Naturally ventilated spaces shall be permanently open to and within 20 feet (6096 mm) of operable wall or roof openings to the outdoors, the openable area of which is not less than 5 percent of the conditioned floor area of the naturally ventilated space. Where openings are covered with louvers or otherwise obstructed, openable area shall be based on the free unobstructed area through the opening.
The means to open required operable openings shall be readily accessible to building occupants where the space is occupied.
Each space that is not naturally ventilated in accordance with Section E605.1.1 shall be ventilated with a mechanical system capable of providing an outdoor air rate not less than 15 ft3/min (0.007 m3/s) per person times the expected number of occupants. Mechanical ventilation shall comply with this code.
A Mechanical exhaust system, supply system, or combination thereof shall be installed to operate for each dwelling unit to provide continuous dwelling-unit ventilation with outdoor air rate not less than the rate specified in Section E605.1.3.1. [ASHRAE 62.2:4.1]
The total required ventilation rate (Qtot) shall be as specified in Table E605.1.3.1 or, alternatively, calculated in accordance with Equation E605.1.3.1.
For SI units: 1 cubic foot per minute = 0.00047 m3/s, 1 square
foot = 0.0929 m2
For SI units: 1 square foot = 0.0929 m2, 1 cubic foot per minute = 0.00047 m3/s
Qtot = 0.03Afloor + 7.5(Nbr + 1) (Equation E605.1.3.1)
|Qtot||=||total required ventilation rate, cubic feet per minute (ft3/min)|
|Afloor||=||dwelling unit square foot (ft2)|
|Nbr||=||number of bedrooms; not to be less than one|
Exceptions: Dwelling-unit mechanical ventilation systems shall not be required where the Authority Having Jurisdiction determines that window operation is a locally permissible method of providing ventilation and provided one or more of the following conditions is met:
- The building has no mechanical cooling and is located in zone 1 or 2.
- The building is thermally conditioned for human occupancy for less than 876 hours per year. [ASHRAE 62.2:4.1.1]
Effective Annual Average Infiltration Rate (Qinf) shall be calculated using Equation E605.1.3.2:
* Replace 7.3 with 1.44 for metric units. [ASHRAE 62.2:4.1.2(e)]
Qinf(cfm) = (NL x wsf x Afloor) / (7.3)* [Equation E605.1.3.2]
|wsf||=||weather and shielding factor from ASHRAE 62.2.|
|Afloor||=||floor area of residence, ft2 (m2)|
Required Mechanical Ventilation Rate (Qfan) shall be calculated using Equation E605.1.3.3:
Qfan = Qtot - (Qinf x Aext) [Equation E605.1.3.3]
|Qfan||=||required mechanical ventilation rate, cfm (L/s)|
|Qtot||=||total required ventilation rate, cfm (L/s)|
|Qinf||=||may be not greater than 2/3 x Qtot|
|(see ASHRAE 62.2 for exceptions for existing buildings)|
|Aext||=||1 for single-family detached homes, or the ratio of exterior envelope surface area that is not attached to garages or other dwelling units to total envelope surface area for single-family attached homes. [ASHRAE 62.2:4.1.2(f)]|
Table E605.1.3.1 and Equation E605.1.3.1 assume two persons in a studio or one-bedroom dwelling unit and an additional person for each additional bedroom. Where higher occupant densities are known, the rate shall be increased by 7.5 ft3/min (0.003 m3/s) for each additional person. Where approved by the Authority Having Jurisdiction, lower occupant densities shall be permitted to be used. [ASHRAE 62.2:4.1.3]
The dwelling-unit mechanical ventilation system shall consist of one or more supply or exhaust fans and associate ducts and controls. Local exhaust fans shall be permitted to be part of a mechanical exhaust system. Where local exhaust fans are used to provide dwelling-unit ventilation, the local exhaust airflow shall be permitted to be created towards the whole dwelling-unit ventilation airflow requirement. Outdoor air ducts connected to the return side of an air handler shall be permitted as supply ventilation where manufacturer's requirements for return air temperature are met. See ASHRAE 62.2 for guidance on selection of methods. [ASHRAE 62.2:4.2]
The dwelling-unit mechanical ventilation system shall consist of one or more supply or exhaust fans and associated ducts and controls. Local exhaust fans shall be permitted to be part of a mechanical exhaust system. Where local exhaust fans are used to provide dwelling-unit ventilation, the local exhaust airflow shall be permitted to be credited towards the whole dwelling-unit ventilation airflow requirement. Outdoor air ducts connected to the return side of an air handler shall be permitted as supply ventilation where manufacturer's requirements for return air temperature are met. See ASHRAE 62.2 for guidance on selection of methods. [ASHRAE 62.2:4.2]
The airflow required by this section shall be the quantity of outdoor ventilation air supply, indoor air, or both exhausted by the mechanical ventilation system as installed and shall be measured according to the ventilation equipment manufacturer's instructions, or by using a flow hood, flow grid, or other airflow measuring device at the mechanical ventilation fan's inlet terminals/grilles, outlet terminals/grilles, or in the connected ventilation ducts. Ventilation airflow of systems with multiple operating modes shall be tested in all modes designed to be in accordance with this section. [ASHRAE 62.2:4.3]
A readily accessible manual ON-OFF control, including but not limited to a fan switch or a dedicated branch-circuit overcurrent device, shall be provided. Controls shall include text or an icon indicating the system's function.
Exception: For multifamily dwelling units, the manual ON-OFF control shall not be required to be readily accessible. [ASHRAE 62.2:4.4]
Dwelling-unit mechanical ventilation systems designed to provide variable ventilation shall comply with Section E605.1.7.1 or Section E605.1.7.2 or Section E605.1.7.3. Section E605.1.7.2 and Section E605.1.7.3 also require compliance with ASHRAE 62.2 and require verification with supporting documentation from the manufacturer, designer, or specifier of the ventilation control system that the system meets the requirements of these sections. Where the dwelling-unit ventilation rate varies based on occupancy, occupancy shall be determined by occupancy sensors or by an occupant-programmable schedule. [ASHRAE 62.2:4.5]
To comply with this section, a variable ventilation system shall be installed to provide an average dwelling-unit ventilation rate over any three-hour period that is greater than or equal to Qfan as determined in accordance with Section E605.1.3.3. [ASHRAE 62.2:4.5.1]
This section shall only be allowed to be used where one or more fixed patterns of designed ventilation are known at the time compliance to Section E605.0 is being determined. Such patterns include those both clock-driven and driven by typical meteorological data. Compliance with this section shall be in accordance with either Section E605.1.7.2.1 or Section E605.1.7.2.2. [ASHRAE 62.2:4.5.2]
An annual schedule of ventilation complies with this section when the annual average relative exposure during occupied periods is not more than unity as calculated in accordance with ASHRAE 62.2. [ASHRAE 62.2:126.96.36.199]
The schedule of ventilation complies with this section when it is broken into blocks of time and each block individually has an average relative exposure during occupied periods that is not more than unity as calculated in ASHRAE 62.2. [ASHRAE 62.2:188.8.131.52]
A real-time ventilation controller complies with this section when it is designed to adjust the ventilation system based on real-time input to the ventilation calculations so that the average relative exposure during occupied periods is not more than unity as calculated in ASHRAE 62.2. The averaging period shall be not less than one day but not more than one year and shall be based on simple, recursive or running average, but not extrapolation. [ASHRAE 62.2:4.5.3]
A dwelling-unit ventilation system shall be designed and operated in such a way as to provide the same or lower annual exposure as would be provided in accordance with Section E605.1.3. The calculations shall be based on a single zone with a constant contaminant emission rate. The manufacturer, specifier, or designer of the equivalent ventilation system shall certify that the system is in accordance with this intent and provide supporting documentation. [ASHRAE 62.2:4.6]
Except where a whole house energy recovery system is used, a mechanical exhaust fan vented to the outdoors shall be provided in each room containing a bathtub, shower, or tub/shower combination. The ventilation rate shall be not less than 50 ft3/min (0.02 m3/s) for intermittent operation and 20 ft3/min (0.009 m3/s) for continuous operation. Fans shall comply with the Energy Star Program.
Heating and air conditioning filters shall have a MERV rating of 6 or higher. The air distribution system shall be designed for the pressure drop across the filter.