Attn. Plumbers Residential home question

[kenmac]

Yes, you are right. Not sure fiberboard is still out there. I did notice a big hunk of flex at the end of the picture, we don't allow more than 5 to 6 ft of flex to be used.

duct board is still used here (somewhat) the issue is that the new code requires it to be much thicker than in years past. So, it you use it,you have to make it larger to account for the xtra thickness of the material. Sometimes When making it larger, you run into headroom issues.
Most people are moving away from having insulation on the inside as you can make the duct smaller, and health issues associated with having the fiberglass insulation inside the duct.

Having no insulation inside the duct work will most times cause wind noise if using smooth round metal pipe for run outs.
Using flex run outs will damper this wind noise due to the flex being spiral inside.

Some cities here will only allow 10' of flex. while others will only allow 5 ft