The provisions of this chapter shall not be construed to do any of the following:
 1. Apply to a person licensed as an engineer pursuant to chapter 542B, licensed as a manufactured home retailer or certified as a manufactured home installer pursuant to chapter 103A, licensed as an architect pursuant to chapter 544A, or licensed as a landscape architect pursuant to chapter 544B who provides consultations or develops plans or other work concerning plumbing, HVAC, refrigeration, sheet metal, or hydronic work and who is exclusively engaged in the practice of the person’s profession.
 2. Require employees of municipal utilities, electric membership or cooperative associations, public utility corporations, rural water associations or districts, railroads, or commercial retail or industrial companies performing manufacturing, installation, service, or repair work for such employer to hold licenses while acting within the scope of their employment. This licensing exemption does not apply to employees of a rate-regulated gas or electric public utility which provides plumbing or mechanical services as part of a systematic marketing effort, as defined pursuant to section 476.80.
 3. Prohibit an owner of property from performing work on the owner’s principal residence, if such residence is an existing dwelling rather than new construction and is not larger than a single-family dwelling, or farm property, excluding commercial or industrial installations or installations in public use buildings or facilities, or require such owner to be licensed under this chapter. In order to qualify for inapplicability pursuant to this subsection, a residence shall qualify for the homestead tax exemption.
 4. Require that any person be a member of a labor union in order to be licensed.
 5. Apply to a person who is qualified pursuant to administrative rules relating to the storage and handling of liquefied petroleum gases while engaged in installing, servicing, testing, replacing, or maintaining propane gas utilization equipment, or gas piping systems of which the equipment is a part, and related or connected accessory systems or equipment necessary to the operation of the equipment.
 6. Apply to a person who meets the requirements for a certified well contractor pursuant to section 455B.190A while engaged in installing, servicing, testing, replacing, or maintaining a water system, water well, well pump, or well equipment, or piping systems of which the equipment is a part, and related or connected accessory systems or equipment necessary to the operation of the water well.
 7. Require a helper engaged in general manual labor activities while providing assistance to an apprentice, journeyperson, or master to obtain a plumbing, mechanical, HVAC-refrigeration, sheet metal, or hydronic license. Experience as a helper shall not be considered as practical experience for a journeyperson license.
 8. Apply to a person who is performing work subject to chapter 100C.
 9. Apply to an employee of any unit of state or local government, including but not limited to cities, counties, or school corporations, performing work on a mechanical system or plumbing system, which serves a government-owned or government-leased facility while acting within the scope of the government employee’s employment.
 10. Apply to the employees of manufacturers, manufacturer representatives, or wholesale suppliers who provide consultation or develop plans concerning plumbing, HVAC, refrigeration, sheet metal, or hydronic work, or who assist a person licensed under this chapter in the installation of mechanical or plumbing systems.
 11. Prohibit an owner or operator of a health care facility licensed pursuant to chapter 135C, assisted living center licensed pursuant to chapter 231C, hospital licensed pursuant to chapter 135B, adult day care center licensed pursuant to chapter 231D, or a retirement facility certified pursuant to chapter 523D from performing work on the facility or requiring such owner or operator to be licensed under this chapter; except for projects that exceed the dollar amount specified as the competitive bid threshold in section 26.3.
 12. Apply to a person who performs the laying of pipe that originates or connects to pipe in the public right-of-way or property that is intended to become public right-of-way, even if such pipe extends under the property and up to the building. However, the person shall not make any interior pipe connections within a building under this exemption. This exemption does not restrict local jurisdictions from requiring licensure under this chapter if required by local ordinance, resolution, or by bidding specification.
 13. Prohibit a rental property owner or employee of such an owner from performing routine maintenance on the rental property.
 14. Apply to a person who is performing work on a volunteer, non-paid basis or assisting a property owner performing non-paid work on the owner’s principal residence.