Mineral wool is a widely employed material mainly used for the insulation of residential buildings. A mineral fiber insulation was investigated in a round robin test by means of the guarded hot plate apparatus (GHP 456 Titan) and heat flow meters (HFM 436 series) between 10°C and 30°C. As it is typical for most insulating materials, there is a linear increase in the thermal conductivity results around room temperature. The results obtained with the different measuring systems are in good agreement. This round robin test further confirms that by means of the absolute measurement method (GHP), an accuracy of <2% can be obtained.