Utah

N1102.2.1.1. Unvented attic and unvented enclosed rafter assemblies.

Unvented attic and unvented enclosed rafter assemblies conforming to Section R806.5 shall be provided with an R-value of R-22 (maximum U-Factor of 0.045) in Climate Zone 3-B or an R-value of R-26 (maximum U-factor of 0.038) in Climate Zones 5-B and 6-B provided all the following conditions are met:

• The unvented attic assembly complies with the requirements of the International Residential Code, R806.5.
• The house shall attain a blower door test result < 2.5ACH 50.
• The house shall require a whole house mechanical ventilation system that does not rely solely on a negative pressure strategy (must be positive, balanced or hybrid).
• Where insulation is installed below the roof deck and the exposed portion of roof rafters are not already covered by the R-20 depth of the air-impermeable insulation, the exposed portion of the roof rafters shall be wrapped (covered) by minimum R-3 unless directly covered by drywall/finished ceiling. Roof rafters are not required to be covered by minimum R-3 if a continuous insulation is installed above the roof deck.
• Indoor heating, cooling and ventilation equipment (including ductwork) shall be inside the building thermal envelope.

Citation: HB532 (2023)