What determines whether insulated or non insulated ducting gets used for A/C?

COST

I am thinking cost. I believe it is so the cool air stays cool till it reaches its exit point. Why let cool air escape or warm air enter the ducting?,especially in hiden voids or compartments.

Not worried whether I spend $11 or $17 for duct for a 25' peice. The insulated I think has no draw back, other than running it because of the larger size, which I am trying to work around. The A/C unit and 1/2 of the duct will be in the cabin, but do to the unit placement, I have to run the supply duct through the cabin wall and into a void between that wall and the cockpit liner, which is open to the side storage compartments and the bilge in the back of the side compartments. So not quite the same as running duct work thru the engine compartment directly.

Damn I type slow.

Thanks

I ran duct through a forward cabin bulk head and only cut it big enough for the 4 inch material to pass through. I ran the insulation around both pieces on either side and everywhere else it was convienent to use.....the last 1-1.5 feet weren't insulated either due to space constraints.

US1, Insulated duct should always !!!!!!!! be run in non -conditioned areas. If not you have the potential to form condensate on the outside of the duct because of the temperature difference.
Dave

Bingo........!!!

PMT, Are you in the business ?

Yessir...