Astria.us.com
900720-00E
6
Unusually tight construction is defi ned as con-
struction 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,
between sole plates and floors, between
wall-ceiling joints, between wall panels, at
penetrations for plumbing, electrical, and gas
lines, and at other openings.
If your home meets all three criteria above, you
must provide additional fresh air. See
Ventilation
Air From Outdoors
,
Page 8
.
If your home does not meet all three criteria
above, proceed to
Determining Fresh-Air Flow For
Heater 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 con-
fi 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 considered 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.
DETERMINING FRESH-AIR FLOW FOR
FIREPLACE LOCATION
Determining if You Have a Confi ned or
Unconfi ned Space Using the Standard Method
AIR FOR COMBUSTION AND VENTILATION
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, 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 appliances 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 fol-
lowing ventilation classifi cations:
1. Unusually Tight Construction
2. Unconfi ned Space
3. Confi ned Space
The information on
Pages 6–8
will help you clas-
sify 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 unusually tight
construction, you must provide additional fresh air.
WARNING: This heater shall not
be installed in a room or space un-
less 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 instructions to ensure
proper fresh air for this and other fuel-
burning appliances in your home.
