According to Section 312.0, when must piping be protected from freezing?

• Piping must be protected from freezing only when exposed to temperatures below 20°F.
• Piping must always be protected from freezing, regardless of location.
• Piping must be protected from freezing only when located underground.
• Piping in exterior walls or other locations subjected to freezing temperatures must be protected, unless it is located in a heated space.