Field & trade terms
Air barrier
An air barrier is the continuous layer that stops air from passing through the enclosure — sheet, membrane, sealed sheathing or the right combination, joined so it forms one unbroken plane around the conditioned space. Air carries far more moisture and energy than diffusion ever does, so a leaky enclosure both wastes conditioning and drives hidden condensation. Unlike a vapor retarder, which slows diffusion, the air barrier's whole job is continuity: it only works if every joint, seam and hole is sealed.
How it shows up on site
The air barrier is the taped sheathing seams, the sealed sheet, the transition membranes at slab, roof and openings, and the sealant around every pipe, conduit and duct that punches through. Its weak points are exactly the transitions — where one material hands off to another and where the trades put their holes.
What an inspector looks at
The check is continuity: are seams and laps sealed, are transitions detailed and taped, is every penetration closed, and does the plane actually connect from foundation to roof without a gap left for later. Gaps behind soon-to-be-covered assemblies get the hardest look.
Because RTI closes items on a photo, the air barrier is documented while it's reachable — sealed seams, transition details and penetration seals shot before cladding, insulation or finishes make them impossible to verify.
Standards it's verified against
Checklists that put air barrier to work
Free, field-ready checklists, each with the photo every item needs before it can be submitted.
Related terms
- Vapor barrierA sheet material that limits how much water vapor diffuses through an assembly, placed to keep condensation from forming inside the wall or floor.
- FlashingThin sheet material lapped into an assembly to direct water back out at joints, edges and openings before it can get behind the finish.
- PenetrationAny point where a pipe, conduit, duct or cable passes through a wall, floor or roof — a hole that has to be sealed back to match the assembly it crosses.
- MEP (mechanical, electrical, plumbing)The mechanical, electrical and plumbing trades — the systems run through a building's structure that get inspected at rough-in and again at final.
- FirestoppingSealing openings where pipe, conduit or cable pass through a fire-rated wall or floor so the assembly's rating is restored.
- Backflow preventionA device or assembly that keeps used or contaminated water from reversing back into the potable supply through a cross-connection.
Knowing the term is step one. Proving it is the job.
RTI holds the submit button until every mandatory item is answered and the photos are attached, then chains the record so it can be proven untouched later.