The use of LCC and optimisation in determining optimum insulation thickness: Case of Ankara, Turkey

In energy-efficient design, the thickness of the building’s insulation is a critical factor. Because the material is thicker than the optimum level, the initial investment costs of the structure rise, whereas the running costs of the building rise if the level is thinner. For this reason, the thickness of the optimum insulation must be calculated correctly in the early design process. Previous research attempted to solve this problem by calculating the optimum insulation thickness for a 10-year period while only considering the external wall. However, structures should be addressed as a whole, and the economic life cycle for residential buildings has been specified as 30 years in Article 2 (14) of the Energy Performance of Buildings Directive. This study aims to uncover the most optimum insulation thickness with the correct lifespan in terms of life cycle cost by addressing the entire building and demonstrating the inaccuracy of prior studies with the novel methodology based on life cycle costing and optimization algorithms. In the study, thirty different insulation thicknesses and two different materials have been used. The new methodology has been applied to the mass housing unit constructed in Ankara in the last 10 years to give information about insulation thicknesses used in the Turkish housing environment. Optimum insulation thicknesses based on the third climate zone for a period of 30 years are calculated as 0.12 m for the external walls. This study reveals that accurate calculations using the right lifespan will result in huge savings in energy and cost. In the case study, which was selected by applying the optimum insulation thickness, the annual energy expenses are decreased by 13%. These findings have indicated that for buildings constructed in the third climatic zone, the optimal insulation thicknesses should be reviewed. The results of the methodology may be utilized as important inputs throughout the decisionmaking processes of the construction sectors.

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