Installation of a vänEE AI Series V230H75RT air exchanger (Virtuo Air Technology) in Hinchinbrooke, Haut-Saint-Laurent Township

A 231 CFM HRV suspended from the joists of an unheated utility room: the project that changes the usual rules

At Hinchinbrooke, the house did not present a sizing problem. It presented a location problem. The only available space for a central air exchanger was in a utility room with exposed framing, adjoining a finished room, without continuous insulation around the perimeter and with no guarantee that the ambient temperature would remain above freezing during a February cold snap in Montérégie.

Installing an HRV in such a space is neither prohibited nor unusual. It is simply an installation where four technical decisions—suspension, duct insulation, drainage protection, and defrost mode selection—cease to be execution details and become the system's survival requirements. At AirGreen, we approach this type of space exactly as we approach a bungalow attic in Repentigny or a condo service cavity in Griffintown: assuming the room will freeze, then building the system so that this has no consequences.

Sizing: why 231 CFM instead of 150

The V230H75RT covers a range of 65 to 231 CFM at 0.2 in. w.g. and maintains 65 to 225 CFM at 0.4 in. w.g.—a drop of barely 6 CFM under doubled resistance. This performance matters more than the maximum advertised figure.

In a system run over long distances, with insulated flexible ductwork and several elbows, the actual static pressure quickly rises beyond the reference value of 0.2 in. w.g. A unit whose performance curve collapses between 0.2 and 0.4 in. w.g. delivers, once installed, airflow far below what the specifications suggested. This is the most common difference between an HRV on paper and an HRV in a home.

A clarification about BTUs

Homeowners often ask us about the BTU output of their air exchanger. The question is understandable, but it does not apply: an HRV does not produce heat. It transfers heat from outgoing air to incoming air through a core. Its performance is therefore measured in CFM (the volume processed) and sensible recovery efficiency (SRE)—never in BTUs. A unit that listed a BTU output would be an electric duct preheater, a separate accessory we discuss further below.

The V230H75RT data we validated

The 67% SRE at −25 °C is the figure that justifies using this unit in this area. Despite its southerly latitude, the Haut-Saint-Laurent experiences nights below −25 °C every winter. An HRV that retains two-thirds of its recovery at that temperature avoids turning mandatory ventilation into an additional heating load.

Recirculation defrosting: the technical reason for the choice

There are two strategies for preventing the core from freezing. They are not equally suitable in every context.

Exhaust defrosting temporarily stops the intake of outdoor air and lets indoor air pass through the core to defrost it. Simple and economical—but it creates negative pressure in the house during each cycle.

Recirculation defrosting, selected here, closes a motorized damper and circulates indoor air in a loop through the unit. The house remains pressure-balanced throughout the cycle.

This difference becomes critical as soon as a combustion appliance shares the living space: a wood stove, fireplace, or naturally vented water heater. Repeated negative pressure during the coldest periods of winter is precisely the condition that promotes combustion-gas backdrafting. In the rural Haut-Saint-Laurent area, where supplemental wood heating remains common, we systematically favor recirculation.

Suspension: decouple first

When loaded, the unit weighs approximately 50 lb. It is suspended from the joists by chains at all four anchoring points specified by the manufacturer, with eye hooks screwed into solid wood—never into lath, and never into an engineered structural member without validation.

The chain lengths were adjusted so that the cabinet was perfectly level along both axes. On a unit with recirculation defrost, this level determines whether condensate flows properly toward the intended drainage outlets rather than into the bottom of the cabinet.

Chain decoupling serves a second, less obvious purpose: at 231 ft³/min, two ECM motors running continuously generate a low but permanent structural vibration. Rigidly attached to a floor joist, this vibration is transmitted into the room above and manifests as a hum that the homeowner eventually deals with by turning the unit off.

The ducts: insulation is not optional here

The visible network combines 6 in insulated flexible duct with galvanized rigid duct. This mixed approach is deliberate:

• Rigid duct on straight sections and main runs, to minimize pressure loss.
• Insulated flexible duct on connections and direction changes near the unit, to absorb fan noise and avoid tight sheet-metal bends.

In an unheated mechanical room, all four ducts must be insulated, not just the two that run outdoors. This is the nuance we correct most often during construction rework. The distributed fresh-air duct carries air at 5 or 8 °C in January; if it passes through a room at 2 °C without a continuous vapor barrier, it condenses on its outer wall, and the water falls onto the ceiling of the room below.

Sealing, in order

1. Slide the flexible duct over the rigid collar by at least 2 in.
2. Tighten a metal clamp, not just a plastic cable tie.
3. Seal the joint with approved aluminum tape or duct adhesive.
4. Bring the insulation and vapor barrier over the joint, then seal the vapor barrier separately.

Step 4 is the one people skip. It is also the one that determines whether the duct condenses or not.

Drainage in a room that may freeze

The V230H75RT drains its condensate through two outlets joined to a common drain. In a room where the temperature is not guaranteed, three measures are added to the standard installation:

• Primed trap on every outlet; otherwise, the exhaust fan's negative pressure draws air through the drain.
• Short, continuous slope to the drain. Every horizontal length of pipe in a cold area is a potential freezing point.
• Insulate the drainage tube along its entire exposed length, or route the tube through the heated space as soon as possible.

A drain frozen in January does not trigger an alarm. It shows up as water overflowing from the cabinet and appearing two weeks later as a stain on the ceiling.

The control housing and automatic balancing

The metal housing with an LCD screen and navigation buttons, mounted on the side of the unit, provides access to the Virtuo Air Technology platform functions: ventilation mode selection, maximum and minimum airflow adjustment, airflow test initiation, and diagnostic readings.

This test replaces manual balancing with a manometer. The unit electronically measures the actual airflow of each fan in the network as built, then adjusts the PMSM ECM motors until the supply airflow equals the exhaust airflow. Two rules govern its use:

• The test is started after all ducts have been fully connected and the exterior hoods installed.
• Any subsequent modification to the duct network — adding a register, changing a hood, or replacing a filter with a more restrictive model — requires rerunning the test.

Is an electric duct preheater needed

On some projects, we add an electric preheater upstream of the fresh-air intake. Common models in the vänEE line range from 1 kW to 2,000 W (220 V, 6 in. diameter, adjustable setpoint from 0 to 40 °C).

This accessory is justified when the HRV serves a very airtight home with a combustion appliance, or when the fresh-air distribution opens directly into a living area rather than into the return of a central system. It is not justified as a fix for an undersized unit or a poorly insulated duct network — in that case, it is a heater that masks an installation defect at the homeowner's expense every winter.

The maintenance schedule provided to the homeowner

Every 3 months — Remove the MERV 8 filters and clean or replace them. A loaded filter increases static pressure, throws off the balance established during testing, and makes the motors work harder.

Every autumn — Remove the core, vacuum it, and rinse it with warm soapy water. Check that the defrost damper pivots freely: on a recirculating unit, a stuck damper neutralizes all frost protection.

Twice a year — Inspect the exterior hoods. In agricultural areas, crop dust and insects clog the screens faster than they do in the city.

Every winter — Confirm that the drains are flowing. Pouring a simple glass of water into the pan verifies this in ten seconds.

Financial assistance: what we verify rather than promise

In Quebec, installing an air exchanger alone generally does not qualify as a subsidized measure in its own right. Provincial energy-efficiency programs assess the home as a whole and direct assistance toward insulation and air sealing; mechanical ventilation is treated as an indoor-air-quality requirement accompanying this work rather than as a standalone eligible measure. The criteria and amounts are revised from year to year. We therefore confirm eligibility at the time of the estimate, on a case-by-case basis, rather than announcing an amount that may no longer exist when the agreement is signed.

What this Hinchinbrooke project brings to homeowners in the region

An HRV installed in an unheated utility room is not a compromise, provided the installation accounts for it from the design stage: insulated ducts along all four runs, short, trapped drainage, decoupled suspension, and recirculation defrost to ensure the house never becomes depressurized during cold-weather cycles.

The vänEE AI Series V230H75RT provided the combination sought here — 231 CFM, 78% SRE at 0°C, 67% at −25°C, 6-inch top ports, ECM motors, and electronic self-balancing. For a more compact home, we would have recommended a 150 CFM unit; for a duplex in Verdun or a new build in Blainville, the calculation would start again from the volume and number of rooms.

At AirGreen, we carry out this type of HVAC installation and HVAC maintenance in Montreal, Laval, Longueuil, on the North Shore, on the South Shore, and as far as the rural municipalities of Haut-Saint-Laurent. The method does not change with the postal code: measure, size, install cleanly, balance, document.