No, the BC Building Code Does Not Require an HRV

What the code actually says

The relevant text is Section 9.32 of Division B of the BC Building Code 2024. Article 9.32.3.1 sets the requirement: "Every dwelling unit that is supplied with electrical power shall be provided by a mechanical ventilation system that conforms to a) CAN/CSA-F326-M, 'Residential Mechanical Ventilation Systems,' b) this Subsection, or c) for ducted mechanical ventilation systems serving more than one dwelling unit in a house with a secondary suite ... Part 6."

Read that carefully. The requirement is a mechanical ventilation system. The word ventilator appears nowhere in it, and neither does heat recovery. What the code demands is that the house move air on purpose using a machine, to a specified rate, controlled by the occupant.

The confusion is understandable. Almost every new house on the North Shore ends up with an HRV, so people reasonably conclude the code made them do it. Something else made them do it, and we will get there.

The four compliant paths

Article 9.32.3.4.(1) is the sentence that settles the argument. It says "a principal ventilation system shall mechanically provide supply air in accordance with Sentence (2), (3), (4) or (5)." Four sentences follow, and each one describes a different legal way to build the system.

Two of those four involve no heat recovery whatsoever. A ducted forced-air heating system on its own is a compliant principal ventilation system. So is a ducted central-recirculation ventilation system. Neither one recovers heat from the exhaust stream, and both satisfy the code.

The code gives you four legal options for the supply air side of the system, and heat recovery appears in two of them. A designer choosing an HRV is making a design decision, and it is a defensible one on the North Shore for reasons that come later in this post.

The principal ventilation fan, and why yours is labelled

Whichever of the four paths you take, Article 9.32.3.3 requires a principal ventilation fan. Article 9.32.3.5 tells that fan how to behave: it "shall a) run continuously, and b) provide at least the air-flow rate specified in Table 9.32.3.5."

Continuously means continuously. Not on a timer, not when someone remembers. The code anticipates that homeowners will find this irritating, which is why it also caps the noise. Sound from the principal ventilation fan "shall not exceed 1.0 sone." And the fan needs a dedicated on and off switch, placed where it is "not likely to be turned off inadvertently" and "clearly marked 'PRINCIPAL VENTILATION EXHAUST FAN.'"

That labelled switch is one of the more human things in the building code. Someone sat in a committee and worked out that people turn off machines that hum, so the machine has to be quiet and its switch has to announce what it is. On the projects we run, this is still the single most common source of confusion at handover. The homeowner finds a switch running something they cannot identify, flips it off, and six months later has condensation on the windows.

The air-flow rate itself is a lookup, not a fixed number. Table 9.32.3.5 sets the rate by floor area and bedroom count, running from 14 L/s for a home under 140 square metres with zero or one bedroom, up to 78 L/s for a home over 700 square metres with eight or more bedrooms. Rates are measured at 50 Pa external static pressure, which matters because a fan rated at free air and a fan rated against real ductwork are very different machines. Table 9.32.3.6 adds the local exhaust requirements: 47 L/s intermittent for a kitchen, and for a bathroom either 23 L/s intermittent or 9 L/s continuous.

• The principal ventilation fan runs continuously, not on demand
• Maximum 1.0 sone, so it is quiet enough that nobody wants it off
• A dedicated switch, labelled PRINCIPAL VENTILATION EXHAUST FAN
• Rate comes from Table 9.32.3.5 by floor area and bedroom count, 14 to 78 L/s
• Rated at 50 Pa external static pressure, against real duct resistance

Why mechanical ventilation became mandatory at all

The code explains its own reasoning here, and the explanation is the most useful paragraph in the whole section for a homeowner. Note A-9.32.3 says: "Previous editions of the British Columbia Building Code relied on ventilation through the building envelope in combination with a principal exhaust fan. However, with the increased attention on the continuity of the air barrier system in buildings, builders can no longer rely on uncontrolled ventilation through the building envelope."

In plain terms: old houses leaked, and the leaking was doing a job. Air moved in through gaps around windows, through the rim joist, through every unsealed penetration, and that accidental air exchange carried moisture and stale air out. Nobody designed it. It just happened, and it was enough.

Then the industry got good at air sealing. The gaps closed. The accidental ventilation stopped, and nothing replaced it unless someone put a machine in.

We see the consequence on North Shore renovations regularly, and it always arrives the same way. A 1970s house in Lynn Valley or Edgemont gets new triple-glazed windows, spray foam in the rim joist, and proper air sealing at every penetration. The heating bill drops, which is what the owner wanted. Then in November the windows start streaming, there is mould on the closet wall on the north side, and the bathroom takes two days to dry out. Nothing broke. The leaks that used to ventilate the house by accident are gone, and no mechanical system was added to replace them.

Does the Step Code force an HRV? No article says so

This is the second half of the myth, and it is equally worth clearing up. No article of the Step Code names a heat recovery ventilator or requires one.

Steps 3, 4 and 5 are performance targets. They are expressed as an airtightness level, a mechanical energy use intensity, and a thermal energy demand intensity. How you hit those three numbers is left to the design team. Heat recovery appears in the code only as an input to the energy model, under Sentence 9.36.6.2.(3)(f), listed among the things the modelling has to account for: "heat recovery from exhaust ventilation."

So the honest position is that the Step Code creates the conditions in which an HRV is the sensible answer without ever mandating one. The strongest official support for the practical claim comes from the Province's own costing work. The BC Energy Step Code Best Practices Guide v3.0, published in June 2024, assumes that "typically one heat recovery ventilator is needed per home regardless of size." That is the Province budgeting for an HRV in every home, in a document about how much the steps cost to reach. It is an assumption rather than a requirement, and that distinction is the whole point of this post.

It also explains why the myth spreads. The Province expects one. Designers specify one. Energy modellers model one. Nobody along that chain is wrong. The sentence that gets lost is the one that says you are allowed to solve it another way if your energy model works out.

Airtightness levels, and why the numbers do not line up

Airtightness is where the Step Code and ventilation meet. Subsection 9.36.7 sets how tightness is tested and how tight is tight enough for each step.

Testing is prescribed in Article 9.36.7.3 as "a multi-point depressurization test carried out in accordance with CAN/CGSB-149.10." That is a blower door test, run by a certified energy advisor with a fan sealed into an exterior door, measuring how much air the house leaks at a set pressure.

The maximum permitted values sit in Table 9.36.7.4, and there is a naming quirk worth knowing before you read it. The airtightness levels are labelled AL-1, AL-3 and AL-4. There is no AL-2, and the level numbers do not correspond to the step numbers. Step 3 uses AL-1. Step 4 uses AL-3. Step 5 uses AL-4. We have watched more than one experienced person misread that table because the numbers look like they should match and they do not.

What the District of North Vancouver requires, which is the number that governs here

Step 3 has been the province-wide minimum for Part 9 buildings since May 1, 2023. Information Bulletin B23-01 put it plainly: "it will no longer be necessary for local authorities to adopt by bylaw either the Step 3 standard for Part 9 buildings ... as these standards will become universally applicable province-wide as the new minimum acceptable standard." Emissions Level 1 of the Zero Carbon Step Code became mandatory province-wide on March 10, 2025 through Ministerial Order BA 2024 05.

The District of North Vancouver went further. Its own Zero Carbon information guide states: "On July 24, 2023, Council adopted new requirements that increase the minimum performance level for new Part 5 and Part 9 homes to Step 4 and align the District's low carbon compliance pathway with Emissions Level 3 of the Zero Carbon Step Code." Since November 1, 2023, a new Part 9 home in the District must meet Step 5, or Step 4 combined with Emissions Level 3.

Put that next to Table 9.36.7.4 and you get the number that matters. The Step 4 route means AL-3, a maximum of 1.5 ACH50. The Step 5 route means AL-4, a maximum of 1.0 ACH50. Either way a new Part 9 home in the District is a full step tighter than the provincial floor of 2.5 ACH50.

At 1.5 air changes per hour, and certainly at 1.0, the house has almost no accidental air exchange left. Note A-9.32.3 describes exactly this condition. Meeting the required continuous ventilation rate through a system with no heat recovery means throwing conditioned air out of a house that was built expensively tight, and the energy model tends to reflect that. An HRV recovers most of the heat from that exhaust stream. That is why it wins here. No article names it. The airtightness requirement makes it the answer.

That is the whole resolution of the myth. The code gives you four legal options. The tightness the District demands narrows them, in practice, to the two involving heat recovery. If you are building in the City of North Vancouver or West Vancouver, confirm the current step and emissions level directly with the municipality, because each one sets its own and they change.

Renovations: the code applies, but there is no dollar trigger

The question we get asked most often is whether a renovation pulls the house into these requirements. People expect a threshold, some percentage of the home's value or a dollar figure above which the rules switch on. There is no such number in the BC Building Code, and the Province says so directly.

The code does apply to alterations. Division A, Sentence 1.1.1.1.(1) says the Code applies to "a) the design and construction of a new building ... d) an alteration of any building, e) an addition to any building." An alteration is in scope.

What happens next is discretion. Information Bulletin B23-01, issued May 1, 2023, states: "Discretion and judgement must be exercised by designers and enforcement officials when applying the acceptable solutions in Division B to the alteration to an existing building... Each alteration to each existing building requires unique consideration. As outlined in Division A, it is up to the local governments that administer and enforce the BCBC to determine what is appropriate and practical on a case-by-case basis."

That is the honest answer, and it comes from the Province rather than from us. Your building official decides what is appropriate and practical for your specific alteration. A bathroom refresh and a full envelope retrofit with new windows are different conversations, and the same municipality can reasonably reach different conclusions on each.

Our practical advice for a deep energy retrofit is to raise ventilation at the design stage rather than at inspection. If the scope includes new windows, envelope air sealing, or insulation upgrades across most of the house, the physics from Note A-9.32.3 will apply to your house whether or not the building official asks about it.

Secondary suites, and the smoke control problem

A second widespread belief is that adding a secondary suite means adding a second ventilation system. The code does not require that.

What it does require is that a shared system handle smoke. Sentence 9.32.3.2.(4) states: "In a house with a secondary suite ... where a heating or ventilation system serves more than a single dwelling unit, the system shall be designed and installed to prevent the circulation of smoke upon a signal from a duct-type smoke detector." Share the ductwork between the main house and the suite, and you have taken on a smoke control obligation.

The code's own commentary is unusually frank about the tradeoff. Note A-9.32.1.2.(2) says: "Although providing a second ventilation system to serve the two dwelling units is expensive, and potentially difficult in an existing building, it is an ideal solution for achieving a minimum acceptable level of fire safety. Other solutions ... must address smoke control. Although smoke dampers restrict the spread of smoke ... their installation ... is not considered to be an ideal solution because they are very expensive, require regular inspection and maintenance, and must be reset after every activation."

Read that as a warning about lifetime cost. Separate systems cost more up front. Dampers cost more up front than most people expect, plus inspection, plus maintenance, plus a reset every time they trip. On a suite conversion where the ducting is being redone anyway, separating the systems is often the cheaper decision over ten years.

One more finding worth stating, because it surprises people. Table 1.1.1.1.(6) sets out alternate compliance methods for adding a secondary suite to an existing house, and it relaxes several things: ceiling heights drop from 2.1 m to 1.95 m, doorway sizes ease, and there are alternate provisions for fire ratings and sound. We went through all nine rows. None of them relax ventilation. The suite gets the same ventilation requirements as any other dwelling unit.

What actually makes an HRV hard in an existing house

For a new build, none of this is difficult. The ducts get designed before the framing goes up and the HRV takes its place alongside everything else.

In a finished house, the unit is the easy part. Routing is the hard part. An HRV needs supply runs to bedrooms and living areas and exhaust runs from bathrooms, kitchen, and laundry, and every one of those runs has to find a path through a house that has drywall on it. On the North Shore that usually means a 1960s or 1970s home with a low crawlspace, joists running the wrong way, and a finished basement ceiling that somebody would rather not open.

This is what drives the cost, and occasionally it decides feasibility. We have priced the same model of HRV into two houses on the same street and had the installed cost differ by a factor that had nothing to do with the equipment. One had an unfinished basement and a mechanical room in a sensible place. The other had a finished lower suite, a coffered ceiling in the main living space, and no chase between floors.

So if you are planning a whole-home renovation and expect to add ventilation, work it out before the drywall goes back on. Ventilation routing has to be sequenced with the framing and the finishing, and it is the item most often left until the point where every good path is already closed.