3.1602.1 Air Sealing Duct System

Topic: 
Ducts
Subtopic: 
Duct Sealing
Desired Outcome: 
Ducts and plenums sealed to prevent leakage
TitleSpecification(s)Objective(s)
3.1602.1a
New component to new component sealant selection

Any closure system used will be in accordance with IRC IRC International Residential Code Chapter 16

Ensure effectiveness of air sealing system

3.1602.1b
New component to existing component

Seams, cracks, joints, holes, and penetrations less than ¼" will be sealed using fiberglass mesh and mastic

Mastic alone will be acceptable for holes less than ¼" that are more than 10' from air handler

Seams, cracks, joints, holes, and penetrations between ¼" and ¾" will be sealed in two stages:

  • They will be backed using temporary tape (e.g., foil tape) as a support prior to sealing
  • They will be sealed using fiberglass mesh and mastic

Eliminate air leakage into or out of ducts and plenums

Ensure adhesion of primary seal (mastic and fiberglass mesh) to the duct

Reinforce seal

Support mastic and fiberglass mesh during curing

3.1602.1c
Existing component to existing component

Seams, cracks, joints, holes, and penetrations less than ¼" will be sealed using UL UL Underwriters Laboratories 181 fiber-embedded mastic

Seams, cracks, joints, holes, and penetrations between ¼" and ¾" will be sealed in two stages:

* They will be backed using temporary tape (e.g., foil tape) as a support prior to sealing
* They will be sealed using fiberglass mesh and mastic

Seams, cracks, joints, holes, and penetrations larger than ¾" will be repaired using rigid duct material

Mastic will overlap repair joint or existing temporary tape by at least 1" on all sides
 

Eliminate air leakage into or out of ducts and plenums

Ensure adhesion of primary seal (fiberglass mesh and mastic) to the duct

Reinforce seal

Support fiberglass mesh and mastic during curing