Nolan Kienitz
01-01-2009, 09:15 AM
To begin with I know the IRC does not allow taking return air from a 'garage':
M1602.2 Prohibited sources.
Outside or 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) from 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 there is the presence of flammable vapors; 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 such 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 such 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 such room or space.
4. A closet, bathroom, toilet room, kitchen, garage, mechanical room, furnace room or other dwelling unit.
5. A room or space containing a fuel-burning appliance where such room or space serves as the sole source of return air.
On a recent inspection (new home construction) a fellow inspector noted a return jumper from a garage to the main return on the HVAC system plenum. Not hard to make note of ...
However, the home has the spray foam (possibly Icenyne) throughout and he (and myself) are wondering if changing the building envelope with the foam insulation has also opened up some possibilities for changes in HVAC design/installation?
I've been doing searches, but can't come up with anything that gives me direct link. I'll be making some calls to some HVAC contacts I have to help learn more, but thought I'd toss this out for observation here.
M1602.2 Prohibited sources.
Outside or 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) from 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 there is the presence of flammable vapors; 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 such 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 such 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 such room or space.
4. A closet, bathroom, toilet room, kitchen, garage, mechanical room, furnace room or other dwelling unit.
5. A room or space containing a fuel-burning appliance where such room or space serves as the sole source of return air.
On a recent inspection (new home construction) a fellow inspector noted a return jumper from a garage to the main return on the HVAC system plenum. Not hard to make note of ...
However, the home has the spray foam (possibly Icenyne) throughout and he (and myself) are wondering if changing the building envelope with the foam insulation has also opened up some possibilities for changes in HVAC design/installation?
I've been doing searches, but can't come up with anything that gives me direct link. I'll be making some calls to some HVAC contacts I have to help learn more, but thought I'd toss this out for observation here.