Air Sealing Checklist for BC Step Code Compliance

This checklist is the field-level companion to our Step Code checklist. Where the Step Code checklist covers the project management workflow, this one covers the specific air sealing details that determine whether your home passes or fails the blower door test.

Print this checklist, tape it to your site trailer wall, and walk through it at each phase of construction. If your team ticks every box, you’re in good shape for Step Code 3. If you’re targeting Step 4 or 5, add AeroBarrier as your verification layer on top.

Phase 1: Foundation and Slab

The foundation-to-wall transition is one of the most common air leakage points in BC residential construction. Get it right before framing.

Foundation Walls

• Concrete foundation cured and broom-clean before sill plate installation
• Sill gasket (closed-cell foam) installed continuously under all sill plates
• Anchor bolts do not cut or tear sill gasket
• Any foundation penetrations (plumbing, electrical conduit) sealed with closed-cell spray foam or foundation sealant
• Form tie holes patched with hydraulic cement
• Weeping tile and foundation drainage do not compromise air barrier at interior side

Slab on Grade

• Vapor barrier continuous under slab (6 mil minimum) with taped seams
• Vapor barrier extended up exterior walls and taped to future air barrier location
• All slab penetrations (plumbing rough-ins) sealed at both vapor barrier and concrete pour stages
• Slab-to-wall connection detailed for air barrier continuity

Basement/Crawl Space

• Rim joist area accessible for air sealing after framing
• Closed-cell spray foam planned for rim joist (minimum 2 inches)
• Exterior below-grade insulation continuous with above-grade air barrier strategy
• Crawl space vents sealed or designed for conditioned crawl space

Phase 2: Framing

Framing is where the air barrier strategy has to be visible and intentional. Sloppy framing creates gaps that become expensive to fix later.

Wall Framing

• Exterior sheathing installed with sheathing tape on all vertical and horizontal joints
• Sheathing tape extends over corners and transitions without gaps
• Window and door rough openings sized correctly (not oversized) to reduce air gap
• Jamb extensions and rough bucks detailed for eventual flashing tape
• Electrical boxes on exterior walls specified as airtight (rated or retrofitted)
• Plumbing rough-ins planned for interior walls wherever possible to avoid penetrating the air barrier

Rim Joist

• Rim joist exposed and accessible
• Closed-cell spray foam applied to full rim joist depth (2 inches minimum)
• Foam continuous across all band joist corners
• Foam extended to sill plate and subfloor without gaps

Roof Framing

• Truss heels sized to allow full depth insulation over exterior wall top plates
• Attic access hatch location identified and detailed for air sealing
• Any roof deck penetrations (attic vents, plumbing stacks, chimneys) planned with air barrier in mind
• Cathedral ceiling assemblies have explicit air barrier strategy (interior or exterior)

Phase 3: Windows and Doors

Windows and doors are concentrated leakage points if rough openings and flashing aren’t detailed carefully.

Window Installation

• Rough opening flashing tape applied to sill, jambs, and head with proper lap sequence
• Sill flashing installed with back dam where applicable
• Window shimmed level and square
• Backer rod installed around window frame before sealant
• Sealant applied continuously around window frame at interior
• Sealant applied continuously around window frame at exterior (or per manufacturer spec)
• Window trim detailed to not block air barrier work
• Triple pane windows on colder-climate elevations where specified by energy model

Exterior Doors

• Door sill pan or sill flashing installed under threshold
• Door frame jambs and head sealed to rough opening
• Weatherstripping installed per manufacturer spec on all edges
• Threshold and bottom sweep adjusted for tight seal
• Exterior trim and casing detailed after air sealing is complete

Phase 4: Penetrations

This is where even diligent builders lose points. Every penetration through the air barrier is a potential leak.

Plumbing

• All plumbing stacks through the ceiling sealed at both top plate and roof deck
• Drain, waste, and vent pipes through exterior walls sealed at penetration
• Bathroom exhaust fan ducts sealed at ceiling penetration
• Dryer duct penetration sealed at exterior wall
• Refrigerator water line penetration sealed
• Dishwasher supply and drain sealed where passing through walls

Electrical

• All exterior wall electrical boxes airtight rated or caulked from back
• Cable and wire penetrations through top plates sealed with fire-rated foam
• Electrical panel interior gaps sealed behind cover
• Smoke detector, CO detector, and recessed light penetrations detailed
• Electrical conduit through foundation sealed at entry point

HVAC and Ducts

• Furnace flue and combustion air intake sealed at exterior wall and roof
• HRV/ERV intake and exhaust ducts sealed at penetrations
• Range hood duct sealed at wall or roof penetration
• Any duct boots at ceiling sealed to drywall surface
• Return air duct sealed at framing and penetrations
• Heat pump line set penetration through wall sealed with closed-cell foam

Structural

• Beam pockets and cantilever transitions sealed with spray foam
• Chase openings between floors sealed at the top and bottom
• Stair stringers and landing connections detailed for air barrier continuity

Phase 5: Attic Prep

Attic access and attic air barrier details often get forgotten because they’re above the ceiling.

Top Plate

• Interior partition wall top plates sealed to drywall ceiling
• Exterior wall top plate sealed to sheathing and to interior air barrier
• Continuous bead of sealant at drywall-to-framing connection before drywall is hung

Attic Hatch

• Attic hatch opening framed with raised curb (minimum 2 inches above ceiling plane)
• Hatch cover insulated to match attic R-value
• Weatherstripping gasket installed around hatch perimeter
• Latch or fastener compresses gasket for air seal

Attic Penetrations

• All wiring, plumbing, and duct penetrations through the ceiling sealed from above
• Recessed light housings are IC-rated and airtight
• Plumbing stacks sealed where they penetrate the ceiling drywall
• Bathroom fan housings sealed to ceiling drywall

Phase 6: Pre-Drywall Inspection and Testing

This is the single most valuable inspection point in the entire project. Walk the site with your checklist in hand before drywall goes up.

Site Walk

• Air barrier clearly identifiable (sheathing + tape, or interior poly, or both)
• No visible gaps in sheathing tape or corner details
• All penetrations visibly sealed
• Rim joist spray foam complete and continuous
• Window flashing tape visible and properly lapped
• No tears or damage to air barrier materials

Pre-Drywall Blower Door Test

• Energy advisor or AeroBarrier technician scheduled for pre-drywall test
• All penetrations temporarily sealed for test day
• Interior doors open, exterior doors closed
• HVAC off
• Test result documented

Kelowna mid-construction rebate: City of Kelowna offers a $325 mid-construction test rebate (max 3 per builder per year) specifically to incentivize this step.

Phase 7: Drywall and Finishes

Drywall is your interior air barrier in many assemblies. Details matter here too.

Drywall Installation

• Continuous sealant bead at top plate and bottom plate before drywall is attached
• Drywall screws tight but not over-driven
• No uncorrected gaps at top of wall or corners
• Taped and mudded before any trim installation

Finish Trim

• Baseboard and casing do not hide unsealed gaps
• Interior door trim does not compromise frame-to-wall seal
• Any post-drywall electrical box adjustments sealed

Phase 8: Final Test Preparation

The day before the final blower door test, walk through and confirm:

• All exterior doors and windows closed and latched
• Range hood, bathroom fans, dryer vents closed
• Fireplace dampers closed
• Interior doors open
• HVAC off
• No construction debris blocking air movement
• All penetrations verified sealed

For Projects Targeting Step 4 or 5

If your project targets 1.5 ACH50 or lower, add these to the baseline checklist:

• AeroBarrier applied at pre-drywall stage as aerosol sealing layer
• All wall assemblies inspected with continuous air barrier documentation
• Triple-pane windows on north and high-exposure elevations
• Mechanical systems coordinated with air barrier penetrations (HRV/ERV instead of traditional bath fans where possible)
• Energy advisor modeling verified against actual construction at key phase reviews

Frequently Asked Questions

Can I download this checklist?

Copy the page and print it, or save it as a bookmark. We’re working on a downloadable PDF version. In the meantime, this page is optimized to print cleanly from a browser.

Who should use this checklist - the builder or the trades?

Both. The general contractor walks through at each phase inspection. Each trade should understand the items relevant to their scope. The air sealing specialist (if using AeroBarrier) uses the pre-drywall and final test items for their work.

What’s the single most important item on this list?

If you can only focus on one, it’s the pre-drywall blower door test. It catches everything else you might have missed, and gives you a chance to fix problems while they’re still cheap.

How does this checklist apply to retrofits?

For retrofit air sealing, focus on the penetrations section and the attic prep section. Wall assemblies in existing homes are harder to address without opening drywall, but attic and penetration detail work can make a big difference. See our retrofit air sealing service.

Do I need all of this for Step 3?

Most of it, yes. Step 3 at 2.5 ACH50 is achievable with traditional methods and disciplined execution. Missing any category on this checklist can push you over the target. Step 4 at 1.5 ACH50 adds the AeroBarrier insurance layer because the margin for error is smaller.

What if my blower door test still fails after completing this checklist?

Call us. Okanagan AeroBarrier Inc. handles blower door test rescues regularly. AeroBarrier can often seal hidden leaks that this checklist couldn’t catch because the leak is behind finished drywall.

Next Steps

This checklist is most valuable when it’s used, not just read. Print it. Walk through it. Train your trades on the items relevant to their work.

If you want help implementing a reliable air sealing strategy from day one, call 250-864-8727 or get a free consultation. Okanagan AeroBarrier Inc. provides Step Code compliance support across the BC Interior.