In this work particularities of thermal conductivity measurements of fibrous or fiber having heat insulation materials using hot wire methods EN 993-14 and ISO 8894-2 were investigated. Dependence of the thermal conductivity on the test temperature, heating current and hot wire orientation with reference to fiber direction was determined experimentally. Heat insulation materials investigated included: rock wool of various densities, glass fiber and extrusion polystyrene. Measured thermal conductivities determined by both test methods coincide pretty well. Mismatch never exceeded the error induced by the measurement device itself.