3.1602.21 Air Sealing System—Mid and High Rise

Topic: 
Ducts
Subtopic: 
Duct Sealing
Desired Outcome: 
Ducts and plenums are sealed to prevent leakage
TitleSpecification(s)Objective(s)
3.1602.21a
New component to new component sealant selection

Any closure system used will meet or exceed applicable standards

Ensure effectiveness of air sealing system

3.1602.21b
New component to existing component

Seams, cracks, joints, holes, and penetrations less than 1/4" will be sealed using fiberglass mesh and mastic

Mastic alone will be acceptable for holes less than 1/4" that are more than 10' from air handler

Seams, cracks, joints, holes, and penetrations between 1/4" and 3/4" will be sealed in two stages:

  • They will be backed using temporary tape (e.g., duct 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 the seal

Support the mastic and fiberglass mesh during curing

3.1602.21c
Existing component to existing component

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

Fiberglass mesh and mastic will become the primary seal

Seams, cracks, joints, holes, and penetrations larger than 3/4" will be repaired using rigid duct material

Eliminate air leakage into or out of ducts and plenums

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

Reinforce the seal

Support the mastic and fiberglass mesh during curing