Which type of sealant is specifically discouraged for use around pipe penetration through exterior walls?

The correct answer highlights the importance of using appropriate materials for sealing around pipe penetrations in exterior walls. Flashing is typically used to redirect water away from the wall and its components, which is crucial for preventing moisture intrusion. However, when it comes to pipe penetrations, flashing is not suitable as it does not provide a complete seal against air and water leaks.

Using a proper sealant that is designed to expand or contract with temperature fluctuations and that adheres well to various surfaces is essential for ensuring that penetrations remain watertight. Materials like caulk, foam sealant, or gasketing systems are better suited for this application because they can effectively fill gaps and provide a resilient barrier against the elements.

In summary, the choice of material is crucial for both the durability of the seal and the integrity of the structure surrounding the pipe penetration, with flashing not being an adequate option in this case.