B Vent Height Above Roof

Notice that metallic salts washing off of the metal bracing and other runout of the chimney flashing itself are preventing black algae from growing on some areas of this roof.

B vent height above roof.

Metal bracket on a b type vent metal chimney. Table of rooftop chimney clearances for metal b vent chimneys flues. The 1992 vent sizing tables require that all type b gas vents terminate above the roof with a listed cap or listed roof assembly in accordance with the manufacturer s instructions. Type b vents must be equipped with their own special chimney caps.

1 0 foot above the roof surface 1 7 12 to 8 12. Minimum height above the roof surface 1 flat to 7 12. Please note that this rule doesn t generally apply to pellet and gas vent systems. In the case of type b or type l vents each length extending above the roof line must be certified for exterior use and so identified.

Photo at above left. Although a large portion of the flue gas is composed of water vapor amerivent type b gas vent carries it out of the structure before it can condense. So 28 inches plus 24 inches is a chimney height of only 52 inches. 2 5 feet above the roof surface.

1 5 feet above the roof surface. Roof pitch rise run in inches. Above the roof plumbing vent height. This reduces the actual required height by 12 inches from our previous calculation of 64 inches.

If the cap is damaged or lost it should not be substituted with something not recommended by the manufacturer. Per the 10 and 2 rule once you are at the level of the peak you only need to be 2 feet above it. 2 0 feet above the roof surface. However b vent chimney caps 12 and smaller may terminate a distance above the roof if 8 feet or more away from a vertical surface as given in this table.

One of the fire safety features of double wall type b gas vent is that its outer wall insulated by the airspace beneath it requires only 1 clearance to combustible material in the structure. Upc i 906 1 and 906 2.