Builder’s Checklist for Step Code 4 Compliance

Key takeaway: Step 4 is not something you bolt on at the end. The decisions made before ground breaks determine 80% of your compliance outcome. Use this checklist phase by phase.

Phase 1: Pre-Construction

• Hire an energy advisor at design stage. Not after framing. They run the initial energy model and identify the most cost-effective path.
• Set targets. For CZ5: airtightness 1.5 ACH50, TEDI ~35 to 45 kWh/m2/year, MEUI varies by equipment.
• Simplify geometry. Every bump-out and bay window adds cost. Simple footprint = cheaper Step 4.
• Specify wall assembly. CZ5 typical: 2x6 + R-5 to R-8 continuous exterior insulation = R-22 to R-28 effective.
• Choose air barrier strategy. Interior poly, taped exterior sheathing, or liquid-applied membrane.
• Choose mechanical system. FortisBC hybrid pathway qualifies for $9,000 to $15,000 rebate.
• Budget. Add $17,000 to $33,500 over base code. After rebates: $5,000 to $20,000 net. See cost breakdown.

Phase 2: Foundation and Framing

• Sill gasket at foundation-to-framing. Continuous closed-cell foam or EPDM gasket.
• Bottom plate sealant on ALL plates. Exterior walls, interior partitions, closets, bathtub alcoves. No gaps.
• Rim joist sealing. 2 inches closed-cell spray foam minimum, or rigid foam sealed at edges.
• Thermal bridging mitigation. Continuous exterior insulation over sheathing with taped joints.
• Window rough openings. Flash with self-adhering membrane integrated with air barrier plane.

Phase 3: Insulation and Air Barrier

• Full cavity insulation. No voids or compression.
• Install primary air barrier. Poly: 6-mil, 4-inch overlap, taped seams. Sheathing: all joints and penetrations taped. Liquid-applied: continuous coverage.
• Seal ALL penetrations. Every wire, pipe, duct, and conduit through the air barrier.
• Seal electrical boxes in exterior walls with vapour barrier pads or airtight boxes.
• Seal plumbing penetrations. Pay attention to second-floor bathroom rough-ins hidden by tubs.
• Ceiling air barrier. Continuous before insulation is blown. AT-rated pot lights.

Phase 4: Mid-Construction Testing

• Schedule the blower door test. Book 2 to 3 weeks in advance.
• Walk the air barrier yourself before the energy advisor arrives.
• Attend the test. Walk with the advisor. Mark every leak.
• Interpret and act:
  • Below 1.5: proceed with drywall
  • 1.5 to 2.0: fix identified leaks, consider aerosol sealing
  • Above 2.0: do not proceed until major leaks are addressed

Phase 5: Mechanical Installation

• Install heat pump. Cold-climate rated to -25C for the Okanagan.
• Install and commission HRV. At 1.5 ACH50, the HRV is the building’s lungs. Balanced airflow, accessible filters.
• Seal all HVAC penetrations through the air barrier with mastic.
• Install water heater. Heat pump or high-efficiency gas per energy model.

Phase 6: Final Test and Compliance

• Complete all finishing. Trim, flooring, cabinetry.
• Prepare for final blower door test. Close all exterior doors/windows, open interior doors, seal intentional openings.
• Pass at 1.5 ACH50 or better. Energy advisor completes as-built compliance report.
• Submit FortisBC rebate application. Include as-built report, equipment invoices, commissioning sheet.

Common Pitfalls

• Energy advisor engaged too late. Post-framing involvement costs thousands in redesign.
• Underestimating the airtightness jump. 2.5 to 1.5 ACH50 is a 40% tighter target. Step 3 methods do not scale.
• Skipping mid-construction test. 3 to 10 times more expensive to fix after drywall.
• Oversizing mechanical equipment. A tight Step 4 home needs less heating capacity.
• Not training trades. A 15-minute site meeting on air barrier continuity prevents most problems.