4
74D0009
VENT INSTALLATION
3. Cut a hole in the roof using the locating hole as a center point. (Cover any exposed open vent pipes before
cutting hole in roof). The 9
1
/
" x 9
1/
" (241 mm x 241 mm) hole must be measured on the horizontal. Actual
length may be larger depending on the pitch of the roof. There must be a 1" minimum clearance from the vent
pipe to combustible materials. (Insulation should be considered a combustible material).
4. Connect a section of pipe and extend up through the hole.
NOTE: If an offset is needed to avoid obstructions, you must support the vent pipe every three (3) feet.
Use wall straps for this purpose. Refer to Figure 23, page 22. Whenever possible, use 45° elbows instead
of 90° elbows. The 45° elbow offers less restriction to the flow of the flue gases and intake air.
5. Place the flashing over the pipe section(s) extending through the roof. Secure the base of the flashing to the
roof and framing with roofing nails. Be sure roofing material overlaps the top edge of the flashing. There must
be a 1" clearance from the vent pipe to combustible materials.
6. Continue to add pipe sections until the height of the vent cap meets the minimum building code require-
ments.
NOTE: You must increase vent height for steep roof pitches. Nearby trees, adjoining roof lines, steep
pitched roofs, and other similar factors may cause poor draft or down-drafting in high winds. Increasing
the vent height may solve this problem.
NOTE: If the vent pipe passes through any occupied areas above the first floor, including storage spaces
and closets, you must enclose pipe. You may frame and sheetrock the enclosure with standard construction
material. Make sure to meet the minimum allowable clearances to combustibles. Do not fill any of the
required clearance spaces with insulation.
ROOF PITCH
H (feet)
Flat to 6/1
1.0
Over 6/1 to 7/1
1.5
Over 7/1 to 8/1
1.5
Over 8/1 to 9/1
.0
Over 9/1 to 10/1
.5
Over 10/1 to 11/1
3.5
Over 11/1 to 1/1
4.0
*H = Minimum height from roof to lowest
discharge oopening of vent.
Figure 28 - Minimum Chimney Clearance
Summary of Contents for Direct Vent BLDV400
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