Installing insulation around knob-and-tube wiring is considered hazardous due to several critical factors related to how this older electrical system operates. Knob-and-tube wiring, which was commonly used in homes built before the 1940s, relies on air circulation for heat dissipation and is not designed to be covered by insulation. When insulation is placed around this type of wiring, it can trap heat and cause the wires to overheat, increasing the risk of electrical fires.
Moreover, knob-and-tube systems may not have grounding conductors, posing a heightened risk of electrical shock or short-circuiting. Therefore, insulating around these wires compromises their safety and function, contributing to a hazardous condition within the home.
In general, the installation of insulation must be approached with care, particularly in older homes where such wiring systems are present, underscoring the importance of understanding the materials and practices involved in home inspections.