Spray Foamed Insulated Ducts
The 2 part spray foam seals off any air penetrations in the duct. The spray foam also gives the duct more insulation.
Ducts
Insulated air ducts will still leak air through the seams and ridges. Insulation just acts as a filter for the air.
Insulated Walls
Dense packing wall fills each cavity in the wall with insulation very tightly. This makes a room a lot more insulated as well as the insulation acts as a sound barrier.
Air Sealing
This room above the crawlspace was air sealed from the underside. This eliminated are from leaking into the crawlspace as well as the nasty air from the crawlspace leaking into the room. This improved the air quality of thier room greatly.