The purpose of this graduation thesis is to analyze the influence of particles' size on chipboard thermal insulation. For this purpose three different boards (size: 200x200mm) were prepared. Every board was composed of partices of different sizes. The first board was composed of small particles of the size 1,27mm, 1mm, 0,6mm and 0,23mm. The second board was composed of medium particles of the size 2mm and 1,5mm. The third board was composed of large particles of the size 4mm and 6,14mm. Thermal conductivity was measured by two thermocouples that were positioned on the upper and underside of the board. A third thermocouple was used to record the ambient temperature. The conclusion was reached that particles size affects thermal conductivity. The chipboard composed of large size particles proved to have the best insulation properties.