(1)(a) Not later than January 1, 1991, the state building code council, in consultation with the department of commerce, shall establish interim requirements for the maintenance of indoor air quality in newly constructed residential buildings. In establishing the interim requirements, the council shall take into consideration differences in heating fuels and heating system types. These requirements shall be in effect July 1, 1991, through June 30, 1993.

(b) The interim requirements for new electrically space heated residential buildings shall include ventilation standards which provide for mechanical ventilation in areas of the residence where water vapor or cooking odors are produced. The ventilation shall be exhausted to the outside of the structure. The ventilation standards shall further provide for the capacity to supply outside air to each bedroom and the main living area through dedicated supply air inlet locations in walls, or in an equivalent manner. At least one exhaust fan in the home shall be controlled by a dehumidistat or clock timer to ensure that sufficient whole house ventilation is regularly provided as needed.

(c)(i) For new single-family residences with electric space heating systems, zero lot line homes, each unit in a duplex, and each attached housing unit in a planned unit development, the ventilation standards shall include fifty cubic feet per minute of effective installed ventilation capacity in each bathroom and one hundred cubic feet per minute of effective installed ventilation capacity in each kitchen.

(ii) For other new residential units with electric space heating systems the ventilation standards may be satisfied by the installation of two exhaust fans with a combined effective installed ventilation capacity of two hundred cubic feet per minute.

(iii) Effective installed ventilation capacity means the capability to deliver the specified ventilation rates for the actual design of the ventilation system. Natural ventilation and infiltration shall not be considered acceptable substitutes for mechanical ventilation.

(d) For new residential buildings that are space heated with other than electric space heating systems, the interim standards shall be designed to result in indoor air quality equivalent to that achieved with the interim ventilation standards for electric space heated homes.

(e) The interim requirements for all newly constructed residential buildings shall include standards for indoor air quality pollutant source control, including the following requirements: All structural panel components of the residence shall comply with appropriate standards for the emission of formaldehyde; the back-drafting of combustion by-products from combustion appliances shall be minimized through the use of dampers, vents, outside combustion air sources, or other appropriate technologies; and, in areas of the state where monitored data indicate action is necessary to inhibit indoor radon gas concentrations from exceeding appropriate health standards, entry of radon gas into homes shall be minimized through appropriate foundation construction measures.

(2) No later than January 1, 1993, the state building code council, in consultation with the department of commerce, shall establish final requirements for the maintenance of indoor air quality in newly constructed residences to be in effect beginning July 1, 1993. For new electrically space heated residential buildings, these requirements shall maintain indoor air quality equivalent to that provided by the mechanical ventilation and indoor air pollutant source control requirements included in the February 7, 1989, Bonneville power administration record of decision for the environmental impact statement on new energy efficient homes programs (DOE/EIS-0127F) built with electric space heating. In residential units other than single-family, zero lot line, duplexes, and attached housing units in planned unit developments, ventilation requirements may be satisfied by the installation of two exhaust fans with a combined effective installed ventilation capacity of two hundred cubic feet per minute. For new residential buildings that are space heated with other than electric space heating systems, the standards shall be designed to result in indoor air quality equivalent to that achieved with the ventilation and source control standards for electric space heated homes. In establishing the final requirements, the council shall take into consideration differences in heating fuels and heating system types.

Explanatory statement—2023 c 470: See note following RCW 10.99.030.

Findings—Intent—Part headings not law—Effective date—1996 c 186: See notes following RCW 43.330.904.

Effective dates—1990 c 2: See note following RCW 19.27.040.

Findings—Severability—1990 c 2: See notes following RCW 19.27A.015.