Montgomery County, MD HVAC permit requirements

2021 IRC as amended by Montgomery County Executive Regulation 13-24 (Council Res. 20-687, effective December 10, 2024). Maryland context: the 2021 IBC/IRC/IECC (MBPS, COMAR 09.12.51) have been state-effective since May 29, 2023, and local jurisdictions had to enforce them by May 29, 2024.

2021 IECC Residential Provisions with ER 13-24 amendments. IRC Chapter 11 is replaced by '2021 IECC-Residential Provisions, Chapters 1 to 6 as amended by this Executive Regulation'. Amendments include: R401.2.5 additional efficiency (different rules for all-electric and mixed-fuel buildings, with a new R408.3 'Maryland' additional energy features table), R404.6 electrification-ready conduit for combustion equipment (heat pump sized per R403.7), R405 performance at 95% (all-electric) or 85% (mixed-fuel) of reference annual energy cost, and a replacement Table R406.5 max ERI (CZ4: 54 all-electric / 47 mixed-fuel). R403.7 is not amended.

IRC 2021 M1401.3 and IECC R403.7 are kept without county amendment. ER 13-24's IRC mechanical amendments touch only M1305.1.2, and Chapter 11 is replaced by the amended IECC. DPS residential mechanical ePlans: 'ACCA Manual J Calculations (Eighth edition) for residential properties that duct work is being installed/added to an existing or new system in compliance with the International Residential Code Sections N1103.6 Equipment Sizing & M1401.3 Sizing must be submitted' and 'If the required Manual J calculation is not submitted with the permit application, the application will not be processed.' For new construction, DPS 2021 IECC guidance says: 'A completed HVAC System Design Form must be provided with each building permit application' (Manual J / S / D). DPS policy RCFCCP 2-2025 (11/5/2025) corrects the Manual J design criteria: 39°N; winter 14°F outdoor / 70°F indoor (HTD 56°F); summer 92°F outdoor / 75°F indoor / 50% RH (CTD 17°F); coincident WB 76°F; daily range M.

IRC 2021 M1601.1 is kept without county amendment. Its text: 'Duct systems serving heating, cooling and ventilation equipment shall be installed in accordance with the provisions of this section and ACCA Manual D, the appliance manufacturer's installation instructions or other approved methods.' The DPS 'Residential Plans Examiner Review Form for HVAC System Design' (11/06/2025) lists as REQUIRED ATTACHMENTS: 'Manual J1 Form', 'OEM performance data', 'Manual D Friction Rate Worksheet', 'Manual S Equipment Selection form', 'Duct distribution system sketch', with a section 'HVAC DUCT DISTRIBUTION SYSTEM DESIGN (IRC M1601.1)'. The form is required with building permit applications. The mechanical-only ePlans page lists only Manual J.

Permit required: 'A mechanical permit is required to erect, install, enlarge, alter, repair, remove, convert or replace a mechanical heating, ventilating and air-conditioning system.' Only 'Replacement of any minor part that does not alter the approval of equipment or an appliance or make such equipment or appliance unsafe' is exempt. The DPS Manual J submittal is triggered where 'duct work is being installed/added to an existing or new system'. DPS publishes no Manual J submittal requirement for an equipment-only changeout.

Per DPS 2021 IECC guidance: Prescriptive R401-R404 plus R408 additional efficiency (all-electric: ONE of E, ASEV, HVAC, WH, DUCT; mixed-fuel: ONE of E or ASEV plus TWO of HVAC, WH, DUCT), with 'REScheck or similar' listed for the permit application. Also: Total UA alternative R402.1.5; 'MD Prescriptive R-Value Alternative R402.1.3'; Total Building Performance R405 (third-party compliance report); ERI R406. Every path requires the HVAC Form.

Apply electronically ('Permits must be applied for electronically via Apply Online'). Submit 'Properly marked site plan(s) for residential properties that outdoor heating/cooling equipment and tanks are being installed or relocated' and 'ACCA Manual J Calculations (Eighth edition)' as a single PDF in the DOCUMENTS folder when ductwork is installed or added. File names are limited to 20 characters, all uploads are due within 5 business days, and locations must meet zoning setbacks. For new construction, the construction documents list includes 'Mechanical system design criteria ACCA Form' and the HVAC System Design form (Manual J1, Manual S, Manual D friction rate, duct sketch) with the contractor's declaration.

Maryland (state) proposal [26-074-P-I], published 53:13 Md. R. 593 on 6-26-2026, would update COMAR 09.12.50/09.12.51 (MBPS) to the 2024 IBC, 2024 IRC, 2024 IECC, 2024 IPC and 2024 IMC. It also 'removes the prescriptive energy path option adopted by Maryland during the last code cycle'. Comments were accepted through July 27, 2026. No state effective date was found. For the 2021 cycle, local jurisdictions had one year after state adoption to enforce. No Montgomery County 2024 executive regulation was found.

www.montgomerycountymd.gov/DPS/Services/eServices.html