69% humidity on the display, dehumidistat set to OFF, 24°C outside: what this display allowed us to diagnose
The call began like dozens of others: “our air exchanger is not working; the house is humid.” Yet the wall control showed a unit running in CONTINUOUS mode, with no error code. Three data points side by side on the same screen told the whole story: 69% relative humidity, the dehumidistat set to OFF, and 24°C outside.
The unit was not malfunctioning. It was doing exactly what it was designed to do, and that was not what the homeowners expected. Here is the complete reading of this screen, the resulting diagnosis, and the installation of the VENMAR AVS EKO 1.5 that followed in this Saint-Isidore home.
Reading the screen, one element at a time
A Venmar Altitude-generation wall control displays five pieces of information on a single page. Each one has a specific meaning.
CONTINUOUS mode
The unit ventilates continuously at the programmed speed, without an off cycle. This is the recommended steady-state setting in an occupied home, and it is the default setting we leave in place on almost all our start-ups.
The alternative—a 20-minute-per-hour intermittent mode—is suitable for a cottage or a home that is unoccupied during the day. It is not suitable for a family of four.
The fan line
The second line shows the current ventilation speed and allows you to change it. This is the only setting most occupants adjust, and often the only one anyone has explained to them.
The humidity line and the OFF indicator
The third line displays the measured relative humidity—here, 69%—followed by OFF. This does not mean that the sensor is disconnected or that the unit is turned off. It indicates that the dehumidistat function is inactive: the unit will not trigger automatic overventilation in response to the displayed humidity level.
Many homeowners read this line as a thermostat: they see a number and assume the unit is working to bring it down. That is not what a dehumidistat does, especially in summer.
Outdoor temperature
The upper-right corner displays the outdoor temperature, here 24 °C, measured by a sensor positioned in the fresh-air stream. This value is not decorative: it controls the humidistat's automatic standby mode and the initiation of defrost cycles in winter.
Where the humidity sensor is actually located
This is the point that almost no ventilation article addresses, and it completely changes how a figure like 69% should be interpreted.
On this type of control, the humidity sensor is integrated into the wall-mounted housing. It therefore measures the air at one wall, at a given height, in one particular room—not the house-wide average.
Locations that distort the reading
- Near a bathroom: the control records every shower and displays spikes that have nothing to do with the overall condition of the house.
- Near the kitchen: the same spikes occur every time a pot is used.
- On an uninsulated or poorly insulated exterior wall: the wall's cold surface locally lowers the air temperature and causes the measured relative humidity to rise, sometimes by 5 to 10 percentage points.
- In direct sunlight or above an electric baseboard heater: the opposite effect occurs—the local air is warmed, and the displayed relative humidity becomes artificially low.
- In a stairwell or near a basement door: the control reads air from an area that is not representative.
Our installation guidelines: an interior wall, at standard switch height, in a circulation hallway, well away from a bathroom, kitchen, heat source, and direct sunlight.
What 69% means—and what it does not mean
A reading of 69% in summer, measured on the ground floor of a house in Montérégie, is high but not abnormal: July outdoor air contains a lot of water. The same reading in January would be an emergency.
That is why relative humidity is never interpreted on its own. It is always read together with the indoor temperature, outdoor temperature, and season. A display that shows all three at the same time, like this one, makes diagnosis possible in a few seconds—but you still need to know how to connect them.
The July trap: an air exchanger does not dry out a house in summer
Dew point determines everything
An HRV exchanges indoor air for outdoor air while recovering heat in the process. It does not remove water from the air.
In winter, that is enough: cold outdoor air contains very little water, so every cubic metre brought in dries the house. That is why an HRV is so effective at clearing fogged-up windows in February.
In July, the logic is reversed. When the outdoor air is 24 °C with a high dew point, it contains more water than the air inside the air-conditioned house. Every cubic metre introduced adds moisture. Increasing ventilation makes the problem worse instead of solving it.
Why the dehumidistat goes into standby
That is exactly why the dehumidistat function goes into standby when the outdoor temperature is mild. Without this protection, the unit would respond to the displayed 69% by switching to high speed and would introduce humid outdoor air into the house for hours.
The OFF indication on the display in midsummer is not a malfunction. It is a protection feature doing its job.
What actually solves the problem
In this house, the selected plan had three components, in this order:
- Address the sources. We return to this below: this is almost always where the real improvement lies.
- Actually dehumidify. A basement dehumidifier, or the existing air conditioning used properly—a wall-mounted heat pump dehumidifies by cooling, provided it is not set to fan-only mode.
- Ventilate at the proper setting. The HRV supplies fresh air and exhausts pollutants year-round, and takes over humidity control in the fall.
The moisture sources found in the area
Saint-Isidore is a largely agricultural municipality in the Roussillon RCM, with a dispersed residential area, many homes supplied by private wells and septic systems, and basements often in direct contact with a high water table. The moisture sources we most often identify in this context:
- An open sump pit, without a sealed cover, allowing moisture to evaporate continuously.
- A basement slab without a vapor barrier, on which carpeting has been installed.
- An improperly connected dryer, whose duct leaks or ends in the crawl space.
- An ineffective French drain and grading that directs rainwater toward the foundation.
- Gutters discharging at the base of the wall, without extensions.
- An uncovered dirt-floor crawl space.
No air exchanger, regardless of its brand, can compensate for an open sump pit. We document these points in the report before discussing equipment.
Installing the VENMAR AVS EKO 1.5, and what we would do differently elsewhere
The original unit, an entry-level model with PSC motors installed about fifteen years earlier, was nearing the end of its life: noisy bearings, a core that had never been removed, and clogged filters.
Why the EKO 1.5
The specification-sheet data
- Model: EKO 1.5 HRV, number 43901
- Top ports, oval collars accepting 6-in. round duct
- Selectable airflow rates: four low/high ranges, from 40–80 CFM up to 80–156 CFM, measured at 0.4 in. w.g. (100 Pa)
- Sensible apparent effectiveness (ASE): 83% at 0°C at low speed — the highest value in Venmar's current residential range
- Power consumption: 24 W at 49 CFM, 32 W at 81 CFM
- Dimensions: 24 9/16 in. (H) x 23 9/16 in. (W) x 14 15/16 in. (D), 52 lb (23.6 kg)
- ENERGY STAR certified in Canada
- Limited lifetime warranty on the HRV core, 5 years on parts
- Washable core filters
ECM motors and what they change on your electricity bill
The EKO 1.5 uses electronically commutated motors. Venmar claims average electrical savings of 67 % compared with equivalent PSC motors.
The difference is clear in the figures: 24 W at 49 CFM on the EKO, compared with 56 W at low speed on the Constructo 1.5V, which nevertheless shares the same cabinet architecture but uses two PSC motors.
On a unit running 24 hours a day, 365 days a year, a difference of about thirty watts represents approximately 260 kWh per year. That is not spectacular per unit; it is significant over fifteen years, and it costs nothing in comfort.
The interchangeable core: the summer escape route
This was the deciding argument in this case. The EKO is designed to be converted from a heat recovery ventilator (HRV) to an energy recovery ventilator (ERV) by simply replacing the core, without changing the cabinet, ductwork, or controls.
An ERV core transfers moisture in addition to heat. In summer, it limits the amount of water the incoming air brings into the house; in winter, it retains some indoor moisture instead of exhausting it.
Two honest clarifications accompany this possibility:
- An ERV is not a dehumidifier. It reduces the amount of outdoor moisture brought in; it does not remove water already present in the house.
- The HRV core in the EKO range has a sensible apparent effectiveness (ASE) of 73 %, compared with 83% for the HRV core. Some winter heat recovery is traded for better summer performance.
We installed the EKO in HRV configuration, with the conversion documented as an option to be reassessed after a full summer of measurements. The homeowners know that the option exists and what it costs.
Installation and balancing
- Removal of the old unit, complete inspection of the existing ductwork, and replacement of two collapsed sections of flexible duct.
- Suspending the EKO 1.5 from the joists, with leveling checked on both axes and front clearance maintained for core removal.
- Connections to the oval collars, using 6-inch round duct, with aluminum tape on every joint.
- Condensate drain rerouted with a loop trap and continuous slope toward the floor drain.
- Exterior hoods replaced, properly spaced to prevent stale air from being drawn back into the intake, and positioned well away from the dryer exhaust.
- Balancing with a manometer, using an airflow meter suited to the duct diameter, until the difference between supply and exhaust is less than 10%.
The EKO is explicitly designed to make this step easier: the manufacturer's documentation lists it among the product's features. We record the measured airflow rates, the selected speed range, the static pressure, and the date in the commissioning report.
Settings left to the client
- CONTINUOUS mode as the baseline setting, year-round.
- A dehumidistat set to 45% for the heating season, with automatic standby during mild weather left enabled.
- A timed button near the bathroom for occasional boost ventilation.
- A written instruction: in July, a displayed level of 60 to 65% is not corrected by increasing ventilation.
The mistakes we correct most often
- Reading the humidity level without checking the outdoor temperature. The two figures only make sense together.
- Installing the wall control near a bathroom. The built-in sensor becomes unusable.
- Interpreting the OFF indicator as a malfunction. It is seasonal protection.
- Increasing ventilation in summer to lower humidity. The result is the opposite of what you are trying to achieve.
- Replacing a unit without addressing the sump, slab, or gutters. The new equipment inherits the same problem.
- Choosing an HRV to address basement humidity. An HRV limits incoming moisture; it does not dry the space.
Grants
The Rénoclimat program provides $500 for the installation or replacement of an HRV or ERV. The unit must be listed in section 3 of the Home Ventilating Institute certified product directory. An energy assessment before the work and a second one after the work are mandatory, and the heat-recovery unit cannot be the only measure: installed on its own, it may increase the building's energy consumption and cancel the grant.
Hydro-Québec's LogisVert program does not cover air exchangers. It mainly targets heat pumps, water heaters, and building-envelope work.
Maintenance
- Washable core filters: warm, soapy water every 3 months, in both airstreams.
- Core: remove and rinse annually, in the fall.
- Exterior hoods: spring inspection; remove lint and insect nests.
- Drain and trap: check twice a year.
- Wall control sensor: light dusting, without product, once a year.
- Airflows: new manometer reading at every professional service.
Our other ventilation projects in the region
This project joins a series of recent installations in the Roussillon RCM and elsewhere on the South Shore: several HRV replacements in the Longueuil area, residential ventilation projects in Vaudreuil-Soulanges, a unit recessed into a high-rise condo soffit in Laval, a side-vented model in an upper-floor apartment without a basement in Montréal-Nord, and installations in the Lower Laurentians.
Let's talk about your project
At AirGreen, we design, install, balance, and maintain residential and commercial ventilation systems in Saint-Isidore, Mercier, Saint-Rémi, Sainte-Catherine, Delson, and Saint-Constant, throughout the South Shore, in Longueuil, Montréal, Laval, and on the North Shore. Our teams hold the required RBQ licences and work with VENMAR, vänEE, Broan-NuTone, Lifebreath, Fantech, and Greentek product lines.
If your wall control displays a humidity level that does not decrease, write to us at sales@airgreen.ca or call (514) 316-2973. The diagnostic begins with a control-panel reading and an inspection of the sources—not with an equipment quote.