A new home too airtight to breathe on its own: our ventilation project in Havelock
Havelock has 800 residents, maple groves, country roads stretching toward the border, and new homes built far from major centers. In winter, it also has nights reaching -28 °C, when outdoor air drops below 20% relative humidity while indoor air becomes saturated. The project discussed here involved a 1,600 sq. ft. single-story residence with three bedrooms and an unfinished basement, self-built by the homeowners and completed in the fall. Sound framing, carefully installed air barrier membrane, spray foam at the rim joists, and triple-glazed windows. A tight envelope, exactly as required today by the Quebec Construction Code.
And that is precisely where mechanical ventilation stops being optional. A house that reaches 1.5 air changes per hour at 50 Pa no longer purges itself through leaks. Moisture produced by cooking, showers, breathing, and drying laundry stays indoors, as do volatile organic compounds from new materials, and CO₂ rises overnight in the closed bedrooms. At AirGreen, we see this scenario every season, in Havelock as well as Saint-Chrysostome, Ormstown, Huntingdon, and Hemmingford.
What the homeowners described to us before our visit
The homeowners did not call for theory. They called about three concrete observations recorded during their first winter:
- Persistent condensation at the bottom of the bedroom windows whenever the outdoor temperature dropped below -15 °C.
- A musty smell upon waking in the primary bedroom, with the door closed, despite it being a new house.
- A basement that maintained a relative humidity of 65% to 70% in February, measured with their own hygrometer.
The third point is what made us accelerate. A new concrete slab releases moisture for 12 to 18 months, and an unfinished basement that reaches 70% relative humidity in the middle of winter is a basement preparing mold in the mineral wool as soon as the walls are closed in.
Our on-site assessment: airflow calculation before choosing any unit
Before naming a brand, we calculate. CSA F326 and the Building Code establish a total ventilation capacity by room: 10 L/s for the primary bedroom, 5 L/s per additional bedroom, 5 L/s for the living room, dining room, and kitchen, and 10 L/s for an unfinished basement. For this house, the total came to approximately 45 L/s, or nearly 95 cu. ft./min. of required total capacity, with a target continuous exhaust airflow of around 50 to 55 cu. ft./min. at low speed.
This figure changes everything. An entry-level unit with a maximum capacity of 90 cu. ft./min. would have been struggling as soon as it was asked to run at high speed with a real duct network, its elbows, and its pressure drop. Conversely, a 230 cu. ft./min. unit would have been oversized, more expensive, bulkier beneath the joists, and unable to modulate properly at the low end.
Why the vänEE AI Series V160H75RS for this house
We selected the vänEE AI Series V160H75RS, a heat recovery ventilator (HRV) with side ports. The data that drove the decision:
- Airflow range of 35 to 159 cu. ft./min. at 0.2 in. of water, placing our requirement of 55 cu. ft./min. right in the middle of the curve, where a unit is quiet and efficient.
- Sensible recovery efficiency (SRE) of 77% at 0°C and, above all, 67% at -25°C. This second figure is what matters in the Haut-Saint-Laurent. Many units collapse below -20°C; this one retains two-thirds of the heat from stale air at the harshest temperature of the year.
- Apparent sensible efficiency of 81% at 0°C.
- PMSM ECM motors on both fans. Continuous electricity consumption is an expense incurred 8,760 hours a year: that is where the difference between a PSC motor and a permanent-magnet motor becomes tangible on the Hydro-Québec bill.
- Recirculation defrost, which temporarily isolates the outdoor air intake and circulates indoor air through the core to defrost it, without ever depressurizing the house.
- Virtuo technology with airflow verification and automatic balancing, plus an integrated LCD screen on the unit.
- Washable MERV 8 filters and HVI certification, an administrative detail with dollar value, as we explain below.
- Dimensions: 19 1/8 in. high, 23 1/2 in. wide, and 16 3/8 in. deep, weighing 35 lb. A compact housing that fits beneath 9 1/4-inch joists without reducing the basement's headroom.
The recirculation defrosting point deserves particular emphasis here because this house is supplemented by a wood stove for heating. A unit that defrosts by shutting off the fresh-air supply while continuing to exhaust air puts the house under negative pressure. In a very airtight house with a combustion appliance, this negative pressure can reverse the chimney draft. Choosing an HRV with recirculation defrosting is not a technical refinement: it is a safety decision.
The installation process, item by item
Two technicians, one and a half days on site.
Suspension and vibration isolation
The unit is suspended by chains and springs, attached to hooks screwed directly into the floor joists near the water heater. The springs are not decorative: they isolate the housing from the wooden structure. Without them, the slightest motor vibration would be transmitted to the joists and travel up through the living-room floor, where it would become a background hum that the client hears every night. We also left enough clearance at the front to open the access door and remove the core with both hands, without disconnecting a duct.
Connecting the four outlets
The four 6-inch outlets were connected with insulated flexible ducts for the two exterior runs (fresh-air intake and stale-air exhaust), and with a flexible aluminum duct for the short interior-side connection. Insulation on the two exterior ducts is never negotiable: a bare duct carrying air at -25 °C through a 20 °C basement will become covered in condensation along its entire length, which then drips onto the insulation and framing.
Each connection was clamped at the collar, sealed, and supported at regular intervals. The flexible ducts were stretched as much as possible: a sagging or crushed flexible duct can double the pressure loss along a run and cause a properly sized unit to lose 20 cfm.
Exterior hoods
The fresh-air intake and exhaust hoods were installed more than 6 ft apart, on different façades, well away from the dryer vent and plumbing vent. In Havelock, prevailing winter winds come from the west-southwest, so we placed the air intake out of direct exposure to limit powder snow being drawn into the grille.
Dedicated distribution network
Because the house does not have a forced-air system, we installed a fully dedicated duct network: exhaust in both bathrooms and the laundry room, fresh-air supply in all three bedrooms and the living room, plus a basement return to target slab moisture directly. The wall grilles are individually adjustable Whisper-style registers.
Drain and condensate
The HRV produces condensate in winter. The drain was connected with a properly filled trap loop, sloping continuously toward the floor drain. Without a trap or with a reverse slope, the unit can blow air through the drain or collect water in the pan until it overflows.
Balancing and commissioning
The system was balanced during commissioning, with supply and exhaust airflow measured and adjusted until equal flow rates were achieved. An unbalanced HRV is not an HRV: if it exhausts more than it supplies, it creates negative pressure that draws unconditioned air through cracks and increases the risk of backdrafting from the wood stove. If it supplies more than it exhausts, it pushes humid air into the walls, where the vapor condenses against the air barrier.
Measured results three weeks after commissioning, during a severe cold snap: relative humidity stabilized between 38% and 42% on the main floor, 52% in the basement, and window condensation disappeared.
Our HRV installation benchmarks, from Haut-Saint-Laurent to Montreal, Laval, and the South Shore
The Havelock project follows principles that we apply everywhere. On the North Shore, in Blainville and Terrebonne, we regularly install HRVs in Novoclimat-certified homes, where the air exchanger is an integral part of the program requirements. On the South Shore, in Saint-Bruno and Chambly, we replace many units from the 1990s whose cores are clogged and whose PSC motors have become noisy. In Longueuil, in triplexes, the challenge is sharing duct routes between dwellings. In Montreal, on the Plateau and in Rosemont, space is the constraint: the unit often ends up in a storage closet, which means planning access to the core before even drilling the first hole. In Laval, renovated and re-insulated 1970s bungalows almost all fall into the category of “homes too airtight to ventilate themselves.”
The mistakes we correct most often
- Choosing the unit based on price rather than airflow. An undersized HRV runs at high speed continuously, uses more energy, makes more noise, and wears out faster.
- Placing the two exterior hoods too close together. Less than 6 ft apart, and the unit re-entrains its own stale air. Measured efficiency drops without any warning light coming on.
- Neglecting the insulation on the exterior ducts. We have opened basements where the insulation beneath the duct had been blackened over three feet by years of condensation.
- Never balancing the system. A unit delivered and connected without airflow measurements is a unit whose actual performance no one knows.
- Turning off the HRV in winter to save money. This is the time of year when it is most useful, and when heat recovery offsets the electricity consumed most quickly.
- Forgetting the interior filters. Clogged interior filters restrict both airflows simultaneously.
Maintenance: the schedule we provide to our customers
- Every 3 months: remove and wash the interior filters MERV 8 in warm, soapy water, and let them dry completely before reinstalling them.
- Every 6 months: remove the core, vacuum it, rinse it if necessary, and check the drain pan and drain trap.
- Every 12 months: inspect the grilles on the exterior hoods (insects, leaves, ice), check the tension of the flexible ducts, and revalidate the airflow rates.
- Every 5 years: complete balancing, especially if the ductwork has been modified or rooms have been added in the basement.
Financial assistance: the HRV is eligible
The Rénoclimat program provides financial assistance of $500 for the installation or replacement of an HRV or ERV, provided that the unit appears in section 3 of the certified product directory of the Home Ventilating Institute (HVI). The vänEE AI Series is HVI certified, making the application eligible. Two practical conditions to know: an energy evaluation must be completed before and after the work, and the home's EnerGuide rating must improve between the two visits. In practice, an HRV installed on its own rarely generates enough savings to trigger the grant; combined with insulation, air sealing, or the replacement of a heating system, it becomes a cost-effective addition to the application. We help our clients sequence their work in this order.
Why entrust your air exchanger installation to AirGreen
We are a Montreal HVAC company, licensed under RBQ 5645-9605-01, with more than fifteen teams on the road. We calculate airflow rates before recommending a unit, systematically balance the system during commissioning, provide the measured values in writing, and serve both major urban centres and rural municipalities in Montérégie: Havelock, Franklin, Hemmingford, Ormstown, Huntingdon, Saint-Chrysostome, Sainte-Martine, and the entire Haut-Saint-Laurent.
For an air exchanger installation, replacement of an aging HRV, balancing, or complete maintenance in Montreal, Laval, Longueuil, the North Shore, the South Shore, or Montérégie, email us at sales@airgreen.ca or call us at (514) 316-2973. We assess your home, calculate your actual airflow rates, and provide you with an accurate quote with no surprises.