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6
AIR FOR COMBUSTION AND VENTILATION
Unusually tight construction is defined as construction where:
a. walls and ceilings exposed to the outside atmosphere have a
continuous water vapor retarder with a rating of one perm (6 x
10
-11
kg per pa-sec-m
2
) or less with openings gasketed or sealed
and
b. weather stripping has been added on openable windows and
doors and
c. caulking or sealants are applied to areas such as joints around
window and door frames, between sole plates and floors, be-
tween wall-ceiling joints, between wall panels, at penetrations
for plumbing, electrical and gas lines and at other openings.
If your home meets all of the three criteria above, you must provide
additional fresh air. See Ventilation Air From Outdoors,
Page 7
.
If your home does not meet all of the three criteria above, proceed to
Determining Fresh-Air Flow For Heater Location,
Page 7
.
Confined and Unconfined Space
The
National Fuel Gas Code, ANSI Z223.1/ NFPA54
allows two meth-
ods for determining whether the space in which the heater is being
installed is confined or unconfined space. The standard method defines
a confined space as a space whose volume is less than 50 cubic feet
per 1,000 Btu per hour (4.8 m
3
per kw) of the aggregate input rating
of all appliances installed in that space and an unconfined space as a
space whose volume is not less than 50 cubic feet per 1,000 Btu per
hour (4.8 m
3
per kw) of the aggregate input rating of all appliances
installed in that space. Rooms communicating directly with the space
in which the appliances are installed*, through openings not furnished
with doors, are considered a part of the unconfined space.
This appliance shall not be installed in a confined space or unusually
tight construction unless provisions are provided for adequate com-
bustion and ventilation air.
Where the air infiltration rate of a structure is known, the Known Air
Infiltration Rate Method may be used. Follow The National Fuel Gas
Code, ANSI Z223.1/NFPA 54 to use this method to determine if the
space is confined or unconfined.
* Adjoining rooms are communicating only if there are doorless
passageways or ventilation grills between them.
WARNING: This heater shall not be installed in a
room or space unless the required volume of indoor
combustion air is provided by the method described
in the National Fuel Gas Code, ANSI Z223.1/NFPA 54,
the International Fuel Gas Code, or applicable local
codes. Read the following instructions to ensure proper
fresh air for this and other fuel-burning appliances
in your home.
Today’s homes are built more energy efficient than ever. New materials,
increased insulation and new construction methods help reduce heat
loss in homes. Homeowners apply weather strip and caulk around
windows and doors to keep the cold air out and the warm air in. During
heating months, homeowners want their homes as airtight as possible.
While it is good to make your home energy efficient, your home
needs to breathe. Fresh air must enter your home. All fuel-burning
appliances need fresh air for proper combustion and ventilation.
Exhaust fans, some fireplaces, clothes dryers and some fuel-burning
appliances draw air from the house to operate. You must provide ad-
equate fresh air for these appliances. This will ensure proper venting
of vented fuel-burning appliances.
PROVIDING ADEQUATE VENTILATION
The following are excerpts from National Fuel Gas Code, ANSI Z223.1/
NFPA 54, Air for Combustion and Ventilation.
All spaces in homes fall into one of the three following ventilation
classifications:
1. Unusually Tight Construction
2. Unconfined Space
3. Confined Space
The information on
Pages 6 through 7
will help you classify your
space and provide adequate ventilation.
Unusually Tight Construction
The air that leaks around doors and windows may provide enough
fresh air for combustion and ventilation. However, in buildings of
unusually tight construction, you must provide additional fresh air.
