FMI VENT FREE UNIVERSAL MASONRY FIREBOX MM39/44/49VF - Manual (Page 11)

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Interior Wall Materials:
Wall materials, such as drywall, should be set flush with
the rough front face of the Vent-Free fireplace. This will allow
for placement of required non-combustible surround material in
such a way that the surround material can lay flat against the
finished wall surface and also align with the leading edge of the
fire brick interior of the Vent-Free fireplace (see Figure 15).
Trim Facings:
Parts of the combustible mantle assembly located along
the sides of the firebox opening, which project more than one
and one-half inches (1-1/2”) from the face of the fireplace, shall
be kept at least eight inches (8”) from the firebox opening.
Adjoining Room Walls:
Interior wall surfaces of adjoining room walls must be at a
minimum horizontal measure of twenty four inches (24”) away
from the finished opening of the Vent-Free fireplace.
D1
W
1-1/2”
8” MIN. NON-COMBUSTIBLE MATERIAL
FRAMING
Figure 14
Model W D1
MM39VF 43” 73-1/2”
MM44VF 48” 77”
MM49VF 53” 80-1/2”
1-1/2”
8” MIN
20”
MIN
8” MIN. NON-COMBUSTIBLE MATERIAL
FRAMING
Figure 15
Air for Combustion and Ventilation
Energy efficient homes require homes to be airtight but at the
same time provide sufficient fresh air to breathe. Fresh air
enters the home through air conditioning duct vents, around
doors and windows but also must provide enough fresh air for
proper combustion on all fuel-burning appliances in the home.
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.
Non-combustible
Flex Hose
Figure 16
Exterior
Providing Adequate Ventilation
In accordance with the National Fuel Gas Code NFPA 54/ANSI
Z223.1, Section 5.3, 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 following information 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 homes 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 outside atmosphere have
a continuous water vapor retarder with a rating of one perm*
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
other openings.
* A perm is a unit of permeance or water vapor transmission,
the US perm-inch is defined as the passage of 1 grain of vapor
through 1 square foot of 1 inch thick material in 1 hour under a
pressure difference of 1 inch of mercury.
If your home meets all the three criteria above, you must provide
additional fresh air.