The primary means of establishing the thermal performance of loose-fill insulation is ASTM Standard Practice C 687. To provide information for the development of a statement of precision and bias for this Standard Practice, a round robin was carried out by eleven laboratories measuring apparent thermal conductivity of four common loose-fill insulation products (cellulose, rock/slag wool, and bonded and unbonded glass fiber) and a glass fiber blanket.

The test results on the glass fiber blanket indicate that the measurement capability of the participants can be characterized by an imprecision of 3.0%, as measured by two standard deviations, and a negligible bias of the mean. The measurements on the loose-fill materials are characterized by an imprecision ranging from 21% for cellulose to 10% for the rock/slag wool. The increase in imprecision for the loose-fill materials is attributed primarily to inadequately defined procedures for preparing and conditioning the specimens.