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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 6 through 8 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 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 out-
side atmosphere have a continuous
water vapor retarder with a rating of one
perm (6 x 10
-11
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 these three criteria,
you must provide additional fresh air. See
Ventilation Air From Outdoors, page 8.
If your home does not meet all of the three
criteria above, proceed to Determining
Fresh-Air Flow For Fireplace Location.
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/hr (4.8 m
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/hr (4.8 m
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 doorless passageways or ventilation
grills between them.
123502-01E
kg per pa-sec-m
) or less
2
per kw) of the aggregate
3
per kw) of the aggregate
3
www.fmiproducts.com
Continued
DETERMINING FRESH-AIR FLOW
FOR FIREPLACE 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
fireplace 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 16 ft. (length) x 14 ft.
(width) x 8 ft. (ceiling height) = 1792 cu. ft.
(volume of space)
If additional ventilation to adjoining room
is supplied 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 = (Maxi-
mum Btu/Hr the space can support)
Example: 1792 cu. ft. (volume of space) x
20 = 35,840 (maximum Btu/Hr the space
can support)
3. Add the Btu/Hr of all fuel burning appliances
in the space.
Vent-free fireplace
Gas water heater*
Gas furnace
Vented gas heater
Gas fireplace logs
Other gas appliances* + ________ Btu/Hr
Total
* Do not include direct-vent gas appliances.
Direct-vent draws combustion air from the
outdoors and vents to the outdoors.
Example:
Gas water heater
Vent-free fireplace
Total
4. Compare the maximum Btu/Hr the space can
support with the actual amount of Btu/Hr used.
________Btu/Hr (maximum space can support)
______ Btu/Hr (actual amount used)
Example: 35,840 Btu/Hr (maximum the
__________ Btu/Hr
__________ Btu/Hr
__________ Btu/Hr
__________ Btu/Hr
__________ Btu/Hr
= _________ Btu/Hr
30,000
________ Btu/Hr
+ 10,000
________ Btu/Hr
= 40,000
________ Btu/Hr
space can support)
40,000 Btu/Hr (actual amount of
Btu/Hr used)
7
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