Review of kM coefficients of building materials

The Design of a lightning protection system requires the determination of the separation distance according to DIN EN 62305-3 (VDE 0185-305-3). The coefficient km is used to take into account construction material in a given separation distance calculation. Only two values can be applied, 1 for air and 0.5 for concrete and bricks. Due to the introduction of new materials used in structures of buildings the question of a revision of the existing km coefficients came up.