The surface renewal model of wall turbulence is coupled with the classical eddy diffusivity/mixing length approach for the turbulent core to analyze turbulent variable property gas flows with moderate heating and cooling. The analysis indicates that the mean frequency of wall turbulence is decreased by heating and increased by cooling, with the heating effect being significantly greater than the cooling effect. The analysis also gives rise to mean velocity and temperature distributions, friction factors and Stanton numbers that are consistent with most of the experimental data for both heating and cooling.