RESNET Defines Cavity and Attic Volume

The RESNET Standards Development Committee 300 has adopted a formal standard interpretation for 380-16-01 Definitions, Cavity and Attic Volume.

The RESNET Standard Development Equipment Sub-Committee recommended approval for an interpretation for the meaning of “cavity” as it is used in Standard ANSI/RESNET/ICC 380-2016 definitions for Conditioned Floor Area, Conditioned Space Volume, Infiltration Volume and Unconditioned Space Volume and as it applies to attic volume.

Interpretation:

As it applies to the definition of Conditioned Floor Area, Conditioned Space Volume, Infiltration Volume and Unconditioned Space Volume, the term “cavity” is to be interpreted as follows:

  • In the case of walls, cavity is to be interpreted as the full thickness of the wall
  • In the case of floors, cavity is to be interpreted as the full depth of the floor

As it applies to attics, the attic volume shall include all space volume between the interior ceiling and knee wall surfaces of the attic (e.g: drywall) and the roof and gable sheathing surfaces (e.g. decking), including all framing members and insulation at the ceiling, knee walls, roof plane and gable walls or other bounding planes of the attic.

Rationale: The term “cavity” is not defined by the standard and has a common definition which is not intended by the subject definitions in this standard. The volume of attics is not defined in the standard.

You can find the adopted Interpretation 380-16-01 Definitions Cavity and Attic Volumeunder the interpretations section on the RESNET Consensus Standards Page.