How is new home ductwork constructed vs in the past?

[SteveROntario]

It may seem like a weird question but I don't have the opportunity to snoop around basements in people's new homes.  Is all of the supply duct insulated in new homes in Ontario now?  Any big changes other than the HRV and dedicated return ducts instead of using the joists?

The reason I ask is that I bought a side-split that was built in 1978 and the furnace room is like a sweat lodge with a labyrinth of ducts going all over the place to the various registers.    I was pondering changing the 5" duct pipes of insulated flex ducts to gain some head room and get more of the heat to its destination.

Cheers, Steve