. 3, pp. 44-58, 2008.

L.F. Cabeza, L. Rincón, V. Vilariño, G. Pérez, and A. Castell, “Life cycle assessment (LCA) and life cycle energy analysis (LCEA) of buildings and the building sector: A review,” Renewable and Sustainable Energy Reviews, vol. 29, pp. 394–416, 2014.

A. Ferrández-García, V. Ibánez-Forés, and M.D. Bovea, “Eco-efficiency analysis of the life cycle of interior partition walls: a comparison of alternative solutions,” Journal of Cleaner Production, vol. 112, pp. 649–665, 2016.

A. Atmaca, “Life-cycle assessment and cost analysis of residential buildings in South East of Turkey: Part 2—A case study,” Intatnational Jornal of Life Cycle Assessment, vol. 21, pp. 925–942, 2016.

K. Valancius, T. Vilutiene, and A. Rogoža, “Analysis of the payback of primary energy and CO2 emissions in relation to the increase of thermal resistance of a building,” Energy and Buildings, vol. 179, pp. 39–48, 2018

M. Ashouri, F. R. Astaraei, R. Ghasempour, M. H. Ahmadi, and M. Feidt, ”Optimum insulation thickness determination of a building wall using exergetic life cycle assessment,” Applied Thermal Engineering, vol. 106, pp. 307–315, 2016.

E. A. Rad, and E. Fallahi, “Optimizing the insulation thickness of external wall by a novel 3E (energy, environmental, economic) method,” Construction and Building Materials, vol. 205, pp. 196–212, 2019.

U. Y. A. Tettey, A. Dodoo, and L. Gustavsson, “Effects of different insulation materials on primary energy and CO2 emission of a multi-storey residential building,” Energy and Buildings, vol. 82, pp. 369–377, 2014.

E. Işık, M. İnallı, and E. Celik, “ANN and ANFIS approaches to calculate the heating and cooling degree day values: The case of provinces in Turkey,” Arabian Journal for Science and Engineering, vol. 44, pp. 7581–7597, 2019.

G. Kahraman, “Comparison of heat transfer and condensation on the walls of buildings constructed with iron profiles versus other classic models,” Heat Transfer Research, vol. 52, pp. 1-10, 2021.

D. Evin, and A. Ucar, “Energy impact and eco-efficiency of the envelope insulation in residential buildings in Turkey,” Applied Thermal Engineering, vol. 154, pp. 573–584, 2019.

A. Ucar, “Thermoeconomic analysis method for optimization of insulation thickness for the four different climatic regions of Turkey,” Energy, vol. 35, pp. 1854–1864, 2010.




How to Cite

A. Uçar, “Optimization of insulation thickness of walls and roofs using energy, exergy, economic and environmental (4E) analyses”, J. Mech. Eng. Sci., vol. 18, no. 1, pp. 9959–9975, Apr. 2024.