Participation is invited for a round-robin study that will determine the sorption isotherms of building materials according toThe American Society for Testing and Materials' (ASTM) C 1498, Standard Test Method for Hygroscopic Sorption isotherms of Building Materials, approved May 10. The study is being conducted by a task group of ASTM Subcommittee C 16.33 on Insulation Finishes and Moisture, part of Committee C16 on Thermal Insulation.