# Exposed fiberglass insulation in a return air plenumn?



## jpranch

This just dose not sound right but I'm having trouble nailing down a code section that prohibits this. Any help would be appreciated.

Forgot to mention that the insulation is unfaced.


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## Coug Dad

It is permitted if it has a flame spread less than 25 and smoke developed of 50.


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## mtlogcabin

Agree it is permitted

Now where is it located? If it is laying on ceiling tile in a commercial building I don't belive that is permitted under the energy code.


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## fatboy

It should be OK........


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## jpranch

I got this from Owens Corning:  "Due to the potential for skin irritation, unfaced Thermal Batt Insulation should not be used for exposed applications where it will be subject to human contact."

So if they do not want it exposed in walls or ceilings... Thoughts?


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## fatboy

Assuming the plenum is on the return side, air would be filtered before coming back to the supply side, I would think airborne fibers should not cause a problem.


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## mtlogcabin

How will insulation installed in the attic be subject to human contact by the building occupants?

Any fiberglass that may be picked up in the air flow of the return air plenum would be miniscule and would likely have to pass through the reurn air filters on the unit before being discharged through the fiberglass duckwork located on the supply side.


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## Gregg Harris

jpranch said:
			
		

> This just dose not sound right but I'm having trouble nailing down a code section that prohibits this. Any help would be appreciated.Forgot to mention that the insulation is unfaced.


Take a look at IMC 604.13 internal insulation


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## KZQuixote

jpranch said:
			
		

> This just dose not sound right but I'm having trouble nailing down a code section that prohibits this. Any help would be appreciated.Forgot to mention that the insulation is unfaced.


If the insulation is part of the thermal envelope it is required to have an air wash covering. Don't know the code section but any insulation contractor should know it's required.

Found it! Section 402.4.2.2 2009 IECC Visual inspection Option from Table 402.4.2 "Exterior thermal envelope insulation for framed walls is in substantial contact and continuous alignment with the building envelope air barrier."

Chapter 4 is residential. I'll look for a commercial equivalent.

Bill


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## conarb

Don Quixote said:
			
		

> Found it! Section 402.4.2.2 2009 IECC Visual inspection Option from  Table 402.4.2 "Exterior thermal envelope insulation for framed walls is  in substantial contact and continuous alignment with the building  envelope air barrier."


Interesting, I didn't know an air barrier was required, a weather resistant barrier yes, but the usual air barrier is just the interior finish, like sheetrock.  Does the IECC now require air barriers?  If so we are in a world of hurt since sealing walls prevents them from "breathing", like the disasters caused by dual barriers, especially using cheap polyethylene sheeting in walls. I  know nothing about the IECC since we in California have our own energy code.


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## KZQuixote

Hi Conarb,

The air barrier can be the drywall, the paint or the polyethylene sheeting under the drywall. What's new is that the insulation must fit tight to the air barrier. Example might be insulation in the wall but a cabinet soffit that pulls the air barrier away from the insulation.

The requirement that all six sides of a batt of insulation be covered is a best practice not a code requirement. The Energy Trust folks here in Oregon require that all their approved subcontractors cover all exposed insulation with something to prevent air washing. They maintain that an open back side will reduce the R value by 2/3's.

Bill


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## mtlogcabin

KZQuixote said:
			
		

> The new requirement is that the insulation cannot be exposed to air washing on the attic side.


We where taught the same thing in an energy code class last year but darned if I can find a code section for it.


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## Fort

Don't see this requirement either.


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## Big Mac

Makes sense that it should be covered.  How much loose insulation fibers floating in the air, too much?


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## Pop Alexandra

I'd also recommend taking all precautions if possible. Free-floating fibers are a real health concern for all fiberglass panels.


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