Which activity does NOT require a license or permit?

The activity of installing thermostats as part of an alarm system does not require a license or permit due to the nature of the work. Thermostats that are part of an alarm system are typically considered low-voltage wiring systems and are usually exempt from the stringent regulations that apply to more traditional mechanical installations involving gas, plumbing, or electrical systems.

In contrast, other activities listed involve systems that impact home heating or compliance with specific safety codes, which require oversight by licensed professionals. For instance, installing water heaters and outdoor wood heaters must adhere to local building codes and manufacturer guidelines to ensure safety and efficiency. Similarly, direct vent fireplaces in a garage are subject to specific regulatory criteria to mitigate fire hazards and ensure proper ventilation. These installations necessitate expertise and, consequently, proper licensing or permitting to ensure compliance with safety regulations.

Thus, installing thermostats as part of an alarm system remains a do-it-yourself task for many homeowners or technicians without the need for a specialized license or permit.