What is the minimum distance double wall (B vent) needs to be from combustibles?

The minimum distance that a double wall (B vent) needs to be from combustible materials is 1 inch. This requirement is based on safety standards designed to prevent heat transfer that could potentially ignite nearby combustible materials. The double wall design of a B vent helps to contain the heat generated by the venting of gas appliances, ensuring that the exterior does not reach a temperature that would pose a fire risk to surrounding structures.

Maintaining this 1-inch clearance allows for adequate ventilation and ensures that any dissipated heat does not adversely affect the combustibles in proximity to the vent. This standard is established by various safety codes and guidelines, reaffirming the importance of adhering to such distances for safe operation.