Tubing is measured at the inside diameter, so yes, you need 1/2" hose to fit on a 1/2" barb.
Is this at the bottom of a boil kettle? If so, then yes, get silicone (high temp) hose.
Keg #1: RHESB 6.2
Keg #2: Cascadian Stout
Keg #3: BMC West
Fermenter #1 Bourbon/Oak Vanilla Porter
Bottled: Mjolnir Mead, Lazy Daze Hefe, The Bollocks ESB, Dark Matter stout.