Insulated Flex Duct You may wonder why it is important to have insulated flex ducts in your home.  Or, does this type of duct make a difference vs. standard ducting?  The ducts listed in this section are UL181 listed, have an R-Value of 6 and come with a 10 year warranty.  Why insulated duct?  The insulation in the ducting will prevent condensation from forming on the duct.  Condensation forming on the duct is not a good thing.  Another benefit of the insulated flexible ducting is that it further reduces any "air noise" caused by the exhaust fan, so your ventilation system works even quieter. Click one of the 3 duct sizes below for more detailed information on the ducting.