A sentence was added to these sections to clarify that outdoor air needs to be supplied to all habitable spaces per Section 403.8.5.1.
C. Ray Allshouse
WAC 51-52-0403 Section 403-Mechanical ventilation.
403.2 Outdoor air required. The minimum ventilation rate of outdoor air shall be determined in accordance with Section 403.3.
| |
EXCEPTIONS: | 1. Where the registered design professional demonstrates that an engineered ventilation system design will prevent the maximum concentration of contaminants from exceeding that obtainable by the rate of outdoor air ventilation determined in accordance with Section 403.3, the minimum required rate of outdoor air shall be reduced in accordance with such engineered system design. |
| 2. Alternate systems designed in accordance with ASHRAE Standard 62.1 Section 6.2, Ventilation Rate Procedure, shall be permitted. |
403.2.1 Recirculation of air. The air required by Section 403.3 shall not be recirculated. Air in excess of that required by Section 403.3 shall not be prohibited from being recirculated as a component of supply air to building spaces, except that:
1. Ventilation air shall not be recirculated from one dwelling to another or to dissimilar occupancies.
2. Supply air to a swimming pool and associated deck areas shall not be recirculated unless such air is dehumidified to maintain the relative humidity of the area at 60 percent or less. Air from this area shall not be recirculated to other spaces where 10 percent or more of the resulting supply airstream consists of air recirculated from these spaces.
3. Where mechanical exhaust is required by Note b in Table 403.3, recirculation of air from such spaces shall be prohibited. All air supplied to such spaces shall be exhausted, including any air in excess of that required by Table 403.3.
(Item 4 is not adopted.)
403.3 Outdoor airflow rate. Ventilation systems shall be designed to have the capacity to supply the minimum outdoor airflow rate determined in accordance with this section. The occupant load utilized for design of the ventilation system shall not be less than the number determined from the estimated maximum occupant load rate indicated in Table 403.3. Ventilation rates for occupancies not represented in Table 403.3 shall be those for a listed occupancy classification that is most similar in terms of occupant density, activities and building construction; or shall be determined by an approved engineering analysis. The ventilation system shall be designed to supply the required rate of ventilation air continuously during the period the building is occupied, except as otherwise stated in other provisions of the code.
With the exception of smoking lounges, the ventilation rates in Table 403.3 are based on the absence of smoking in occupiable spaces. Where smoking is anticipated in a space other than a smoking lounge, the ventilation system serving the space shall be designed to provide ventilation over and above that required by Table 403.3 in accordance with accepted engineering practice.
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EXCEPTION: | Where occupancy density is known and documented in the plans, the outside air rate may be based on the design occupant density. Under no circumstance shall the occupancies used result in outside air less than one-half that resulting from application of Table 403.3 estimated maximum occupancy rates. |
Table 403.3
REQUIRED OUTDOOR VENTILATION AIR
| | | | | |
Occupancy Classification |
Occupant Density #/1000 ft2a |
People Outdoor Airflow Rate in Breathing Zone Rp cfm/Person |
Area Outdoor Airflow Rate in Breathing Zone Ra cfm/ft2a |
Exhaust Airflow Rate cfm/ft2 |
Offices |
|
|
|
|
|
Conference rooms |
50 |
5 |
0.06 |
- |
|
Kitchenettes |
- |
- |
- |
0.30 |
|
Office spaces |
5 |
5 |
0.06 |
- |
|
Reception areas |
30 |
5 |
0.06 |
- |
|
Telephone/data entry |
60 |
5 |
0.06 |
- |
|
Main entry lobbies |
10 |
5 |
0.06 |
- |
Private dwellings, single and multiple |
|
|
|
|
|
Garages, common for multiple unitsb |
- |
- |
- |
0.75 |
|
Garages, separate for each dwellingb |
- |
- |
- |
100 cfm per car |
|
Kitchensb |
- |
- |
- |
25/100f |
|
Living areasc |
Based on the number of bedrooms. First bedroom, 2; each additional bedroom, 1 |
See Tables 403.8.1 and 403.8.5.1 |
- |
- |
|
Toilet rooms, bathrooms and laundry areasg, i |
- |
- |
- |
20/50f |
Sports and amusement |
|
|
|
|
|
Disco/dance floors |
100 |
20 |
0.06 |
- |
|
Bowling alleys (seating areas) |
40 |
10 |
0.12 |
- |
|
Game arcades |
20 |
7.5 |
0.18 |
- |
|
Ice arenas, without combustion enginesj |
- |
- |
0.30 |
0.5 |
|
Gym, stadium, arena (play area)j |
- |
- |
0.30 |
- |
|
Spectator areas |
150 |
7.5 |
0.06 |
- |
|
Swimming pools (pool and deck area) |
- |
- |
0.48 |
- |
|
Health club/aerobics room |
40 |
20 |
0.06 |
- |
|
Health club/weight room |
10 |
20 |
0.06 |
- |
Storage |
|
|
|
|
|
Janitor closets, trash rooms, recycling rooms |
- |
- |
- |
1.0 |
|
Repair garages, enclosed parking garageb, d |
- |
- |
- |
0.75 |
|
Storage rooms, chemical |
- |
- |
- |
1.5 |
|
Warehouses |
- |
- |
0.06 |
- |
| |
For SI: | 1 cubic foot per minute = 0.0004719 m3/s, 1 ton = 908 kg, 1 cubic foot per minutes per square foot = 0.00508 m3/(s.m2), °C = [(°F) -32]/1.8, 1 square foot - 0.0929 m2. |
a. | Based upon net occupiable floor area. |
b. | Mechanical exhaust required and the recirculation of air from such spaces is prohibited (see Section 403.2.1, Item 3). |
c. | Spaces unheated or maintained below 50°F are not covered by these requirements unless the occupancy is continuous. |
d. | Ventilation systems in enclosed parking garages shall comply with Section 404. |
e. | Rates are per water closet or urinal. The higher rate shall be provided where the exhaust system is designed to operate intermittently. The lower rate shall be permitted only where the exhaust system is designed to operate continuously while occupied. |
f. | Rates are per room unless otherwise indicated. The higher rate shall be provided where the exhaust system is designed to operate intermittently. The lower rate shall be permitted only where the exhaust system is designed to operate continuously while occupied. |
g. | Mechanical exhaust is required and recirculation is prohibited. |
h. | For nail salons, each nail station shall be provided with a source capture system capable of exhausting not less than 50 cfm per station. |
i. | A laundry area within a kitchen or bathroom is not required to have local exhaust. For the laundry area to qualify as being within the kitchen, the laundry room door must open directly into the kitchen and not into an adjacent corridor. Where there are doors that separate the laundry area from the kitchen or bathroom the door shall be louvered. |
j. | When combustion equipment is intended to be used on the playing surface, additional dilution ventilation and/or source control shall be provided. |
403.8 Ventilation systems for Group R occupancies. Each dwelling unit or sleeping unit shall be equipped with local exhaust and whole house ventilation systems and shall comply with Sections 403.8.1 through 403.8.11. All public corridors and other than Group R occupied spaces that support the Group R occupancy shall meet the ventilation requirements of Section 402 or Sections 403.1 to 403.7.
403.8.1 Minimum ventilation performance. Ventilation systems shall be designed and installed to satisfy the ventilation requirements of Table 403.3 or Table 403.8.1. Breathing zone ventilation rates from Table 403.3 shall be calculated per Section 403.3.1.1 and corrected per zone air distribution effectiveness requirements per Section 403.3.1.2.
Table 403.8.1
VENTILATION RATES FOR ALL GROUP R PRIVATE DWELLINGS, SINGLE AND MULTIPLE
(CONTINUOUSLY OPERATING SYSTEMS)
| | | | | | | | | | | |
Floor Area |
|
Bedrooms1 |
|
(ft2) |
0-1 |
|
2-3 |
|
4-5 |
|
6-7 |
|
?7 |
|
<1500 |
|
30 |
|
45 |
|
60 |
|
75 |
|
90 |
|
1501 - 3000 |
|
45 |
|
60 |
|
75 |
|
90 |
|
105 |
|
3001 - 4500 |
|
60 |
|
75 |
|
90 |
|
105 |
|
120 |
|
4501 - 6000 |
|
75 |
|
90 |
|
105 |
|
120 |
|
135 |
|
6001 - 7500 |
|
90 |
|
105 |
|
120 |
|
135 |
|
150 |
|
?7500 |
|
105 |
|
120 |
|
135 |
|
150 |
|
165 |
|
| |
| 1Ventilation rates in table are minimum outdoor airflow rates measured in cfm. |
403.8.2 Control and operation.
1. Location of controls. Controls for all ventilation systems shall be readily accessible by the occupant.
2. Instructions. Operating instructions for whole house ventilation systems shall be provided to the occupant by the installer of the system.
3. Local exhaust ventilation systems. Local exhaust ventilation systems shall be controlled by manual switches, dehumidistats, timers, or other approved means.
4. Continuous whole house ventilation systems. Continuous whole house ventilation systems shall operate continuously. Exhaust fans, forced-air system fans, or supply fans shall be equipped with "fan on" as override controls. Controls shall be capable of operating the ventilation system without energizing other energy-consuming appliances. A label shall be affixed to the controls that reads "Whole House Ventilation (see operating instructions)."
5. Intermittent whole house ventilation systems. Intermittent whole house ventilation systems shall comply with the following:
5.1 They shall be capable of operating intermittently and continuously.
5.2 They shall have controls capable of operating the exhaust fans, forced-air system fans, or supply fans without energizing other energy-consuming appliances.
5.3 The ventilation rate shall be adjusted according to the exception in Section 403.8.5.1.
5.4 The system shall be designed so that it can operate automatically based on the type of control timer installed.
5.5 The intermittent mechanical ventilation system shall operate at least one hour out of every four.
5.6 The system shall have a manual control and automatic control, such as a 24-hour clock timer.
5.7 At the time of final inspection, the automatic control shall be set to operate the whole house fan according to the schedule used to calculate the whole house fan sizing.
5.8 A label shall be affixed to the control that reads "Whole House Ventilation (see operating instructions)."
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EXCEPTION: | Engineered central ventilation systems serving dwelling units or sleeping units are not required to have individual controls for each dwelling unit or sleeping unit when designed for continuous operation and approved by the code official. |
403.8.3 Outdoor air intake locations. Outdoor air intakes shall be classified as either operable openings or mechanical air intakes and shall be located per the following criteria. The intake locations for operable openings and mechanical air intakes shall comply with the following:
1. Openings for mechanical air intakes shall comply with Section 401.4. Operable openings shall comply with Section 401.4 items 2 and 4 only.
2. Intake openings shall not be located closer than 10 feet from an appliance vent outlet unless such vent outlet is 3 feet above the outdoor air inlet. The vent shall be permitted to be closer if specifically allowed by Chapter 8 or by the International Fuel Gas Code.
3. Intake openings shall be located where they will not pick up objectionable odors, fumes, or flammable vapors.
4. Intake openings shall be located where they will not take air from a hazardous or unsanitary location.
5. Intake openings shall be located where they will not take air from a room or space having a fuel-burning appliances.
6. Intake openings shall not be located closer than 10 feet from a vent opening of a plumbing drainage system unless the vent opening is at least 3 feet above the air inlet.
7. Intake openings shall not be located where they will take air from an attic, crawl space, or garage.
403.8.4 Local exhaust ventilation requirements. Local exhaust ventilation systems shall exhaust at least the volume of air required for exhaust in Table 403.3. Exhaust shall be provided in each kitchen, bathroom, water closet, laundry area, indoor swimming pool, spa, and other room where water vapor or cooking odor is produced.
403.8.4.1 Local exhaust systems. Exhaust systems shall be designed and installed to meet all of the criteria below:
1. Local exhaust shall be discharged outdoors.
2. Exhaust outlets shall comply with Section 501.3.
3. Pressure equalization shall comply with Section 501.4.
4. Exhaust ducts in systems which are designed to operate intermittently shall be equipped with back-draft dampers.
5. All exhaust ducts in unconditioned spaces shall be insulated to a minimum of R-4.
6. Terminal outlet elements shall have at least the equivalent net free area of the ductwork.
7. Terminal outlet elements shall be screened or otherwise protected as required by Section 501.3.2.
8. Exhaust fans in separate dwelling units or sleeping units shall not share common exhaust ducts unless the system is engineered for this operation.
9. Where permitted by Chapter 5, multiple local exhaust ducts may be combined. If more than one of the exhaust fans in a dwelling unit or sleeping unit shares a common exhaust duct then each exhaust fan shall be equipped with a back-draft damper to prevent the recirculation of exhaust air from one room to another room via the exhaust ducting system.
403.8.4.2 Local exhaust fans. Exhaust fan construction and sizing shall meet the following criteria.
1. Exhaust fans shall be tested and rated in accordance with the airflow and sound rating procedures of the Home Ventilating Institute (HVI 915, HVI Loudness Testing and Rating Procedure, HVI 916, HVI Airflow Test Procedure, and HVI 920, HVI Product Performance Certification Procedure).
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EXCEPTION: | Where a range hood or down draft exhaust fan is used for local exhaust for a kitchen, the device is not required to be rated per these standards. |
2. Installation of the system or equipment shall be carried out in accordance with manufacturers' installation instructions.
3. Fan airflow rating and duct system shall be designed and installed to deliver at least the exhaust airflow required by Table 403.3. The airflows required refer to the delivered airflow of the system as installed and tested using a flow hood, flow grid, or other airflow measurement device.
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EXCEPTIONS: | 1. An exhaust airflow rating at a pressure of 0.25 in. w.g. may be used, provided the duct sizing meets the prescriptive requirements of Table 403.8.4.2. |
| 2. Where a range hood or down draft exhaust fan is used to satisfy the local exhaust requirements for kitchens, the range hood or down draft exhaust shall not be less than 100 cfm at 0.10 in. w.g. |
TABLE 403.8.4.2
PRESCRIPTIVE EXHAUST DUCT SIZING
| | | | | | | | | |
Fan Tested cfm at 0.25 inches w.g. |
Minimum Flex Diameter |
Maximum Length in Feet |
Minimum Smooth Diameter |
Maximum Length in Feet |
Maximum Elbows1 |
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 inches2 |
|
NA |
4 inches |
|
20 |
3 |
|
80 |
|
5 inches |
|
15 |
5 inches |
|
100 |
3 |
|
80 |
|
6 inches |
|
90 |
6 inches |
|
No Limit |
3 |
|
100 |
|
5 inches2 |
|
NA |
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 |
|
| |
1. | For each additional elbow, subtract 10 feet from length. |
2. | Flex ducts of this diameter are not permitted with fans of this size. |
403.8.5 Whole house ventilation requirements. Each dwelling unit or sleeping unit shall be equipped with one of the following four types of mechanical whole house ventilation systems: A system using exhaust fans (see Section 403.8.6); a system integrated with forced-air systems (see Section 403.8.7); a system using supply fans (see Section 403.8.8); or a heat or energy recovery ventilation system (see Section 403.8.9). The whole house exhaust system is permitted to be one of the local exhaust systems required by Section 403.8.4 as long as the requirements of this section, in addition to the requirements of Section 403.8.5, are met.
403.8.5.1 Outdoor air. Outdoor air shall be distributed to each habitable space.
Where outdoor air supply intakes are separated from exhaust vents by doors, means shall be provided to ensure airflow to all separated habitable spaces by installing distribution ducts, installed grilles, transoms, doors undercut to a minimum of 1/2-inch above the surface of the finish floor covering, or other similar means where permitted by the International Building Code.
The mechanical system shall operate continuously to supply at least the volume of outdoor air required in Table 403.3 or Table 403.8.1.
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EXCEPTION: | Intermittently operating ventilation systems: The whole house mechanical ventilation system is permitted to operate intermittently where the system has controls that enable operation for not less than 25 percent of each 4-hour segment and the ventilation rate prescribed in Table 403.3 or Table 403.8.1 is multiplied by the factor determined in accordance with Table 403.8.5.1. |
TABLE 403.8.5.1
INTERMITTENT WHOLE HOUSE MECHANICAL VENTILATION RATE FACTORSa, b
| | | | | | |
RUN-TIME PERCENTAGE IN EACH 4-HOUR SEGMENT |
25% |
33% |
50% |
66% |
75% |
100% |
Factora |
4 |
3 |
2 |
1.5 |
1.3 |
1.0 |
| |
| a For ventilation system run-time values between those given, the factors are permitted to be determined by interpolation. |
| b Extrapolation beyond the table is prohibited. |
403.8.5.2 Whole house supply system general requirements. Whole house ventilation systems integrated with a forced-air system, systems using supply fans and systems using a heat or energy recovery ventilation system shall comply with the following.
1. Outdoor air louvers shall be adequately sized for the required airflow and shall comply with Section 401.5. Outdoor air intake locations shall comply with mechanical air intakes requirements of Section 403.8.3.
2. Outdoor air ducts for dedicated or central supply systems and exhaust ducts for heat or energy recovery systems shall be provided with a means for balancing the system to the required airflow via balance dampers or other devices.
3. Outdoor air ducts for dedicated or central systems shall be provided with motorized dampers.
| |
EXCEPTIONS: | 1. Outdoor air ducts at heat or energy recovery ventilation systems are not required to have motorized dampers. |
| 2. Outdoor air ducts at continuous ventilation systems are not required to have motorized dampers. |
4. Outdoor air ducts in the conditioned space shall be insulated to a minimum of R-4. In heat or energy recovery ventilation systems, ducts upstream of the heat exchanger shall also be insulated to at least R-4.
5. All outdoor air ducts shall be designed and installed to deliver at least the outdoor airflow required by Section 403.8.5.1. The airflows required refer to the delivered airflow of the system as installed and tested using a flow hood, flow grid, or other airflow measurement device.
| |
EXCEPTION: | The outdoor air duct for supply fan systems and heat or energy recovery systems may be prescriptively sized per Table 403.8.5.2 for dedicated outdoor air ducts upstream of the supply fan. Supply fans shall have the capacity to provide the amount of outdoor air required by Section 403.8.5.1 at 0.40 in. w.g. as per HVI 916 (April 1995). When prescriptively sized the system shall be tested and balanced using a flow hood, flow-grid, or other airflow measurement device. |
6. Whole house ventilation controls for intermittent operation shall allow concurrent operation of the forced-air fan and the associated outdoor air motorized damper.
7. Whole house ventilation controls for continuous operation shall be provided at the forced-air fan.
| |
EXCEPTION: | Engineered central ventilation systems serving dwelling units or sleeping units are not required to have individual controls for each dwelling or sleeping unit when designed for continuous operation and approved by the code official. |
TABLE 403.8.5.2
PRESCRIPTIVE SUPPLY FAN DUCT SIZING
| | | | |
Supply Fan Tested cfm at 0.40" w.g. |
Specified Volume from Table 408.1 |
Minimum Smooth Duct Diameter |
Minimum Flexible Duct Diameter |
50 - 90 cfm |
4 inch |
|
5 inch |
|
90 - 150 cfm |
5 inch |
|
6 inch |
|
150 - 250 cfm |
6 inch |
|
7 inch |
|
250 - 400 cfm |
7 inch |
|
8 inch |
|
403.8.6 Whole house ventilation with exhaust fan systems. This section establishes minimum requirements for mechanical whole house ventilation systems using exhaust fans.
403.8.6.1 Outdoor air. Exhaust fan only ventilation systems shall provide outdoor air to each occupiable space through one of the following methods:
1. Outdoor air may be drawn through air inlets installed in exterior walls or windows. The air inlets shall comply with all of the following:
1.1. Inlets shall have controllable, secure openings and shall be designed to not compromise the thermal properties of the building envelope.
1.2. Inlets shall be accessible to occupants, including compliance with Section 1109.13 of the International Building Code for designated accessible units, Type A units and Type B units.
1.3. Inlets shall be screened or otherwise protected from entry by insects, leaves, or other material.
1.4. Inlets shall provide not less than 4 square inches of net free area of opening for each 10 cfm of outdoor air required in Table 403.3 or Table 403.8.1.
1.5. Any inlet or combination of inlets which provide 10 cfm at 10 Pascals as determined by the Home Ventilation Institute Air Flow Test Standard (HVI 901 (November 1996)) are deemed equivalent to 4 square inches of net free area.
1.6. Each occupiable space shall have a minimum of one air inlet that has a minimum of 4 square inches of net free area.
2. In high-rise buildings, outdoor air may be drawn in through operable windows, doors, louvers or other operable openings to the outdoors. Exterior spaces shall have a minimum openable area of 4 percent of the total floor area being ventilated. Doors exiting to a corridor, court or public way shall not be used to provide outdoor air. The operable openings shall comply with the following:
2.1. Openings shall be controllable, securable, and shall be designed to not compromise the thermal properties of the building envelope.
2.2. Openings shall be accessible to occupants, including compliance with Section 1109.13 of the International Building Code for designated accessible units, Type A units and Type B units.
3. For interior adjoining spaces without outdoor air openings, one of the following two options shall be used to ventilate the interior adjoining space:
3.1. Provide a whole house transfer fan at the interior adjoining space sized to provide a minimum of the ventilation rate required per Section 403.8.5.1. The transfer fan shall circulate air between the interior room or space and the adjacent habitable space. The transfer fan may operate continuously or intermittently using controls per Section 403.8.2.
3.2. Provide a permanent opening to the interior adjoining space. Opening shall be unobstructed and shall have an area of not less than 8 percent of the floor area of the interior adjoining space, but not less than 25 square feet.
403.8.6.2 Outside air intake locations. All outside air intake opening types described in Section 403.8.6.1 shall be classified operable openings and shall not be classified as mechanical air intakes. The intake locations shall comply with Section 403.8.3.
403.8.6.3 Whole house exhaust system. Whole house exhaust system shall be designed and installed to meet all of the applicable criteria below:
1. Whole house ventilation exhaust shall be discharged outdoors.
2. Exhaust outlets shall comply with Section 501.2.
3. Exhaust ducts in systems which are designed to operate intermittently shall be equipped with back-draft dampers.
4. All exhaust ducts in unconditioned spaces shall be insulated to a minimum of R-4.5. Terminal outlet elements shall have at least the equivalent net free area of the ductwork.
5. Terminal outlet elements shall be screened or otherwise protected as required by Section 501.2.2.
6. One of the required local exhaust fans for the laundry room or bathroom may be designated as the whole house exhaust fan.
7. Exhaust fans in separate dwelling units or sleeping units shall not share common exhaust ducts unless the system is engineered for this operation.
8. Where permitted by Chapter 5 whole house exhaust ducts may be combined with other local exhaust ducts. If more than one of the exhaust fans in a dwelling unit or sleeping unit shares a common exhaust duct then each exhaust fan shall be equipped with a back-draft damper to prevent the recirculation of exhaust air from one room to another room via the exhaust ducting system.
403.8.6.4 Whole house exhaust and transfer fans. Exhaust fan construction and sizing shall meet the following criteria.
1. Exhaust and transfer fans shall be tested and rated in accordance with the airflow and sound rating procedures of the Home Ventilating Institute (HVI 915, HVI Loudness Testing and Rating Procedure, HVI 916, HVI Airflow Test Procedure, and HVI 920, HVI Product Performance Certification Procedure).
2. Installation of system or equipment shall be carried out in accordance with manufacturers' design requirements and installation instructions.
3. Fan airflow rating and duct system shall be designed and installed to deliver at least the outdoor airflow required by Table 403.3 or Table 403.8.1. The airflows required refer to the delivered airflow of the system as installed and tested using a flow hood, flow grid, or other airflow measurement device.
| |
EXCEPTION: | An airflow rating at a pressure of 0.25 in. w.g. may be used, provided the duct sizing meets the prescriptive requirements of Table 403.8.5.2. |
403.8.6.5 Fan noise. Whole house exhaust and transfer fans located 4 feet or less from the interior grille shall have a sone rating of 1.0 or less measured at 0.10 inches water gauge. Manufacturer's noise ratings shall be determined as per HVI 915. Remotely mounted fans shall be acoustically isolated from the structural elements of the building and from attached ductwork using insulated flexible duct or other approved material.
403.8.7 Whole house ventilation integrated with forced-air systems. This section establishes minimum requirements for mechanical whole house ventilation systems using forced-air system fans.
403.8.7.1 Outdoor air. Forced-air system fan ventilation systems shall provide outdoor air through one of the following methods:
1. A dedicated outdoor air louver and outdoor air duct for each dwelling unit or sleeping unit shall supply outdoor air to the return side of the forced-air system fan; or
2. A central outdoor air delivery system that supplies multiple dwelling units or sleeping units shall supply outdoor air to the return side of the forced air system fan.
403.8.7.2 Whole house forced-air system. Where outdoor air is provided to each habitable dwelling unit or sleeping unit by a forced-air system, the outdoor air duct shall be connected to the return air stream at a point within 4 feet upstream of the forced-air unit. It shall not be connected directly to the forced-air unit cabinet in order to prevent thermal shock to the heat exchanger. At a minimum, filtration of the outdoor air shall be provided at the forced-air unit. The filter shall be accessible for regular maintenance and replacement. The filter shall have a Minimum Efficiency Rating Value (MERV) of at least 6. Each habitable space in the dwelling or sleeping unit shall be served by a forced-air system with outdoor air connection.
403.8.8 Whole house ventilation with supply fan systems. This section establishes minimum requirements for mechanical whole house ventilation systems using supply fan systems.
403.8.8.1 Outdoor air. Supply fan ventilation systems shall provide outdoor air through one of the following methods:
1. A dedicated outdoor air louver and outdoor air duct for each dwelling unit or sleeping unit shall supply outdoor air to a supply fan; or
2. A central outdoor air supply fan system shall distribute unconditioned or conditioned air to multiple dwelling units or sleeping units.
403.8.8.2 Whole house supply system. Where outdoor air is provided to each habitable dwelling unit or sleeping unit by supply fan systems the outdoor air shall be filtered.
The system filter may be located at the intake device or inline with the fan. The filter shall be accessible for regular maintenance and replacement. The filter shall have a Minimum Efficiency Rating Value (MERV) of at least 6.
403.8.9 Whole house ventilation with heat recovery or energy recovery ventilation systems. This section establishes minimum requirements for mechanical whole house ventilation systems using heat recovery or energy recovery ventilation systems.
403.8.9.1 Outdoor air. Heat recovery or energy recovery ventilation systems shall provide outdoor air through one of the following methods:
1. A dedicated outdoor air louver and outdoor air duct for each dwelling unit or sleeping unit shall supply outdoor air to the heat recovery or energy recovery ventilator; or
2. A central outdoor air heat recovery or energy recovery unit shall distribute conditioned air to multiple dwelling units or sleeping units.
403.8.9.2 Whole house heat recovery ventilator system. Where outdoor air is provided to each habitable dwelling unit or sleeping unit by heat recovery or energy recovery ventilator the outdoor air shall be filtered. The filter shall be located on the upstream side of the heat exchanger in both the intake and exhaust airstreams with a Minimum Efficiency Rating Value (MERV) of at least 6. The system filter may be located at the intake device or inline with the fan. The filter shall be accessible for regular maintenance and replacement. Each habitable space in the dwelling or sleeping unit shall be served by a heat recovery ventilator system with outdoor air connection.
403.8.10 Local exhaust ventilation and whole house ventilation alternate performance or design requirements. In lieu of complying with Sections 403.8.4 or 403.8.5 compliance with the section shall be demonstrated through engineering calculations by an engineer licensed to practice in the state of Washington or by performance testing. Documentation of calculations or performance test results shall be submitted to and approved by the building official. Performance testing shall be conducted in accordance with approved test methods.
403.8.11 Alternate systems. When approved by the code official, systems designed in accordance with ASHRAE Standard 62.2 shall be permitted.
Reviser's note: The brackets and enclosed material in the text of the above section occurred in the copy filed by the agency.
