When an NDG house finally breathes: the day stale air stopped going around in circles
On the maple-lined streets of Côte-des-Neiges–Notre-Dame-de-Grâce, the homes have character, original woodwork, and, very often, an envelope that has been tightened over the course of renovations. Replaced windows, renewed caulking, blown-in attic insulation, finished basement: each improvement made the house more airtight, and therefore more energy-efficient. But no one had adjusted the ventilation accordingly.
The homeowners contacted us, describing three very specific issues: condensation on the bottoms of the second-floor windows on cold mornings, a persistent stale smell in the finished basement, and headaches late in the evening in the primary bedroom with the door closed. Three classic signs of a house lacking fresh air.
We installed a FANTECH HERO 150H heat recovery ventilator, an HRV (heat recovery ventilator) with top ports, connected to the existing central system. Here is how we proceeded, what we measured, and the technical decisions that make the difference between a unit that works and one that works well.
The pre-installation diagnosis: measure rather than assume
Before proposing anything, we went through the house with a hygrometer and an anemometer.
What we found:
- Indoor relative humidity of 58% one January morning, whereas a reasonable target during a Montreal winter is between 30% and 40%, depending on the outdoor temperature. Above that level, water vapor migrates toward cold surfaces and condenses.
- No mechanical fresh-air intake. The house had two bathroom fans and a kitchen range hood, all exhaust-only. In winter, exhausting air without compensating for it puts the house under negative pressure.
- A finished basement without adequate air return, which explained the odor: air was stagnating there and accumulating moisture against the foundation walls.
- A water heater and a heating appliance on the same level as the mechanical equipment, making depressurization an especially important issue to monitor.
This last point deserves attention because it is too often overlooked. When a tight house is depressurized by exhaust fans, air has to enter somewhere. If it enters through the chimney or vent of a combustion appliance, this is called combustion gas backdrafting. A properly sized air exchanger addresses the problem at its source because it operates as balanced ventilation: the same volume of air is exhausted and supplied, keeping the home's pressure neutral.
Why the FANTECH HERO 150H for this home
Choosing an HRV is not based solely on airflow. It also depends on compatibility with the home's mechanical layout, performance in extreme cold, and available space.
Technical specifications of the HERO 150H
| Specification | Value |
|---|---|
| Airflow range | 36 to 150 CFM at 0.4 in. w.g. |
| Duct connections | 6 in, round, top-mounted |
| Power supply | 120 V / 1 phase, max. current 1.4 A |
| Power consumption | 59 W (low speed) / 180 W (high speed) |
| Fan efficiency | 1.2 CFM/W at 0 °C |
| Adjusted sensible recovery efficiency | 86 % |
| ERS at 0 °C | 80 % |
| ERS at –25 °C | 65 % |
| Defrost type | Recirculation |
| Dimensions | 24 7/8 in H × 27 7/8 in W × 13 3/8 in D |
| Weight | 51 lb (23 kg) |
Three figures deserve to be highlighted for a climate like ours.
The first: 65% sensible recovery efficiency at –25 °C. This is the figure that really matters in Montreal, because a unit that performs at 0 °C but collapses in January does not deliver the expected service. The HERO 150H retains two-thirds of the outgoing air's heat during the coldest nights of winter.
The second: 59 W at low speed. A properly adjusted air exchanger runs continuously. At this consumption level, operating 24 hours a day at low speed costs a few dollars a month, which is negligible compared with the energy that would be wasted by opening a window.
The third: the 36 to 150 CFM range. It provides genuine modulation headroom. We were able to set the low continuous airflow for basic operation and reserve the higher setting for peak periods (showers, cooking, entertaining).
Recirculation defrost: the detail that determined the model
This is the most important technical point of the project. FANTECH offers two frost-control mechanisms in its residential range: supply fan shutdown and recirculation defrost. The HERO series uses recirculation defrost, and that was precisely what was needed here.
Why? Because the unit is integrated into the central system. A fan-shutdown model stops supplying the house with fresh air during the defrost cycle while continuing to exhaust air, temporarily recreating the depressurization we were specifically trying to eliminate. Recirculation defrost, on the other hand, circulates indoor air through the core to thaw it without unbalancing the house. HERO models are also equipped with a mechanical backdraft damper controlled by the unit, which blocks outdoor air when the unit is not operating. In an installation connected to a central system, this is what prevents cold air from infiltrating the ductwork by gravity when the furnace fan is running without the HRV operating.
This is the kind of trade-off we make with every HVAC installation, and it never appears on an invoice. However, it shows very clearly in the comfort level in February.
The installation, step by step
The positioning: on the floor, on an anti-vibration stand
The mechanical room in this Notre-Dame-de-Grâce home shares space with the water heater and a copper and PEX plumbing network. The clearance beneath the joists did not allow for conventional chain suspension with the clearance needed to service the interior filters.
We therefore mounted the unit on the floor, on a raised metal stand, with vibration isolators. Three concrete advantages:
- Full access to the front door remains available for servicing the interior filters and core, without dismantling any ductwork.
- The condensate drain runs by gravity to the floor drain, with a properly primed loop trap.
- No vibration is transmitted to the structure, so there is no humming in the floor of the room above. For a unit that runs continuously, this is far from a cosmetic detail.
The connection: four ducts, two distinct functions
The HERO 150H is a top-port unit, which greatly simplifies routing in a confined space. The four 6 in connections exit through the top, avoiding tight bends at the unit outlet and the resulting pressure losses.
The two insulated ducts (exterior side):
They connect the unit to the exterior wall hoods—one for the fresh-air intake, one for the stale-air exhaust. They are insulated and vapor-barrier sealed, without exception. An uninsulated duct carrying air at –20 °C through a heated basement becomes covered in condensation along its entire length, and that water eventually stains a ceiling or rots a joist. This is one of the most common failures we see in installations we take over.
We also maintained a minimum separation of 6 ft between the two exterior hoods, positioning the intake upwind of the prevailing winds and away from the dryer vent, range hood outlet, and plumbing vent. A poorly positioned intake draws back in what the house has just expelled.
The two rigid galvanized ducts (interior side):
In the installation photo, they are identified with marker: EXTRACTION (arrow pointing down) and DISTRIBUTION (arrow pointing up). This is not decorative. These labels allow the next technician—ours or someone else's—to understand the airflow direction in three seconds without dismantling anything.
- The extraction system draws stale air from the central system's return-air network.
- The distribution system feeds the tempered fresh air back into the downstream side of the home's distribution network.
This configuration, which FANTECH describes as a partially dedicated installation, combines dedicated extraction points with a fresh-air supply through the existing network. It offers the best performance-to-cost ratio in a home that already has a central network of ducts in good condition, which was the case here.
Electrical interlock and wall control
The unit is powered by a nearby dedicated 120 V outlet, and the low-voltage terminal block on top receives the control harness. We interlocked the HRV with the central system's fan: when the air exchanger switches to high speed, the distribution fan starts to prevent fresh air from stagnating in the ducts instead of reaching the bedrooms.
The wall control was installed on the main floor, away from wet areas and direct heat sources. FANTECH offers several options depending on the need: RTS 4 push-button timers in bathrooms, EDF3 or EDF8 multifunction controllers, and the Eco-Touch IAQ touchscreen control with total VOC detection for automatic operation. For this house, we chose a main-floor control, supplemented by a bathroom timer.
Balancing: the step too many installers skip
An unbalanced air exchanger is a unit that works against the house. If it supplies more air than it exhausts, it pressurizes the building and pushes indoor moisture into the walls. If it exhausts more than it supplies, it recreates exactly the depressurization we wanted to eliminate.
We systematically balance the system using the pressure ports on the collars and the conversion chart affixed to the unit door, which converts the measured pressure into actual airflow based on air temperature. Readings are taken on both sides—supply and exhaust—and the dampers are adjusted until the difference is negligible. The final values are then written directly on the ducts for future reference.
Without this step, the 150 CFM listed in the catalog remains a theoretical figure.
What this changes in practical terms, and what to avoid
The results measured in this house
We returned to the site three weeks after commissioning, in the midst of a cold snap.
- Relative humidity dropped to 36%, within the target range, without excessive drying.
- Condensation disappeared from the second-floor windows.
- Basement odor eliminated, thanks to a dedicated exhaust point in the finished room.
- Measured power consumption of the HRV in continuous low-speed operation: less than 60 W.
Homeowners mainly mentioned one thing that we often hear about after the installation of an air exchanger: sleep. A closed bedroom where CO₂ no longer builds up for eight hours—that is noticeable when you wake up.
Mistakes to avoid with an air exchanger
We have redone enough botched installations in Montréal, Laval, Longueuil, on the North Shore and the South Shore to put together a reliable list.
- Do not insulate the exterior ducts. Condensation is guaranteed, and water damage is likely.
- Place the air intake too close to an exhaust outlet, parking area, or dryer vent. You then bring in exactly what you are trying to exhaust.
- Omit the condensate drain trap, or install it without priming it. A dry trap lets air through, and the drain stops evacuating water.
- Skip the balancing. It is the most common and costly mistake when it comes to comfort.
- Choose a unit with a fan shutdown for integration with the central system. Recirculation defrosting is the recommended configuration in this situation.
- Neglect the indoor filters. A clean core behind clogged indoor filters loses its efficiency within a few months.
- Turn off the unit in winter to “save money.” This is precisely the season when the house is closed up and fresh air is most needed.
Maintenance: simple, but not optional
- Every 3 months: clean or replace the indoor filters. MERV 8 and MERV 13 options are available for the HERO series for those who want enhanced filtration, particularly for seasonal allergies.
- Every 6 months: rinse the heat recovery core with warm, soapy water, and check the drain and trap.
- Annually: inspect the exterior grilles (insect nests and plant debris reduce airflow faster than you might think), and check the balancing and sealing belts.
Regular HVAC maintenance maintains the advertised 86% adjusted recovery efficiency. A neglected unit can lose 20 to 30% of its airflow in two years without any warning light coming on.
Compliance, rebates, and resale value
In Quebec, balanced mechanical ventilation is required for new homes covered by the Building Code and is a condition of the Novoclimat program. For an existing home like this one, adding an HRV is generally not directly subsidized, unlike insulation, air-sealing, and heat pump measures. However, it improves the building's energy rating during an assessment and often becomes necessary when the building envelope is tightened as part of a renovation program. We always confirm eligibility with the client before the work rather than afterward, because the order of the interventions directly affects the amount that can be recovered.
In the Côte-des-Neiges–Notre-Dame-de-Grâce resale market, an air exchanger that has been properly installed, balanced, and documented is a tangible advantage when dealing with a home inspector.
Why entrust us with your installation
At AirGreen, we install air exchangers, wall-mounted and central heat pumps, air conditioners, and heating systems in Montreal, Laval, Longueuil, the North Shore, and the South Shore. We have been doing so long enough to know that a high-performance unit that is poorly installed delivers mediocre results, while an average unit that is properly installed delivers excellent results. Naturally, we aim for both.
Every HVAC installation we carry out includes a preliminary assessment, sizing based on floor area and the number of bedrooms, model selection according to the actual mechanical configuration, documented balancing, and commissioning with the client. We hold licence RBQ # 5645-9605-01.
For an assessment of your ventilation needs or a quote for a FANTECH air exchanger, contact us at (514) 316-2973 or sales@airgreen.ca. We respond quickly and serve the entire Greater Montreal area.