Types of Venting

A Type - Double Wall, Stainless and Insulated between walls

B Type – Double Wall, Air between walls (Galvanized outer - Aluminum inner)

C Type – Single Wall Stainless (Z-Vent)

Roof Pitch by Degrees

Roof Pitch and the corresponding degrees:
12/1 = 4 degrees
12/2 = 9.5
12/3 = 14
12/4 = 18.5
12/5 = 22.5
12/6 = 26.5
12/7 = 30.5
12/8 = 33.75
12/9 = 37
12/10 = 40
12/11 = 42.5
12/12 = 45

High Altitude NG Or LP Ratings

For operation at elevations above 2000 feet, the equipment ratings (NG or LP gas) shall be reduced 4% for each 1000 feet above 2000 feet.

From 4000 to 10,000 feet a CO2 adjustment with a flue gas analyzer should be used for all gas appliances.