The Wisconsin Mechanical Code is the set of state rules governing the design, installation, and maintenance of heating, ventilating, and air conditioning systems, administered by the Department of Safety and Professional Services (DSPS) under Chapters SPS 361–366 of the Administrative Code. Commercial buildings and places of employment follow Chapter SPS 364, while one- and two-family homes fall under the separate Uniform Dwelling Code at SPS 323. The state builds on a national model code but layers its own cold-climate and administrative modifications on top, and knowing which chapter governs your project is the first step toward compliance.
Which Code Applies to Your Project
Pick the wrong chapter and you end up on the wrong regulatory track entirely. The split is based on building type.
Chapter SPS 364 governs HVAC in commercial structures, public buildings, and places of employment: offices, retail, restaurants, warehouses, schools, hospitals, and anything else that is not a one- or two-family home.1Wisconsin State Legislature. Wisconsin Administrative Code Chapter SPS 364 – Heating, Ventilating and Air Conditioning The DSPS Division of Industry Services reviews plans for these buildings before construction begins.2Department of Safety and Professional Services. Commercial Buildings
Projects in one- and two-family homes fall under the Uniform Dwelling Code, with mechanical requirements in SPS 323.3Wisconsin State Legislature. Wisconsin Administrative Code SPS 323 – Heating, Ventilating And Air Conditioning Installing a heating or air conditioning system in a dwelling is not mandatory, but if one is installed, it must comply with the code and must be sized based on calculated heating or cooling loads.4Cornell Law Institute. Wisconsin Admin Code SPS 323.03 – Selection of Equipment The dwelling code also reaches certain adult family homes, small community-based residential facilities, foster homes, and manufactured homes installed on-site.5Wisconsin State Legislature. Wisconsin Administrative Code Chapter SPS 320
What the Code Is Built On
Wisconsin adopted the 2021 International Mechanical Code as the base for its commercial mechanical rules, with the updated commercial building code taking effect on October 1, 2025.6Wisconsin Department of Safety and Professional Services. Wisconsin Code SPS 361 – SPS 366 On top of that base, SPS 364 contains Wisconsin’s own additions and omissions, numbered to match the IMC’s section numbers so you can cross-reference them against your copy of the national code.7Wisconsin State Legislature. Wisconsin Administrative Code SPS 364.0100 – Changes, Additions or Omissions to the International Mechanical Code DSPS publishes insert pages that drop directly into the IMC and show every point where Wisconsin departs from the national standard.
Core Technical Requirements
Ventilation and Indoor Air
Mechanical systems must deliver a calculated volume of outdoor air based on each space’s occupancy and floor area. Natural ventilation through operable windows or louvers can satisfy the requirement in some buildings, but most commercial projects rely on fans and ductwork. Outdoor air intakes must be kept away from plumbing vents, exhaust outlets, and vehicle exhaust, and minimum separation distances apply between exhaust discharges and nearby intakes to keep contaminants from recirculating. Duct construction must meet sealing and insulation standards, and contractors verify airflow against design through testing and balancing reports.2Department of Safety and Professional Services. Commercial Buildings In densely occupied spaces, the energy code at SPS 363 adds a demand-controlled ventilation requirement that modulates fresh air based on actual occupancy.8Wisconsin State Legislature. Wisconsin Administrative Code Chapter SPS 363
Fuel Gas Appliances
Furnaces, water heaters, and other fuel-burning appliances fall under Chapter SPS 365.9Wisconsin State Legislature. Wisconsin Code SPS 365 – Fuel Gas Appliances Gas piping installations must comply with NFPA 54, the National Fuel Gas Code, and chimneys and vents must maintain specified clearances from combustible materials.10Wisconsin State Legislature. Wisconsin Administrative Code SPS 365 – Fuel Gas Appliances Wisconsin adds a cold-weather rule: when air entering the heat exchanger drops to 30°F or below, both the heat exchanger and burners must be made from corrosion-resistant materials to handle the condensation that forms during cold operation.
Commercial Kitchen Exhaust
Grease ducts in commercial kitchens must be built from heavy-gauge steel with liquid-tight joints, equipped with dedicated fire suppression, and fitted with regular access panels for cleaning. All appliances regulated under SPS 364 must be listed and labeled by an approved testing agency before installation, unless DSPS grants specific approval through its product approval process.6Wisconsin Department of Safety and Professional Services. Wisconsin Code SPS 361 – SPS 366
Refrigerants
Anyone who services, maintains, repairs, or disposes of equipment containing refrigerants must hold EPA Section 608 Technician Certification under the Clean Air Act. The EPA offers four certification types: Type I for small appliances, Type II for high-pressure equipment, Type III for low-pressure equipment, and Universal for all types.11US EPA. Section 608 Technician Certification Requirements Section 608 also prohibits intentional venting of ozone-depleting substances and their substitutes, including hydrofluorocarbons.12US EPA. Stationary Refrigeration and Air Conditioning These federal rules apply on top of whatever the Wisconsin code requires.
Energy Code Overlaps
Heating and cooling loads must be calculated using the methods in SPS 363.0302 or ASHRAE 90.1–2019, and equipment must be sized to meet those loads without significant oversizing. Supply air economizers are required on all packaged rooftop units and on any cooling system of 60,000 BTU per hour or more. When multiple air systems serve a single space, Wisconsin aggregates their cooling capacity in deciding whether an economizer is required. Ductwork outside the building envelope is treated as exterior duct for insulation purposes, and new buildings require monitoring equipment to track total electrical energy use, with tenant-level monitoring where applicable.8Wisconsin State Legislature. Wisconsin Administrative Code Chapter SPS 363
Who Is Allowed to Do the Work
Wisconsin requires anyone who installs or services HVAC equipment in a commercial or residential setting to hold a state-issued HVAC Contractor registration through DSPS, under SPS 305.70.13Department of Safety and Professional Services. HVAC Contractor It is one of the first things an inspector checks. Three exemptions matter:
- You can service HVAC equipment in a building you own without a registration, but you cannot install new equipment.
- You can install or service HVAC equipment in a dwelling you own and live in, or will live in.
- The HVAC registration does not cover electrical or plumbing tasks associated with an HVAC installation; those require separate credentials.
Wisconsin also offers an HVAC Qualifier certification under SPS 305.71. A business that employs an HVAC Qualifier is treated as a certified HVAC business and cannot be required to obtain a separate local license to work in any municipality in the state.14Department of Safety and Professional Services. HVAC Qualifier For contractors working across jurisdictions, that statewide preemption is a meaningful advantage.
Plan Review, Documentation, and Fees
Commercial HVAC projects must go through state plan review before construction begins. The process runs through the DSPS eSLA online portal, and hard copy submittals are not accepted.15Wisconsin Department of Safety and Professional Services. Wisconsin Commercial Building and Heating Codes You create an eSLA account, answer technical questions about the project, upload plan sets and supporting documentation, and pay review fees in a single electronic submission.16Department of Safety and Professional Services. eSLA User Guides and Videos
The main application is Form SBD-118, “Application for Review – Buildings, HVAC, Fire and Components.”17Wisconsin Department of Safety and Professional Services. Application for Review – Buildings, HVAC, Fire and Components – SBD-118 For HVAC plan reviews, DSPS requires structural calculations, building envelope calculations (such as COMcheck or equivalent), heat loss calculations, and hydraulic calculations, each stamped and sealed by a registered professional.18Department of Safety and Professional Services. Heating, Ventilation, and Air Conditioning Construction documents must be prepared, signed, and sealed by a Wisconsin-registered architect or engineer, though projects in buildings containing less than 50,000 cubic feet of total volume are exempt from that supervision requirement.19Wisconsin State Legislature. Wisconsin Administrative Code SPS 361.31(3)(a)
Plan review fees are based on total gross square footage of the building or affected area, and the schedule differs depending on whether the project sits in a delegated municipality or a non-delegated area. In non-delegated areas, HVAC plan review fees range from $180 for spaces under 2,500 square feet up to $13,500 for buildings exceeding 500,000 square feet. In delegated municipalities, the range runs from $150 to $12,100. Every submission carries a $100 plan entry fee, resubmissions after a denial cost $250 per plan, and revisions to previously approved plans cost $75.20Wisconsin State Legislature. Wisconsin Administrative Code Chapter SPS 302 – Fee Schedule
DSPS estimates commercial plan reviews take about 27 business days from the time payment is received.21Department of Safety and Professional Services. Division of Industry Services Plan Review The department’s own guidance tells applicants to allow six weeks and build in buffer time for potential delays.15Wisconsin Department of Safety and Professional Services. Wisconsin Commercial Building and Heating Codes Getting the submission right the first time saves both money and weeks.
Inspections and Who Shows Up
After plan approval, on-site inspections verify that the installed work matches the approved drawings. Buildings are inspected at various stages during construction, and the identity of your inspector depends on location.2Department of Safety and Professional Services. Commercial Buildings
Wisconsin lets DSPS delegate plan review, permitting, and inspection to municipalities or other local government entities.22Department of Safety and Professional Services. DSPS Division of Industry Services Delegated Agents In a delegated municipality, a local inspector handles the work. In non-delegated areas, a state commercial building inspector from DSPS performs inspections. DSPS publishes lists of delegated municipalities by function (commercial structural and HVAC, plan review, fire suppression, electrical, plumbing), so check your jurisdiction early. It affects which office you coordinate with, what you pay, and how fast you can get on an inspector’s calendar.
Penalties for Noncompliance
For commercial buildings and places of employment, each day a person or business fails to comply with a DSPS order counts as a separate violation. Penalties run from $10 to $100 per violation per day.23Wisconsin State Legislature. Wisconsin Administrative Code SPS 314.01 Those numbers sound modest, but they accumulate quickly when a problem persists for weeks. For one- and two-family dwellings under the Uniform Dwelling Code, the range is steeper: $25 to $500 per violation, with each day of continued violation counting as a separate offense.24Wisconsin State Legislature. Wisconsin Statutes 101.63
DSPS can also issue special orders directing immediate cessation of work when a project lacks required plan approval or otherwise fails to comply. Beyond the fines, operating without proper HVAC contractor registration, installing unlisted equipment, or ignoring ventilation requirements can lead to failed inspections that freeze the whole project until the violations are corrected. The cost of ripping out and reinstalling noncompliant work almost always dwarfs the fines.