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9 
9 Chase Installations 
Firestop
Spacer
Metal Chase Top
Round Termination Cap
False Ceiling
Insulation in the
outside walls
of the chase
Attic 
Insulation
Shield
Chimney
Firestop 
Spacer
Tabs
False Ceiling
False Ceiling
Insulation
Insulation
Figure 9.1  Chase Assembly
123
1.  Fireplace and chimney enclosed in an exterior chase.
2.  Chimney offset through exterior wall and enclosed in chase.
3.  Chase constructed on roof.
Note:In cooler climates, all chase walls should be insulated.
Figure 9.2  Chase Constructions
WARNING! You must install false ceilings and ceiling 
fi restops at each fl oor of the chase or every 10 ft (3.05 m) 
to control spread of fi re.
WARNING! Risk of Fire! You must maintain a minimum 
2 in. (51 mm) air space clearance to insulation and other 
materials surrounding the chimney system.
•  Insulation and other materials must be fi rmly secured to 
prevent accidental contact with chimney system.
•  The chase must be properly blocked to prevent blown 
insulation or other combustibles from entering and 
making contact with fi replace or chimney.
•  Failure to prevent contact between insulation or other 
materials and chimney system may cause overheating 
and fi re.
WARNING! Risk of Fire! DO NOT seal area between fi re 
stop opening and chimney pipe. Restricting air fl ow around 
chimney may cause fi re.
A. Construct the Chase
A chase is a vertical boxlike structure built to enclose the 
fi replace and/or its vent system. Vertical chimneys that 
run on the outside of a building must be installed inside a 
chase.
Construction of the chase may vary with the type of build-
ing. These instructions are not substitutes for the require-
ments of local building codes. Local building codes MUST 
be checked.
A chase should be constructed in the manner of all 
outside walls of the home to prevent cold air drafting 
problems. The chase should not break the outside build-
ing envelope in any manner. All outer walls need to be 
insulated.
Building codes require false ceiling and ceiling fi restops 
at each fl oor of the chase or every 10 ft (3.05 m) of clear 
space to control spread of fi re.
Walls, ceiling, base plate and cantilever fl oor at the fi rst 
level of the chase should be insulated. See Figure 9.1. 
Vapor and air infi ltration barriers should be installed in the 
chase as per regional codes for the rest of the home. Ad-
ditionally, Hearth & Home Technologies recommends that 
the inside surfaces be sheet rocked and taped (or the use 
of an equivalent method) for maximum air tightness.
Gas line holes and other openings should be caulked with 
high temperature caulk or stuffed with unfaced fi berglass 
insulation. If the fi replace is being installed on a cement 
slab, we recommend that in cold climates, a sheet of 
plywood or other raised platform be placed underneath to 
prevent conducting cold up into the room.
Three examples of chase applications are shown in Fig-
ure 9.2.
Heatilator • A36C & A42C • 28396 • Rev AG  • 11/08