Minnesota Administrative Rules
Agency 151 - Labor and Industry Department
Chapter 1323 - COMMERCIAL ENERGY CODE
Part 1323.0513 - SECTION 5.1.3, ENVELOPE ALTERATIONS

3. Alterations to roof, wall, or floor cavities that are insulated to full depth with insulation having a minimum nominal value of R-3.0/inch and having either integral vapor retarder qualities or a membrane vapor retarder. The membrane vapor retarder shall prevent moisture from accumulating in the cavities and allow drying to the interior and shall be installed to separate the insulation from the conditioned space in accordance with the Minnesota Building Code.

8. Historical buildings undergoing renovations or a change of occupancy shall not be required to comply with this rules chapter for those portions or elements of the building determined by the historical authority having jurisdiction as contributing to the historic significance of the building and upon approval of the building official. Portions or components that can be modified to comply with this rules chapter without impacting the historic significance of the building shall be modified to comply to the greatest extent possible.

9. Where insulation is provided above the roof deck, and the required R-value for a roof replacement cannot be provided because of existing structural capacity limitations or because of the thickness limitations that occur with the existing rooftop conditions, including heating, ventilation and air conditioning equipment curbs, low door or glazing heights, parapet heights, or proper roof flashing heights, the maximum insulation compatible with the available space and existing rooftop conditions shall be installed, as approved by the building official. New insulation shall have the highest R-value per inch available, and in no case shall the R-value of the roof insulation be reduced or the U-factor of the roof assembly be increased as part of the roof replacement.