The three classes define freeze protection level. An ASSE Class I enclosure is heated and engineered to maintain a minimum internal temperature of 40°F when the external temperature drops to -30°F, with a minimum R-value of 8.0.
A Class II enclosure is freeze-retardant — insulated, with or without a heater — designed to hold 40°F for a 24-hour period in climates where temperatures rarely stay below 33°F.
A Class III enclosure provides no freeze protection and carries no R-value requirement; it addresses security and weather protection only. Safe-T-Cover recommends a Class I heated enclosure for any installation where a freeze event is possible, including traditionally warm regions.