The humidity increase of the thermal insulation material, as well known, raises value of the thermal conductivity and reduces the overall thermal resistance of buildings. The article presents the thermal conductivity of insulation material on an example of the thermal insulation material "Fiberteks". This information was obtained experimentally: 0,022; 0,031; 0.092 W/mK (density of the material is 30kg/m3 and humidity is 0%; 12%; 23%. The dependence of thermal conductivity and the material density were identified. Also the reduced resistance to heat transfer for the three wall structures was calculated. "Fiberteks" was presented with different humidity: W = 6%, W = 10%, and W = 23%. As a result of the calculation we analyzed the dependence of thermal resistance to heat transfer and humidity of "Fiberteks": by increasing the humidity content material‘s ability to thermal resistance decreases. Because of this the overall thermal resistance of the enclosure also decreases.