In cold climates, uninsulated single-wall pipe shall NOT be used for what purpose?

Using uninsulated single-wall pipe for outdoor venting of gas appliances in cold climates poses significant risks. In such environments, the temperatures can drop low enough to cause condensation within the pipe. This condensation can lead to water forming inside the vent, which can create a hazardous situation by promoting corrosion of the pipe material and ultimately leading to vent failures. Additionally, if moisture accumulates, it may result in blockage, which could prevent proper venting of combustion gases and increase the risk of dangerous backdrafts or leaks.

Proper venting requires materials that can withstand temperature variations and prevent condensation accumulation, making insulated or double-wall pipes the preferable options in these conditions. This ensures that the gases are vented safely and effectively without the risks associated with uninsulated materials, especially in colder climates where the operational integrity of the venting system is critical to safety.