Step Code 4 Is 8 Months Away. Here’s What Changes for Your Builds.

Step Code 4 is expected to become the provincial minimum for Part 9 residential buildings in January 2027. That is roughly eight months from today. If you are a builder in the Okanagan or anywhere in BC’s interior, this is not a distant policy change. It is your next permit cycle.

The reality is that most builders in the Okanagan have not yet completed a single project at Step 4. The majority of new homes being permitted right now still target Step 3 compliance. That gap between where most builders are and where they need to be is closing fast.

This article breaks down exactly what changes, why the airtightness jump from Step 3 to Step 4 is the hardest part, and what you should be doing right now to avoid scrambling in January.

What Changes from Step 3 to Step 4

Step Code 4 tightens every major performance metric. This is not a minor bump. It is a meaningful shift in how you design, insulate, seal, and condition a home.

Here is what the numbers look like for Climate Zone 5 (Kelowna, West Kelowna, Vernon, Kamloops, Penticton, Lake Country):

Airtightness: ACH50

Step 3: 2.5 ACH50 maximum
Step 4: 1.5 ACH50 maximum

That is a 40% reduction in allowable air leakage. At 2.5, a careful crew with good detailing can get there consistently. At 1.5, every missed penetration, every unsealed top plate, every gap behind a bathtub drain becomes a potential blower door failure.

For a deeper look at what each step requires, see the full Step Code 4 overview.

TEDI (Thermal Energy Demand Intensity)

Step 3: Approximately 50 kWh/m2/yr in CZ5
Step 4: Approximately 35 kWh/m2/yr in CZ5

TEDI measures how much energy the building envelope needs to maintain stable interior temperature. Hitting the Step 4 target means your walls, roof, and foundation need to do significantly more work. In practice, this pushes most builders toward continuous exterior insulation as a standard part of their wall assembly. For strategies on wall design, see the wall assemblies guide.

MEUI (Mechanical Energy Use Intensity)

Step 3: Approximately 55 kWh/m2/yr in CZ5
Step 4: Approximately 40 kWh/m2/yr in CZ5

MEUI captures total mechanical energy use: heating, cooling, ventilation, and domestic hot water. The drop from 55 to 40 effectively requires a heat pump for space heating. A standard gas furnace will not get you there. High-efficiency water heaters (heat pump water heaters or drain water heat recovery) also become part of the conversation.

For equipment selection guidance, see the HVAC for Step Code guide.

HRV Efficiency

At Step 4, your HRV needs to deliver 75% or higher Sensible Recovery Efficiency (SRE). Many budget HRV units fall short of this. If you are still spec’ing the same unit you used at Step 3, check the rating. Your energy advisor can model the impact of different HRV options on your overall MEUI.

Continuous Exterior Insulation

While not explicitly mandated as a prescriptive requirement, continuous exterior insulation becomes effectively standard at Step 4. Without it, meeting TEDI in Climate Zone 5 is extremely difficult. Most energy advisors will model at least 1.5 inches of exterior mineral wool or rigid foam as part of a Step 4 wall assembly.

Why 1.5 ACH Is a Different Game

This is where most builders hit the wall. The jump from 2.5 to 1.5 ACH50 is not linear in difficulty. It is exponential in precision.

At 2.5 ACH50, you can achieve compliance with careful caulking, taping, and spray foam at key penetrations. A good crew that follows the air barrier plan will pass the blower door test most of the time.

At 1.5 ACH50, “most of the time” is not good enough. Every electrical box, every plumbing penetration, every framing intersection, every window rough opening, and every duct boot needs to be sealed with intention. A single missed area can push you from 1.4 to 1.7, and suddenly you are looking at remediation.

For the most common failure points, see the common air leaks guide.

How to Hit Step Code 4 in BC: Air Sealing Method Comparison

The best way to improve ACH50 for Step Code depends on your budget, your timeline, and how much risk you are willing to accept on blower door day.

Here is how the three primary methods compare:

Method	Typical ACH50	Step 3 (2.5)	Step 4 (1.5)	Time	Cost
Caulk + tape	1.8 - 3.5	Usually	Rarely	2-3 days	$500 - $1,500
Spray foam + detailing	1.0 - 2.5	Yes	Sometimes	1-2 days	$1,500 - $3,000
Aerosol sealing (AeroBarrier)	0.5 - 1.2	Yes	Yes	2-4 hours	$2,500 - $4,500

For a full comparison of sealing approaches, see the air sealing methods page.

AeroBarrier vs Traditional Air Sealing BC

The core difference between aerosol sealing and traditional methods comes down to consistency. Manual sealing depends on crew skill, attention to detail, and the ability to find every gap in a complex 3D structure. Aerosol sealing pressurizes the building and lets aerosolized sealant find and fill gaps automatically, regardless of where they are.

For Step 3 at 2.5 ACH50, traditional methods work well enough for experienced crews. For Step 4 at 1.5 ACH50, the margin for error disappears. Aerosol sealing removes the guesswork.

Key differences at a glance:

Consistency: Aerosol sealing delivers sub-1.5 ACH50 reliably. Manual methods vary by crew and project.
Speed: AeroBarrier takes 2 to 4 hours. Manual sealing and detailing takes 2 to 3 days.
Verification: Aerosol sealing includes real-time blower door monitoring during the process. You know your number before the crew leaves.
Risk: Manual sealing carries meaningful risk of blower door failure at 1.5 ACH50. Aerosol sealing carries very low risk.

For more on the blower door testing process, see the blower door testing guide.

The Cost Math: Why Aerosol Sealing Pays for Itself

Let’s look at the actual numbers for air sealing cost for Step Code 4.

AeroBarrier Cost

A typical AeroBarrier application for a single-family home in the Okanagan runs $2,500 to $4,500, depending on house size and complexity. This is a one-time cost during the construction phase, typically applied after rough-in and before drywall.

Failed Blower Door Remediation

If you go the traditional route and fail your blower door test, remediation is expensive. Tearing back drywall to access air barrier failures, re-sealing, and re-testing typically costs $3,000 to $10,000. That does not include the schedule delay, which can ripple through your entire project timeline.

FortisBC Rebates at Step 4

FortisBC offers performance-based rebates that increase with each step level. At Step 4, builders can access $9,000 to $15,000 in rebates depending on the specific program and home configuration. These rebates are available to the builder or homeowner and can be factored into your project budget from day one.

For current rebate details and eligibility, see the FortisBC rebates page.

Net Cost Analysis

Here is how the math works for a typical Step 4 build:

Item	Cost
AeroBarrier application	$2,500 - $4,500
FortisBC Step 4 rebate	($9,000) - ($15,000)
Net position	($4,500) - ($12,500) ahead

Aerosol sealing pays for itself through rebate capture alone. The rebate at Step 4 more than covers the cost of AeroBarrier, and you avoid the risk of failed blower door remediation entirely.

Use the rebate calculator to model the numbers for your specific next build.

How to Pass Blower Door Test Step Code 4

Passing the blower door test at 1.5 ACH50 comes down to three things:

Design for airtightness from the start. Work with your energy advisor at the design stage, not after framing.
Seal every penetration. Use the common air leaks checklist to identify and address every failure point.
Consider aerosol sealing. If your target is 1.5 ACH50 or below, aerosol sealing is the most reliable path to a first-time pass.
Run a mid-construction blower door test. Test before drywall so you can address issues while the air barrier is still accessible.

What Builders Should Do Now

Do not wait until January. The builders who will transition smoothly to Step 4 are the ones who start preparing now. Here is your action list for the next eight months.

1. Build One Step 4 Project Before the Mandate Hits

The single best thing you can do is complete one home at Step 4 before it becomes mandatory. You will learn where your current processes fall short, which trades need additional training, and what the real cost delta looks like for your specific build type. Treat it as a learning build.

2. Engage an Energy Advisor at Design Stage

At Step 4, the energy advisor cannot be an afterthought. They need to be involved during schematic design so they can optimize the building shape, window placement, and mechanical strategy before you commit to a floor plan. Find a qualified advisor through the energy advisor guide.

3. Budget for Aerosol Sealing from Day One

If you plan to use AeroBarrier or a similar aerosol sealing system, build that cost into your project budget from the start. Do not treat it as a contingency. At Step 4, it is a planned line item. The FortisBC rebate more than offsets the cost, but you need to account for the upfront spend.

4. Use the Rebate Calculator to Model Your Next Build

Run the numbers before you commit to a design. The rebate calculator shows you exactly what incentives are available at each step level and how different equipment choices affect your total cost.

5. Run a Mid-Construction Blower Door Test

A mid-construction test at the pre-drywall stage gives you a chance to find and fix air leakage before the walls are closed. This is inexpensive insurance. If your air barrier has a weak spot, you want to know before drywall, not after. For more on testing timing, see the blower door testing guide and the pre-drywall air sealing guide.

Municipality Notes: Where You Are Building Matters

All of the major Okanagan and interior municipalities fall within Climate Zone 5. The Step 4 targets listed in this article apply to:

Some municipalities on the coast are already enforcing Step 4 or higher. Vancouver and Whistler have been operating at Step 4 levels for some time. If you work across regions, check the specific requirements for each municipality.

For a complete list of municipal requirements and timelines, see the Step Code timeline page.

The Bottom Line

Step Code 4 is expected in January 2027. Eight months is enough time to prepare if you start now. It is not enough time if you wait until permits start getting rejected.

The biggest challenge for most builders will be airtightness. Going from 2.5 to 1.5 ACH50 is a 40% reduction that changes how you approach air sealing. The most reliable path is aerosol sealing, which pays for itself through FortisBC rebates and eliminates blower door failure risk.

Build one Step 4 home now. Learn the process. Lock in your air sealing approach. When January hits, you will be ahead of every builder who waited.

Use the rebate calculator to see how Step 4 affects your next project, or check the full Step Code 4 requirements for a detailed breakdown of every compliance metric.