Manual J. Calculations are required with Mechanical Permit Applications for residential properties that: Install/replace HVAC; Install/add duct work to an existing or new system in compliance with International Residential Code Sections N1103.6 Equipment Sizing & M1401.3 Sizing. Applicants shall submit two (2) copies of the ACCA Manual J Worksheets/calculations with the application for Mechanical Permit. If the Manual J calculation is not submitted with the permit application, the application will not be processed.