Insulation Tape Fishmouths
Fishmouths in foil/FSK tape open the vapor barrier and can let moisture reach cold duct surfaces.
What This Helps With
Fishmouths in foil/FSK tape open the vapor barrier and can let moisture reach cold duct surfaces.
Apprentice words: fishmouth tape, FSK tape wrinkle, insulation tape seam, vapor barrier patch
Common problem: Tape wrinkles, lifts at corners, or bridges over seams instead of sealing tight.
Check First
What Not To Do
Do not tape over dust, oil, wet insulation, or loose facing. Do not leave fishmouths because 'it looks close enough.'
What can go wrong: Tape wrinkles, lifts at corners, or bridges over seams instead of sealing tight.
Better Foreman Question
Do you want this insulation tape seam reworked where it fishmouthed, or is there a required patch method?
Verify With
Source to verify: Insulation manufacturer instructions, project insulation spec
Safe wording: Tape type and overlap depend on insulation facing and project spec.