Is it right to install the fiber glass insulation inside the duct?

in the first2 meter only to reduce the noise criteria (especial fiber glass) ..its called acoustic .

Fiber glass is normally used for external insulation of duct to reduce heat transfer and minimise the condensation above the duct. Alternately we are using arma flex ruber insulation for the same pupose. For internal accoustic liner is used to reduce the noise creating the high pressure air in aide the duct. As per ASHRAE standar3 mtr from the fcu or ahu

yes is possible o install the glass insulation inside the duct

Usually rockwool used for outside insulation .

But fiber glass is not a common way to insulate .

Using the fiber glass board insulation inside the ducts is not the right method, due to this is applicable for using only external ducts. For internal using you have to use the acoustic liner for avoiding the high noise and high air velocity.

If you used glass board insulation inside the ducts it will start removing after a certain period of time because of air pressure. That may cause creating one kind of allergy/suffocation inside the rooms.

 

Why put duct insulation inside and not outside the duct, and the question is how calculated a friction, air speed and dynamics pressure How do you calculate the static pressure, in fact you need a new a charts and equations in this account, If to reduce the noise In the duct you have managed by readjust  a duct grills. That the limits of my knowledge, I f you having a right answer, pleas correct me if possible