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103425
UNVENTED (VENT-FREE) GAS LOG HEATER
AIR FOR
COMBUSTION AND
VENTILATION
Today’s homes are built more energy efficient
than ever. New materials, increased insula-
tion, and new construction methods help re-
duce 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.
During 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
appliances need fresh air for proper com-
bustion and ventilation.
Exhaust fans, fireplaces, clothes dryers, and
fuel burning appliances draw air from the
house to operate. You must provide ad-
equate fresh air for these appliances. This
will insure proper venting of vented fuel-
burning appliances.
PROVIDING ADEQUATE
VENTILATION
The following are excerpts from National
Fuel Gas Code. NFPA 54/ANS Z223.1, Sec-
tion 5.3, 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 4 through 6 will
help you classify your space and provide
adequate ventilation.
Unusually Tight Construction
The air that leaks around doors and win-
dows may provide enough fresh air for com-
bustion and ventilation. However, in build-
ings of unusually tight construction, you
must provide additional fresh air.
Unusually tight construction is de-
fined 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, be-
tween 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 ad-
ditional fresh air. See
Ventilation Air
From Outdoors
, page 6.
If your home does not meet all of the
three criteria above, proceed to
De-
termining Fresh-Air Flow for Heater
Location,
page 5.
Confined and Unconfined Space
The National Fuel Gas Code (ANS Z223.1,
1992 Section 5.3) 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
unconfining 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 in-
stalled*, through openings not furnished
with doors, are considered a part of the
unconfined space.
This heater shall not be installed in a con-
fined space or unusually tight construction
unless provisions are provided for adequate
combustion and ventilation air.
* Adjoining rooms are communicating only
if there are doorless passageways or ventila-
tion grills between them.
WARNING: This heater shall
not be installed in a confined space
or unusually tight construction
unless provisions are provided
for adequate combustion and ven-
tilation air. Read the following in-
structions to insure proper fresh
air for this and other fuel-burning
appliances in your home.