According to the 10-3-2 rule, do all class-B chimney vent pipes need to protrude at least 36” at the point the chimney vent pipe exits the roof and why?
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Larry
and the Awards Committee
I don’t go to links to find answers. The answers must be placed in the post by the potential winner.
Thank you for your assistance. 
The prize is a box of “NOW” books…
If the roof pitch is above 10/12, it shall extend at least 2’ higher than any portion of the building within 10’ and also will be not less than 3’ above the highest point that it passes through the roof.
Sorry, David…
Maybe read the question again?
It is Mother’s Day, so if I have to leave, I’ll check the 1st correct answer when I return.
To all: Please do not edit your posts as the Awards Committee can see that time stamp in the edited post…it just makes our sorting it out more cumbersome.
Type B vent minimum 2 feet above vertical walls within 8 feet.
Without knowing roof pitch or vent diameter, it’s hard to figure out which rules apply.
It can be 1 foot on a 6/12.
Lo siento, pero no. (I’m sorry, but no.)
Where are you guys getting the “within 8 feet of wall”?
I believe it really is a simple question. :-k
Chimney Vent caps larger than 12" must be located at least 2 feet above the highest point and 2 feet higher than any portion of the building within a horizontal distance of 10 feet.
This is to prevent downdraft.Particularly with gas fired appliances, the lack of adequate draft for any reason, including a chimney flue that is too short, can result in improper combustion and the production of dangerous, potentially fatal carbon monoxide gases. And the same inadequate draft that affects combustion in the heater can increase the risk that the gas backdrafts out into the buildings.
I thought this question would be one of the questions answered the quickest. :shock:
Does this help?
A Type B or Type L gas vent must terminate at least 5 feet in vertical height above the highest connected appliance’s draft hood or flue collar. A Type B-W gas vent must terminate at least 12 feet in vertical height above the bottom of the wall furnace.
Gas vents shall extend through the roof flashing, roof jack, or thimble, and terminate with a listed cap or assembly.
Type B vents are vents suitable only for listed, draft hood-equipped, gas-fired appliances, including most domestic heating and hot water systems.
They may not be used with any of the following appliances:
Type B vents must be equipped with their own special chimney caps. If the cap is damaged or lost, it should not be substituted with something not recommended by the manufacturer. The clearance required from combustible materials is printed on the flue’s exterior metal surface, and is generally 1 or 2 inches.
Chimneys should extend at least 2 feet higher than any portion of a building within 10 feet, but shall not be less than 3 feet above the highest point where the chimney passes through the roof. This, again, is known as the Chimney 3-2-10 Rule.
This is straight from the Course.
I had to look it up!
Yes… Downdraft potential.
Yes to prevent downdraft .
The question has not been answered correctly yet and I’ll admit the question is a little tricky but simple…IMO
It could. Does a wood burning appliance correctly use a B-vent? :shock:
No, Class B can protrude less if the roof is flat.:mrgreen:
Close….
And, don’t forget “why”?
No, it can be less than of roof is flat because vent can be connected to draft hood and flat roofs can produce own draft.
No, because class b can vent horizontally.
Type B pipe is never suitable to be used with wood-burning or coal-burning appliances. It should also never be used as free-standing exhaust pipe for high-temperature venting.
If the roof pitch is below 10/12, it doesn’t need to extend 36"
Having it above the highest point of the roof will help to prevent downdraft problems.