Ventilating an electrically heated home when there are no ducts to use as a starting point
In most suburban homes, installing an air exchanger means connecting a unit to an existing duct network. On the Plateau-Mont-Royal, that approach falls apart. The apartments are heated by electric baseboards, with no furnace, plenum, or central return. The small white thermostat displaying 22.0 °C beneath this apartment’s wall control confirms it at a glance: before we arrived, there was no air-distribution network in this home.
At AirGreen, we designed and installed a fully dedicated system around a FANTECH HERO 120H in a second-floor 5½ apartment in a 1924 plex, a few streets from Laurier Park. Here is how the project actually unfolded, the constraints specific to Montréal’s older buildings, and the decisions that make the difference between a unit that hums and one that truly ventilates.
A 1,050-square-foot 5½ apartment with no air outlets
The home has two bedrooms, a double living room arranged in sequence, a kitchen at the rear, a bathroom, and an adjoining storage room. The ceilings are 9 feet high, the walls are plaster over lath, the moldings are original, and the windows were replaced six years ago. That replacement is precisely what created the situation: by tightening the envelope, the owners eliminated the uncontrolled air leaks that had previously provided unintended air exchange. The result: heavy condensation on the frames in January, cooking odors that linger until the next day, and a rear bedroom that feels noticeably stuffier in the morning.
The room-by-room calculation, established according to the logic of the CSA F326 standard, showed:
- Primary bedroom: 10 L/s
- Second bedroom: 5 L/s
- Living room: 5 L/s
- Dining room: 5 L/s
- Kitchen: 5 L/s
- Bathroom: 5 L/s
Total: 35 L/s, or approximately 74 CFM. A modest figure, but one that must be achieved continuously, not in bursts.
Why the HERO 120H instead of a larger model
In an older home, the temptation is to oversize “to be sure.” It’s an expensive mistake: an oversized unit runs too rarely, defrosts more often than it should, and unbalances the home with every cycle.
The HERO 120H matched the target precisely:
- Net airflow of 133 CFM at 0.1 in. water gauge and 72 CFM at 0.8 in. water gauge — a range that comfortably covers the 74 CFM requirement even with a loaded duct network.
- Adjusted sensible recovery efficiency of 80% at 0 °C and 63% at -25 °C. In a home heated with baseboards, every efficiency point shows up directly on the Hydro-Québec bill, with no intermediary.
- 5 in. round connections on top, with rubber gaskets. The reduced diameter made it possible to run the branches through a dropped ceiling only 8 in. deep.
- Internal recirculation defrost, active below -5 °C. The unit never stops extracting stale air during defrosting, avoiding pressurization of the dwelling during cold snaps.
- Counterflow core made of thermoformed polymer plates, washable.
- 165 W at full capacity, 1.2 A, on a dedicated 120 V circuit.
- 41.4 lb with core, measuring 24 ¼ in. high by 23 ¼ in. wide and 11 ½ in. deep, with 12 in. of front clearance required to remove the core.
- HVI certified, ENERGY STAR qualified (Canada), compliant with UL 1812, CSA C22.2 No. 113, and CSA F326.
- Washable electrostatic internal filters, with optional MERV 8 filtration on the supply side. Note: this filter reduces net airflow and must be accounted for in the calculations, not added afterward.
The real challenge: moving air through a building that was never designed for it
This is where 80% of the work on a Montreal plex happens.
The unit. We suspended it in the storage room adjoining the bathroom, using chains and vibration isolators anchored to the joists, away from the party wall. A unit mounted directly on a party wall in a plex transmits its vibrations to the neighbor, and that is the kind of detail that is difficult to fix afterward.
The supply ductwork. Three insulated 5 in. branches to the two bedrooms and the living room, concealed in a dropped ceiling built along the corridor. We deliberately followed the corridor layout rather than drilling through the joists of the main rooms, preserving the original ceilings.
The exhaust system. Two dedicated branches: bathroom and kitchen. The kitchen grille was positioned more than 3 m from the stove — an air exchanger never replaces a range hood, and grease clogs a core within a few months if the grille is poorly positioned.
A 4-foot silencer installed on the supply trunk, immediately downstream of the unit. In an open-concept dwelling with high ceilings, the difference is immediately noticeable in the evening.
The exterior caps and the façade constraint
On the Plateau-Mont-Royal, the street-facing façade is governed by the borough's planning regulations, and openings for mechanical equipment should be avoided there. We therefore relocated the two 5-inch caps to the rear wall, on the alley side, with:
- A separation of 1.8 m between the fresh-air intake and the stale-air exhaust, measured rather than estimated.
- A height of 60 cm above the rear balcony level, to remain above accumulated snow.
- A deliberate distance from nearby dryer exhaust outlets and the alley parking areas.
- Large-mesh grilles that do not become clogged with frost.
The drain. Without a floor drain on the second floor, the condensate was connected to the washing machine drainpipe, with a mandatory loop trap. A direct connection without a trap allows sewer odors to rise into the unit and then into the dwelling.
The wall control, the alcove, and the thermostat: three interacting elements
The FANTECH control is installed in a narrow corridor alcove, directly above the electronic thermostat for the electric baseboard heater, which displays 22.0°C. This stacking is not insignificant.
An alcove is a pocket of relatively stagnant air. Two measuring devices share the space: the heating thermostat, which reads temperature, and the ventilation control, which reads humidity and air quality. Each influences its immediate surroundings.
Our approach on this project:
- Installation height of 1.45 m, providing clear vertical clearance above the thermostat, outside the plume of warm air that rises along the wall when the baseboard heater is calling for heat.
- Cross-validation over 48 hours with a calibrated hygrometer placed in the center of the corridor, outside the alcove. Measured difference: less than 2% relative humidity.
- Cold-season humidity setpoint kept low, between 20% and 25%. In a brick triplex with newer windows and old frames, aiming for 40% in January guarantees condensation at the joints.
A screen that turns off does not indicate a malfunction
This is the service call we receive most often after this type of installation. In the photo, the control appears gray and switched off: this is simply the backlight entering standby mode after a period of inactivity. The unit continues to ventilate, monitor air quality, and modulate its speed. Touching the screen reactivates the display. We systematically explain this behavior to clients before leaving the site.
Two days on site, and the figures at completion
Day 1 — Building the ceiling bulkhead, routing the insulated branches, drilling through the rear wall, and installing the hoods.
Day 2 — Suspending and connecting the unit, dedicated circuit, drain and trap, grille installation, control programming, and balancing.
Final measurements with a balometer, at maximum speed: 96 CFM supply, 94 CFM exhaust. In continuous mode: 52 CFM. The 2 CFM difference between the two airflows is what ensures that the unit remains pressure-neutral—a critical point in a plex, where depressurization draws air from the neighboring unit through the party walls rather than from outside.
The plasterer came back the following week to finish the bulkhead.
What to avoid in a Montréal plex
- Connecting the exhaust to the range hood. The core becomes clogged and efficiency plummets.
- Drilling through the street-facing façade without checking the borough's regulations.
- Mounting the unit on the party wall. Vibrations travel through it.
- Skipping the balancing step. Without measurements, the installation remains a guess.
- Installing the hoods too close to each other or too low in relation to snow in the alley.
- Neglecting the condensate drain trap.
- Choosing an oversized unit because it cost the same.
Rénoclimat: what applies to a plex, and what changes compared with a house
The Rénoclimat program provides $500 for the installation or replacement of a heat recovery ventilator (HRV) or energy recovery ventilator (ERV), subject to two conditions: the unit must be listed in section 3 of the Home Ventilating Institute (HVI) certified products directory—the HERO 120H is certified there—and the grant is conditional on an improvement in the EnerGuide rating between the pre- and post-renovation assessments.
For a plex, two specific considerations deserve attention:
- Duplexes, triplexes, and residential buildings of no more than 3 above-ground floors with a maximum floor area of 600 m² are eligible, but when the units share spaces that allow air to circulate, the assessment covers the entire building, not just one unit.
- In a condominium, registration is handled through the condominium association, which becomes the recipient of the financial assistance.
It is also important to know that installing an air exchanger on its own increases the building’s electricity consumption. If carried out in isolation, the project may not meet the requirement for improving the rating. We recommend pairing it with insulation or air-sealing work and having the initial assessment performed before the first hammer blow.
The maintenance schedule provided to property owners
- Every 3 months: rinse the washable interior filters, and dry them completely before reinstalling them.
- Annually: remove and rinse the core, and inspect the drain trap.
- Twice a year: check the grilles on the alley side, where dust and lint from neighboring dryers accumulate faster than you might expect.
- Every 3 to 5 years: take new airflow measurements using an instrument.
Our approach to ventilation in Montreal’s older buildings
Plateau-Mont-Royal, Rosemont, Villeray, Le Sud-Ouest, and Hochelaga all pose the same challenge: homes that have become airtight, no original air-distribution system, heritage façades, and immediate neighbors. We work there regularly, as well as in the West Island, where we recently replaced first-generation units, and throughout Greater Montreal, in Laval, Longueuil, on the North Shore, and on the South Shore.
What we consistently deliver: an airflow calculation before the quote, a ductwork layout drawn up before the ceilings are opened, and a measured balancing report provided at the end. An HVAC installation in a century-old building must be planned on paper before the saw comes out.
To assess the ventilation in your home or building, contact our team at (514) 316-2973 or sales@airgreen.ca. RBQ 5645-9605-01.