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121880-01B
5
aIR FoR CoMBUsTIoN aNd 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
(6x10
-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 7.
If your home does not meet all of the three
criteria above, proceed to
Determining Fresh-
Air Flow For Heater Location
, page 6.
Confined and Unconfined Space
The
National Fuel Gas Code, ANSI Z223.1/
NFPA 54
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 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 un
-
confined space.
* Adjoining rooms are communicating only if
there are doorless passageways or ventilation
grills between them.
WARNING: This heater shall
not be installed in a confined
space or unusually tight con-
struction unless provisions are
provided for adequate combus-
tion and ventilation air. Read the
following instructions to insure
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. Home owners weather
strip and caulk around windows and doors to
keep the cold air out and the warm air in. Dur
-
ing heating months, home owners 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, fireplaces, clothes dryers and
fuel burning appliances draw air from the
house to operate. You must provide adequate
fresh air for these appliances. This will insure
proper venting of vented fuel-burning appli
-
ances.
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 5 through 7 will help
you classify your space and provide adequate
ventilation.
