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6
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 appliances.
PROVIDING ADEQUATE
VENTILATION
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 fol-
lowing 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.
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.
Unusually tight construction is defined
as construction where:
a. Walls and ceilings exposed to the out
-
side 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 of the three
criteria above, you must provide ad
-
ditional 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 Appliance Location
.
Confined and Unconfined Space
The
National Fuel Gas Code, ANSI Z223.1/NFPA
54
defines a confined space as a space whose vol-
ume 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 communicating directly with
the space in which the appliances are installed*,
through openings not furnished with doors, are
considered a part of the unconfined space.
* Adjoining rooms are communicating only if
there are odorless passageways or ventilation grills
between them.
DETERMINING FRESH-AIR FLOW
FOR APPLIANCE LOCATION
Determining if You Have a Confined or
Unconfined Space
Use this work sheet to determine if you have a
confined or unconfined space.
Space:
Includes the room in which you will install
appliance plus any adjoining rooms with door-
less 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 20 ft. (length) x 16 ft.
(width) x 8 ft. (ceiling height) = 2560 cu. ft.
(volume of space)
If additional ventilation to adjoining room is sup-
plied 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 =
(Maximum Btu/Hr the space can support)
Example:
2560 cu. ft. (volume of space) x
20 = 51,200 (maximum Btu/Hr the space can
support)
3. Add the Btu/Hr of all fuel burning appliances
in the space.
Vent-free appliance
_________Btu/Hr
Gas water appliance*
_________Btu/Hr
Gas furnace
_________Btu/Hr
Vented gas appliance
_________Btu/Hr
Gas fireplace logs
_________Btu/Hr
Other gas appliances* +_________Btu/Hr
Total
=_________Btu/Hr
AIR FOR COMbUSTION
AND VENTILATION
Continued
