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126712-01C
8
AIR FOR COMBUSTION AND VENTILATION
Unusually tight construction is defi ned as
construction where:
a. walls and ceilings exposed to the out-
side 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 fl oors, between 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 10.
If your home does not meet all of the three
criteria above, proceed to Determining
Fresh-Air Flow For Firebox Location.
Confi ned and Unconfi ned 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 confi ned or unconfi ned space. The
standard method
defi nes a confi ned 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 unconfi ned
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 consid-
ered a part of the unconfi ned space.
Where the air infi ltration rate of a structure is
known, the Known Air Infi ltration 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 confi ned
or unconfi ned.
* Adjoining rooms are communicating only if
there are doorless passageways or ventilation
grills between them.
Today’s homes are built more energy effi cient
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
effi cient, 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 fi replaces, 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
Combustion and Ventilation
.
All spaces in homes fall into one of the three
following ventilation classifi cations:
1. Unusually
Tight
Construction
2. Unconfi ned Space
3. Confi ned Space
The information on
Pages 8 through 10
will
help you classify your space and provide ad-
equate 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 un-
usually tight construction, you must provide
additional fresh air.
WARNING: This heater shall
not be installed in a room or space
unless the required volume of in-
door 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.
