How many letters does the top answer for “not able to conduct heat or electricity or sound” have?

The most common answer is nonconducting (13 letters).

Crossword clue: not able to conduct heat or electricity or sound

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

nonconducting 13 letters wn-def

not able to conduct heat or electricity or sound

nonconductive 13 letters wn-def

not able to conduct heat or electricity or sound