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 pliable, non-toxic compound is easily molded by hand to form a plug around the wire bundle where it passes through the back. Air leakage from electrical boxes, outlets, and wiring is a common cause of energy loss in commercial buildings. Air leaks from these areas can significantly drive up heating and cooling costs, and compromise the integrity of fire-rated assemblies. Let's start with the “other equipment”. Typically, the biggest hole an electrician will make in a home's envelope will be for the main electrical service. 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.
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