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126700-01C
8
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,
between wall-ceiling joints, between
wall panels, at penetrations for plumb-
ing, 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 10
.
If your home does not meet all of the three
criteria above, proceed to
Determining Fresh-
Air Flow For Firebox Location
.
Confined and Unconfined Space
The National Fuel Gas Code, ANSI Z223.1/
NFPA54
allows two methods 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 ag
-
gregate 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 ag
-
gregate 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.
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.
DETERMINING FRESH-AIR FLOW FOR
HEATER LOCATION
Determining if You Have a Confined or
Unconfined Space Using the Standard
Method
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 heat
-
ing 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 ap-
pliances 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 adequate
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 Com-
bustion 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 8 through 10
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.
WARNING: This heater shall not
be installed in a room or space un-
less 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.
