# Can you help me find the proper code section?



## EricWatkins (Jun 16, 2016)

I'm sure I've read that ventilation air can not be drawn from an attic or crawlspace but I'll be darned if I can find it.  Can anyone help?  It pertains to a residence.


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## cda (Jun 16, 2016)

??

7.5. Stud wall cavities in the outside walls of building envelope assemblies shall not be utilized as air plenums.


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## cda (Jun 16, 2016)

# 4



*SECTION M1602 RETURN AIR 

M1602.1 Return air. *
Return air shall be taken from inside the _dwelling._ Dilution of return air with outdoor air shall be permitted. *

M1602.2 Prohibited sources. *
Outdoor and return air for a forced-air heating or cooling system shall not be taken from the following locations: 

1. Closer than 10 feet (3048 mm) to an _appliance _vent outlet, a vent opening from a plumbing drainage system or the discharge outlet of an exhaust fan, unless the outlet is 3 feet (914 mm) above the outside air inlet.
2. Where flammable vapors are present; or where located less than 10 feet (3048 mm) above the surface of any abutting public way or driveway; or where located at grade level by a sidewalk, street, alley or driveway.
3. A room or space, the volume of which is less than 25 percent of the entire volume served by the system. Where connected by a permanent opening having an area sized in accordance with ACCA Manual D, adjoining rooms or spaces shall be considered as a single room or space for the purpose of determining the volume of the rooms or spaces. *

Exception: *The minimum volume requirement shall not apply where the amount of return air taken from a room or space is less than or equal to the amount of supply air delivered to the room or space.
4. A closet, bathroom, toilet room, kitchen, garage, boiler room, furnace room, unconditioned attic or other _dwelling unit._ *

Exception: *Dedicated forced-air systems serving only a garage shall not be prohibited from obtaining return air from the garage.
5. A room or space containing a fuel-burning _appliance _where such room or space serves as the sole source of return air. *

Exceptions: *
1. The fuel-burning _appliance _is a direct-vent _appliance _or an _appliance _not requiring a vent in accordance with Section M1801.1 or Chapter 24.
2. The room or space complies with the following requirements:
2.1. The return air shall be taken from a room or space having a volume exceeding 1 cubic foot for each 10 Btu/h (9.6 L/W) of combined input rating of all fuel-burning_appliances _therein.
2.2. The volume of supply air discharged back into the same space shall be approximately equal to the volume of return air taken from the space.
2.3. Return-air inlets shall not be located within 10 feet (3048 mm) of a draft hood in the same room or space or the combustion chamber of any atmospheric-burner_appliance _in the same room or space.
3. Rooms or spaces containing solid-fuel burning _appliances,_ if return-air inlets are located not less than 10 feet (3048 mm) from the firebox of those _appliances._
6. An unconditioned crawl space by means of direct connection to the return side of a forced air system. Transfer openings in the crawl space enclosure shall not be prohibited. 
*M1602.3 Inlet opening protection. *
Outdoor air inlets shall be covered with screens having openings that are not less than 1/4 inch (6.4 mm) and not greater than 1/2 inch (12.7 mm).


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## mtlogcabin (Jun 16, 2016)

R303.5 Opening location.
Outdoor intake and exhaust openings shall be located in accordance with Sections R303.5.1 and R303.5.2.

R303.5.1 Intake openings.
Mechanical and gravity outdoor air intake openings shall be located a minimum of 10 feet (3048 mm) from any hazardous or noxious contaminant, such as vents, chimneys, plumbing vents, streets, alleys, parking lots and loading docks, except as otherwise specified in this code. Where a source of contaminant is located within 10 feet (3048 mm) of an intake opening, such opening shall be located a minimum of 3 feet (914 mm) below the contaminant source

The key is the opening must be outdoors not witnin the exterior envelope of the building such as an attic or crawlspace


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## ICE (Jun 16, 2016)

The rules for combustion air have a certain size opening if the air is taken entirely from outdoors.  That set of rules will call an attic that communicates with the exterior... outdoors.  So if the same were true with outdoor intake openings the code would tell us that an attic can qualify....that is not the case so attics and underfloor do not qualify as a source for outdoor air.

Both are contaminated.


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## mtlogcabin (Jun 17, 2016)

The intent is in the definitions


VENTILATION AIR. That portion of supply air that comes from the outside (outdoors), plus any recirculated air that has been treated to maintain the desired quality of air within a designated space.

OUTDOOR AIR. Air taken from the outdoors, and therefore not previously circulated through the system.

ENVIRONMENTAL AIR. Air that is conveyed to or from occupied areas through ducts which are not part of the heating or air-conditioning system, such as ventilation for human usage, domestic kitchen range exhaust, bathroom exhaust, domestic clothes dryer exhaust and parking garage exhaust.


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