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Under-Insulated duct

S

StephNow

Registered User
Joined
Oct 20, 2009
Messages
75
Location
Home of Larry Holmes
This is hard to believe, but, I have a contractor who started an HVAC job without a permit, and most of the system and duct work was completed by the time I found him. He had installed fiberglass duct board in the unconditioned basement that doesn't meet the minimum R-value as per 2009 IRC. Is there an avenue in which the contractor can add some sort of insulation to the duct board?

My initial position is no because of the issues associated with adding insulation on top of a vapor barrier. Furthermore, through online searching I have yet to find any acceptable method to add insulation to duct board.

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snowroski said:
This is hard to believe, but, I have a contractor who started an HVAC job without a permit, and most of the system and duct work was completed by the time I found him. He had installed fiberglass duct board in the unconditioned basement that doesn't meet the minimum R-value as per 2009 IRC. Is there an avenue in which the contractor can add some sort of insulation to the duct board?My initial position is no because of the issues associated with adding insulation on top of a vapor barrier. Furthermore, through online searching I have yet to find any acceptable method to add insulation to duct board.

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Click to expand...
Bubble wrap
 
Our company has allowed under insulated duct board to be wrapped. We cannot find anything that would prohibit it and it still meets or exceeds the same R-Value.
 
Under-Insulated duct

Bubble wrap was brought up, but manufacturer doesn't provide any installation instructions or r-value added for wrapping fiberglass duct board. There are instructions and specs for wrapping sheet metal which adds to my concern of adding faced insulation over faced insulation.

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snowroski said:
Bubble wrap was brought up, but manufacturer doesn't provide any installation instructions or r-value added for wrapping fiberglass duct board. There are instructions and specs for wrapping sheet metal which adds to my concern of adding faced insulation over faced insulation.Sent from my iPhone using Tapatalk
Click to expand...
The delta T between the inside of the duct and the exterior would never be great enough to cause an effect. There are no specifics in NAIMA (except that adding may be required) because the product chosen would determine the R vale/ Reflectex with airspace can double or triple the R value.
 
snowroski said:
Bubble wrap was brought up, but manufacturer doesn't provide any installation instructions or r-value added for wrapping fiberglass duct board. There are instructions and specs for wrapping sheet metal which adds to my concern of adding faced insulation over faced insulation.Sent from my iPhone using Tapatalk
Click to expand...
The delta T between the inside of the duct and the exterior would never be great enough to cause an effect. There are no specifics in NAIMA (except that adding may be required) because the product chosen would determine the R vale/ Reflectex with airspace can double or triple the R value.
 
Gregg Harris said:
The delta T between the inside of the duct and the exterior would never be great enough to cause an effect. There are no specifics in NAIMA (except that adding may be required) because the product chosen would determine the R vale/ Reflectex with airspace can double or triple the R value.
Click to expand...
That has been our opinion and we realized that the airspace between the R value rated wrap and the R value rated duct would increase the overall value more than just adding them together.

In the OP's case, if they were caught without a permit and he is not comfortable allowing wrap, his i within his right to have them rip it out and replace it with the correct duct.
 
jar546 said:
That has been our opinion and we realized that the airspace between the R value rated wrap and the R value rated duct would increase the overall value more than just adding them together. In the OP's case, if they were caught without a permit and he is not comfortable allowing wrap, his i within his right to have them rip it out and replace it with the correct duct.
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My opinion, no permit rip it out. Just adding that it is possible to increase R value if needed in a legit job.
 
I too am inclined to say replace with code compliant duct/insulation. Ne need to feel remorse, the contractor should have installed the correct material to begin with... actually should have started with a permit application and specs to be reviewed.
 
The duct board may meet the requirements depending on what thickness that was used.

1 inch = 4.3

1 and 1/2" = 6.5

2 inch equals 8.7

It is in an unconditioned basement and not a crawl space or attic.
 
Is there insulation in the floor assembly above the basement that defines the thermal envelope? Is that how you are saying that the duct is outside the thermal envelope? If there is no insulation above (defining the envelope) then the exterior basement walls are defining the building thermal envelope. Installing a new mechanical system does not allow you to require another part of the building to be upgraded (thermal envelope).

I live in a 1950's home with ZERO insulation in the above grade exterior walls. That is still my "building thermal envelope". If I install new ductwork, I am still within that envelope and meet the exception for duct insulation.

Duct insulation is not based on "conditioned area" as much as the "building thermal envelope". There are lots of thermal envelopes that aren't up to current code and there are areas within that envelope that aren't supplied a direct source of heat, and that doesn't mean they aren't still IN the thermal envelope.

I would also suggest looking at the definitions for "conditioned area" and "conditioned space".

I think more details are needed before we can respond "rip it out!" Without insulation in the floor assembly, there's already tons of heat migrating to the basement. Seems senseless to freak about insulation...unless there are additional details to the situation.
 
Glenn said:
Is there insulation in the floor assembly above the basement that defines the thermal envelope? Is that how you are saying that the duct is outside the thermal envelope? If there is no insulation above (defining the envelope) then the exterior basement walls are defining the building thermal envelope. Installing a new mechanical system does not allow you to require another part of the building to be upgraded (thermal envelope).I live in a 1950's home with ZERO insulation in the above grade exterior walls. That is still my "building thermal envelope". If I install new ductwork, I am still within that envelope and meet the exception for duct insulation.

Duct insulation is not based on "conditioned area" as much as the "building thermal envelope". There are lots of thermal envelopes that aren't up to current code and there are areas within that envelope that aren't supplied a direct source of heat, and that doesn't mean they aren't still IN the thermal envelope.

I would also suggest looking at the definitions for "conditioned area" and "conditioned space".

I think more details are needed before we can respond "rip it out!" Without insulation in the floor assembly, there's already tons of heat migrating to the basement. Seems senseless to freak about insulation...unless there are additional details to the situation.
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Precisely Glenn IRC 402.2.7. Not enough data from the OP
 
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