Installation of a Broan-NuTone AI Series V180H75RT air exchanger in Rivière-Beaudette

The Duct Decides the Airflow: What an Installation in Rivière-Beaudette Reveals About Residential Ventilation

An air exchanger is selected based on a technical sheet, but it never delivers what the sheet claims. It delivers what the ductwork allows it to deliver. The difference between the two can reach 30 or 40 percent, and nothing on the unit reveals it until measurements are taken.

At Rivière-Beaudette, at the western end of Vaudreuil-Soulanges, we installed a Broan-NuTone AI Series V180H75RT air exchanger in a cramped utility room where the geometry of the ductwork was the determining factor. This article is therefore less about the unit than about what surrounds it—because that is where actual performance is determined.

A sector where winter leaves no room for approximations

Rivière-Beaudette borders Lake Saint-François, near the Ontario border. Wind moves across the water unobstructed, temperature swings are pronounced, and part of the housing stock consists of seasonal buildings converted into permanent residences over the decades.

This conversion creates a precise imbalance: an envelope tightened by successive renovations—windows, insulation, membranes—without ventilation ever being rethought. The house becomes airtight through accumulated renovations, not by design. The moisture produced by the occupants then has no controlled way out.

What the Duct System Actually Does to Airflow

The Two Technical-Sheet Columns Nobody Reads

On the product sheet for the V180H75RT, the airflow range is listed twice:

• 65 to 193 CFM (31 to 91 L/s) at 0.4 in. w.g.
• 65 to 184 CFM (31 to 87 L/s) at 0.6 in. w.g.

The second line is the most informative. It shows what the unit still delivers when the system imposes 50 percent more resistance. A manufacturer that publishes this second column is saying something important: the system's static pressure is a design variable, not an installation detail.

In a poorly designed system, resistance far exceeds 0.6 in. w.g., and the unit then falls completely outside its certified operating range. It continues to run. It no longer ventilates the house at the intended airflow.

The bend radius, the most underestimated constraint

A 6-inch flexible duct that starts a 90-degree turn directly at the unit's port creates much more pressure loss than an elbow made 12 inches farther downstream. The trade rule we apply: the centerline radius of the duct must be at least one and a half times its diameter, or approximately 9 inches for a 6-inch duct.

Three aggravating factors almost always combine in restricted mechanical rooms:

• The immediate elbow at the port, required by a low ceiling above the unit.
• Untaut flexible duct. A flexible duct installed with 15 percent slack can more than double its pressure loss compared with the same duct properly stretched. At 30 percent, the degradation becomes severe.
• Excess lengths left in place because the duct would have had to be cut back and the connection redone.

That is precisely why, in a confined space, we favor a short rigid straight section extending a few inches from each port before starting the change in direction, followed by taut insulated flexible duct for the rest of the run. The gain is invisible in a photo and fully measurable during commissioning.

The selected unit: Broan-NuTone AI Series V180H75RT

The features that motivated the choice for this residence:

• Range of 65 to 193 CFM (31 to 91 L/s), with sufficient reserve to absorb the actual resistance of the installed duct system.
• Sensible recovery efficiency of 78% at 0 °C (at 64 CFM) and 68% at -25 °C (at 83 CFM). Apparent sensible efficiency reaches 82% at 0 °C.
• ENERGY STAR certification and HVI certification.
• PMSM ECM motors, 120 V / 60 Hz / 3 A / 200 W power supply at maximum speed.
• 6-inch top-mounted ports, included washable MERV 8 filter, MERV 13 option.
• Homeshield defrost, active at -5 °C and below—a criterion that truly matters at this latitude, where prolonged periods below -20 °C are not unusual.
• Assembled weight of approximately 47 lb (21.4 kg), mounted here on wall brackets anchored to the structure.

What sets this platform apart is the integrated airflow measurement. A conventional HRV displays fan speed. This one displays actual, measured airflow on each of the two sides. The difference between the two approaches is the difference between an intention and proof.

Commissioning: the airflow test as proof

The sequence always proceeds in the same order, and the order is non-negotiable:

1. The complete system installed and sealed, with exterior hoods installed.
2. The home's doors and windows closed.
3. New or clean filters in place.
4. Starting the airflow test from the unit or from the advanced touchscreen wall control.
5. Reading the maximum airflow that can actually be achieved and identifying the limiting side.
6. Programming the minimum and maximum settings.
7. Selecting the installation configuration corresponding to the actual system.

Why the limiting side is the most useful information

The screen does more than display a number: it indicates which of the two circuits—fresh-air supply or stale-air exhaust—reaches its limit first. This information immediately guides the diagnosis.

A limiting exhaust side points to the return ducts in the bathrooms, often the longest and most convoluted in a residential system. A limiting intake side points to the exterior hood, its grille, or a duct crushed in a narrow passage. Without this reading, a technician spends an hour searching; with it, they know where to climb the ladder.

The unit's label also states an instruction we would like to see printed on every mechanical-room door in Quebec: any modification made to the ductwork requires resetting the settings and rerunning the airflow test. Adding a grille, moving a line, shortening a section—each of these actions invalidates the previous calibration.

Flexible or rigid: our position

The debate is common, and the honest answer is nuanced.

The rigid duct offers significantly lower pressure loss, can be cleaned, and does not sag over time. It is the default choice for the main runs, and it is also what Novoclimat requires on the warm side of the system.

Insulated flexible duct has two real advantages: it absorbs vibrations and allows obstacles in the structure to be crossed without multiplying connections. Used over short lengths, pulled tight, with generous bends, it is perfectly acceptable. Used as thirty feet of slack in a ceiling cavity, it cancels out a good portion of what the homeowner paid for.

Our approach on job sites in Vaudreuil-Soulanges, on the South Shore, and on the North Shore: rigid for the main runs and anything passing through a cold zone, insulated flex duct pulled tight for connections and the final few feet.

Drain, power supply, and exterior hoods

Three details that generate the majority of reminders in HVAC maintenance:

• The condensate drain slopes downward with a loop forming a trap, keeping at least 2 inches between the appliance and the loop. An HRV that produces water is operating normally; an HRV that smells bad almost always has a missing or dried-out trap.
• The power supply must use a dedicated 120 V outlet within cord reach, in a room where the temperature remains above 10 °C year-round. An appliance placed in an unheated garage falls outside its operating range.
• The exterior hoods must maintain a minimum separation of 6 feet between the intake and exhaust, a height above the expected snow accumulation, and a distance of at least 10 feet from any dryer vent, chimney, or plumbing vent. On an exposed property like those along Lake Saint-François, the orientation relative to prevailing winds also deserves a moment's thought.

A realistic maintenance schedule

• Four times a year: vacuum and then wash the interior filters in warm, soapy water, rinse them, and let them dry completely before reinstalling them.
• Once a year, ideally in the fall: clean the core, check the exterior hood screens, and inspect the drain trap.
• After any renovation affecting the ducts: run the airflow test again.
• Every two to three years: complete inspection by a technician, including checking measured airflow rates against the design values.

Building code, Novoclimat, and financial assistance

The Quebec Construction Code has required balanced mechanical ventilation in applicable dwellings since 2012, with a minimum heat recovery rate of 54% at -25°C. The V180H75RT, certified at 68% at -25°C, is well above that level and also exceeds the 60% threshold required by Novoclimat when paired with the advanced touchscreen wall control.

When it comes to subsidies, our answer does not vary from one client to another: an air exchanger installed as part of a renovation is generally not eligible in Quebec for direct financial assistance comparable to that offered for heat pumps. What the investment provides is compliance, measurable air quality, protection of the structure against moisture-related damage, and a better result during an energy assessment conducted under Rénoclimat. Any promise of a subsidy should include the program name and the specific component.

AirGreen: ventilation guided by the numbers, from Rivière-Beaudette to Montreal

What distinguishes a successful HVAC ventilation installation from an average one is not visible in a photo. It comes down to decisions made before the first drill is used: the layout of the ductwork, the selected diameter, the number of bends accepted, the position of the hoods, and the final measurement that confirms everything.

We provide residential ventilation services in Rivière-Beaudette, Sainte-Justine-de-Newton, Les Coteaux, and Salaberry-de-Valleyfield, as well as in the densely populated neighbourhoods of Montreal, the cottages of Laval and the North Shore, and the recent developments of Longueuil and the South Shore.

At the end of a project, the homeowner leaves with four things: the airflow calculation according to CSA F326, the measured result of the airflow test on their actual system, the settings programmed into the unit along with an explanation, and a complete demonstration of routine maintenance. An air exchanger whose actual airflow is unknown is not a finished installation—it is simply a plugged-in appliance.

For an assessment of your ventilation system, an air exchanger replacement, or a complete ductwork design in Montreal, Laval, Longueuil, the North Shore, the South Shore, or Vaudreuil-Soulanges, contact us.