The maximum length of the exhaust duct shall be 35 feet (10 668 mm) from the connection to the transition duct from the dryer to the outlet terminal. Where fittings are used, the maximum length of the exhaust duct shall be reduced in accordance with Table M1502.4.5.1. The maximum length of the exhaust duct does not include the transition duct.
DRYER EXHAUST DUCT FITTING EQUIVALENT LENGTH
|DRYER EXHAUST DUCT FITTING TYPE||EQUIVALENT LENGTH|
|4-inch radius mitered 45-degree elbow||2 feet 6 inches|
|4-inch radius mitered 90-degree elbow||5 feet|
|6-inch radius smooth 45-degree elbow||1 foot|
|6-inch radius smooth 90-degree elbow||1 foot 9 inches|
|8-inch radius smooth 45-degree elbow||1 foot|
|8-inch radius smooth 90-degree elbow||1 foot 7 inches|
|10-inch radius smooth 45-degree elbow||9 inches|
|10-inch radius smooth 90-degree elbow||1 foot 6 inches|
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 degree = 0.0175 rad.
Where space for a clothes dryer is provided, an exhaust duct system shall be installed. Where the clothes dryer is not installed at the time of occupancy the exhaust duct shall be capped or plugged in the space in which it originates and identified and marked "future use."
Exception: Where a listed condensing clothes dryer is installed prior to occupancy of the structure.
Where domestic cooking exhaust equipment is provided, it shall comply with one of the following:
Domestic open-top broiler units shall be provided with a metal exhaust hood, having a minimum thickness of 0.0157 inch (0.3950 mm) (No. 28 gage). Such hoods shall be installed with a clearance of not less than 1/4 inch (6.4 mm) between the hood and the underside of combustible material or cabinets. A clearance of not less than 24 inches (610 mm) shall be maintained between the cooking surface and the combustible material or cabinets. The hood width shall not be less than the width of the broiler unit and shall extend over the entire unit.
Domestic cooking exhaust equipment shall discharge to the outdoors through a duct. The duct shall have a smooth interior surface, shall be airtight, shall be equipped with a backdraft damper and shall be independent of all other exhaust systems. Ducts serving domestic cooking exhaust equipment shall not terminate in an attic or crawl space or areas inside the building.
Exception: Where installed in accordance with the manufacturer's instructions, and where mechanical or natural ventilation is otherwise provided, listed and labeled ductless range hoods shall not be required to discharge to the outdoors.
Ducts serving domestic cooking exhaust equipment shall be constructed of galvanized steel, stainless steel or copper.
Where one or more gas, liquid or solid fuel-burning appliance that is neither direct-vent nor uses a mechanical draft venting system is located within a dwelling unit's air barrier, each exhaust system capable of exhausting in excess of 400 cubic feet per minute (0.19 m3/s) shall be mechanically or passively provided with makeup air at a rate approximately equal to the exhaust air rate. Such makeup air systems shall be equipped with not fewer than one damper complying with Section M1503.6.2.
Exception: Makeup air is not required for exhaust systems installed for the exclusive purpose of space cooling and intended to be operated only when windows or other air inlets are open.
Where makeup air is required by Section M1503.6, makeup air dampers shall comply with this section. Each damper shall be a gravity damper or an electrically operated damper that automatically opens when the exhaust system operates. Dampers shall be located to allow access for inspection, service, repair and replacement without removing permanent construction or any other ducts not connected to the damper being inspected, serviced, repaired or replaced. Gravity or barometric dampers shall not be used in passive makeup air systems except where the dampers are rated to provide the design makeup airflow at a pressure differential of 0.01 in. w.c. (3 Pa) or less.
The length of exhaust and supply ducts used with ventilating equipment shall not exceed the lengths determined in accordance with Table M1504.2.
Exception: Duct length shall not be limited where the duct system complies with the manufacturer's design criteria or where the flow rate of the installed ventilating equipment is verified by the installer or approved third party using a flow hood, flow grid or other airflow measuring device.
Air exhaust openings shall terminate as follows:
Whole-house ventilation supply and exhaust fans specified in this section shall have a minimum efficacy as prescribed in the Washington State Energy Code. Design and installation of the system or equipment shall be carried out in accordance with manufacturers' installation instructions. Whole-house ventilation fans shall be rated for sound at no less than the minimum airflow rate required by Section M1505.4.3.1. Ventilation fans shall be rated for sound at a maximum of 1.0 sone. This sound rating shall be at a minimum of 0.1 in. w.c. (25 Pa) static pressure in accordance with HVI procedures specified in Sections M1505.4.1.2 and M1505.4.1.3.
Exception: HVAC air handlers, ERV/HRV units, and remote-mounted fans need not meet the sound requirements. To be considered for this exception, a remote-mounted fan must be mounted outside the habitable spaces, bathrooms, toilets, and hallways, and there must be at least 4 feet (1219 mm) of ductwork between the fan and the intake grille.
The whole-house supply fan shall provide ducted outdoor ventilation air to each habitable space within the residential unit.
Exception: Interior joining spaces provided with a 30 cfm (0.0141 m3/s) whole-house transfer fan or a permanent opening with an area of not less than 8 percent of the floor area of the interior adjoining space but not less than 25 square feet (2.3 m2) do not require ducted outdoor ventilation air to be supplied directly to the space. Whole-house transfer fans shall meet the sone rating of Section M1505.4.1.1 and shall have whole-house ventilation controls that comply with Section M1505.4.2.
Systems using space heating and/or cooling air handler fans for outdoor air supply distribution are not permitted.
Exception: Air handler fans shall have multi-speed or variable speed supply airflow control capability with a low speed operation not greater than 25% of the rated supply airflow capacity during ventilation only operation. Outdoor air intake openings must meet the provisions of Sections R303.5 and R303.6 and must include a motorized damper that is activated by the whole-house ventilation system controller. The motorized damper must be controlled to maintain the outdoor airflow intake airflow within 10% of the whole-house mechanical exhaust airflow rate. The flow rate for the outdoor air intake must be tested and verified at the minimum ventilation fan speed and the maximum heating or cooling fan speed. The results of the test shall be submitted and posted in accordance with Section M1505.4.1.7.
The whole-house mechanical ventilation system shall be provided with controls that comply with the following:
The whole-house mechanical ventilation system shall provide outdoor air at a continuous rate as determined in accordance with Table M1505.4.3(1) or Equation 15-1.
WHOLE-HOUSE MECHANICAL VENTILATION AIRFLOW RATE
|DWELLING UNIT (square feet)||NUMBER OF BEDROOMS|
|0 - 1||2||3||4||5 or more|
|Airflow in cfm|
|501 - 1,000||30||35||40||50||55|
|1,001 — 1,500||30||40||45||55||60|
|1,501 - 2,000||35||45||50||60||65|
|2,001 - 2,500||40||50||55||65||70|
|2,501 - 3,000||45||55||60||70||75|
|3,001 - 3,500||50||60||65||75||80|
|3,501 — 4,000||55||65||70||80||85|
|4,001 — 4,500||60||70||75||85||90|
|4,501 — 5,000||65||75||80||90||95|
For SI: 1 square foot = 0.0929 m2, 1 cubic foot per minute = 0.0004719 m3/s.
SYSTEM COEFFICIENT Csystem)
|SYSTEM TYPE||DISTRIBUTED||NOT DISTRIBUTED|
INTERMITTENT OFF WHOLE-HOUSE MECHANICAL VENTILATION RATE FACTORSa,b
|RUN-TIME % IN EACH |
The minimum whole-house ventilation rate from Section 1505.4.3 shall be adjusted by the system coefficient in Table M1505.4.3(2) based on the system type not meeting the definition of a Balanced Whole-House Ventilation System and/or not meeting the definition of a Distributed Whole-House Ventilation System.
Local exhaust systems shall be designed to have the capacity to exhaust the minimum airflow rate determined in accordance with Table M1505.4.4(1). If the local exhaust fan is included in the whole-house ventilation system, in accordance with Section 1505.4.1, then the exhaust fan shall be controlled to operate as specified in Section M1505.4.2.
MINIMUM LOCAL EXHAUST RATES
|AREA TO BE EXHAUSTED||EXHAUST RATES|
|Kitchens||100 cfm||30 cfm|
|Bathrooms—Toilet Rooms||50 cfm||20 cfm|
PRESCRIPTIVE EXHAUST DUCT SIZING
|FAN TESTED CFM AT |
0.25 INCHES W.G.
|MAXIMUM LENGTH |
|MAXIMUM LENGTH |
|50||4 inches||25||4 inches||70||3|
|50||5 inches||90||5 inches||100||3|
|50||6 inches||No Limit||6 inches||No Limit||3|
|80||4 inchesb||Not Allowed||4 inches||20||3|
|80||5 inches||15||5 inches||100||3|
|80||6 inches||90||6 inches||No Limit||3|
|100||5 inchesb||Not Allowed||5 inches||50||3|
|100||6 inches||45||6 inches||No Limit||3|
|125||6 inches||15||6 inches||No Limit||3|
|125||7 inches||70||7 inches||No Limit||3|
NA = Not Allowed
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 cubic foot per minute = 0.0004719 m3/s, 1 inch water gage = 249 Pa.
Exhaust fans shall meet the following criteria: