B Vent Height Above Roof

1 0 foot above the roof surface 1 7 12 to 8 12.

B vent height above roof. 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. 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. This reduces the actual required height by 12 inches from our previous calculation of 64 inches. So 28 inches plus 24 inches is a chimney height of only 52 inches.

The clearance required from combustible materials is printed on the flue s exterior metal surface and is generally 1 or 2 inches. 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. Vent pipes should extend to outdoors above the building roof and should terminate vertically not less than 6 above the roof surface nor more than 24 and must be at least 12 from any vertical surface such as a nearby sidewall. Above the roof plumbing vent height.

Table of rooftop chimney clearances for metal b vent chimneys flues. Roof pitch rise run in inches. 7 14 4 a chimney shall extend not less than 3 ft 900 mm above the highest point where it passes through the roof of a building and not less than 2 ft 600 mm higher than any portion of a building within a horizontal distance of 10 ft 3 m. Photo at above left.

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. If the cap is damaged or lost it should not be substituted with something not recommended by the manufacturer. Please note that this rule doesn t generally apply to pellet and gas vent systems. 2 0 feet above the roof surface.

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. Type b vents must be equipped with their own special chimney caps. Minimum height above the roof surface 1 flat to 7 12. Metal bracket on a b type vent metal chimney.

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. Upc i 906 1 and 906 2.