Insulating duct work - inside or out?

[ct_hvac_tech]

OK, I am curious how Y'all insulate your duct work on installs: Do you wrap it on the outside, or do you line it on the inside?

Let's here where you are and how you do it.

I am in Connecticut, and it is mostly wrapped on the outside. However, when I lived in Kansas, it was all insulated on the INSIDE, before it was put together and taken to the job site.

Which brings me to another question: Do Y'all build your duct work on site, or do you do it at the shop, and then bring it to the jobsite?

[selfemployed]

This came up at the CE Class I atteneded on saturday. We have to use R8 now on supply ducts. Some are mixing - liner and wrap. Some are using 2" R8 liner. Some are just wraping. Some use 2" duct board, mostly at the coast. Those ducks are getting bigger with that 2" liner and metal isn't cheap. I did hear someone say that the R8 wrap didn't look good (saging) due to the weight. Pins were the only thing that helped.

[totaleclipse]

Almost everything we do is external wrap. I dont like internal liner in a res. duct system.

[flyrfan]

We wrap supply...always! Sometimes we'll line the return ducts for sound attenuation for conference rooms, etc.

I think that a fiberglass liner exposes you to all kinds of liability issues....from mold growth to fiberglass particles linked to cancer.

[des30506]

I wrap, But when I need to control noise, I usually line the inside and use felx duct. As for the sagging R8 I usually wire ty the insulation to control this.

[hvacker]

Due to the roughness factors liner affects system performance. It's actually sold a acoustic liner not insulation, although it does have some insulation qualities. I also have seen liner fall and block duct work. All glues fail in time and pins break off.

There is a fairly new product I read about designed to replace acoustic liner w/o some of the liners problems. Maybe someone remembers what this is. I think I saw an ad in a trade mag.

[behappy]

This came up at the CE Class I atteneded on saturday. We have to use R8 now on supply ducts. Some are mixing - liner and wrap. Some are using 2" R8 liner. Some are just wraping. Some use 2" duct board, mostly at the coast. Those ducks are getting bigger with that 2" liner and metal isn't cheap. I did hear someone say that the R8 wrap didn't look good (saging) due to the weight. Pins were the only thing that helped.

We haven't been forced to this yet.... But I hear your pain!
This area is almost 100% ductboard in resi....
We have found a ninch with metal wrapped on the outside for IAQ.


I used this at our house for a test (and it works great).
Will this fly with your "code"????

http://www.insulation4less.com/prodex_Ffmf.asp

[selfemployed]

I asked about it and the answer was. Show in writing it is R8 and no problem. Yes duct spacers can be use to get R8. Only one person in class (30) said they didn't like it. Don't know how many have tried it though.

[behappy]

I asked about it and the answer was. Show in writing it is R8 and no problem. Yes duct spacers can be use to get R8. Only one person in class (30) said they didn't like it. Don't know how many have tried it though.

I agree we have started using bubble wrap in resi, not commerical (yet).
But the above product is "R-14" and not bubble wrap. It is a little stiffer to put on and pricer.

[selfemployed]

Sorry I missed the R-value in the literature. Thanks for the link.

[Catpower]

If it needs to be insulated, we always line it, and shop build, make a quicker easier installation. We glue and stud weld it in place, haven't had any come loose yet. It does make the system much quieter, and there will probably be some kind a lawsuit someday,the lawyers just haven't figured it out quite yet.

There was a want ad in the Dallas Morning News from a law firm looking for furnaces that were installed in the '60's, so guess they've figured out how to sue somebody for 40 year old technology.

The road goes on forever and the party never ends!