NOTE: DIAGRAMS & ILLUSTRATION ARE NOT TO SCALE.
4
WARNING
If the area in which the heater may be
operated does not meet the required
volume for indoor combustion air,
combustion and ventilation air shall
be provided by one of the methods
described in the National Fuel gas
Code, ANSI Z223.1/NFPA 54, the Inter-
national Fuel gas Code, or applicable
local codes.
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 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 un-
usually tight construction, you must provide
additional fresh air.
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
WARNING
Heaters installed in these appli-
ances 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 instruc-
tions to ensure proper fresh air for
this and other fuel-burning appli-
ances in your home.
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, in the In-
stallation and Operation manual for the heater.
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 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 com-
municating 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
Use this work sheet to determine if you have
a confined or unconfined space.
Space: Includes the room in which you will
install heater plus any adjoining rooms with
doorless passageways or ventilation grills
between the rooms.
1. Determine the volume of the space (length
x width x height).
Length x Width x Height =__________cu.
ft. (volume of space)
Example: Space size 22 ft. (length) x 18
ft. (width) x 8 ft. (ceiling height) = 3,168
cu. ft. (volume of space)
If additional ventilation to adjoining room
is supplied with grills or openings, add the
volume of these rooms to the total volume
of the space.
2. Multiply the space volume by 20 to determine
the maximum BTU/Hr the space can support.
________ (volume of space) x 20 = (Maxi-
mum BTU/Hr the space can support)
Example: 3,168 cu. ft. (volume of space) x
20 = 63,360 (maximum BTU/Hr space can
support)
3. Add the BTU/Hr of all fuel burning appli-
ances in the space.
Vent-free fireplace ________ BTU/Hr
Gas water heater* ________ BTU/Hr
Gas furnace
________ BTU/Hr
Vented gas heater ________ BTU/Hr
Gas fireplace logs ________ BTU/Hr
Other gas appliances* + _______ BTU/Hr
Total
= ________ BTU/Hr
* Do not include direct-vent gas appli-
ances. Direct-vent draws combustion
air from the outdoors and vents to the
outdoors.
Example:
Gas water heater 40,000 BTU/Hr
Vent-free fireplace + 39,000 BTU/Hr
Total
=
79,000 BTU/Hr
4. Compare the maximum BTU/Hr the space
can support with the actual amount of BTU/
Hr used.
_______ BTU/Hr (maximum the space can
support)
_______ BTU/Hr (actual amount of BTU/Hr
used)
Example: 63,360 BTU/Hr (maximum the
space can support)
79,000 BTU/Hr (actual amount
of BTU/Hr used)
The space in the example is a confined space
because the actual BTU/Hr used is more than
the maximum BTU/Hr the space can support.
You must provide additional fresh air. Your
options are as follows:
A. Rework worksheet, adding the space of an
adjoining room. If the extra space provides
an unconfined space, remove door to
adjoining room or add ventilation grills
between rooms. See Ventilation Air From
Inside Building, in the Installation and
Operation manual for the heater.
B. Vent room directly to the outdoors. See
Ventilation Air From Outdoors, in the Instal-
lation and Operation manual for the heater.
C. Install a lower BTU/Hr appliance, if lower
BTU/Hr size makes room unconfined.
If the actual BTU/Hr used is less than the
maximum BTU/Hr the space can support, the
space is an unconfined space. You will need no
additional fresh air ventilation.
COMBUSTION AND VENTILATION AIR
