Cloth-insulated wiring with brittle, crumbling insulation at the panel indicates:

Early rubber and cloth-insulated conductors were adequate when installed, but the insulation embrittles with age, heat and oxidation. At the panel the deterioration is usually worst, because that is where conductors have run warmest and where they have been flexed during every service call. Brittle, crumbling insulation means bare conductor may be exposed inside the enclosure and that any future handling will break more of it away, so the condition is progressive and the panel is the place it is most likely to cause a fault. What the inspector can say is bounded: the conductors are aged and the insulation is failing where visible, and an electrician should evaluate the extent, since the condition of wiring concealed in walls cannot be assessed and the remedy may range from repairs at the panel to partial rewiring.

Brittle, crumbling insulation is age-related deterioration of the conductor's covering, and it is progressive. The inspector reports the observed condition and recommends an electrician evaluate the extent, since concealed portions cannot be assessed.

Rubber and cloth-insulated branch wiring degrades with age, heat and oxidation, becoming brittle and shedding insulation. Deterioration is typically most advanced at the panel and at fixtures, where temperatures are highest and conductors have been disturbed.

Old Insulation Crumbles at the Hot End. What you see at the panel is the leading edge; what is in the walls you cannot see at all.

Note that this is distinct from knob-and-tube and from aluminum branch wiring. Each has its own risks and remedies, and the exam tests whether you can tell them apart.

• •Attributing age-related embrittlement to recent service work
• •Describing period-appropriate wiring as defective when installed
• •Reporting only what is visible without noting that concealed runs were not assessed