2. Waiver. After written petition from a building owner, the commissioner commission shall grant a waiver from subsection 1 if the building design conforms to the residential standards set forth in subsection 3 or 4. A waiver granted by the commissioner commission under this subsection must be in writing and state the commissioner's commission's reason for granting the waiver.

3. Residential standards; electric heat. If the commissioner commission grants a waiver under subsection 2, the building owner shall renovate the building or construct a new building so that the entire building conforms to the minimum energy efficiency standards established in this section. If a waiver is granted under subsection 2 for a building to be remodeled or a building that receives an addition, only the remodeled portion of the building or the addition must conform to the following minimum energy efficiency standards.

A. All ceilings that face an outdoor or unheated space must be insulated to an R-value of 57 or greater.

B. All walls that face an outdoor or unheated space must be insulated to an R-value of 38 or greater.

C. All floors over unheated spaces must be insulated to an R-value of 25 or greater.

D. Slab-on-grade floors must have perimeter insulation of either:

(1) R-15 when the insulation extends downward from the top of the slab to the design frost line; or

(2) R-15 when the insulation extends around the perimeter and horizontally or diagonally beneath or away from the slab for a distance equivalent to the depth of the frost line.