Mechanical / HVAC Permit in Unincorporated Ada County, Idaho
Required for heating, ventilation, air conditioning, fuel gas piping, and related mechanical installations in unincorporated Ada County. Residential and commercial mechanical permits are both issued by Ada County Development Services — Building Division. Governed by the 2018 International Mechanical Code (IMC) and 2018 International Fuel Gas Code (IFGC) as adopted via Ordinance #919. Applications submitted digitally by email.
Verified 2026-06-29 · Source
When you need this permit
- All installation, replacement, or repair of heating, cooling, ventilation, or fuel gas systems
- Residential: submit Residential Mechanical Permit application by email to mechanical@adacounty.id.gov
- Commercial: submit Commercial Mechanical Permit application by email to mechanical@adacounty.id.gov
- Idaho contractor registration number required for commercial applicants
Required documents
- Req
Residential Mechanical Permit Application (2025)
One-page application listing all mechanical work items; available at adacounty.id.gov/developmentservices/permitting-division/applications-forms-templates/
- Opt
Commercial Mechanical Permit Application (2025)
Commercial mechanical permit form with total bid amount; available on the Applications, Forms, and Templates page
Fee schedule
| Fee type | Amount | Notes |
|---|---|---|
| Residential Mechanical Permit — Base fee | $35.00 | Ada County Residential Mechanical Permit Application (2025) |
| Residential — Furnace, air conditioner, heat pump, condenser, boiler (not supplying potable water), pool heater, or any other permanent space conditioning appliance | $25.00 for each | Ada County Residential Mechanical Permit Application (2025) |
| Residential — Exhaust duct or ventilation duct, head unit (mini-split), fireplace, hydronic system (closed loop only), residential energy storage system | $15.00 for each | Ada County Residential Mechanical Permit Application (2025) |
| Residential — Fuel gas piping | $5.00 per outlet | Ada County Residential Mechanical Permit Application (2025) |
| Commercial Mechanical Permit — Base fee plus percentage | $35.00 base + 2% of total bid amount | Ada County Commercial Mechanical Permit Application (2025) |
Review timeline
~1–5 business days
Typical estimate — confirm current times with the Unincorporated Ada County building department
Inspection process
- 1
Gas Piping Pressure Test
Required before concealing gas piping — verify no leaks under test pressure per 2018 IFGC
- 2
Rough-In / Ductwork
Mechanical equipment and ductwork installed before walls closed — verify clearances and support per 2018 IMC. Request by 4:30 PM by phone or before midnight by email for next-day scheduling.
- 3
Final
Equipment operational, combustion air verified, venting correct per 2018 IMC/IFGC
Tips
- Residential mechanical permits use a per-item fee schedule: $25 per furnace/AC/heat pump/pool heater, $15 per mini-split/fireplace/exhaust duct/hydronic system, $5 per gas outlet.
- Commercial mechanical permits use $35 base + 2% of total bid amount.
- HVAC design (Manual J, D, and S) is required to accompany the building permit application for new dwellings — not a separate submittal under the mechanical permit.
- Submit the residential or commercial mechanical permit application by email to mechanical@adacounty.id.gov as a PDF.
Frequently asked questions
- Do I need a mechanical permit to replace my furnace in unincorporated Ada County?
- Yes. Replacing a furnace requires a Residential Mechanical Permit from Ada County Development Services — Building Division. Fee: $35 base + $25 for the furnace appliance = $60 minimum for a furnace-only replacement. Submit the Residential Mechanical Permit application by email to mechanical@adacounty.id.gov. Source: Ada County Residential Mechanical Permit Application (2025).
- How much does a mechanical permit cost in unincorporated Ada County?
- Residential: $35 base, plus $25 per furnace/AC/heat pump/pool heater, $15 per mini-split/fireplace/exhaust duct/closed-loop hydronic, $5 per gas outlet. Commercial: $35 base + 2% of total bid amount. Source: Ada County Mechanical Permit Applications (2025), adacounty.id.gov/developmentservices/permitting-division/applications-forms-templates/
Sources & verification
Verified against official sources. Last reviewed 2026-06-29.
- Ada County Development Services — Building Division — official building department
- Residential Mechanical Permit Application (2025) — PDF | Ada County Development Services
- Commercial Mechanical Permit Application (2025) — PDF | Ada County Development Services
- Applications, Forms, and Templates | Ada County Development Services
Fees, timelines, and adopted codes are researched from each jurisdiction's published records — see how we verify. Requirements change and vary by project, so always confirm the current details with the Unincorporated Ada County building department before you submit. PermitBase is an independent reference and is not affiliated with any government agency.
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