Numerical investigation of the effect of clothing air gap distribution and environmental air speed on dry heat transfer underneath clothing

•Heat transfer from dressed human body was simulated using a validated CFD method.•Heat transfer distributes unevenly over human body covered with homogeneous air layer.•Considering only average value of the air gap thickness underestimates heat transfer.•Environmental air enters air layer through clothes openings and promote heat transfer.•Air speed decreases the threshold of air gap thickness for the onset of convection.