A unit without balancing ports on the door, suspended at ceiling height: how we adjust it anyway
Most residential HRVs sold in Quebec have balancing ports drilled directly into the access door. A manometer probe is inserted into one, a pressure reading is taken, it is converted to airflow, and the dampers are adjusted. Three minutes per airstream.
The LIFEBREATH RNC 95 does not. It is one of the few models in the RNC line without balancing ports on the door, along with the METRO models. On the job we carried out in the Saint-Hubert borough of Longueuil, this feature dictated the entire commissioning method—and explains why a large number of units of this type installed on the South Shore, as elsewhere, have never been balanced at all.
The context: a single-story home without a mechanical room
A single-story home from the early 1970s, approximately 1,150 sq. ft., with three bedrooms, a slab-on-grade foundation and a low, inaccessible crawl space. There is no mechanical room: heating is provided by electric baseboards and a wall-mounted heat pump in the living room, while the water heater occupies a kitchen closet.
This type of home is very common in Saint-Hubert and parts of Greenfield Park. There simply is no mechanical room. When a homeowner wants to add an air exchanger, the question is not “which unit?” but “where?”
The chosen solution: a 30-in.-wide storage closet in the central hallway, with the unit suspended high up, a few inches from the ceiling, and all four ducts passing through the ceiling to the attic. The bottom of the closet remains usable for storage.
The RNC 95: why this model for this configuration
The vertical format: the deciding factor
The RNC 95 measures 25 in. high, 18 1/2 in. wide, and 16 in. deep. It is the only unit in the RNC series whose cabinet is taller than it is wide. In a 30-in. closet, this orientation leaves room on each side for the straps and the technician's hand, which a 33-in. horizontal cabinet never would have allowed.
Weight: 52 lb (23.6 kg). Suspended from the 99-80-102 adjustable straps supplied with the unit—four buckle straps and four S-hooks—anchored into the ceiling joists. The excess lengths were rolled up and secured with elastic bands, preventing them from hanging into the closet and being pulled accidentally.
Performance
- Net supply airflow: 68 CFM (32 L/s) at 0.1 in. w.c., 66 CFM (31 L/s) at 0.2 in. w.c., 64 CFM at 0.3 and 59 CFM at 0.4 in. w.c.
- Apparent sensible effectiveness (ASE): 88% at 0°C and 60 CFM — the highest value in its category in the Lifebreath range
- Sensible recovery efficiency (SRE): 75% at 0°C (60 CFM), 73% at 0°C (70 CFM), and 68% at -25°C (61 CFM)
- Power consumption: 120 V, 59 W at low speed, 89 W at high speed, 0.9 A
- Three selectable high speeds, recirculation damper defrost
- Certified ENERGY STAR, HVI, CSA, and UL approved, ISO 9001
- Lifetime warranty on the recovery core, 5 years on parts
The 66 CFM available at 0.2 in. w.c. covered the calculated requirement for this house. A 200 CFM unit would have provided nothing but a cabinet that was impossible to fit and unnecessary noise.
5 in. round, 6 in. oval: a detail that causes equipment orders to fail
The RNC 95 accepts 5 in. (127 mm) round fittings, but its oval collars are 6 in. (152 mm). This dual sizing appears in a note at the bottom of the specification sheet and is regularly missed by estimators, who order a complete set of 5 in. fittings and find themselves stuck on the morning of installation.
We check this line on every specification sheet before preparing a truck.
The absence of balancing ports and the method it requires
This is the heart of the project. Without ports on the cabinet, there are three ways to actually measure the airflow of an HRV.
The inline airflow measurement station
Lifebreath offers dedicated airflow measurement stations in 5, 6, 7, and 8 in., installed inline in the duct to provide a permanent reading point. This is the solution we selected here, on both the supply and exhaust ducts, upstream of the first branches.
The benefit goes beyond commissioning: in three years, during maintenance, the measurement can be repeated in a few minutes without dismantling anything. For a unit suspended at ceiling height in a closet, that argument carries considerable weight.
The Pitot tube across the duct
When no permanent station is available, we drill into the duct and take a Pitot-tube reading with a manometer at several points across the section, then average the results. The method is reliable but takes longer, and it leaves perforations that must be properly sealed.
Reading pressure at the collars
On certain installations, airflow can be estimated from the static pressure measured at the collars and the unit’s performance curve. This is an approximation, not a measurement. We never use it as the final reading.
Gross and net airflow: why the two figures differ
A close reading of the RNC 95 data sheet reveals an instructive discrepancy. At 0.2 in. w.g., the unit shows a gross supply airflow of 72 CFM, a net supply airflow of 66 CFM, and a gross exhaust airflow of 85 CFM.
Net airflow accounts for the recirculation defrost cycle, during which the unit temporarily stops introducing outdoor air. This is the figure that matters for verifying Code compliance, and it is not given directly by an instantaneous manometer reading. A technician who measures 72 CFM and declares the unit compliant at 72 CFM is reading the wrong column.
We record both values in the commissioning report, together with the measurement location.
What this Longueuil job teaches us about ceiling penetrations
Four ducts penetrating the building envelope
The four insulated flexible ducts of the RNC 95 rise vertically from the collars, pass through the corridor ceiling, and reach the attic before descending again to the supply and exhaust grilles. Each of these four penetrations is a breach in the air-sealing and vapor-barrier plane.
This is the point ventilation articles address the least, and the one that causes the most delayed damage.
Continuity of the air barrier and vapor barrier
A poorly sealed penetration allows warm, humid indoor air to escape into the attic. In January, this moisture condenses and freezes on the roof decking, then melts during the first thaw. The homeowners then call a roofer about a roof leak that is not actually a roof leak.
On this job, every penetration was treated the same way: a mechanically fastened metal ceiling collar, acoustic sealant around the interior-side perimeter, vapor-barrier tape connected to the existing membrane, followed by drywall and joint-compound repairs. No bare canned foam left as the sole seal.
Duct insulation in unconditioned space
In the attic, the outdoor air flowing through the intake duct is at ambient temperature—well below the dew point of the attic air during the shoulder seasons. An uninsulated duct, or one insulated with a jacket whose vapor barrier is torn, becomes covered in condensation along its entire length.
We use insulated flexible duct with a continuous jacket, with joints sealed using aluminum tape rather than cloth tape, and we extend the insulation uninterrupted to the ceiling collar. Runs are kept short and supported at regular intervals: flexible duct that sags in an accordion shape in an attic loses a considerable portion of its airflow and accumulates water in its low points.
The outdoor exhaust and intake
The two exterior hoods were installed on the gable wall, spaced according to the minimum distance required to prevent stale exhaust air from being drawn back into the intake, and fitted with rodent screens. Directing moist exhaust air toward a ventilated soffit is a classic mistake: the moisture is drawn directly into the attic.
Service clearance when the unit is installed high up
The RNC 95 manual recommends 25 inches of front clearance for maintenance. On a unit suspended at ceiling height, this requirement becomes very concrete: you must be able to open the door, remove the core, and take it out horizontally while balancing on a stepladder.
We therefore positioned the unit so that its door opens toward the closet opening, not toward the side wall, and we left the storage shelves only below the unit, never in front of it. The commissioning report specifies the core's location and removal procedure, with photos.
The rating plate: the only proof that counts
On the side of the unit, a plate displays the HVI CERTIFIED seal, the ETL/cETL mark, the electrical data, and the table of certified airflow rates and efficiencies.
It is this plate, not the manufacturer's brochure, that documents the unit actually installed. We systematically photograph it at the end of the project and attach the image to the client's file. When a grant application is reviewed, or when a buyer requests the equipment specifications during a sale, this is the document that settles the matter in thirty seconds.
The mistakes we correct most often
- Seal a ceiling penetration with foam alone. Foam blocks airflow, but it does not restore vapor-barrier continuity.
- Apply cloth duct tape to a duct connection. It dries out, peels off, and leaves an invisible leak in an attic.
- Let a flexible duct sag between two supports. Every dip is a condensate trap and a source of pressure loss.
- Declare a unit balanced without a measurement point. On a model without ports at the door, this almost always means that no measurement was taken.
- Order fittings without checking whether they are round or oval. Five minutes of reading the specification sheet can prevent half a day of wasted work.
- Position the unit so that its door opens against a wall. The core becomes impossible to remove, and maintenance stops being performed.
Grants: what the program actually requires
The Rénoclimat program provides $500 for the installation or replacement of an HRV or energy-recovery ventilator. The unit must be listed in section 3 of the directory of products certified by the Home Ventilating Institute — hence the importance of the HVI seal on the rating plate. The RNC 95 is listed there.
Two conditions apply to the amount:
- An energy assessment before the work and a second one afterward are mandatory. A unit installed before the first assessment is not eligible for any assistance.
- An HRV cannot be the only measure. The program explicitly notes that an independently installed heat-recovery unit may increase the building's energy consumption, which lowers the rating between the two assessments and cancels the assistance.
Hydro-Québec's LogisVert program does not cover heat-recovery ventilators; it primarily targets heat pumps, water heaters, and building-envelope work.
Maintaining a unit installed at height
- Washable filters in both air streams: wash with warm, soapy water every 3 months. For a unit installed at height, we recommend setting the date to the time change to avoid forgetting.
- Core: remove and rinse once a year, in the fall.
- Exterior hoods: spring inspection and removal of lint and nests.
- Ceiling penetrations: visual inspection of the sealant every two or three years, along with a look in the attic.
- Airflow rates: new readings at the measurement stations during every professional maintenance visit.
Our other ventilation projects on the South Shore and elsewhere
This project is part of a series of recent installations: several HRVs in the Laurentians, a unit recessed into the soffit of a condo tower in Laval, a side-vented model in an upper-floor apartment without a basement in Montréal-Nord, integration into the central system of a home in the West Island, and residential and commercial ventilation projects in the Longueuil agglomeration, Brossard, Boucherville, and Saint-Bruno-de-Montarville.
Let's talk about your project
At AirGreen, we design, install, balance, and maintain residential and commercial ventilation systems in Longueuil — Vieux-Longueuil, Saint-Hubert, and Greenfield Park —, throughout the South Shore, in Montreal, Laval, and on the North Shore. Our teams hold the required RBQ licences and work with LIFEBREATH, Fantech, Broan-NuTone, and Greentek product lines.
For adding a heat-recovery ventilator to a home without a mechanical room, reworking ceiling penetrations, or documented balancing of your existing unit, write to us at sales@airgreen.ca or call (514) 316-2973.