Are radiant barriers junk?

[gururu2]

Looking at options to insulate some duct work in my garage and washroom. Prefer not to do fiberglass as I am afraid that fibers over time will escape into the rooms or ventilation. Is it a non-issue and/or are reflective bubble pack insulations (reflectix) not going to save me any money?

 

[Humpy]

They only work if they are facing an airspace, so it depends on what exactly your goal is.

 

[MagnusTheBrewer]

When installed correctly, it's a none issue.

 

[3chordcharlie]

Unless you have duct work running through un-heated areas, or have temperature imbalances that you can't fix by adjusting registers (i.e. your garage gets 'too much heat') you probably don't need to worry about this.

 

[Scarpozzi]

What kind of ductwork is it? These days, you can buy 6-8" round ductwork from lowes/home depot for pretty cheap. You could just replace the duct with something new/insulated if you have access to it....ultimately, I want to say it was like $27/25 feet last time I saw it.

If you're talking the metal ducts, you shouldn't worry much about fiberglass getting sucked into it. Usually the duct will be pressurized and (hopefully sealed). Stuff doesn't get sucked into ducts unless they're on the intake side of the air handler.

 

[gururu2]

What kind of ductwork is it? These days, you can buy 6-8" round ductwork from lowes/home depot for pretty cheap. You could just replace the duct with something new/insulated if you have access to it....ultimately, I want to say it was like $27/25 feet last time I saw it.

If you're talking the metal ducts, you shouldn't worry much about fiberglass getting sucked into it. Usually the duct will be pressurized and (hopefully sealed). Stuff doesn't get sucked into ducts unless they're on the intake side of the air handler.

Ok thanks to all. Its about 10' of preinstalled exposed box duct running through the ceiling of my garage and feeds into the upstairs bedroom. Part of it is covered in a wood support which I wont be able to insulate. There is a vent also in this section which regulates the garage climate. I hate to cool the garage during the summer, but if I close the vent, the entirety of the exposed duct condenses a lot of water which drips onto the garage floor. I thought insulating it might prevent this.
I was thinking about radiant barriers, but it seems they are not good for insulation, but rather heat deflection. It seems that I wont get around the traditional fiberglass variant.

 

[monkeydelmagico]

Look into spray on foam. You want to make sure you get a decently air tight barrier so no condensation continues to form on the duct work. You will get mold if not careful.

Scarpozzi's idea is probably better. The flexi pre insulated ducts are not going to get condensation.