© 2017 Journal of Thermal Engineering.The aim of this study is to investigate transient buoyancy driven free convection heat transfer in domical (with a dome) structures or curved roofs is numerically. Two- and three-dimensional turbulent free convection are considered for the Rayleigh number intervals (108≤ Ra≤1010). The aspect ratios of H/L=1 and 2, with respect to the heated length, are considered. The heating is provided from a lateral surface while cooling is from opposing lateral surface. The hot and cold surfaces are kept isothermal, and all other surfaces are adiabatic. The Boussineq approximation is used for modeling the buoyancy flow. The RNG k-ε turbulence model is used. The pertinent transient equations are solved using Fluent 6.3.26 software. The flow of air (streamlines) and temperature distribution (isotherms) are produced. The mean Nusselt number is evaluated over the isothermal hot wall is computed, and the results are analyzed with respect to the flow and geometric variations. The mean Nusselt number using the 2-D simulations indicate that the mean Nusselt number does not significantly change with H/L ratio. The 3-D simulations yield higher mean Nusselt numbers, but they are smaller than those of obtained for flat top enclosures.