Highest "R" for duct, plenum, boot insulation?

[HighPotential]

Aside from the regular "glass-fiber" stuff (which I think is R4/inch), does anyone recommend and superior types of insulation for sheet-metal plenums, boxes, boots, etc?

Thanks!

 

[lilliput1]

There may be better R values but none that can meet fiberglass smoke & fire characteristic, acoustic property & no health concerns if sealed & kept dry.

 

[KenRad]

HighPotential,

I avoid lined duct and plenums whenever possible. That being said, Armaflex (possibly some other companies as well) makes a closed cell, elastomeric liner material that has some properties that, I believe, make it superior to the traditional fiberglass liner. Similar to their pipe insulation, it will not absorb water like fiberglass, and is much more resistant to biological growth and capture of dirt. R-value is comparable. The only thing that I can't vouch for is its acoustic properties as compared to fiberglass, but depending on your application, this may not matter.

I guess it's all in how you define "superior," but you might want to check it out.

---KenRad

 

[HighPotential]

Hmmm. I'm wondering now if I should be concerned. I specified all of my supply air and return air plenums to be lined on the inside for ease of installation and noise. It would be too late for me to change that now though.

 

[lilliput1]

You should not use elastomer insulation thicker than 1/2" inside buildings. Above 1/2", its fire & smoke rating will be above the 25-50 Code requirement!