I'm not quite sure why, other than the difficulty of doing it, but as far as I know, semi acoustics generally aren't shielded. Anyone got a view?
I only asked, as I have a vague memory of a guitarist mate of mine having an Ibanez semi from the eighties, I have an even vaguer memory of that having a sort of tinfoil bath around the controls (on the inside of course).
Having said that, I fully accept that I'm not as young as I was, and memory can be a finicky mistress.
In short, I might be talking total sh*t.....