Thermal efficiency standards for unvented attic and unvented enclosed rafter assemblies.

(1) Unvented attic and unvented enclosed rafter assemblies that are insulated and air sealed with a minimum of R-20 air-impermeable insulation meet the requirements of Section R402 of the Florida Building Code, 8th Edition (2023), Energy Conservation, if all of the following apply:

(a) The building has a blower door test result of less than 3 ACH50.

(b) The building has a positive input ventilation system or a balanced or hybrid whole-house mechanical ventilation system.

(c) If the insulation is installed below the roof deck and the exposed portion of roof rafters is not already covered by the R-20 air-impermeable insulation, the exposed portion of the roof rafters is insulated by a minimum of R-3 air-impermeable insulation unless directly covered by a finished ceiling. Roof rafters are not required to be covered by a minimum of R-3 air-impermeable insulation if continuous insulation is installed above the roof deck.

(d) All indoor heating, cooling, and ventilation equipment and ductwork is inside the building thermal envelope.

(2) The commission shall review and consider this section and any technical changes thereto and report such findings to the Legislature by December 31, 2024.