Installation of a Broan-NuTone HRV120 Compact Flex heat recovery ventilator in L'Île-Perrot, in Vaudreuil-Soulanges

Eleven inches of clearance between two joists: the Île-Perrot project

A 1974 bungalow in Île-Perrot, with a partially finished basement, a low ceiling, and a joist bay barely eleven inches above the mechanical-room partition. That was all the space available to install a complete air exchanger, with its four ducts, electrical supply, and service access.

The homeowner called us after three rejected quotes. The three previous contractors had proposed the same thing: lower the basement ceiling or install the unit in the unheated garage. The first option cost more than the air exchanger itself. The second is simply a technical mistake in Quebec's climate: an HRV installed in an unheated space freezes, condenses, and is destroyed.

At AirGreen, we offer complete HVAC solutions throughout Greater Montreal, and this kind of space constraint represents a significant share of our renovation ventilation projects. The answer was not to demolish. It was to choose the right appliance format.

Living between two lakes: what Île-Perrot imposes on a house

Île-Perrot occupies a unique meteorological position. Caught between Lake Saint-Louis and Lake of Two Mountains, the island is surrounded by moisture-laden air for much of the year. The spring floods of 2017 and 2019 left a lasting mark on the area: a high water table, sump pumps working in the spring, and basement slabs sweating in June.

This context completely changes the ventilation calculation compared with an identical house built in Laval or on the North Shore, far from a body of water. We regularly measure relative humidity levels of 65% to 72% in summer in the basements of Pincourt, Notre-Dame-de-l'Île-Perrot, and Terrasse-Vaudreuil, along with a characteristic musty smell and storage furniture developing mold.

In this specific house, the initial readings showed:

• 68% relative humidity in the basement in June, 58% on the ground floor
• No mechanical ventilation other than the original, noisy bathroom fan with almost no airflow
• A portable dehumidifier running continuously, needing to be emptied twice a day
• Early signs of oxidation on tools stored beside the electrical panel

A portable dehumidifier is a symptom, never a solution. It removes water without ever replacing the air, heats the room, and consumes between 300 and 700 W continuously. It is the most common bandage we find in the island's basements.

Why the Compact Flex series, and why top connections

Broan-NuTone's Compact Flex Series was designed precisely for this kind of situation: apartments, condos, and homes where available space dictates the choice. Two features solved the problem in L'Île-Perrot.

The size. With top connections, the HRV120 measures 16¼ in. high by 23⅜ in. wide and 19¹³⁄₁₆ in. deep, and weighs 42 lb. Suspended beneath the joists, it kept the passage clear below the unit while maintaining service clearance in front of the access door.

The dual port configuration. The same model is available with side connections (HRV120S) or top connections (HRV120T). This flexibility seems minor in a catalog. On a job site, it determines whether the ductwork can run cleanly up to the joists or whether three additional elbows must be improvised, choking the airflow for the next twenty years. We selected the HRV120T version, with top connections.

Broan-NuTone HRV120: the specification sheet, without the sales pitch

How to read a specification sheet without being sold hot air

Three figures appear in every air exchanger quote, and two of them are mainly there to impress.

Apparent sensible efficiency (74% here) is the most flattering figure. It does not account for the heat added by the fan motors or the energy used by the defrost cycle. This is the number salespeople put in bold.

ASE, sensible recovery efficiency (65% at 0 °C), is the only figure that matters. It includes fan power consumption and defrosting. That's the honest number.

The ASE at −25 °C (60% here) is the figure almost no one cites. It reveals how the unit performs in January, when heat recovery actually has value. A difference of only five points between 0 °C and −25 °C, as with the HRV120, indicates a stable core and defrost strategy. Some competing units lose fifteen points or more over the same interval.

The HVI Certified logo visible on the access door of the installed unit also deserves an explanation. The Home Ventilating Institute is an independent organization that verifies manufacturers' advertised airflow rates, efficiencies, and sound levels in a laboratory. A non-HVI-certified unit publishes figures that no one has validated. We refuse to propose non-certified air exchangers, and we urge our clients to demand this designation on every competing quote.

HRV or ERV: same casing, different core

The HRV120 and ERV120 share the same chassis, footprint, and nearly the same airflow rates (64 to 130 CFM for the ERV120). The difference lies in the core.

• The HRV transfers heat only. It exhausts indoor moisture outdoors.
• The ERV transfers heat and some moisture. It retains moisture indoors in winter and limits its entry in summer.

In L'Île-Perrot, with a basement at 68% relative humidity and a permanent source of moisture coming from the ground, the HRV was the obvious choice. An ERV would have retained some of exactly what the house needed to get rid of. We recommend ERVs more often in overheated condos in Montreal and Longueuil, where indoor air drops below 25% relative humidity in January and static electricity and dry sinuses become the dominant problem.

“Air exchanger” and “heat recovery ventilator” are not synonyms

Common vocabulary in Quebec creates a costly confusion. Broan-NuTone catalogs a unit called AE60, a true air exchanger: 30 to 55 CFM, mesh filter, fan efficiency of 0.3 CFM/watt, and no heat recovery. It exhausts stale air and brings in fresh air, period.

In January, at −20 °C, that fresh air enters the house at −20 °C. The heating system reheats it entirely, at your expense. The HRV120 does the same job while recovering 60% of the heat along the way, with four times the fan efficiency.

A unit without heat recovery may be defensible in a utility room or heated garage. In an occupied Québec home, it costs more to operate than it cost to purchase.

Chain suspension: the detail that determines acoustic comfort

The unit was suspended from the joists by chains at all four designated anchor points, never rigidly screwed to the wood.

This is an absolute rule for us. An air exchanger bolted directly to the framing transmits vibrations from both fans throughout the entire structure. The noise does not appear in the room where the unit is installed; it shows up two floors higher, in the master bedroom, as a low hum that is impossible to locate. We have been called more than once on the South Shore to diagnose exactly this problem in systems installed by others, and the correction always consists of unhooking the unit and rehanging it properly.

The chains must also be the same length, and the unit must be perfectly level both laterally and longitudinally. A tilted housing prevents condensate from reaching its drain point.

Flexible ducts: what is acceptable and what is not

This job uses insulated flexible ducts for most of the run, with a transition to rigid galvanized duct and a wide-radius bend toward the wall penetration. This choice is entirely defensible in a constrained basement, provided you follow rules that most hastily installed systems ignore.

Our rules for flexible duct:

1. Stretch the duct as tight as possible. A slack flexible duct loses its effective diameter. Every corrugation creates turbulence. A loosely installed 5-inch duct performs like a 4-inch duct, and airflow collapses.
2. No tight bends. The minimum radius should be at least one and a half times the diameter. A flexible duct bent at a right angle against a joist is a blockage.
3. Seal every collar with aluminum tape, never with fabric duct tape, which dries out and peels off after three winters. In the job-site photo, aluminum tape is visible at every connection.
4. Support the flexible duct every four feet using a wide strap to prevent sagging between support points.
5. Continuous insulation and vapor barrier on both ducts connecting the unit to the outdoors. Without this, the fresh-air duct becomes covered in condensation in January, water drips into the ceiling, and the matter eventually becomes an insurance claim.
6. Switch to rigid ductwork as soon as the run is long or straight. Flexible ducting is used to absorb offsets and stresses; it should not make up most of the system.

Electrical power supply

The unit is powered by a cord and plug connected to an existing 120 V outlet located in the same joist bay. This is the configuration specified by the manufacturer, and it offers a real practical advantage: the power can be disconnected for annual maintenance without touching the electrical panel.

Two precautions accompany this choice. The tap must remain accessible at all times, without being enclosed behind a future suspended ceiling, and the hose must never be taut or routed over a sharp metal edge. We systematically secure the excess length to prevent it from hanging in the traffic area.

The access-door pressure taps and balancing

The Compact Flex series incorporates pressure taps on the access door, visible as two small openings on the galvanized front panel. They allow a manometer to be connected and the supply and exhaust airflow rates to be read directly without disassembling anything.

We use the balancing kit V18222 (0.5 in. and 1 in. water-column scales), and we adjust until the difference between the two airflow rates is less than 10%.

An unbalanced air exchanger puts the house under negative or positive pressure. Under negative pressure, the house draws air in through foundation cracks, the crawl space, and, in the worst case, through the exhaust flue of a combustion appliance. Under positive pressure, humid indoor air is forced into wall cavities, where it condenses on the cold side of the insulation. In both cases, the damage is slow and invisible.

This step takes forty minutes. It is missing from most of the installations we inspect. We leave the measured values on a label affixed to the casing, dated and signed.

Condensate drain and exterior penetrations

An HRV produces water. In winter, warm, humid stale air gives up its moisture as it passes through the cold core.

The drain was connected with a trap and a continuous slope toward the floor drain. A dry trap allows sewer odors to rise; we routinely explain to clients that they should pour a little water into the trap after a long summer absence.

Outside, the fresh-air intake and stale-air exhaust are spaced more than six feet apart, at least eighteen inches above the expected snow level, and away from the dryer vent, water-heater terminal, and parking area. A fresh-air intake located beneath a dryer vent continuously brings damp lint back into the house.

Please note: Broan's VTYIK1 tandem transition kit applies only to units rated at 110 CFM or less. The HRV120 exceeds this threshold and requires two separate wall penetrations. This detail is often overlooked, resulting in installations that will never reach their rated airflow.

What this project teaches you before you sign a quote

Sizing: the calculation, explained

The method recognized by the ASHRAE 62.2-2010 standard is applied as follows:

CFM = 0.01 × floor area (sq. ft.) + 7.5 × (number of bedrooms + 1)

For this 1,400 sq. ft. bungalow with a basement and three bedrooms: 0.01 × 2,100 = 21, plus 7.5 × 4 = 30, for a total of 51 CFM of continuous ventilation. The HRV120's range of 64 to 126 CFM covers this requirement at its lowest speed, while providing a comfortable reserve for peak periods and for summer basement dehumidification.

In Quebec, both Section 9.32 of the Building Code and the CSA F326 standard must be checked in parallel; the required total capacity is calculated room by room. We apply both methods and systematically use the more stringent result.

An undersized unit runs at full capacity constantly: noisy, energy-intensive, and prematurely worn. An oversized unit excessively dries out the house in February and costs more to purchase for no reason.

Subsidies: a necessary clarification

Let's be direct, because this topic is poorly handled online. In Quebec, a standalone air exchanger generally does not qualify for a direct subsidy, unlike a heat pump, which may be eligible under current programs. An HRV becomes relevant as part of a Rénoclimat process, where tightening the building envelope makes mechanical ventilation mandatory, and it is required in Novoclimat-certified homes.

The terms of these programs change from year to year. We verify eligibility for the file before discussing them, rather than promising an amount that will no longer exist when the work is done.

Maintenance: three steps, no more

• Every three months: remove and rinse the washable 30 PPI filter (SV16032), and let it dry completely before reinstalling it. A clogged filter reduces airflow before any other symptom appears.
• Once a year: remove the core, wash it with warm soapy water, and check the drain trap.
• Every fall: clear leaves, nests, and accumulated ice from the outdoor hoods.

An honest note about the filter: 30 PPI media is washable foam whose purpose is to protect the core, not purify the air. It is nothing like a MERV 13 filter and must not be marketed as such. Customers seeking fine allergen filtration should instead consider HE series models, some of which accept a HEPA option.

The result, two months later

Follow-up assessment in August: basement relative humidity stabilized between 48% and 53%, portable dehumidifier stored away, musty odor gone. Airflows measured during balancing: 62 CFM supply, 65 CFM exhaust, a 4.8% difference. The basement ceiling was never lowered.

Our air exchanger installations in the West Island and Greater Montreal

We install HRVs and ERVs in L'Île-Perrot, Pincourt, Notre-Dame-de-l'Île-Perrot, Terrasse-Vaudreuil, Vaudreuil-Dorion, Sainte-Anne-de-Bellevue, and Baie-D'Urfé, as well as throughout Montreal, Laval, Longueuil, the North Shore, and the South Shore.

Every HVAC installation follows the same sequence: a humidity assessment before work begins, documented airflow calculations using both methods, equipment selection based on the actual space constraint rather than the supplier's inventory, a sealed and supported duct network, followed by airflow balancing that is measured, documented, and provided to the customer.

If your basement smells musty, your portable dehumidifier runs nonstop, or you have been told that a ceiling must be demolished to install an air exchanger, contact AirGreen for an assessment.