DuraVent DuraTech - Frame Openings; Cut Roof Opening; Install Firestop Radiation Shield

9
properly). Level the Support Box and secure
it to the framing using at least three 8-penny
nails per side (min. of 12 total). Wrap the
straps of the Support Box around the framing
members (Fig 4), and secure with (2) 8-penny
nails per side. (eight nails total) Alternatively,
you may use 1-1/2” #8 wood screws (min. of
12 total for the Support Box, and 8 total for
the straps), instead of nails. Next, secure
the round or square Trim Collar to the ceiling/
framing members using (4) 1” long, round-
head wood screws.
4. Frame Openings: Frame openings in
each ceiling or oor above the Support Box
(Fig 6). These openings are to hold the
Firestop Radiation Shield and Attic Insulation
Shield. Locate each opening by dropping a
plumb bob to the four corners of the opening
below. Maintain the minimum clearances and
dimensions as specied in Table 2. If Elbows
must be used to avoid an obstruction, refer to
the Offset Elbow Installation section.
5. Cut Roof Opening: Cut an opening in the
roof directly above the opening below, and
at least 4 inches larger than the chimney’s
outside diameter to provide at least a
2-inch clearance all around the chimney.
The chimney must be centered within this
opening and maintain the 2-inch clearance to
combustibles.
Figure 7
Table 2
Inside Square Framing Dimensions
(X" x X")
Chimney Diameter 10" 12" 14" 16" 18" 20" 22" 24"
CHIMNEY INSIDE DIAMETER
16 1/4" 18 1/4" 20 1/4" 22-1/4" na na na na
WALL THIMBLE
16" 18" 20" 22" na na na na
FIRESTOP RADIATION SHIELD
16" 18" 20" 22" 24 1/4" 26 1/4" 28 1/4" 30 1/4"
ATTIC INSULATION SHIELD
16 1/4" 18 1/4" 20 1/4" 22 1/4" 24 1/4" 26 1/4" 28 1/4" 30 1/4"
6. Install Firestop Radiation Shield: A Firestop
Radiation Shield is required in multistory
installations at each oor penetration above
that where the Support Box is located.
Example: in a multistory home where the
appliance is on the ground oor (Support
Box is in the 1st oor ceiling), you would
need a Firestop Radiation Shield at the 2nd
oor ceiling, and at the 3rd oor ceiling, etc.,
including where the chimney penetrates into
the attic. Figure 6 shows a typical 2-story
installation with an attic.
FRAMING
FIRESTOP
RADIATION
SHIELD