The meaning of "let alone insulation"

[Jupiter]

Hi teachers,

I don't really understand the phrase "let alone insulation" in the following extract.

[Pamela]

More context would be more helpful.
Let alone insulation-not to mention isolation. Maybe, the house was detached from other houses or was the only one located in the area.

[Alan]

Hi Jupiter,

Your expression 'let alone' means something llike - even if you don't count/even if you disregard/even if you exclude/even if you ignore/even if you don't mention insulation. A list of faults in the house is given that make it unfit to live in and all that would make you not want to live there and that's without even talking about the lack of insulation.

Alan
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