Drilling through a brick façade when the neighbor is three feet away
A triplex from Cartierville, on a cross street north of the Métropolitaine. A thirty-inch-wide mechanical room in the basement, finished ceiling, shared wall on one side, laneway on the other. The owner wanted an air exchanger in the ground-floor apartment, where his mother lives.
The unit itself posed no problem. The cabinet fits in the corner, suspended by four chains, with the ports facing upward. Twenty minutes of work.
The rest of the project played out outside, around the question no one asks in a quote: where do the two caps exit?
At AirGreen, we offer complete HVAC solutions throughout Montreal, and in dense boroughs such as Ahuntsic-Cartierville, this single question determines whether the installation will work properly or silently fail for twenty years.
An air exchanger needs two openings, and they cannot be just anywhere
Every HRV requires two separate wall penetrations: a fresh-air intake and a stale-air exhaust. Six constraints apply simultaneously, and in urban settings they conflict.
- Minimum separation between the two caps. We aim for six feet. Below that distance, the unit re-intakes the air it has just exhausted, and its performance collapses without any visible symptom appearing.
- Distance from other exhaust outlets. Dryer vent, range hood, plumbing vent, water-heater or combustion-furnace terminal. A fresh-air intake located below a dryer outlet constantly reintroduces damp lint.
- Height above the snow. At least eighteen inches above the anticipated level. In Montreal, you must also account for snow pushed by snow removal in laneways.
- Distance from the gas meter and regulator.
- Position relative to the property line. A shared wall or one located very close to the lot line limits the permitted openings. The rule comes from the Code and the borough’s regulations, not the contractor’s discretion.
- Façade appearance. In certain parts of Ahuntsic-Cartierville, particularly around Sault-au-Récollet, modifications to a façade visible from the street are regulated. Depending on the area and the type of work, authorization from the borough may be required. We check before drilling, not afterward.
What we did on this triplex
The street-facing front brick façade was ruled out immediately, for appearance reasons and because the stale-air exhaust would have ended up at sidewalk level.
The shared wall was not an option.
That left the rear façade and the side wall facing the alley. We placed the fresh-air intake on the rear façade, on the side opposite the highway and away from the upper unit’s dryer vent, and the stale-air exhaust on the alley wall, more than six feet away along the actual path around the building’s corner.
A separation measured “as the crow flies” of six feet is worthless if the two hoods face each other on opposite sides of an inside corner. It is the actual path of the air that matters, not the distance on the plan.
Outdoor air quality in Ahuntsic-Cartierville
An air exchanger brings into the house the air located in front of its intake. In a borough crossed by the Metropolitan Autoroute and Autoroute 15, this detail is no longer theoretical.
Highway corridors generate higher concentrations of fine particles and nitrogen dioxide, and the difference can be measured over just a few hundred metres. Three practical consequences for an installation in Ahuntsic, Cartierville, Bordeaux, or Nouveau-Bordeaux:
- Position the fresh-air intake on the façade farthest from the traffic corridor, even if drilling is more complicated. In the case of this triplex, that meant the rear rather than the street side.
- Choose a higher level of filtration. A basic washable filter protects the unit’s core, and nothing more. It does not filter fine particles. Some Broan-NuTone product lines accept a HEPA option that captures 99.97% of microscopic particles, and this is a worthwhile investment in a densely populated urban environment, particularly for older or asthmatic occupants.
- Use recirculation mode during smoke episodes. The wildfire smoke episodes that have affected Montreal in recent years are the clearest example: on those days, the unit must stop bringing in outdoor air and simply circulate indoor air.
A unit that can be reconfigured: the four ports, airflow, and mode
The unit label, clearly visible in the construction-site photo, is a complete configuration map. It bears three marks: BROAN — Fresh Air System / Air Exchanger, the Virtuo Technology platform from the Broan-NuTone group, and the HVI Certified certification from the Home Ventilating Institute, the independent organization that validates the stated airflow rates and efficiency in the laboratory.
The four numbered ports
Step 1 of the label identifies the four connections, and every homeowner should know this legend:
| Port | Function |
|---|---|
| 1 | Stale-air intake from the building |
| 2 | Fresh-air supply to the building |
| 3 | Stale-air exhaust to outdoors |
| 4 | Fresh-air intake from outdoors |
Ports 1 and 2 are indoors. Ports 3 and 4 are outdoors, and they require a continuous vapor-barrier-insulated duct; otherwise, winter condensation forms along the entire length and drips into the ceiling.
The label also shows two orientation diagrams with a rotation arrow: the port arrangement can be adapted depending on how the unit is mounted. In a thirty-inch mechanical room where the ducts must run in a prescribed direction, this flexibility makes the difference between a clean installation and a tangle of elbows that restricts airflow.
105 and STB mode
Step 2 displays 105, in CFM. This is the airflow selected directly on the unit during commissioning, based on the ventilation calculation specific to that home, rather than a fixed product characteristic. The same cabinet could have been set lower.
Step 3 and the mode-selection box are marked T1 and STB, which are also set during commissioning. These settings define the unit's behavior and are confirmed one by one on the front panel.
The key point for a homeowner: these three values should appear on the commissioning sheet provided to you. Without them, no one—not even the next technician—can know how your system was configured.
“ENERGY STAR only when used in Canada”
The blue ENERGY STAR badge on the label includes a small-print statement worth reading: the certification applies when the unit is used in Canada.
This is not an inconsequential legal subtlety. The ENERGY STAR criteria for heat recovery ventilators are established by Natural Resources Canada and the U.S. agency, and performance thresholds differ depending on the intended market. A unit certified for the Canadian climate meets cold-weather recovery requirements that the U.S. market does not impose everywhere.
When a quote mentions “ENERGY STAR” without specifying further, it is worth asking for the product sheet.
The label’s QR code
The label bears a QR code leading to the manufacturer’s installation and maintenance support. Our recommendation to all clients, regardless of the brand: photograph your unit’s label on the day of installation and keep the image.
This photo shows the model, serial number, installed settings, and access to the documentation. Ten years from now, when the plate is covered in dust and you are looking for a replacement filter, it will save you an hour. In the event of a warranty claim, it is worth even more.
The two condensate lines joined with a tee
Under the unit, the photo shows two transparent vinyl tubes descending and joining at a white plastic tee before continuing as a single line.
An HRV produces water in winter: warm, humid stale air releases its moisture as it passes through the cold core. Some units have two drain points, which must be joined properly.
Three requirements for this connection:
- Continuous downward slope to the discharge point. A reverse slope causes water to stagnate in the tubing.
- Properly formed trap. Without a trap, fan pressure pushes air through the drain instead of allowing water to flow out, and the pan overflows.
- Transparent tubing, intentionally. It lets you check at a glance that the line is clear and that the trap contains water. After a long summer absence, the trap may dry out and allow drain odors to rise: simply pour in a little water.
Chain suspension, even in a finished room
The unit is hung by four chains of equal length, attached to its anchor points. Never rigidly screwed to the structure.
In a multi-unit building, this detail matters more than in a single-family home. Vibrations transmitted to the structure of an apartment building do not remain in the affected unit: they travel up through the partitions and show up in the neighbor’s unit above as a low hum that no one can locate. A tenant complaint about an improperly suspended unit costs more to resolve than installing it correctly.
The low-voltage wiring connecting the wall control to the side control module follows the same rules as everywhere else: never in the same hole as 120 V wiring, conductors fully inserted into the terminal block, and excess length coiled and secured with ties rather than left hanging over a sheet-metal edge.
Ventilating a duplex or triplex: one unit per dwelling
A question comes up constantly in plexes in Ahuntsic, Villeray, Rosemont, or Longueuil: can a single air exchanger serve the entire building?
The answer is no, in almost all cases. Each dwelling must be ventilated independently, for three reasons:
- The transfer of odors and contaminants between dwellings through a shared network is unacceptable.
- The required airflow rates differ according to the number of rooms and occupants in each unit.
- Electricity billing for a shared unit becomes a point of contention between the landlord and tenants.
We install one unit per dwelling, each with its own wall control accessible to the occupants of the unit, and each balanced separately.
The most common urban mistakes
- Both hoods on the same façade, three feet apart, because that was the easiest wall to drill through.
- The fresh-air intake above a parking area or garage door, drawing in exhaust fumes.
- A hood under a balcony or in a recessed area where air stagnates.
- No regulatory review before modifying a façade in a regulated area.
- No balancing. We measure the supply and exhaust airflow, adjust them until the difference is less than 10%, and leave the values on a dated label affixed to the casing.
Maintenance
Three steps are enough: rinse the filters every three months—or every two months near a highway corridor, where they load up faster; wash the core with warm, soapy water once a year while checking the trap; clear the exterior hoods of leaves, nests, and ice every fall. In an alley, you should also check them after snow-removal operations.
Our air-exchanger installations in Montreal and the surrounding areas
We install, configure, and maintain HRVs and ERVs in Ahuntsic-Cartierville, Villeray–Saint-Michel–Parc-Extension, Bordeaux, Cartierville, Saraguay, and Sault-au-Récollet, as well as throughout Montreal, Laval, Longueuil, the North Shore, and the South Shore.
Every HVAC installation ends with the same information sheet provided to the customer: airflow calculation, value programmed into the unit, location and actual separation of the exterior hoods, airflow measured during balancing, and commissioning date.
If you live in a Montreal plex and have been told that installing an air exchanger in your home is impossible, the constraint is almost always in the choice of exterior outlets, not the unit. Contact AirGreen for an on-site assessment.