What needs a mechanical permit
The City of Missoula's Building Division page (read 24 October 2026) says mechanical permits are required "when vents and ducts are added, replaced or relocated", including dryer vents, range hood vents, extending heating ducts, adding registers and "replacing furnaces and air conditioning units".
| Needs a Missoula mechanical permit | Exempt |
|---|---|
| Replacing a furnace or AC unit | Portable heaters, coolers, evaporative coolers and ventilation units |
| Any new HVAC equipment, including small exhaust fans | Steam, hot-water or chilled-water piping inside the equipment itself |
| Installing or altering ductwork, vents or a chimney | Replacing a minor part that does not change the equipment's approval |
| A fireplace insert or gas fireplace | Self-contained refrigeration with 10 lb of refrigerant or less, or motors of 1 hp or less |
| Gas piping between the meter and an appliance | Portable fuel cells not tied to fixed piping or the grid |
| Setting or unlocking a gas meter |
For one- and two-family homes, the City does not review mechanical plans; "compliance will be field verified at the time of inspection".
Inspections
The Building Division says "The holder of the permit shall be responsible for the scheduling of such inspections":
- Underground, after trenches are dug and piping installed, before backfill.
- Rough-in, after framing and before any ducting is covered by walls or ceilings.
- 460 Gas/Mech, with an air test of gas lines, whenever gas piping is involved.
- Final, when the mechanical system is complete.
A permit lapses if work does not start within 180 days of issue or stops for 180 days. The Building Division's pages do not say whether a homeowner may take out a mechanical permit for their own house; ask the permit coordinators at (406) 552-6060 before you apply.
What it costs
From the City's FY2027 permit fee schedule:
| Fee line | Amount |
|---|---|
| Issuing each mechanical permit | $51 |
| Furnace up to 100,000 BTU/hr, with its ducts and vents / over 100,000 | $35 / $41 |
| Compressor (AC, heat pump, package unit) up to 3 tons | $35 |
| Repair, alteration or addition to an existing heating or cooling system | $35 |
| Gas piping system, 1 to 4 outlets | $19 |
| Each ventilation fan on a single duct | $15 |
| Wood stove or solid-fuel appliance | $68 |
| Re-inspection / skipped inspection | $56 / $150 |
| Technology fee on the total; credit card fee | 5%; 3% |
So a furnace-and-AC changeout with a gas connection runs about $51 + $35 + $35 + $19 = $140, plus the 5% technology fee. Starting without a permit costs double the permit fee, with a $250 stop-work-order fee as the floor.
How to apply
Apply for a Mechanical Permit online in the City's Citizen Portal, under the Building record type (Permit Processes and Policies). Code questions go to (406) 552-6630.
What 2,420 Missoula HVAC permits show
| Measure | Missoula HVAC permits |
|---|---|
| Applied for October 2024 to September 2026, and issued | 2,420 (23% of all City permits) |
| October 2024 to September 2025 / October 2025 to September 2026 | 1,245 / 1,175 (−6%) |
| Finished, permits from October 2024 to September 2025 | 92.1% |
| Expired without a final, same permits | 6.7% |
| Busiest / quietest calendar month (index) | June (123) / February (82) |
| ZIPs with the most | 59801 (870), 59808 (500), 59802 (483) |
About one Missoula HVAC permit in fifteen expires without a final inspection. If you are buying a house or paying a contractor, open the permit in the Citizen Portal and check that it reached Final. Monthly counts are on Missoula HVAC permits, every kind of work on Missoula permit statistics, and the rows on browse Missoula permits.
Before you hire
Look up the permit and its Processing Status as described in the Missoula building permit search guide. Rules in other cities are in do I need a permit for HVAC replacement; filed costs in HVAC replacement cost.
What this does not tell you
The City's permit layer names no contractor and carries no job value, so we cannot rank HVAC companies or show costs. Permits are dated by application, not issue, so we show no time to final. It covers the City of Missoula only; Lolo, Frenchtown and the rest of Missoula County permit through the county.
How we know this
Permit requirements, exemptions and inspections are quoted from the City of Missoula Building Division page; fees from the City's FY2027 Building (MEC, PLM, ELC, RFG) Permit Fee Schedule; the portal route from Permit Processes and Policies, all read 24 October 2026. Our counts are the City's AddressesWithPermits_mso layer, read 19 October 2026: mechanical permits applied for October 2024 to September 2026 and issued.
Numbers come from public permit records in 57 cities, data through October 19, 2026. Nobody paid to be on this page and nobody can.
Questions
- Do I need a permit to replace a furnace in Missoula?
Yes. The City's Building Division says mechanical permits are required for replacing furnaces and air conditioning units, adding registers, extending heating ducts and installing any new HVAC equipment, down to small exhaust fans.
- How much is a mechanical permit in Missoula?
Under the FY2027 schedule, $51 to issue the permit plus $35 for a furnace up to 100,000 BTU/hr, or $35 for an AC or heat pump compressor up to 3 tons. A 5% technology fee is added to the total.
- Does a window AC or portable heater need a permit in Missoula?
No. The City exempts portable heating and cooling units, portable evaporative coolers, and self-contained refrigeration systems with 10 pounds of refrigerant or less or motors of 1 horsepower or less.
- How many HVAC permits does Missoula issue?
2,420 HVAC permits were applied for from October 2024 to September 2026 and issued, more than any other kind of work in the City's records; 92.1% of those from the first year had finished by October 2026.
- What inspections does a Missoula mechanical permit need?
Underground (if piping is buried), rough-in before walls and ceilings are covered, and a final. Gas piping needs a 460 Gas/Mech inspection with an air test. The permit holder schedules them; a skipped inspection costs $150.
Build your own list
Pick your city and the kind of work. Every firm with a permit on record, sorted by what you value.
Related guides
- Albuquerque building permit search: how to look up permits on an address
- Building a casita in Albuquerque: the 750 sq ft limit, rear-yard rule, parking, free plans, and who builds them
- Do I need a permit to build a house in Albuquerque? GB-2 or homeowner, the plan set and the fee
- Do I need a solar permit in Albuquerque? Building and electrical permits, the engineer triggers and the fee
- Building Division — City of Missoula Community Planning, Development & Innovation (2026-10-24)
- Building (MEC, PLM, ELC, RFG) Permit Fee Schedule FY2027 (PDF) — City of Missoula (2026-10-24)
- Permit Processes and Policies — City of Missoula (2026-10-24)
- AddressesWithPermits_mso — City of Missoula (ArcGIS Online) (2026-10-19)