Non-hardening electrical putty, also known as duct seal compound or mastic, is the preferred material for sealing wire entries directly inside the box. This practice is a fundamental part of maintaining a structure's envelope. It prevents the uncontrolled movement of air, moisture, and. This article explains how to safely air seal electrical boxes to tighten your home's thermal envelope. Electrical penetrations are often responsible for holes in the most critical locations in your envelope, making them a prime target when your goal is to air seal your home., caulk, fire-retardant caulk, fire-rated spray foam, etc. Whether you are a DIY enthusiast or a professional. If the box is securely mounted to the wall from the outside and filled with silicone sealant or duct seal, it is acceptable.
[PDF Version]