Morning JP...are you sugggesting that limescale will build up on..... people .....in the close vicinity of the kettle ? Et al...sugggests 'other people'...whilst etc. (et cetera) suggests 'and the others'...such as items. Best to not make a linguistic faux pas in polite society and WI coffee mornings ! RS
Surely, any insulation would prevent(even temporarily) heat being transferred to the water. Remember, the element is already encased in the housing(either tube or floor) so it has to heat the housing first. There's energy loss straight away. Add a thickness of say limescale, gotta be more loss. Take it to the extreme to prove it, add 10mm of scale to the whole element. Lots of energy used before heat even gets to the water! Mr. HandyAndy - Really