A 22-foot-wide, three-storey row house with a duct network that has nowhere to run straight
In Ville-Marie, residential ventilation is not designed the same way as in the suburbs. The row houses in Centre-Sud and around Old Montreal are narrow, deep, attached on two sides, and often three storeys high. There is no available side wall, no accessible attic, and the basement often has less than seven feet of headroom.
These three constraints combine to create a network of ducts that is long, winding, and full of bends. In other words: a network with high static pressure. And that is precisely the parameter that determined the equipment choice on the project described here.
The context: a three-storey row house in the Centre-Sud area, undergoing a major renovation—with the building envelope renewed, insulation replaced, windows changed, the basement excavated, and the slab rebuilt. We stepped in while the joists were still exposed, which is the ideal time to properly install an air exchanger .
We installed a GREENTEK PREMIER 1.5H there, a side-port HRV suspended by chains beneath the basement joists.
The blower door test: the figure that made ventilation mandatory
Before the renovation, this house breathed through its defects. Old windows, open masonry joints, and uninsulated rim joists allowed air to enter and leave without anyone asking it to. Uncomfortable and costly, but the air was being renewed.
After the building envelope was renewed, the situation completely reversed. The blower door test performed at the end of construction by the energy evaluator confirmed a major reduction in air leakage compared with the initial assessment.
This is the point that many homeowners undertaking a major renovation fail to anticipate: the tighter the building envelope, the more mechanical ventilation becomes a technical necessity rather than an optional upgrade. A house made airtight without a controlled supply of fresh air accumulates moisture, CO₂, and volatile organic compounds released by new materials—paints, floor adhesives, panels, and insulating foam. During the first six months after a major renovation, this load is at its highest.
We systematically recommend planning the air exchanger during the renovation design stage, not after the drywall is installed. On this project, that sequence was followed, which made it possible to run the ducts through the walls rather than through boxed-out enclosures.
Static pressure: the parameter no one looks at
Why a townhouse penalizes the duct system
An HRV is rated at a reference static pressure of 0.4 in. w.g. In a suburban bungalow with short, straight runs, the actual system often remains below this value. In a three-story townhouse, it exceeds it substantially.
The causes add up:
- Long vertical runs. From the basement to the third-floor bedroom, the supply branch had more than 12 m of developed length.
- Many elbows. Every change in direction consumes pressure. A branch that goes around a beam, a drain, and then rises through a wall can easily accumulate six or seven.
- Sections reduced due to lack of space. In a 2×4 wall, you cannot run a 6 in duct; you use an oval duct or reduce the size, and pressure loss increases.
- An unusable shared wall. It was impossible to exit through the shortest side; everything had to route around to the front or rear.
A unit sized solely on nominal airflow, without considering actual static pressure, will in practice deliver only a fraction of what is advertised. This is the most common gap between a technical data sheet and a measured result.
What the “high static pressure” design changes
The GREENTEK PREMIER series is specifically designed for high-static-pressure applications requiring high performance. In practical terms, its fan curve maintains usable airflow where a basic unit collapses.
For this project, that meant being able to target a true continuous airflow in the rooms served, rather than a theoretical airflow measured at the unit outlet. That is the difference between ventilating the house and ventilating the mechanical room.
GREENTEK PREMIER 1.5H features
| Specification | Value |
|---|---|
| Type | HRV (heat recovery ventilator) |
| Airflow range | 60 to 150 CFM at 0.4 in. w.g. |
| Duct connections | 6 in (152 mm), side |
| Power supply | 120 V / 1 phase, max. current 1.4 A |
| Power consumption | 54 W (low) / 168 W (high) |
| Fan efficiency | 1.2 CFM/W at 0 °C |
| Sensible recovery efficiency at 0 °C | 74 % |
| Core | Cross-flow, transfer of up to 75% |
| Defrost | Supply fan shutdown, triggered at –5 °C |
| Dimensions | 21 7/16 in H × 23 7/8 in W × 11 11/16 in D |
| Weight | 42 lb (19 kg) |
| Filtration | Washable electrostatic MERV 3 standard; MERV 8 or MERV 13 optional |
| Mounting | Series of chains, optional wall bracket |
The 11 11/16-inch depth is worth noting. In a row-house mechanical room, where the cabinet shares space with the water entry, electrical panel, main drain, and often a water heater, every inch of depth matters.
GREENTEK defrosting: a distinct operation
This is a technical feature that distinguishes this unit and deserves to be understood because it affects how the house behaves in January.
The defrost mechanism activates automatically when the outdoor air temperature drops to –5 °C or lower. During the cycle:
- The supply fan stops.
- The exhaust fan switches to high speed to maximize defrosting efficiency by passing as much warm indoor air as possible through the core.
This strategy defrosts effectively, but it temporarily puts the house under greater negative pressure than simply stopping the supply fan. This requires a check that we never bypass.
The question to ask before making any choice: is there a naturally drafted combustion appliance in the house? A wood-burning fireplace connected to a masonry chimney, an atmospheric-vented water heater, or an older gas furnace. In Centre-Sud houses, original fireplaces are common—sometimes decommissioned, sometimes not.
On this project, the house was entirely electric after renovation—a multizone wall-mounted heat pump for heating and cooling, an electric water heater, no combustion appliances in operation, and the original fireplace decommissioned and sealed. The defrost strategy therefore posed no constraints. If a fireplace had been put back into service, we would have recommended a recirculation-defrost unit equipped with an interlocked backdraft damper.
Two hoods on a single façade: the constraint specific to attached downtown houses
The separation puzzle
An air exchanger requires two exterior openings: the fresh-air intake and the stale-air exhaust. They must be far enough apart to prevent the unit from drawing back in what it has just expelled—a short circuit that completely undermines efficiency without producing any obvious symptoms.
In a detached house, the two hoods can be placed on two different façades and the issue is resolved. In a 22-foot-wide row house, attached on both sides, only the front and rear remain.
Our solution here:
- Stale-air exhaust hood on the upper part of the rear façade, away from the balcony and patio door.
- Fresh-air intake hood also on the rear façade, but offset horizontally as far as the available width allows and positioned lower, creating both lateral separation and a difference in height.
- Accounting for the prevailing westerly winds by placing the intake upwind rather than downwind of the exhaust.
- Checking the distance from the dryer vent, plumbing vent, and range hood exhaust, all concentrated on the same façade in this type of home.
We systematically measure these distances before drilling and record them. A misplaced hood cannot be corrected: it leaves a hole in a century-old brick masonry wall.
Borough regulations: check before drilling
In Ville-Marie, several areas are subject to zoning requirements governing façade appearance, particularly street-facing façades and buildings of heritage interest. Adding a ventilation hood visible from the public right-of-way may be regulated.
We verify this issue before the work rather than afterward, and our office helps clients check the regulations applicable to their borough. On this project, placing both hoods on the rear façade resolved the issue without technical compromise—but that is not always possible, and it is better to know this at the design stage.
Chain suspension and the one-piece foam cabinet
The unit comes with its chain suspension kit, which is how we mounted it: four chains anchored to the joists, with vibration isolators. A wall bracket is available as an option, but this home’s mechanical room had no clear wall space.
The PREMIER series’ one-piece foam cabinet offers two advantages in this specific context:
- Acoustic performance. In a row house, the mechanical room is often adjacent to a living space, and sometimes to the party wall shared with the neighbor. A foam cabinet absorbs some of the fan noise rather than reflecting it as bare sheet metal would.
- Lightweight design. At 42 lb, anchoring it to the joists remains simple and secure, which matters when suspending a unit beneath a century-old wood floor.
Integrated balancing ports
The PREMIER series features quick-connect balancing ports directly on the front panel, with the balancing chart affixed to the cabinet. In the installation photo, both connections are visible on the front, and the pressure-to-airflow reference label occupies the top of the panel.
Our method: measure at both ports, read the corresponding value on the chart, adjust the dampers, measure again, and record the final values. The branches are marked with a felt-tip pen during installation— in the photo, the intake duct bears the inscription “Fresh”, allowing the next technician to understand the airflow direction without dismantling anything.
Washable electrostatic filters: one less recurring cost
The PREMIER comes with washable MERV 3 electrostatic filters. They can be rinsed and reused, eliminating the need to purchase disposable filters for routine maintenance.
However, we clarify two things to our customers:
- A MERV 3 filter protects the unit, not the house. It protects the core and fans from large particles. It does not capture fine particles.
- For actual filtration, MERV 8 and MERV 13 options are available, and these must be replaced periodically. In Ville-Marie, given the traffic density downtown, MERV 13 is often justified—provided its additional pressure drop is factored in during balancing, not afterward.
The EHC 2.5 control
The recommended control for this series is the EHC 2.5 multifunction control, which offers three operating modes:
- Ventilation mode — exhausts stale air and replaces it with outdoor air.
- Recirculation mode — redistributes indoor air from one zone to another without introducing outdoor air.
- Standby mode — the unit remains inactive until indoor relative humidity exceeds the setpoint.
Four speeds can be selected: low, medium, normal, and 20 min/h. For a freshly renovated home, we program a higher initial setting for the first few months—as the new materials finish off-gassing—then adjust it downward during a follow-up visit.
Mistakes to avoid during a major renovation
- Planning the air exchanger after the drywall is installed. The ducts then end up in add-on bulkheads, with bends dictated by the finishing work.
- Choosing the unit based on nominal airflow without assessing the system's static pressure. This is the predominant error in tall, narrow houses.
- Placing the two hoods too close together on the same façade. The short circuit is invisible and permanent.
- Drilling through a regulated façade without prior approval.
- Neglecting the defrost strategy when there is a fireplace or combustion appliance. The only point on this list that concerns safety.
- Consider the standard MERV 3 filter as protecting the air quality system, not as air-quality filtration. It protects the unit, nothing more.
- Ventilate at a minimum during the first few months after renovation. This is the period when the concentration of volatile organic compounds is highest.
PREMIER 1.5H maintenance
- Every 3 months — rinse washable electrostatic filters, or replace them if MERV 8 or MERV 13 filters have been installed.
- Every 6 months — clean the cross-flow core, inspect the condensate drain and trap, and check the clamps at the collars.
- Annually — clear both exterior hoods, check the condition of the vapor barrier on the insulated ductwork, and revalidate the airflow rates at the balancing ports.
In a home with high static pressure, this final check is more important than elsewhere: a heavily loaded duct system is much less forgiving of gradual buildup than a short, direct system.
Compliance and programs
For new homes covered by the Quebec Construction Code, balanced mechanical ventilation is required and is a condition of the Novoclimat program. For major renovations, the approach is different but aligned: as soon as the building envelope is tightened, mechanical fresh-air intake becomes essential, and energy-efficiency renovation assistance programs rely on a before-and-after assessment carried out by a recognized advisor. The order of the work directly affects what is eligible; we discuss this with the client during planning, not after the work is completed.
For your project in Ville-Marie or elsewhere
At AirGreen, we approach townhouses, plexes, and older downtown buildings as unique design cases: mapping the ductwork layout before selecting the unit, assessing actual static pressure, checking combustion appliances, thoughtfully locating exterior hoods, carrying out measured and documented balancing, and then demonstrating the system to the occupants.
We carry out HVAC installations — air exchangers, wall-mounted and central heat pumps, air conditioners, and heating systems — in Ville-Marie and throughout Montreal, Laval, Longueuil, the North Shore, and the South Shore. Licence RBQ # 5645-9605-01.
To have your project assessed or to get a quote for a GREENTEK air exchanger, contact us at (514) 316-2973 or sales@airgreen.ca.