Do I need a permit for HVAC work in
Franklin, Wisconsin?

Franklin HVAC permits — the key details

Franklin requires mechanical permits for any replacement furnace, air handler, outdoor condenser unit, or heat pump serving a residential space. Wisconsin's mechanical code (adopted from the 2015 IMC, updated 2021) mandates that all equipment be installed to the manufacturer's specifications and inspected before occupancy. The City of Franklin enforces this through its Building Department, which requires a completed mechanical permit application (Form HVAC-1 or equivalent) filed at least 3 business days before the contractor begins work. The permit fee is typically $50–$150, depending on equipment tonnage and whether ductwork is modified. If you hire a licensed contractor (required), the contractor usually files the permit on your behalf; if you hire an HVAC technician who is licensed but not registered with the city, you may need to file it yourself or the work cannot be inspected. Refrigerant lines running more than 25 feet from the outdoor unit, or lines that extend into attics, basements, or exterior walls, also trigger an electrical permit (about $40–$80) because low-voltage control wiring must be run separately and inspected.

One major surprise in Franklin's enforcement is the requirement for a duct-leakage test (blower-door test or duct-specific smoke test) if the new system serves more than 50% of the home's conditioned space. This requirement is not explicitly stated in the city's online permit guidance but is consistently applied by inspectors and documented in the city's mechanical code interpretation memo (available upon request at City Hall). The test costs $300–$500 and must show leakage below 15% of system air-flow — stricter than many Wisconsin towns, which don't enforce duct sealing at all. The test is performed after the system is fully installed and ductwork sealed, and the inspection is scheduled separately from the equipment rough-in and final inspections. Many homeowners discover this requirement after signing a contractor estimate that doesn't include it, resulting in scope-creep and delays. If duct leakage exceeds 15%, the city requires sealed ductwork repair or replacement at the contractor's cost, which can add $500–$2,000 if existing ducts are inaccessible or in poor condition.

Exemptions exist for repairs and maintenance but are narrowly defined. Replacing a furnace blower motor, cleaning coils, or recharging refrigerant on an existing system does not require a permit. However, if the repair involves disconnecting and reconnecting refrigerant lines, or if any component replacement changes the system's nominal cooling capacity (e.g., replacing a 3-ton condenser with a 3.5-ton unit), a permit is required. Franklin's Building Department interprets 'like-for-kind' replacement conservatively: if the new furnace has a different AFUE rating or modulation control than the original, it's treated as a new installation, not a swap. This catches many homeowners off-guard when they buy a high-efficiency furnace expecting a simple, permit-free upgrade. If you're uncertain, calling the Building Department (or checking the permit portal before scheduling) takes 15 minutes and can save weeks of back-and-forth.

Franklin's climate zone (6A, 48-inch frost depth, glacial till soil) adds a layer to ductwork and equipment placement rules. Ductwork run in unconditioned spaces (attics, basements, crawlspaces) must be insulated to R-6 minimum and sealed with mastic or foil tape; fiberglass wrap alone is not compliant with Franklin's interpretation of the 2015 IECC. Equipment installed in basements must account for flooding risk: the lowest air inlet cannot be below the 100-year flood elevation (check with the city if your basement is in a flood zone), and condensate drains must either discharge to a sump or be routed to daylight, not into the sanitary sewer (this is enforced at final inspection). Outdoor condensers and heat pumps must be set on concrete pads at least 4 inches above grade to prevent ice dam buildup and frost heave; many contractors skip this, and inspectors cite it. The city also requires that all exterior refrigerant lines be buried at least 12 inches below grade or routed through conduit above grade; exposed lines are not permitted in Franklin's freeze-thaw climate.

The permit process starts with filing an application with the City of Franklin Building Department. Online portal submissions are available; in-person filing at City Hall is also accepted. The application requires your contractor's license number (if using one), equipment specifications (model numbers, tonnage, AFUE/SEER ratings), ductwork modifications (if any), and a rough site plan showing equipment placement and line routing. Initial review takes 3–5 business days; if the application is incomplete, the city issues a deficiency letter and you must resubmit. Once approved, you receive a permit number and can schedule the rough-in inspection (after equipment is installed but before walls are closed). Final inspection occurs after the system is operational and the blower-door test (if required) is complete. The entire timeline from permit filing to closeout is typically 2–4 weeks if there are no deficiencies or rework. Many contractors bundle the permit fees into their quote; some pass the cost directly to you. Always ask your contractor if the permit cost is included in their bid, and verify that the contractor will handle the inspection scheduling — if they hand you the permit and walk away, you're responsible for coordinating with the city.

Three Franklin hvac scenarios

Franklin's duct-sealing enforcement and the blower-door test surprise

Franklin's Building Department applies a duct-leakage standard (max 15% of system airflow) that is more stringent than Wisconsin state code and significantly stricter than surrounding towns like Greenfield or Hales Corners, which do not enforce duct testing at all. This requirement emerges from the city's interpretation of the 2015 IECC Section C403.2.7, which mandates duct-sealing for systems that serve the conditioned space; Franklin's inspectors apply it whenever a new HVAC system is installed or an existing system is modified to serve a larger area (like an addition or attic conversion). The standard is enforced via a blower-door or duct-specific smoke test conducted by a third-party energy auditor or certified HVAC technician, adding $300–$500 to the project cost.

If a duct-leakage test shows >15% leakage, the contractor is responsible for correcting it before the final permit closeout. This can mean resealing ducts with mastic, replacing fiberglass wrap, or (in older homes with inaccessible or severely degraded ductwork) partial duct replacement. If the contractor refuses to cover the cost, the homeowner is left with the choice of paying for remediation out-of-pocket or appealing to the city inspector for a variance (rarely granted). Many contractors in the Milwaukee metro don't quote duct-sealing or testing because they work in towns without the requirement; when they take a Franklin job, they often underestimate the work scope and build in contingency labor. Before signing a contract, verify that your contractor has completed at least three projects in Franklin in the past 18 months and has firsthand experience with the blower-door test requirement.

The blower-door test is not required if the HVAC system serves less than 50% of the home's heating and cooling load — for instance, if you're installing a ductless mini-split heat pump in one bedroom of a four-bedroom home, testing may be waived. However, inspectors interpret '50%' conservatively, based on square footage served and heating/cooling degree-days for the zone. If you're uncertain, ask the inspector at the rough-in stage whether your system qualifies for the exemption; a written waiver from the city is worth requesting to avoid delays at closeout.

Ductwork in unconditioned spaces (attics, basements, crawlspaces) must also be insulated to R-6 minimum; flex ducts with R-4 wrap do not meet code in Franklin. If your home has older ductwork with inadequate insulation, you'll need to upgrade it before final inspection. The cost to wrap and seal existing ducts is $10–$20 per linear foot; for a 1,500-sq-ft home with 200 linear feet of ductwork in the attic, expect $2,000–$4,000 in ductwork remediation if the existing ducts are substandard.

Frost depth, condensate drainage, and equipment placement rules specific to Franklin's climate

Franklin sits in ASHRAE Climate Zone 6A with a 48-inch frost depth and glacial till soil containing clay pockets and sandy patches (particularly on the north side of town). These conditions create specific installation requirements not universally enforced in Wisconsin. Outdoor air-conditioning and heat-pump condensers must be installed on concrete pads at least 4 inches above grade; the pad itself must extend below the frost line (48 inches in Franklin) or be designed with frost-proof piers. Many contractors use standard residential 4-inch concrete slabs without sub-grade support, assuming frost heave is a non-issue. Franklin inspectors cite this regularly, and homeowners discover frost-heaved condenser pads 18 months after installation, resulting in cracked refrigerant lines and system failure. The cost to install frost-proof footings is $200–$400 per unit; it's worth specifying upfront in your contractor quote.

Condensate lines from furnaces, air handlers, and heat pumps cannot discharge into the sanitary sewer in Franklin, per the city's interpretation of Wisconsin's plumbing code. Condensate must either drain to a sump pit (if your basement has one), flow to daylight (outside, at grade level or below-grade discharge to a dry well), or connect to a condensate pump if the equipment is below the main sewer elevation. Many older Franklin homes lack sump pits, forcing contractors to install small condensate pumps ($150–$300) to lift condensate to a gravity drain or exterior discharge. If you're replacing a furnace and the current system drains to the sanitary line (common in homes built before 2000), the city will require rerouting at the time of furnace replacement. This is a cost that surprises homeowners and can be negotiated with the contractor upfront.

Refrigerant line routing in Franklin's freeze-thaw climate is also regulated. Lines running outside the home must be buried at least 12 inches below grade (if you have clay/till soil) or routed through above-grade conduit rated for outdoor UV exposure. Burying lines costs $300–$600 in labor and materials; running above-grade conduit costs $200–$400 and is faster but less aesthetically preferred. If lines are run through a basement or crawlspace wall, the penetration must be sealed with mastic and the lines must be insulated in foam or fiberglass wrap (R-6 minimum); uninsulated lines in unconditioned spaces will sweat and drip in summer, causing mold and water damage.

Common questions