Section SPS 327.44 - Ductwork(1) DUCT USE. Ducts designed for the transmission of air shall be used for no other purpose.(2) INTERIOR DUCTS. All interior ducts shall be constructed in accordance with the following: (a)Supply and return air ducts. Supply and return air ducts shall comply with this paragraph except that ducts attached to appliances may be constructed of materials specified in the appliance listing.1. Kitchen exhaust ducts and ducts for air exceeding 250 degrees Fahrenheit shall be constructed of sheet metal or lined with sheet metal or constructed of other noncombustible noncorrugated materials.2. Ducts connected to furnaces shall be constructed of sheet metal for at least 6 feet from the furnace.3. Spaces formed by unlined wood joists, studs or wood I-joists with solid webs may be used as return air ducts. Spaces used as return air ducts shall be cut off from all remaining unused portions of the space by tight-fitting stops of sheet metal or of wood joist material. Bridging shall be removed from the joist space.(b)Under-floor plenums. An under-floor space may be used as a plenum in a camping unit in accordance with this section.1. Except for the floor immediately above the under-floor plenum, supply ducts shall be provided extending from the plenum to registers or other floor levels.2. The under-floor spaces shall not be used for storage, shall be cleaned of all loose scrap material and shall be tightly and substantially enclosed.3. The enclosing material of the under-floor space, including the side wall insulation and vapor barriers, shall not be more flammable than one-inch wood boards.4. Access shall be through an opening in the floor which shall be 18 inches by 24 inches.5. The furnace supplying warm air to the under-floor space shall be equipped with an automatic control which will start the air circulating fan when the air in the furnace bonnet reaches a temperature not higher than 150 degrees Fahrenheit. The control shall be one that cannot be set higher than 150 degrees Fahrenheit.6. The furnace supplying warm air to the under-floor space shall be equipped with an approved temperature limit control that will limit outlet air temperature to 200 degrees Fahrenheit.7. A noncombustible receptacle shall be placed below each floor opening into the air chamber. The receptacle shall be securely suspended from the floor members and shall be not more than 18 inches below the floor opening. The area of the receptacle shall extend 3 inches beyond the opening on all sides. The perimeter of the receptacle shall have a vertical lip at least one inch high at the open sides if it is at the level of the bottom of the joist, or 3 inches high if the receptacle is suspended.8. Floor registers shall be designed for easy removal to permit access for cleaning the receptacles.9. Exterior walls and interior stud partitions shall be firestopped at the floor.10. Each wall register shall be connected to the air chamber by a register box or boot.11. A duct conforming to par. (a) shall extend from the furnace supply outlet at least 6 inches below combustible framing. 12. The entire ground surface and enclosing exterior walls of the under-floor space shall be covered with a vapor barrier having a vapor permeability rating of one perm or less and a flame spread rating of 200 or less.13. Fuel gas lines may not be located within the under-floor space.Wis. Admin. Code Department of Safety and Professional Services SPS 327.44
Adopted by, EmR1703: emerg. cr., eff. 2-6-17; CR 17-017: cr. Register March 2018 No. 747, eff. 4/1/2018