Installation Guide

5
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 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 penetra-
tions for plumbing, electrical, and gas lines,
and at other openings.
If your home meets all
of the three criteria above,
you must provide additional fresh air. See Ventila-
tion Air From Outdoors, page 5.
If your home does not meet all of the three criteria
above, proceed to Determining Fresh-Air Flow for
Appliance Location, page 6.
VENTILATION AIR
Ventilation Air From Inside Building
This fresh air would come from an adjoining unconfined
space. When ventilating to an adjoining unconfined space,
you must provide two permanent openings: one within 12"
of the ceiling and one within 12" of the floor on the wall
connecting the two spaces (see Figure 1). You can also
remove door into adjoining room (see Figure 1). Follow
the National Fuel Gas Code ANSI Z223.1/NFPA 54, Sec-
tion 5.3, Air for Combustion and Ventilation for required
size of ventilation grills or ducts.
Ventilation Air From Outdoors
Provide extra fresh air by using ventilation grills or ducts.
You must provide two permanent openings: one within
12" of the ceiling and one within 12" of the floor. Connect
these items directly to the outdoors or spaces open to the
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Follow the National Fuel Gas Code ANSI Z223.1/NFP
A54, Section 5.3, Air for Combustion and Ventilation
for required size of ventilation grills or ducts.
IMPORTANT: Do not provide openings for inlet or outlet
air into attic if attic has a thermostat-controlled power vent.
Heated air entering the attic will activate the power vent.
Or
Remove
Door into
Adjoining
Room,
Option
3
Ventilation Grills
Into Adjoining Room,
Option 2
Ventilation
Grills
Into Adjoining
Room,
Option 1
12"
12"
Figure 1 - Ventilation Air from Inside Building
Outlet
Air
Ventilated
Attic
Outlet
Air
Inlet
Air
Inlet Air
Ventilated
Crawl Space
To
Crawl
Space
To Attic
Figure 2 - Ventilation Air from Outdoors