This article presents Large Eddy Simulations of thermal boundary layer spatial development in a low-Mach number turbulent channel flow. A coupling between isothermal biperiodic channel and anisothermal open channel is done to obtain a fully developed turbulent inlet. The interaction between a high temperature gradient and a turbulent flow is studied during the thermal boundary layer development. Turbulence and temperature quantities are analyzed for both streamwise and wall-normal directions. The results show how the asymmetrical heating modifies the velocity of the flow. The correlation between turbulence and heat transfers is studied. The mean and the fluctuation profiles are found to be asymmetrical. They evolve along the channel and are perturbed by the thermal gradient. Fluctuation destruction and creation areas in the length of the channel are highlighted.