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Fig. 6: Suggested method to accommodate vent connector passage through a wall composed of a combustible material.
Fig. 7: Alternate constructions that allow reduced clearances to combustible materials.
REDUCTION OF CLEARANCES WITH SPECIFIED FORMS OF PROTECTION:
Type of protection applied to and covering all surfaces of combustible material within the distance
specified as the required clearance with no protection unless otherwise noted, all dimensions in inches,
refer to Fig. 7.
18 inches 9 inches 6 inches
Sides & Sides & Sides &
Required clearance with no protection from the appliance or
chimney connector is:
Above Rear Above Rear Rear
a. 3-1/2" thick masonry wall without ventilation air space…. -- 12 -- 6 -- 5
b. 1/2" insulation board over 1" glass fiber or mineral wool batts… 12 9 6 5 4 3
c. 0.024(24 gauge) sheet metal over 1" glass fiber or mineral
wool batts reinforced with wire on rear face with ventilated air
space… 9 6 5 3 3 3
d. 3- 1/2" thick masonry wall with ventilation air space.. -- 6 -- 6 -- 6
e. 0.024 (24 gauge) sheet metal with ventilated air space. 9 6 5 3 3 2
f. 1/2" thick insulation board with ventilation air space.. 9 6 5 3 3 3
g. 0.024 ( 24 gauge) sheet metal with ventilated air space over
0.024 (24 gauge) sheet metal with ventilated air space…. 9 6 5 3 3 3
h. 1" glass fiber or mineral wool batts sandwiched between two
sheets 0.024 (24 gauge) sheet metal with ventilated air space 9 6 5 3 3 3
A. Equal the required clearance with no protection.
B. Equals the reduced clearance permitted in accordance with the preceding clearance chart.
C. The protection applied to the construction that covers the combustible material should extend far enough
in each direction to make C equal to A.