Comments on: Buried Ducts Allowed in 2018 Building Code

By: Bill Crook

Bill Crook — Mon, 07 Sep 2020 21:47:55 +0000

I have found all of these
I have found all of these discussions informative. Thanks. I am planning to build a single story home near Crystal River, FL. and am thinking on laying the duct work on the attic floor, covering the floor and ducts with 2-3 inches of cc foam, and then blow insulation over all. A raised truss would also be used. I do see articles about closed attics using foam but have trouble with no ventilation and not being able to see roof leaks if the roof sheathing is foamed. Do any of you have thoughts on this subject?

By: Bill Clark

Bill Clark — Sat, 08 Aug 2020 18:59:21 +0000

Great dialog everyone and I
Great dialog everyone and I have learned a lot. I am an architect and amateur home renovator in Atlanta and renovating our small two story 1925 Atlanta house now. I am reluctantly installing a heat pump system in the unconditioned attic serving the upper floor since one system in the basement serves the whole house. My HVAC man frowned when I suggested the possibility of burying ducts. Ducts are installed now and hung from the roof rafters. Based on dialog above I may one day come in behind him and bury the ducts. It kills me that the ducts are floating in 110 degree attic temperatures in Hotlanta even with R-8.

By: Kevin Woodward

Kevin Woodward — Sun, 26 Jul 2020 23:08:28 +0000

Can I use a spray foamed wall
Can I use a spray foamed wall as a duct run ?

By: Leroy Gross

Leroy Gross — Mon, 16 Sep 2019 15:44:41 +0000

I am in CZ2 (Florida). My air
I am in CZ2 (Florida). My air handler is in conditioned space but its plenum penetrates the ceiling to an unconditioned attic. Attached to the duct board plenum are 2 flex ducts that traverse to the 2 wings of the house and connect to rigid round duct distributors. The flex ducts are draped across the rafters and there is sweat on the undersides. I assume the insulation is compressed at each rafter thus lowering the R value. Dewpoints are often as high as 80 degrees. Access is difficult. What is the best way to improve this situation? It would be nice to replace the flex with rigid, but that would be very difficult. Wrapping? Burying? Something else?

By: Travis Crall

Travis Crall — Fri, 01 Mar 2019 14:19:55 +0000

In reply to William Patchen. We recommend to insulate all
We recommend to insulate all attic ductwork above R-40. Your biggest losses come from attic insulation.

By: William Patchen

William Patchen — Fri, 01 Mar 2019 06:30:20 +0000

Just moved in and want to
Just moved in and want to insulate my attic with blown-in insulation. I am on a slab so the ductwork was all run in the attic. I checked th "R" value on the flex duct and found it is only R-6. My metal plenum and trunk duct are all wraped. Don't remenber the "R" value of the wrap. I plan on blowing in celulose insulation to a total value of R-38. I live in indiana with a 5A climate rating. Do I have a problem?

By: Travis Crall

Travis Crall — Tue, 16 Oct 2018 13:14:06 +0000

There is a product designed
There is a product designed and patented specifically for deep attic ductwork burial. The product was developed with funding from the U.S. Dept of Energy. It requires no special tools and achieves a R-38 on top and sides and at least R-19 below. Please feel free to reach out to the ultimate-r@gmail.com for more info.

By: Marty Yeager

Marty Yeager — Wed, 11 Apr 2018 23:20:01 +0000

We are building a new home in
We are building a new home in VA, zone 4A. Neither my builder or his HVAC subcontractor are comfortable with burying the ductwork due to condensation concerns, even after reading this article. Our air handler at least is on the second floor. Who makes integrated R-13 ducts so I could at least do that? I have searched on the internet and can’t find any manufacturer. The HVAC guy has not heard of any and he is hesitant to try and wrap the R-8 ducts. Thanks for your help.

By: Robb Aldrich

Robb Aldrich — Mon, 17 Apr 2017 14:59:33 +0000

In reply to Curt Kinder.

Hi Curt – We tested ducts
Hi Curt – We tested ducts encapsulated in spray foam then buried beneath attic insulation in Jacksonville a few years ago. These were existing homes, and we couldn’t get ducts perfect (you’re right – it can be tricky). But heating and cooling energy was reduced by 5-20% (in 3 houses). More info than you probably want:
https://www1.eere.energy.gov/buildings/publications/pdfs/building_america/encaps_ducts_hothumid.pdf

I think ducts encapsulated (in foam) and buried in fiberglass have been prescriptively allowed since the 2009 IRC. Code requires an ignition barrier over the foam, and my understanding is that fiberglass insulation counts. Some guidelines for doing this:
https://www1.eere.energy.gov/buildings/publications/pdfs/building_america/measure_guide_buried_encap_ducts.pdf

By: abailes

abailes — Thu, 16 Feb 2017 22:03:23 +0000

In reply to David Butler. You're right, David. My

You're right, David. My description of the R-19 requirement wasn't clear. I'm not a big fan of "and/or" so I wrote it a little differently than you suggested. Better?