Static field route #350

What do I do when thinking insulation fixes air leakage instead of sealing duct first?

Insulation, Liner, Vapor Barrier & Condensation.1 field-polished — insulation/rated-detail check

Insulation does not fix duct leakage. Seal/test the duct first, then insulate once the air boundary is ready.

Open in Field Rescue Open category

Field checklist

Check whether the duct joint/collar/seam is sealed before wrap.
Look for missed backsides and hidden corners.
Ask if pressure/leakage testing is required before insulation.
Hold wrap if insulation would hide an unsealed leak path.

Ask foreman

Before I insulate this, is the duct sealing/testing cleared? I don't want to cover a leak path.

Do not

Do not use insulation as an air seal.

Why it matters

Insulation affects access, vapor barrier, condensation control, inspections, TAB/service access, and finished-work quality. Project specs and manufacturer details still control.

Search words: insulation liner vapor barrier misunderstanding