Duct Insulation & type Requirement

[Golestan]

Good Morning,

1- What is the best way to indicate insulation requirements & construction type on mech-plans for duct passing thrugh a basically unconditioned space. This would be a hight pressure primary air from an AHU to a few fan powered boxes.

2- I am looking at some old mech plans from 1971 for a large facility, there are a couple of large boxes shown as induction boxes on the ducting path. What is typically the function of this box?

thanks,