AIR FOR COMBUSTION
AND VENTILATION
Today’s homes are built more energy effi cient
t h a n e v e r. N e w m a t e r i a l s , i n c r e a s e d
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. During heating months, home owners
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, fi replaces, clothes dryers and
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.
The following are excerpts from National Fuel
Gas Code, ANSI Z223.1/NFPA 54, Section
5.3, 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 5 through 7 will
help you classify your space and provide
adequate ventilation.
PROVIDING 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 defi ned 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 ) 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, electri-
cal and gas lines and at other openings.
If your home meets all of these three criteria,
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.
Confi ned and Unconfi ned Space
The National Fuel Gas Code, ANSI Z223.1/
NFPA 54 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 ag-
gregate 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 m3 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-
confi ned space.
* Adjoining rooms are communicating only if
there are doorless passageways or ventilation
grills between them.
5
WARNING: This heater shall
not be installed in a confined space
or unusually tight construction
unless provisions are provided for
adequate combustion and ventila-
tion air. Read the following instru-
ctions to ensure proper fresh air
for this and other fuel-burning
appliances in your home.
