Do I Need a Permit to Replace a Furnace in Idaho?
Furnace replacement permit requirements. Even same-model swaps need a mechanical permit. What inspectors check.
Yes — even a like-for-like furnace swap requires a mechanical permit.
Idaho-specific rules
Adopted code: 2018 International Mechanical Code (IMC) and 2018 International Fuel Gas Code (IFGC) — part of Idaho's statewide baseline under the Idaho Building Code Act, effective January 1, 2021.
Why Even a Swap Needs a Permit
Furnace replacements involve gas connections, venting, and combustion air — all safety-critical systems. Most jurisdictions require a mechanical permit to verify the new furnace is properly vented, has adequate combustion air, and the gas connections are leak-free. This is true even for exact same-model replacements.
High-Efficiency Conversions
Upgrading from a standard-efficiency (80%) to high-efficiency (90%+) furnace changes the venting requirements: standard units use metal B-vent, high-efficiency units use PVC/CPVC. The old metal vent chase may need to be sealed. A condensate drain line is also required for high-efficiency units.
What Inspectors Check
The final inspection covers: gas piping and drip leg, venting type and clearances, combustion air supply (especially in confined spaces), condensate drain (high-efficiency units), thermostat operation, and CO detector presence on every level.
Bundled with AC?
If you're replacing both the furnace and AC unit at the same time, one mechanical permit typically covers both. The inspector will check the AC refrigerant lines, electrical disconnect, and condenser pad in addition to the furnace items.
Yes, always. The permit is $40-$75 and your HVAC contractor handles it. One final inspection. Don't skip it — CO poisoning from bad venting is real.
Permit fees by city in Idaho
Verified from each city’s published fee schedule. Where a city has no separate fee listed for this project, open the city page for the current requirements and amount.
79 rows
| Permit fee | Source | |
|---|---|---|
| American Falls | $23.50Verifiedvia Consolidated Building-Development Permit (New Construction, Additions, Alterations, Repairs, Moving, Demolition, Signs, Grading) | Consolidated Building-Development Permit (New Construction, Additions, Alterations, Repairs, Moving, Demolition, Signs, Grading) → |
| Ammon | $160.00 (includes 3 inspections)Verified | Mechanical / HVAC Permit → |
| Blackfoot | $100Verifiedvia Residential Building Permit (New Construction / Addition / Remodel) | Residential Building Permit (New Construction / Addition / Remodel) → |
| Boise | $130 per dwelling unitVerified | Residential Mechanical / HVAC Permit → |
| Buhl | $23.50Verifiedvia Building Permit (Residential New Construction, Additions, Remodels, Repairs) | Building Permit (Residential New Construction, Additions, Remodels, Repairs) → |
| Burley | $200.00 plus $150.00 per square footVerifiedvia Building Permit (New / Addition / Alteration / Repair / Roof / Move / Remove) | Building Permit (New / Addition / Alteration / Repair / Roof / Move / Remove) → |
| Caldwell | $160.00 per dwelling unitVerified | Residential Mechanical / HVAC Permit → |
| Cascade | 40% of the building permit fee (65% of the building permit fee if an outside plan reviewer is used)Verifiedvia Residential Building Permit | Residential Building Permit → |
| Chubbuck | $30.00Verified | Mechanical / HVAC Permit → |
| City of St. Maries | $24.00Verifiedvia Building Permit | Building Permit → |
| Coeur d'Alene | $40.00 (1 unit, flat)Verified | Mechanical / HVAC Permit → |
| Donnelly | $24.00Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Driggs | $305Verifiedvia Residential Building Permit | Residential Building Permit → |
| Eagle | Base fee $65.00, plus $10.00 per HVAC item up to maximum square footage of the residential buildingVerified | Mechanical / HVAC Permit → |
| Emmett | See city page for the current Residential Building Permit fee | Residential Building Permit → |
| Fruitland | $23.50Verifiedvia Building Permit (New Construction, Additions, Remodels) | Building Permit (New Construction, Additions, Remodels) → |
| Garden City | $150.00Verifiedvia Residential Building Permit (New Construction / Addition / Remodel) | Residential Building Permit (New Construction / Addition / Remodel) → |
| Grangeville | $15.00Verifiedvia Residential Building Permit (New Construction, Additions, Alterations, Repairs) | Residential Building Permit (New Construction, Additions, Alterations, Repairs) → |
| Greenleaf | $50.00 flat, due upon submission of all building permit applicationsVerifiedvia Residential Building Permit (New Construction / Addition / Alteration) | Residential Building Permit (New Construction / Addition / Alteration) → |
| Hailey | $27.78Verifiedvia Building Permit (New Construction, Additions, Remodels — Commercial & Residential) | Building Permit (New Construction, Additions, Remodels — Commercial & Residential) → |
| Harrison | Per Table 1-A of the 1997 Uniform Building Code, applied to project valuation determined from ICBO Building Valuation Data (or the most recent available data if that publication has been discontinued)Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Hayden | $350.00Verified | Mechanical / HVAC Permit → |
| Heyburn | See city page for the current Residential Home Permit (New Construction — Single Family, Duplex, Zero Lot Line, Townhouse) fee | Residential Home Permit (New Construction — Single Family, Duplex, Zero Lot Line, Townhouse) → |
| Idaho City | $23.50Verifiedvia Residential Building Permit (New Construction, Additions & Alterations) | Residential Building Permit (New Construction, Additions & Alterations) → |
| Idaho Falls | $5.10 per installationVerified | Mechanical / HVAC Permit → |
| Jerome | $23.50Verifiedvia Residential Building Permit | Residential Building Permit → |
| Kellogg | See city page for the current Residential Building Permit (New Construction / Addition / Alteration) fee | Residential Building Permit (New Construction / Addition / Alteration) → |
| Ketchum | $24.75 for the first $500, plus $3.20 for each additional $100 or fraction thereofVerifiedvia Residential Building Permit (New Construction / Additions) | Residential Building Permit (New Construction / Additions) → |
| Kimberly | $150.00Verifiedvia Building Permit (New Construction, Additions, Remodels, Repairs, Demolition, Re-Roof) | Building Permit (New Construction, Additions, Remodels, Repairs, Demolition, Re-Roof) → |
| Kootenai County | $59.00Verified | Mechanical / HVAC Permit → |
| Kuna | $70Verifiedvia Residential Building Permit | Residential Building Permit → |
| Lewiston | $216.56, plus $72.20 for each additional 1,000 sq ft or portion thereofVerified | Mechanical Permit (HVAC, Gas Work) → |
| Malad City | See city page for the current Residential Building Permit (New Construction / Addition / Accessory) fee | Residential Building Permit (New Construction / Addition / Accessory) → |
| Melba | See city page for the current Residential Building Permit (New Dwelling / Addition / Remodel) fee | Residential Building Permit (New Dwelling / Addition / Remodel) → |
| Meridian | $50 base feeVerified | Residential Mechanical / HVAC Permit → |
| Middleton | $130.00Verified | Mechanical / HVAC Permit → |
| Minidoka County (Building Authority for Unincorporated County and the Cities of Acequia, Minidoka, Paul, and Rupert) | See city page for the current Residential Building Permit (New Construction, Addition, Remodel) fee | Residential Building Permit (New Construction, Addition, Remodel) → |
| Moscow | $27.50Verifiedvia Residential Building Permit (New Single-Family Dwelling / Addition) | Residential Building Permit (New Single-Family Dwelling / Addition) → |
| Mountain Home | See city page for the current Residential Building Permit (New Construction) fee | Residential Building Permit (New Construction) → |
| Nampa | $180.00 per dwelling unitVerified | Residential Mechanical / HVAC Permit → |
| Notus | See city page for the current Residential Building Permit (New Construction, Additions, Remodels) fee | Residential Building Permit (New Construction, Additions, Remodels) → |
| Osburn | $140.00 per sq. ft. (valuation input)Verifiedvia Residential Building Permit (New Construction / Addition / Alteration) | Residential Building Permit (New Construction / Addition / Alteration) → |
| Payette | $24Verifiedvia Residential Building Permit | Residential Building Permit → |
| Plummer | $23.50Verifiedvia Residential Building Permit | Residential Building Permit → |
| Pocatello | $130Verified | Mechanical / HVAC Permit → |
| Post Falls | $18.00Verified | Mechanical / HVAC Permit → |
| Preston | Set by city inspector, based on valuationVerifiedvia Building Permit (New Construction / Additions / Accessory Buildings) | Building Permit (New Construction / Additions / Accessory Buildings) → |
| Priest River | Per Table 1-A of the 1997 Uniform Building Code (valuation-based)Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Rathdrum | $85.00Verified | Residential Mechanical / HVAC Permit → |
| Rexburg | $130.00Verified | Mechanical / HVAC Permit → |
| Rigby | $26.46Verifiedvia Residential Building Permit (Single-Family Dwelling, Townhouse, New Construction & Additions) | Residential Building Permit (Single-Family Dwelling, Townhouse, New Construction & Additions) → |
| Rupert | Calculated from Project Value using the Building Department's fee schedule; no dollar-per-valuation-bracket table was found published onlineVerifiedvia Residential Building Permit | Residential Building Permit → |
| Salmon | $24Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Sandpoint | $100.00Verified | Mechanical / HVAC Permit → |
| Shelley | $21.00Verifiedvia Building Permit (New Construction, Additions, Remodels) | Building Permit (New Construction, Additions, Remodels) → |
| Soda Springs | $25.00Verifiedvia Residential Building Permit (New Construction / Addition / Remodel) | Residential Building Permit (New Construction / Addition / Remodel) → |
| Spirit Lake | See city page for the current Mechanical / HVAC Permit fee | Mechanical / HVAC Permit → |
| Star | $100.00Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Twin Falls | $120.00Verified | Mechanical / HVAC Permit (MEP) → |
| Unincorporated Ada County | $35.00Verified | Mechanical / HVAC Permit → |
| Unincorporated Bannock County | $23.00Verifiedvia Residential Building Permit (New Construction / Addition) | Residential Building Permit (New Construction / Addition) → |
| Unincorporated Bingham County | $1–$500: $16.50 | $501–$2,000: $16.50 + $2.20/each add'l $100 | $2,001–$25,000: $49.50 + $9.90/each add'l $1,000 | $25,001–$50,000: $277.30 + $7.15/each add'l $1,000 | $50,001–$100,000: $455.95 + $4.95/each add'l $1,000 | $100,001–$500,000: $762.85 + $3.85/each add'l $1,000 | $500,001–$1,000,000: $2,243.45 + $3.30/each add'l $1,000 | $1,000,001–$5,000,000: $3,915.45 + $2.20/each add'l $1,000Verifiedvia Residential Building Permit (New Construction / Addition / Remodel) | Residential Building Permit (New Construction / Addition / Remodel) → |
| Unincorporated Bonneville County | See city page for the current Residential Building Permit (New Construction / Addition) fee | Residential Building Permit (New Construction / Addition) → |
| Unincorporated Canyon County | $280.00Verifiedvia Residential Building Permit (New Construction / Addition / Remodel) | Residential Building Permit (New Construction / Addition / Remodel) → |
| Unincorporated Cassia County | Calculated based on square footage using the IBC 2003 Valuation Table 1Verifiedvia Residential Building Permit (New Construction / Addition) | Residential Building Permit (New Construction / Addition) → |
| Unincorporated Elmore County | $100.00Verifiedvia Residential Building Permit (New Construction / Addition) | Residential Building Permit (New Construction / Addition) → |
| Unincorporated Franklin County | 1% of the assessed value of the proposed buildingVerifiedvia Residential Building Permit (New Construction / Remodel Changing Outside Dimensions) | Residential Building Permit (New Construction / Remodel Changing Outside Dimensions) → |
| Unincorporated Gem County | $1–$500: no fee listed at base tier; $501–$2,000: $23.50 for the first $500 plus $3.05 for each additional $100 or fraction thereof; $2,001–$25,000: $69.25 for the first $2,000 plus $14.00 per additional $1,000 or fraction; $25,001–$50,000: $391.25 for the first $25,000 plus $10.10 per additional $1,000; $50,001–$100,000: $643.75 for the first $50,000 plus $7.00 per additional $1,000; $100,001–$500,000: $993.75 for the first $100,000 plus $5.60 per additional $1,000; $500,001–$1,000,000: $3,233.75 for the first $500,000 plus $4.75 per additional $1,000; $1,000,001+: $5,608.75 for the first $1,000,000 plus $3.65 per additional $1,000Verifiedvia Residential Building Permit (New Construction / Addition / Alteration) | Residential Building Permit (New Construction / Addition / Alteration) → |
| Unincorporated Jefferson County | $26.46Verifiedvia Residential Building Permit (Single-Family Dwelling / New Construction, Additions, ADUs) | Residential Building Permit (Single-Family Dwelling / New Construction, Additions, ADUs) → |
| Unincorporated Latah County | $50.00 flatVerifiedvia Residential/General Building Permit | Residential/General Building Permit → |
| Unincorporated Madison County | $500 for dwellings/non-accessory structures; $100 for accessory structuresVerifiedvia Residential Building Permit (New Construction / Addition / Accessory Structure) | Residential Building Permit (New Construction / Addition / Accessory Structure) → |
| Unincorporated Nez Perce County | $112.65 per sq ft (minimum)Verifiedvia Single Family Residence Building Permit | Single Family Residence Building Permit → |
| Unincorporated Power County | $24 for valuation $1–$500; $24 + $3 per additional $100 (or fraction) up to $2,000; $69 + $11 per additional $1,000 up to $40,000; $487 + $9 per additional $1,000 up to $100,000; $1,027 + $7 per additional $1,000 up to $500,000; $3,827 + $5 per additional $1,000 up to $1,000,000; $6,327 + $3 per additional $1,000 up to $5,000,000; $18,327 + $1 per additional $1,000 above $5,000,000Verifiedvia Residential Building Permit (New Construction / Addition) | Residential Building Permit (New Construction / Addition) → |
| Unincorporated Twin Falls County | Up to 1,500 sq ft: $120.00; 1,501–2,500 sq ft: $170.00; 2,501–3,500 sq ft: $230.00; 3,501–4,500 sq ft: $280.00; over 4,500 sq ft: $280.00 plus $50.00 per additional 1,000 sq ft or portion thereofVerified | Mechanical / HVAC Permit → |
| Unincorporated Valley County | See city page for the current Residential Building Permit (New Construction / Addition / Alteration) fee | Residential Building Permit (New Construction / Addition / Alteration) → |
| Victor | $22.50Verifiedvia Standard Building Permit (Residential New Construction) | Standard Building Permit (Residential New Construction) → |
| Wallace | See city page for the current Residential Building Permit (New Construction / Addition / Alteration) fee | Residential Building Permit (New Construction / Addition / Alteration) → |
| Wilder | $24.00Verifiedvia Residential Building Permit (New Construction / Addition / Remodel / Accessory Structure) | Residential Building Permit (New Construction / Addition / Remodel / Accessory Structure) → |
| Worley | $16.45 for valuation $1-$500; $16.45 for the first $500 plus $2.14 per additional $100 (or fraction) to $2,000; $48.48 for the first $2,000 plus $9.80 per additional $1,000 to $25,000; scaling further per Table 1-A for higher valuationsVerifiedvia Residential Building Permit | Residential Building Permit → |