The conduction heat transfer coefficients of the fibrous insulation materials depend on temperature, especially under high temperature conditions. In this study, the device, called guarded hot plate (GHP), measuring the heat transfer performance of insulation materials under high temperature conditions is improved. Circulation of the cooling fluid inside aluminum cold plates is optimized by numerical results. To prevent leakage of the fluid, metal pipes are inserted into the conduits aiming the fluid to circulate throughout these pipes. Following the design, the cold plates are manufactured and the computational results are validated by the experimental ones. By the new designed cold plate, the system operates and achieves validated measurements for the thermal conductivity of the fibrous insulation materials, under high temperature conditions. (C) 2016 The Authors. Published by Elsevier Ltd.