A material’s thermal conductivity is the capacity to conduct air. Better bricks should have a low thermal conductivity in order to keep the houses cool in summer and warm in winter. Often special insulating bricks are needed in structures for thermal insulation.
Standard red bricks have 0.6 Wm-1K-1 thermal conductivity. For insulating bricks, the value is even lower at 0.15 Wm-1K-1.