Sleeves are required to extend a maximum of ________ on both sides of a wall.

When it comes to installing sleeves for ducts or pipes that extend through walls, it is standard practice to ensure that the sleeves extend a maximum of 6 inches on both sides of a wall. This requirement serves critical purposes in an HVAC system, including maintaining proper insulation, preventing air leaks, and ensuring that the transition from the wall to the duct or pipe doesn't create any obstruction or inefficiency in airflow.

Extending sleeves adequately on both sides allows for proper sealing, which is essential for maintaining system efficiency and performance. It also provides enough space to manipulate and secure the ductwork or piping, facilitating easier adjustments during installation or maintenance.

The other choices do not align with standard installation practices, as they either provide inadequate space for secure installation or, in some cases, could lead to complications with airflow or insulation. Thus, the 6-inch extension is recognized as the optimal measurement for ensuring effective and efficient HVAC system operation while adhering to industry guidelines.