UL-441:2016 pdf free download – STANDARD FOR SAFETY Gas Vents.
13 Roof Assemblies
13.1 The height of a roof assembly shall be such that the flue-gas exit is not less than 2 feet (0.61 m) above the roof.
13.2 A roof assembly installed in accordance with the installation instructions shall resist the entrance of excess water and debris into the building at the point where the gas vent passes through the roof. See Rain Test, Section 27.
13.3 A gas-vent roof assembly shall resist the accumulation of soot and debris when such accumulation obstructs flue-gas or cooling-air passages.
14 Roof Jacks
14.1 A roof jack constructed for placement in contact with combustible roof, rafter, insulation, or ceiling material shall provide a continuous surface or barrier for a vertical distance, measured from the roof line, of at least 6 inches (150 mm).
14.2 When installed in accordance with the manufacturer’s instructions, a roof jack shall protect against the entrance of excess water and debris into the building where the gas vent passes through the roof. See Rain Test, Section 27.
14.3 A roof jack shall be constructed so that soot or debris shall not accumulate therein when such accumulation obstructs flue-gas or cooling-air passages.
15 Fittings
15.1 The nominal cross-sectional area of the flue-gas passage of a gas-vent pipe fitting shall be equivalent to that of the vent piping with which it is intended to be used.
16 Sizes
16.1 A gas-vent pipe or fitting or a roof jack shall have an internal cross-sectional area of not less than 7-1/16 square inches (45.6 cm2).
16.2 The internal cross-sectional area of a gas vent pipe or fitting shall be equivalent to a round pipe
having an internal diameter of integral inches or in units of 25 mm.
16.3 The internal dimension of the cross section of an oval or rectangular gas-vent pipe or fitting, or of a roof jack, measured across the minor axis, shall be not less than 1-1/2 inches (38 mm).
17 Support Assembly
17.1 A support assembly (such as a ceiling or floor support) shall establish and maintain the minimum required clearance between a gas-vent pipe and combustible construction. A support for installation in a joist area shall constitute a complete firestop when tested in accordance with these requirements.
17.2 A support assembly shall sustain a load equivalent to four times the weight imposed upon it by all the gas-vent parts it is intended to support. See Vertical Support Test, Section 24.
17.3 A support assembly intended to be secured by nails or screws shall be arranged so that the load on such holding means is a shear load.
PERFORMANCE
18 General
18.1 When a gas vent or roof jack is tested in accordance with these requirements, specified temperatures on combustible construction shall be maintained.
18.2 After being subjected to the tests specified in Sections 21, Temperature Test — Structures and 22, Temperature Test — Gas Vent Pipe Surfaces, as applicable, a gas vent or roof jack shall be capable of being further used.
18.3 Test results indicating compliance with the requirement of 18.2 include the following:
a) No part of the gas vent or roof jack has become damaged or permanently distorted to an extent that it shall not continue to function as intended.
b) The effectiveness of any required protective coating or finish on metal parts has not been reduced.
c) A ceramic material shows no evidence of cracking, disintegration, or spalling to the extent that serviceability of any part of an assembly has been impaired.