Thermal Performance Evaluation of Domed Roofs Ahmadreza K. Faghih 1,* , Mehdi N. Bahadori 2 1 Yazd University, Yazd, Iran 2 Sharif University of Technology, Tehran, Iran * Corresponding author. Tel: +98 351 8122561, Fax: +98 351 8210699, E-mail: faghih@yazduni.ac.ir Abstract: Domed roofs (DRs) have been used in Iran and many other countries to cover large buildings such as mosques, shrines, churches, schools, etc. They have been also employed in other buildings like bazaars or market places in Iran due to their favorable thermal performance. The aim of this research is to study about DRs thermal performance in order to determine how they can be helpful in reducing the maximum air temperature of inside buildings during the warm seasons considering all parameters like air flow around them, solar radiation, radiation heat transfer with the sky and the ground as well as some openings on the building. The results of the study show that the thermal performance of the investigated DR is better than the building with flat roof (FR), particularly when the dome is covered with glazed tiles. In addition to their aesthetic values, domes covered with glazed tiles have thermal benefits of keeping the inside air of these buildings relatively cool during the summer. Moreover, openings cause passive air flow inside building, which is helpful for human comfort. Keywords: domed roof, thermal performance, air flow, solar radiation, numerical simulation, thermal network Nomenclature C Specific heat................................... J.kg -1 K -1 l ′ Depth of ground ....................................... m C D Discharge coefficient .................................. m Inside building air mass .......................... kg C p Pressure coefficient .................................... m  Air mass flow rate .............................. kg.s -1 D Wall or roof thickness .............................. m q  Heat transfer rate ............................... w.m -2 F View factor.................................................. t Time ........................................................... s H,h Height ...................................................... m β Slope ............................................................ R flow resistance .............................. kg.m -4 .s -1 ε Surface emittance ........................................ T Temperature .............................................C s ε Sky emissivity............................................... V  Volumetric air flow rate .................... m 3 .s -1 ρ Density............................................... kg.m -3 V Velocity ................................................ m.s -1 σ Stefan-Boltzmann constant .............. w.m -2 .k Subscript R Roof............................................................. i Inner surface, Inside building, i opening W Wall, roof .................................................... j j opening ...................................................... H Height ......................................................... m Maximum ..................................................... a Air ............................................................... n Minimum, Natural, North ............................ abs Absorbed ..................................................... o Outer surface, Ambient................................ c Convection .................................................. r Radiation ..................................................... dp Dew point.................................................... rg Radiation with ground ................................. e East ............................................................. rs Radiation with sky ....................................... f Floor ........................................................... s Absorbed solar radiation, Sky, South .......... g Ground........................................................ w West ............................................................. 1. Introduction DRs have traditionally been used throughout the world to cover large areas. Solar energy absorbed by a DR causes its temperature to rise above the ambient air temperature. Wind blowing over the dome increases the convection heat transfer to the ambient air. Furthermore, the heat loss from the roof is increased by thermal radiation to the sky. The rest of the heat absorbed by the dome is conducted through the dome material, and is finally transferred to the 1946