Which of the following is NOT a mandatory measure included in Title 24 Energy Efficiency Standards?

The answer identifies HVAC systems as not being a mandatory measure included in Title 24 Energy Efficiency Standards. However, it's important to note that HVAC systems are typically considered a crucial component of energy efficiency in buildings and are subject to regulations under Title 24.

Mandatory measures as defined by Title 24 include requirements that must be met for most new construction projects in California to promote energy conservation and efficiency. Mechanical systems, building envelope, and fenestration (windows and doors, for example) each play significant roles in reducing energy consumption and ensuring overall building efficiency, which is why they are standard requirements under Title 24.

It's crucial to understand that while all the given options relate to energy efficiency and may have specific guidelines within Title 24, HVAC systems are generally included in these regulations and thus do not correctly fit the description of being a measure that is not mandatory. Each aspect of Title 24 is designed to work together to improve energy performance in buildings, and HVAC systems are a key part of this comprehensive approach.