Air Ventilation Systems
Concrete Basements

Show location of existing furnace and main supply and return ducts. Indicate location and sizes of any new sub-ducts, register and diffuser locations for the finished area. Detail any artificial ventilation that may be proposed for any room/space, such as for new or downsized furnace rooms, bathrooms or any finished room that does not have adequate windows for natural ventilation.

Appliances and equipment, such as furnaces and hot water heaters, must remain accessible for inspection, service, repair and replacement without removing permanent construction. The furnace room shall have an opening or door large enough to permit removal of the largest piece of equipment, but not less than 20 inches wide. An unobstructed working space not less than 30 inches wide and not less than 30 inches high shall be provided along the control side of the equipment when the door of the furnace room is open.

Fuel-burning appliances shall be supplied with combustion air. Furnace rooms must be provided with two permanent openings to adjacent spaces; one shall be located within 12 inches of the top and one within 12 inches from the bottom of the adjoining wall. Each opening shall have free area equal to a minimum of 1 square inch per 1,000 Btu/h input rating of all appliances installed within the furnace room, but not less than 100 square inches. The openings are not required if a louvered door is provided or the furnace room area is greater than 50 cubic feet per 1,000 Btu/h input rating of all appliances installed in the room.

Using inside air: 1 sq.in. shall be provided/1000 BTU/hr. each opening. Openings shall not be less than 100 sq.in. One opening shall be provided within 12" of the ceiling and within 12" above finished floor, no common ducts.

Using outside air:

  1. Horizontal openings
    1 sq. in./2000 BTU/hr. for ducted opening
    1 sq. in./4000 BTU/hr. for direct opening
  2. Vertical openings
    1 sq. in./4000 BTU ducted or direct

Minimum clearance from combustibles is 18 inches, unless the listed manufacturer's installation instructions allow an alternate clearance dimension. 18 inches of clearance is required at the front of the appliance for service.

Clothes dryers shall be independent of all other system, and exhaust to the exterior.

Residential bathrooms without windows for natural ventilation shall exhaust 50 CFM minimum to the exterior. It is not permissible to discharge exhaust to the attic or floor joist area.

Exception: Half-baths without a tub or shower may exhaust to the attic.

For finished rooms without adequate windows, outdoor air (artificial ventilation) shall be supplied at a rate of 0.35 air changes per hour or 15 cubic feet per minute per person, whichever is greater. The estimated occupant load to be used for a large common room/space such as a recreation room or a rathskeller shall be based on 2 for the first bedroom and 1 for each additional bedroom within the house.

Gas piping shall be identified at intervals of no more than 25' when placed in concealed locations.

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