The screen that revealed why a Saint-Eustache home was too dry in January
The homeowner contacted us in the middle of a cold snap. His multi-story house in the Albatros area, in Saint-Eustache, showed 19% relative humidity one morning at −26°C. His partner woke up with an irritated throat, the main-floor engineered wood flooring had gaps opening between the boards, and electricity consumption was rising with no apparent explanation.
His personal diagnosis: “the air exchanger is drying out the house; we should unplug it.” It's the most common conclusion, and it's almost always wrong.
The unit does not dry out a house. A poorly configured air exchanger does. The entire difference comes down to a hand-sized wall control.
What the 99-DXPL02 control displayed when we arrived
Our technician photographed the screen before touching anything. That's our method: the original settings often tell the entire story of an installation.
The screen of the Lifebreath 99-DXPL02 digital control displayed:
- Fan speed: 1 out of 5 available
- Active mode: 20 minutes of ventilation / 40 minutes of recirculation per hour
- Measured relative humidity: 36%
- Dehumidistat setpoint: 35%
These four lines contradict one another, and that was exactly where the problem lay.
The 35% setpoint had remained unchanged since installation
The built-in dehumidistat in the 99-DXPL02 starts high-speed ventilation as soon as the home's humidity exceeds the setpoint. At 36% measured against 35% programmed, the unit was about to switch to high speed—in the middle of −26°C weather—to exhaust humidity that was already too low for the occupants' comfort.
The setpoint had never been adjusted since the house was delivered. Set for a mild November, it worked against the occupants all winter.
The 20/40 recirculation mode was the right choice, but it was poorly used
The displayed mode — 20 minutes of ventilation, 40 minutes of recirculation — is precisely the one we recommend for the heart of winter in the Lower Laurentians. During the 40 minutes of recirculation, the unit circulates indoor air through its filters and ductwork without introducing icy, dry outdoor air. It evens out temperatures between the main floor and the basement without affecting humidity.
So the problem was not the mode. It was the combination of mode + setting + speed, which had never been considered as a whole.
The five modes of the 99-DXPL02 and when we use them
The 99-DXPL02 offers five selectable modes. Here is how we distribute them throughout the year in a typical North Shore home.
| Mode | Period | Reason |
|---|---|---|
| Continuous ventilation | Spring, fall, high occupancy | Constant airflow, gentle control of humidity and CO₂ |
| 20 min ventilation / 40 min recirculation | December to March | Sufficient air exchange without drying the air, circulation between floors |
| 20 min ventilation / 40 min off | Cottage, lightly occupied home | Minimum ventilation, reduced consumption |
| 10 min ventilation / 50 min off | Extended absence | Maintaining air quality at no cost |
| Continuous recirculation | Brief extreme cold, outdoor smoke event | Indoor circulation only, no outdoor air intake |
The last mode deserves an honest qualification: recirculation does not filter air to HEPA standards. It circulates the air and passes it through the unit's washable filters. During a wildfire smoke event, it limits the entry of outdoor air, which is already significant, but it does not replace a high-efficiency filter.
The humidity-setting table we leave with every client
This is the piece of information missing from almost every home we visit in Saint-Eustache, Deux-Montagnes, Boisbriand, and Sainte-Thérèse. The humidistat setting is not a single value: it follows the outdoor temperature.
| Outdoor temperature | Recommended humidity setting |
|---|---|
| 0°C and above | 40 to 45% |
| −10°C | 35 % |
| −20°C | 30 % |
| −30°C | 25 % |
The logic is physical, not aesthetic: the colder it is outside, the colder the interior surface of the windows, and the sooner water vapor condenses on them. Maintaining 45% at −25°C means creating ice on the window frames and, eventually, mold in the corners of exterior walls.
For this client in Saint-Eustache, we raised the setting to 30 % for the coldest period, with a magnetic note on the electrical panel recalling the table above. Humidity stabilized at around 28 to 31% the following week.
The control's location: the detail 90% of installers overlook
The 99-DXPL02 is not just a switch. It contains the system's humidity sensor. Its location therefore determines the validity of the entire control system.
Our installation rules:
- On an interior wall, never on a poorly insulated exterior wall
- Approximately 5 feet above the floor, out of the airflow from a supply grille
- Away from the kitchen and bathrooms, where humidity spikes would skew the reading
- Away from an exterior door and direct sunlight
- In a central hallway, representative of the entire home
On this project, the control was installed in the upstairs hallway, which was appropriate. We simply verified that no supply grille was blowing toward it—a problem that can shift the reading by 4 to 6 points.
The electrical connection
The 99-DXPL02 connects using low voltage, 3-conductor 20-gauge wire, up to 100 feet away. It mounts horizontally and, unlike the BC series controls, does not require a 2 x 4 electrical box. This is a real advantage in renovations: drill, pull the wire, screw on the plate, and avoid cutting into the drywall for a box.
The Techgrille 99-EAG5, the other half of the job
A properly programmed control cannot correct a poorly balanced distribution network. So we redid the home's grilles.
The original fixed grilles were replaced with Techgrilles Lifebreath 99-EAG5 grilles with a 5-inch diameter, the size that matches the collars on the RNC5-TPD, RNC5-TPF, RNC5-ES, METRO 120D, and METRO 120F units. The range also includes the 99-EAG4 (4 in.), 99-EAG6 (6 in.), and 99-EAG8 (8 in.), depending on the duct diameter.
What this grille brings in practical terms:
- A screw-adjustable central cone that modulates airflow at each grille without touching the unit.
- Compression spring clips that hold it in the round duct without visible hardware.
- A non-corrosive white body, suitable for bathroom exhaust grilles exposed to steam.
- Hand removal for maintenance, with the same setting restored.
In this two-story home, the bedroom above the garage historically received too little air. We opened its damper fully and partially closed those in the living room and family room, which were closer to the unit. The temperature difference between this bedroom and the rest of the floor dropped from 3.5 °C to less than 1 °C.
Adding timers without opening the walls
The house was completely finished. The client wanted an override button in the upstairs bathroom, 22 feet from the main control, without any demolition.
The solution: the 99-DET02 wireless timer, exclusive to Lifebreath, which triggers high-speed ventilation for 20, 40, or 60 minutes and communicates with the main control over a range of approximately 40 feet. When distance or the building structure poses a problem, the 99-RX02 repeater plugs into a 120 V outlet halfway between the two and extends the range.
No wires pulled, no walls opened, a twenty-minute installation. This is the type of solution we favor in existing homes in Montreal, Laval, and Longueuil, where opening up a wall is costly to refinish.
The mistakes we correct most often with air exchangers
- Leaving the humidity setting at the factory default. This is the number one cause of homes that are too dry in January and too humid in November.
- Running the unit continuously at high speed all winter. Unnecessary energy use, over-drying, and more frequent defrost cycles.
- Ignoring the service indicator. The 99-DXPL02 has a maintenance reminder and a dedicated RESET button. The supply and exhaust filters are washable: clean them twice a year, plus the core once a year.
- Disconnecting the air exchanger “because it dries out the air.” A tightly sealed home without mechanical ventilation accumulates humidity, volatile organic compounds, and CO₂. The solution is adjustment, not the circuit breaker.
- Choosing an HRV over an ERV without a defrost system. Southern Quebec is in climate zone 2: cold winters, hot and humid summers. An HRV (heat recovery ventilator) is the default choice there; an ERV absolutely requires defrosting.
- Failing to document the balancing. We provide the measured supply and exhaust airflows, along with the percentage difference.
The figures behind the choice of a unit
For a multi-level home in Saint-Eustache, these are the benchmarks we use:
- RNC5-TPD: 156 ft³/min at 0.2 in. w.c., sensible recovery efficiency (SRE) of 61% at 0°C, 5-inch collars, recirculation defrost.
- RNC5-HEX-TPF: counterflow HEX core, 76% SRE, ENERGY STAR certified, for homes seeking superior performance.
- RNC 155: 163 ft³/min at 0.2 in. w.c., 75% SRE, horizontal model with balancing at the doors, suited to larger homes.
- RNC 205: 193 ft³/min, 71% SRE, new top-port design for challenging installations.
All these units are HVI-certified, compliant with CSA and UL standards, and covered by a lifetime warranty on the recovery core as well as 5 years on parts.
Regarding financial assistance, replacing an HRV may qualify under the Rénoclimat program, provided the initial energy assessment takes place before the work. The order matters: an installation completed before the assessment is not recognized. We validate each file before scheduling, rather than announcing an amount that may not materialize.
What we take away from the Saint-Eustache project
No equipment was replaced that day. We reprogrammed a control, adjusted six grille cones, added a wireless timer, and provided a seasonal instruction chart on a laminated sheet. A modest invoice, with measurable results the following week.
This is an important part of our work in HVAC installation and HVAC maintenance: distinguishing faulty equipment from misunderstood equipment. A properly configured Lifebreath heat recovery ventilator is quiet, stable, and unobtrusive in everyday life. When poorly adjusted, it becomes the designated culprit for every discomfort in the home.
At AirGreen, we serve Saint-Eustache, Deux-Montagnes, Boisbriand, Blainville, Sainte-Thérèse and throughout the Lower Laurentians and the North Shore, as well as Montreal, Laval, Longueuil and across the entire South Shore. We measure, adjust, and explain every button to the customer before we leave.