The Thermal Resistance of Spray-Applied Fiber Insulations

Abstract

The thermal resistances of four cellulosic and three mineral fiber spray-applied m- sulations have been determined using the flat Nichrome screen-heater apparatus de veloped at the Oak Ridge National Laboratory. Measurements were also made at Dynatech Scientific, Inc., on two of the same specimens of the cellulosic material and one similar specimen of the same mineral fiber product using conventional guarded hot plate and heat flow meter apparatuses. The experimental data obtained at ORNL were used to calculate R-values at 75°F from data obtained in the range 81 to 133 ° F The R-values obtained at Dynatech in cluded measurements at 75°F as well as measurements from 50 to 100°F for cellu losic insulations and 25 to 150°F for a mineral fiber insulation. The results from the two laboratories for the thermal resistance of identical specimens of spray-applied cellulose agreed to better than 1% while the agreement on similar specimens of a spray-applied mineral fiber insulation differed by less than 3%. The data discussed in this paper include spray-applied insulations that span the density range 1 to 8 lb/ft3 and the results show that material R -values for the spray- applied products can be predicted to within ± 10%, using correlations for the ap parent thermal conductivities of loose-fill insulation of the same type and density. They show further that existing plate and similar longitudinal heat flow methods are most appropriate for evaluating the performance of these types of materials.