It is intended to investigate the relationship between the thernal insulation of the textile fabrics and their thickness, specific volume and porosity. The experiments were carried out with the constant temperature disc method. Also the experimental results wee analysed with the assumption of the heat transfer through a sheet of porous low density solid. The conclusions were followings: 1. The qualitative analysis of the heat transfer through a sheet of porous low density solid was coincided with the experimental results. 2. The exponential relationship between the thickness and the thermal insulation of the textile fabrics was found. 3. The proportional relationship between the thermal insulation and the specific volume, and between the thermal insulation and the porosity were found.