Optimum R-values of building walls under different climatic conditions in the Kingdom of Saudi Arabia

• Optimum wall R-values are determined for different climatic regions in Saudi Arabia.
• Optimum R-values are obtained using dynamic heat transfer and economic models.
• Optimum R-values for Riyadh and Jeddah regions range from 2 to 2.9 m2.K/W.
• Optimum R-values for Abha region range from 1.34 to 1.99 m2.K/W.
• Payback periods using optimum insulation thickness range from 3 to 10 years.

This paper deals with the determination of optimum R-values for building walls under different climatic conditions in the Kingdom of Saudi Arabia (KSA); namely, Riyadh, Jeddah, and Abha. One-layered and two-layered walls made of concrete and red clay blocks are considered. Molded polystyrene, polyurethane board, and rock wool are used as insulation materials. Thermal and economic analyses are carried out in order to determine the optimum insulation thickness (Lopt). The thermal analysis involves calculating temperature distribution and its variation with time across wall sections under steady periodic conditions. This is done by utilizing a previously validated computer model based on the finite-volume implicit method. Yearly transmission loads are calculated for different insulation thicknesses and used in an economic model, based on the present worth method, in order to optimize the insulation thickness and consequently determine the optimum R-values. Cooling and heating loads are separated and treated with different costs. For Riyadh and Jeddah, the optimum R-values are found in the range 2.00 to 2.90 m2.K/W, while those for Abha are found in the range 1.34 to 1.99 m2.K/W. Payback periods determined at Lopt, while considering effect of inflation and discount rates, are found in the range 3 to 10 years.