This chapter is a guide to specifying insulation systems for refrigeration piping, fittings, and vessels operated at temperatures ranging from 35 to –100°F (2 to –70°C). It does not deal with HVAC systems or applications such as chilled-water systems. See Chapters 23, 25, 26, and 27 in the 2021 ASHRAE Handbook—Fundamentals for information about insulation and vapor retarders (barriers) for these systems. Design Considerations for Below-Ambient Refrigerant Piping Insulation Properties at Below Ambient Temperatures Insulation System Moisture Resistance Insulation Systems Installation Guidelines Maintenance of Insulation Systems