HVAC permits

What the model code says

The International Residential Code (IRC) mechanical chapters “regulate the design, installation, maintenance, alteration and inspection of mechanical systems that are permanently installed and used to control environmental conditions within buildings” (M1201.1). Furnaces, air conditioners, heat pumps, ductless mini-splits, and ductwork all fall within that scope.

What is exempt

The 2024 IRC’s mechanical permit exemptions (R105.2) are:

• portable heating appliances, portable ventilation appliances, portable cooling units, and portable evaporative coolers;
• steam, hot-water, or chilled-water piping within heating or cooling equipment regulated by the code;
• “replacement of any minor part that does not alter approval of equipment or make such equipment unsafe”;
• “self-contained refrigeration systems containing 10 pounds (4.54 kg) or less of refrigerant or that are actuated by motors of 1 horsepower (746 W) or less”;
• portable fuel-cell appliances not connected to fixed piping or the grid.

A capacitor, igniter, or thermostat swap is usually a “minor part.” Replacing the furnace, condenser, air handler, or heat pump is not. Neither is adding or modifying ductwork.

Rules inspectors check

• Sizing (M1401.3). “Heating and cooling equipment and appliances shall be sized in accordance with ACCA Manual S or other approved sizing methodologies based on building loads calculated in accordance with ACCA Manual J or other approved heating and cooling calculation methodologies.” The 2024 edition allows larger equipment in limited cases, such as multistage or variable-capacity equipment whose published range covers the calculated load.
• Outdoor equipment (M1401.4). Equipment installed outdoors must be “listed and labeled for outdoor installation.”
• Access (M1305.1). Appliances must be accessible for inspection, service, repair, and replacement “without removing permanent construction.” There must be a level working space at least 30 inches deep and 30 inches wide in front of the control side. Appliances under floors need a clear passageway to them (M1305.1.3), and attic installations have similar rules.
• Condensate (M1411.9). “Condensate from cooling coils and evaporators shall be conveyed from the drain pan outlet to an approved place of disposal,” with a minimum slope of 1/8 inch per foot. A secondary drain or auxiliary pan is required wherever overflow or a clogged drain would damage the building (M1411.9.1).
• Locking refrigerant caps (M1411.15). “Refrigerant circuit access ports located outdoors shall be fitted with locking-type tamper-resistant caps or shall be otherwise secured to prevent unauthorized access.” This is a common inspection failure.
• Fuel-burning appliances. Gas furnaces must meet the fuel-gas chapter for venting, combustion air, gas piping, and shutoffs. In garages, appliances with an ignition source must have it at least 18 inches above the floor unless listed as flammable vapor ignition-resistant (M1307.3).

Ducts and energy code

The IRC energy chapter (Chapter 11) applies when duct systems are installed or altered:

• Design (N1103.3.1). Duct systems serving one or two dwelling units “shall be designed and sized in accordance with ANSI/ACCA Manual D.”
• No framing cavities as ducts (N1103.3.2). “Building framing cavities shall not be used as ductwork or plenums.”
• Leakage testing (N1103.3.7). Each duct system must be tested for air leakage under ANSI/RESNET/ICC 380 or ASTM E1554 at 0.1 inch water gauge (25 Pa), with “a written report of the test results … signed by the party conducting the test and provided to the code official.” The allowed leakage is in Table N1103.3.8 and depends on floor area, the number of returns, and duct location.

How these rules apply to a simple equipment changeout, as opposed to new ducts, varies by jurisdiction. Many states also amend the energy chapter. Ask your permit office.

Refrigerant rules

Two federal rules affect HVAC work, separate from your local permit:

• Technician certification. EPA requires that “technicians who maintain, service, repair, or dispose of equipment that could release ozone depleting refrigerants into the atmosphere must be certified” under Section 608.
• Refrigerant transition. Under EPA’s Technology Transitions rule, new residential air conditioning and heat pump systems had a January 1, 2025 compliance date for lower-global-warming-potential refrigerants. EPA allowed systems using higher-GWP HFCs that were manufactured or imported before that date to be installed until January 1, 2026. Ask your contractor which refrigerant a new system uses and whether existing line sets can be reused.

Zoning, HOA rules, and setbacks

• Outdoor units (condensers, heat pumps, mini-split compressors) may be subject to setbacks, side-yard limits, noise limits, or screening requirements.
• Rooftop or wall-mounted units can trigger design review in historic districts.
• HOAs often regulate visible equipment location and screening.

Permits and inspections you can expect

1. Mechanical permit, often with an electrical permit for the disconnect and circuit, and a gas permit for new gas piping.
2. Submittals in many jurisdictions: equipment specifications, efficiency ratings, and a Manual J/S sizing report.
3. Rough-in inspection for new ductwork, line sets, or gas piping before they are concealed.
4. Duct leakage test report where required.
5. Final inspection of equipment, clearances, condensate, caps, venting, and electrical connections.

What to prepare

• Equipment data: make, model, capacity, and efficiency, for both old and new units.
• Load calculation (Manual J) and equipment selection (Manual S) if your jurisdiction asks for them.
• Duct plan if ducts are being added or changed.
• Location of outdoor equipment relative to property lines.
• Electrical details: breaker size, disconnect, and panel capacity, especially when converting to a heat pump.
• Contractor license and EPA Section 608 certification for anyone handling refrigerant.

How permit fees are calculated

Mechanical permit fees are set locally. Common methods:

• Flat fee per appliance or system (furnace, condenser, heat pump).
• Valuation-based fees using the contract price.
• Per-ton or per-BTU fees in some jurisdictions.

Electrical and gas permits may be charged separately. Check the fee schedule linked from your county’s profile in our directory.

Common mistakes

• Treating a changeout as “maintenance.” Replacing major equipment needs a permit in most places.
• Sizing by rule of thumb instead of a load calculation.
• Missing locking caps on outdoor refrigerant ports.
• Poor condensate disposal, such as a drain onto a walkway or into an improper location, or no secondary drain or auxiliary pan where an overflow would cause damage.
• Blocking service access with new equipment or storage.
• Hiring someone without EPA 608 certification to handle refrigerant.
• Skipping the duct leakage test where the jurisdiction requires it for new or altered ducts.