# Duct  Insulation



## globe trekker (Jan 14, 2011)

In this AHJ, most of the HVAC contractors will install their rigid ducting, throughout a

SFR [ in the attic space, non-conditioned spaces ] correctly, however, when it comes

to installing the thermal insulation on that rigid ducting, they rarely seal the thermal

insulation joints / seams and points-of-connection to other duct trunk lines &

housings, completely! Sometimes, they overlap the insulation onto other insulation...

Is there a section in the IRC that requires that "all" thermal insulation be fully/

completely sealed with an approved tape or material? No, we don't allow ' general

use gray duct ' tape as an approved sealing tape.

Thanks for your responses!

.


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## Mule (Jan 14, 2011)

I believe it is in the energy code............ I'm heading out of the orfice now but maybe someone else can help.


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## Mule (Jan 14, 2011)

Does this help....I looked it up before leaving...

N1103.2.2 Sealing. Ducts, air handlers, filter boxes and building

cavities used as ducts shall be sealed. Joints and seams shall

comply with Section M1601.4. Duct tightness shall be verified

by either fo the following:

1. Post-construction test: Leakage to outdoors shall be less

than or equal to 8 cfm (3.78 L/s) per 100 ft2 (9.29 m2) of

conditioned floor area or a total leakage less than or equal

to 12 cfm (5.66 L/s) per 100 ft2 (9.29 m2) of conditioned

floor area when tested at a pressure differential of 0.1

inch w.g. (25 Pa) across the entire system, including the

manufacturer’s air handler end closure. All register

boots shall be taped or otherwise sealed during the test.

2. Rough-in test: Total leakage shall be less than or equal to

6 cfm (2.83 L/s) per 100 ft2 (9.29m2) of conditioned floor

area when tested at a pressure differential of 0.1 inch w.g.

(25 Pa) across the roughed in system, including the manufacturer’s

air handler enclosure. All register boots shall

be taped or otherwise sealed during the test. If the air

handler is not installed at the time of the test, total leakage

shall be less than or equal to 4 cfm (1.89 L/s) per 100

ft2 (9.29 m2) of conditioned floor area.

Exception: Duct tightness test is not required if the

air handler and all ducts are located within conditioned

space.


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## globe trekker (Jan 14, 2011)

Mule,

Thanks for your input! I looked those code sections that you listed. Do those apply to

just the actual ' ducting', or the insulation on those ducts?

Hard as it is to believe, but I am being challenged by a HVAC contractor as to why I am

being so hard on them, ...to require the sealing of all the joints and seams of the thermal

insulation. I would like to be able to show them something in black & white from the

IRC or a referenced standard from the IRC.

Common sense would tell intelligent people that the rigid ducting insulation should be

completely sealed to prevent heating & cooling loss, but apparently some contractors

( again -   ) do not own a code book, nor bother to keep up on training or

educating themselves.

The Contractor Laziness Factor seems to be increasing.   Anyone else experiencing this?

Sorry for the mini-rant.   

.


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## Mule (Jan 14, 2011)

M1601.4.1 Joints and seams. *Joints of duct systems *shall be

made substantially airtight by means of tapes, mastics, liquid

sealants, gasketing or other approved closure systems. Closure

systems used with rigid fibrous glass ducts shall comply withUL181A and shall be marked181A-P for pressure-sensitive

tape, 181A-M for mastic or 181 A-H for heat-sensitive tape.

Closure systems used with flexible air ducts and flexible air

connectors shall comply with UL 181B and shall be

marked181B-FX for pressure-sensitive tape or 181B-M for

mastic. Duct connections to flanges of air distribution system

equipment or sheet metal fittings shall be mechanically fastened.

Mechanical fasteners for use with flexible nonmetallic

air ducts shall comply with UL 181B and shall be marked

181B-C. Crimp joints for round metal ducts shall have a contact

lap of at least 11/2 inches (38 mm) and shall be mechanically

fastened by means of at least three sheet-metal screws or rivets

equally spaced around the joint. Closure systems used to seal

metal ductwork shall be installed in accordance with the manufacturer’s

installation instructions.

Exceptions:

1. Spray polyurethane foam shall be permitted to be

applied without additional joint seals.

2. Where a duct connection is made that is partially inaccessible,

three screws or rivets shall be equally spaced

on the exposed portion of the joint so as to prevent a

hinge effect.

3. Continuously welded and locking type longitudinal joints

and seams in ducts operating at static pressures less than 2

inches of water column (500 Pa) pressure classification

shall not require additional closure systems.


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## Mule (Jan 14, 2011)

Sorry....I saw you posted inbetween my postings..I believe the bolded print covers you!


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## globe trekker (Jan 14, 2011)

Aye carumba! The bold print is what I will provide. "Much thanks" Mule! You're

still Da man!  

.


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## mtlogcabin (Jan 14, 2011)

A duct system does not include the insulation

DUCT SYSTEM. A continuous passageway for the transmission of air which, in addition to ducts, includes duct fittings, dampers, plenums, fans and accessory air-handling equipment and appliances .

I believe this section of the 2006 energy code is what you need

604.11 Vapor retarders.

Where ducts used for cooling are externally insulated, the insulation shall be covered with a vapor retarder having a maximum permeance of 0.05 perm [2.87 ng/(Pa • s • m2)] or aluminum foil having a minimum thickness of 2 mils (0.051 mm). Insulations having a permeance of 0.05 perm [2.87 ng/(Pa • s • m2 )] or less shall not be required to be covered. All joints and seams shall be sealed to maintain the continuity of the vapor retarder.


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## TimNY (Jan 14, 2011)

Check the insulation instructions.. from JM:

"Wrap insulation around duct with facing to the outside so the

2" (51 mm) flap completely overlaps facing and insulation at the other end of stretch out. Insulation shall be snugly butted.

Secure seams with mechanical fasteners placed approximately

6" (152 mm) on center. If required, seal seam with pressure-sensitive tape designed for use with duct insulation. Insulation on the underside of ducts spanning 24" (610 mm) or greater shall be secured with mechanical fasteners and speed clips spaced approximately 18" (457 mm) on center. Fasteners should be cut off flush after the speed clips are installed, and when required, sealed with the same tape as specified above."

The reason for sealing would be condensation, so if you're looking in the code check for something related to condensation or vapor barriers.

EDIT: mtl beat me to it!


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## Jobsaver (Jan 15, 2011)

Section on vapor retarder also found in the 2009 Mechanical Code.

604.11 Vapor retarders. Where ducts used for cooling are externally insulated, the insulation shall be covered with a vapor retarder having a maximum permeance of 0.05 perm [2.87 ng/(Pa · s · m2)] or aluminum foil having a minimum thickness of 2 mils (0.051 mm). Insulations having a permeance of 0.05 perm [2.87 ng/(Pa · s · m2 )] or less shall not be required to be covered. All joints and seams shall be sealed to maintain the continuity of the vapor retarder.


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## globe trekker (Jan 15, 2011)

Double Aye carumba mtlogcabin!   Much thanks to ya'll for your input.  

.


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