Marc M wrote:Heres a question; help me to understand that if a vent is >2"H within 8' of a vert wall, then how come it then goes to a 10' radius rule? (Like the 3-2-10)
That's not exactly what it says: the Type B gas vent can be 8 feet from the window, but ... if that vent is 7 feet 15/16 inches from the window ... then that vent now needs to go 2 feet higher than the roof above that window.
The only thing the 10 feet does it possibly raise the vent higher, it does not mean the vent has to be 10 feet from the window. An example is below:
Let's say the vent is 7 feet 10 inches from the wall the window is in, and there is a chimney 9 feet 11 inches away in another direction, the vent can remain at that 7 feet 10 inches from the wall the window is in, but that vent needs to be at least 2 feet higher than any part of the structure within 10 feet - if the chimney is higher than the roof above the wall with the window in it, then the vent must be at least 2 feet higher than the chimney, not just at least 2 feet higher than the wall the window is in.
Still defies logic where the vent is allowed to be 1 foot high on a 5/12 sloped roof and 8 feet from the wall the window is in (creating a sense that the clearance required is an 8 foot radius, but it is not), then requiring that vent to be 2 feet higher than the roof above the wall that window is in - let's say that wall is only 4 feet higher than the roof the vent is in, that means the vent only needs to be 6 feet high from a horizontal line from where that roof meets the wall, and the top of the window may be 3 feet high above that line, which means the vent only needs to be 3 feet above the window, Did I say that in such a way that you could follow it?
The "2 feet higher than" may result in a tall vent, or a very tall vent, but there is no '8 foot radius' rule for the clearance. It would be a lot easier for the code to just state that the clearance from a vertical wall or a building opening is 8 feet in every direction ... but the code does not state it that simply, and it is not that simple of a rule (unless the vent is at least 8 feet from the wall, then 'no problem').