Old insulation and exposed outside air
The light from outside shows how outside air can make its way into an attic and impact the temperature. The temperature of an attic can act against the conditioned air travelling through the ducts. An attic with 115 degree air temperatures is like an oven for the HVAC ducts traying to deliver 60 degree air through 20 to 30 feet of ducts.
Poorly insulated HVAC ducts
These ducts have insulation stuffed in and around them and have places where air is able to leak out.
More duct system opportunities
Although it is wrapped, this duct should be buried in insulation to better protect it from the heat/cool in the attic. The thin layer of insulation in this attic tells us that the home and rooms below are not able to keep the conditioned air made by the HVAC system.
HVAC Air Ducts
There is almost always an opportunity to shorten these ducts, making a shorter distance for the conditioned air made by the HVAC system to travel.
Poorly insulated
Imagine going to bed at night and just placing a pillow on your shin rather than using a blanket for your whole body. That is the same effect as placing a loose piece of insulation on top of a duct.
Failed insulation
This ripped and fallen away insulation is no longer providing any service to the HVAC duct.
Hostile environment for conditioned air
This is sitting on top of some rafter boards allowing hot air from the attic to pass above and below. That hot air works against the cold air traveling through the ducts.