Uninsulated single-wall metal pipe is not allowed outdoors where the winter design temperature is below what temperature?

Uninsulated single-wall metal pipe is typically not permitted for outdoor use in environments where the winter design temperature falls below freezing, which is 32°F. At temperatures at or below this level, uninsulated pipes are at risk of freezing, which can lead to pipe bursts and system failures.

The standard construction codes and guidelines focus on preventing damage to piping systems due to exposure to cold. Insulation is essential to protect the integrity of piping systems by maintaining proper operational temperatures and preventing freezing. Therefore, for practical and safety reasons, regulations restrict the use of uninsulated metal pipes outdoors when the winter design temperature is forecasted to drop to freezing levels or below.

In contrast, temperatures above 32°F may be less concerning regarding freezing risks, which is why other choices that represent higher temperatures do not apply in this context.