3.1602.11 Air Sealing System

Topic: 
Ducts
Subtopic: 
Duct Sealing
Desired Outcome: 
Ducts and plenums sealed to prevent leakage
TitleSpecification(s)Objective(s)
3.1602.11a
New component to new component sealant selection

Any closure system used will meet or exceed applicable standards

Ensure effectiveness of air sealing system

3.1602.11b
New component to existing component

Duct surface to receive sealant will be cleaned

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

Holes greater than ¾" will be patched with metal or joint will be rebuilt to reduce the gap size

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 before 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 (fiberglass mesh and mastic) to the duct

Reinforce seal

Support mastic and fiberglass mesh during curing

3.1602.11c
Existing component to existing component

Duct surface to receive sealant will be cleaned

Fiberglass mesh and mastic will overlap temporary tape by at least 1" on all sides

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

Fiberglass mesh and mastic will overlap repair joint by at least 1" on all sides

Fiberglass mesh and mastic will be the primary seal

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 mastic and fiberglass mesh during curing

3.1602.11d
Performance testing

Pre- and post-retrofit duct leakage will be performance tested using a duct blaster or pressure pan, and results will be documented and reported to the homeowner and/or program

Document post-retrofit duct leakage performed