Michigan HVAC Permit Exempt Work — What Needs a Permit and What Doesn't

Not Every HVAC Job Requires a Permit — But Most Do

Michigan's State Construction Code Act (1972 PA 230) requires a mechanical permit for covered installations, major alterations, and replacements of mechanical equipment, subject to minor-part and other listed exemptions. That includes furnace swaps, AC system installations, ductwork modifications, and boiler replacements. The permit triggers a rough-in inspection and a final inspection by the local code authority.

But routine maintenance and minor service work don't require permits. Knowing where the line sits prevents both unnecessary permit costs on simple jobs and code violations on jobs that should have been permitted.

Work That Requires a Mechanical Permit

Under the Michigan Mechanical Code, you need a permit for:

• Covered equipment replacement — replacing a furnace with the same model and BTU rating is still a permitted activity in almost all Michigan jurisdictions, even if it's a "like-for-like" swap
• New installations — adding a central AC system, mini-split, or supplemental heating unit
• Ductwork modifications — extending, rerouting, or significantly altering existing duct runs
• Gas piping work — new gas line connections to appliances or modifications to existing gas distribution
• Venting changes — rerouting exhaust vents, changing vent materials, or modifying combustion air supplies
• Hydronic system work — boiler installations, radiant floor heating, or closed-loop system modifications

The furnace replacement question comes up constantly: yes, replacing a residential furnace requires a mechanical permit in Michigan. Even when the new unit matches the old one's specifications exactly. The permit ensures the installation meets current code for combustion air, venting clearances, condensate drainage, and gas piping connections — standards that may have changed since the original unit was installed.

Work That's Typically Exempt

Routine maintenance and minor service work that doesn't alter the system's configuration generally falls outside the permitting requirement:

• Filter replacement and standard maintenance cleaning
• Thermostat replacement (low-voltage Class 2 control wiring is outside the high-voltage electrical licensing boundary)
• Refrigerant recharging on existing systems (though the technician needs EPA Section 608 certification)
• Diagnostic testing and troubleshooting that doesn't involve removing or replacing components
• Cleaning coils, clearing condensate drains, and similar routine service tasks
• Belt replacement and motor lubrication
• Certain portable or self-contained equipment — portable heating, ventilation, and cooling equipment; evaporative coolers; gas burners under 30,000 Btu/hr; self-contained refrigeration equipment; window air conditioners of not more than 1.5 hp; and oil burners not connected to a flue

The key distinction is whether the work is ordinary maintenance or minor-part replacement, or a covered installation, alteration, or replacement. Swapping a capacitor on an existing AC unit is maintenance. Replacing the condenser with a different-capacity unit is an installation that needs a permit.

The Homeowner Exemption

Michigan law includes a limited exemption for owner-occupants of single-family dwellings. A homeowner can personally install heating or refrigeration equipment in their own home and pull their own mechanical permit — without holding a Mechanical Contractor license.

The conditions are strict:

• The homeowner must personally perform the work (not hire someone unlicensed to do it)
• They must sign an affidavit certifying they'll do the work themselves in compliance with the Michigan Mechanical Code
• The system cannot be covered up or operated until it passes local inspections

It's a civil violation for a homeowner to pull a permit on behalf of an unlicensed contractor to circumvent the licensing requirement. Inspectors can refer this arrangement for enforcement against the licensing violation.

The Cost of Skipping a Permit

Starting work without a required permit can trigger enforcement once discovered — typically during a neighbor complaint, a property sale inspection, or a warranty claim:

• Stop-work order halting the project
• Double-fee penalties in many jurisdictions (the standard permit fee plus an equal penalty amount)
• Re-inspection fees (typically $50 per visit) if the unpermitted work doesn't meet code
• Insurance complications — some policies won't cover damage from unpermitted work

The Michigan HVAC License Guide covers the full permitting process, including which jurisdictions have specific quirks and how to navigate the permit application workflow for residential and commercial jobs.

See more Michigan guides →