Installation of a FANTECH FLEX 100H ES air exchanger in Senneville, West Island of Montreal

The sticker on the unit's door: the only proof that an air exchanger was actually balanced

On the door of this unit suspended in a utility closet in Senneville, there is a printed table that almost no one looks at. Two columns, A and B, a list of airflow rates in cubic feet per minute, and, opposite them, pressures in inches of water column.

This table is the tool that turns an air exchanger installation into a balanced air exchanger. An installer who does not use it does not know the system's actual airflow rates after completing the installation—only those listed in the catalogue.

At AirGreen, we installed a FANTECH FLEX 100H ES in the intergenerational dwelling of a Senneville property, in a 26-inch-wide utility closet shared with the water heater. Here is the project—and above all, the method.

The project: 950 sq. ft. of finished lower-level space

The main property, wooded and secluded like most properties in the village, already had its ventilation. The project involved converting the recently finished lower level into a self-contained dwelling: two bedrooms, a bathroom, a kitchenette, a living-dining room, a separate entrance, and its own electric water heater.

A dwelling of this type presents a constraint that large homes do not: there is nowhere to put the unit. No mechanical room, no accessible crawl space, and no storage closet to sacrifice. The only available space was the recess above the water heater, 26 inches wide, with a finished ceiling directly above it.

The requirement calculated according to the logic of the CSA F326 standard:

• Primary bedroom: 10 L/s
• Second bedroom: 5 L/s
• Living room and dining room: 10 L/s
• Kitchenette: 5 L/s
• Bathroom: 5 L/s

Total: 35 L/s, or approximately 74 CFM.

The FLEX 100H ES: an appliance chosen for its compact size—and embraced as such

• Net airflow of 104 CFM at 0.4 in. w.g., 129 CFM at 0.1 in. w.g., and 70 CFM at 0.8 in. w.g. The margin above the required 74 CFM is adequate without being excessive.
• 21 ½ in. high, 15 ⅝ in. wide, and 14 ½ in. deep, weighing 39 lb with the core. This footprint is what made the installation possible.
• 5-in. oval connections on top, allowing the ducts to run directly to the ceiling without side clearance.
• Aluminum core, washable and more durable than polymer cores in rental applications where maintenance may be neglected.
• Internal recirculation defrost below -5°C.
• 168 W, 1.4 A, with a 3-ft. power cord and three-prong plug supplied from the factory.
• 8.5 in. × 12.5 in. washable electrostatic interior filters.
• HVI-certified and ENERGY STAR qualified in Canada.
• 14 in. of recommended front clearance for removing the core.

One point of technical honesty: the FLEX’s sensible recovery efficiency is around 60 to 65% at 0°C, compared with more than 80% for HERO series units. We do not claim otherwise. In this 26-inch closet, a HERO series unit simply would not fit, and the difference in recovery for a 950-square-foot home amounts to a few dozen dollars per heating season. It was the right compromise. We would have rejected it for a 2,500-square-foot house.

How an Air Exchanger Is Actually Balanced

This is the least visible and most critical part of the job.

The A and B Pressure Ports

FANTECH units have two pressure ports, generally identified as A and B on the door’s printed chart: A for the supply airflow (fresh air pushed into the home), B for the exhaust airflow (stale air expelled outdoors). These are standardized measurement points located on either side of the core.

The Manometer Reading

The unit is turned on at the speed to be balanced. We connect a differential pressure gauge to port A and record the pressure, then to port B and record the second reading. The door chart then converts each pressure reading into the actual airflow in CFM for this specific unit.

On this project, at normal speed:

• First reading, port A: equivalent to 71 CFM
• First reading, port B: equivalent to 88 CFM

A difference of 17 CFM. The dwelling was operating under negative pressure, which would have drawn air from the main house through the slab and partition walls—precisely the opposite of what an intergenerational dwelling should do.

We adjusted the branch registers until we obtained 77 CFM on supply and 76 CFM on exhaust. Then we repeated the measurement at low and maximum speed, because a unit is balanced at one speed only if it has been checked at the others.

The report, provided to the client

The three sets of readings, the converted airflow rates, and the final register positions are recorded and provided to the occupants. This is the document that will allow a technician, eight years from now, to determine whether the system has drifted. Without it, any subsequent diagnosis starts from scratch.

Flexible duct: where performance is lost without anyone noticing

Insulated flexible duct is perfectly acceptable for short connections to the outdoors, and it is often the only realistic choice in a confined space. It still has to be installed correctly.

Three rules we apply without exception:

1. Stretch the flexible duct as much as possible. A flexible duct left loose or compressed to 20% of its length loses a considerable portion of its airflow because each spiral becomes an obstruction. We cut it to the exact length, never “a little longer to be safe.”
2. Limit bends and respect the radius. A tight 90-degree bend in a 5-inch flexible duct is equivalent to several feet of straight duct in terms of pressure loss.
3. Seal the connections in three layers: aluminum tape on the inner duct, a hose clamp, then restore the insulation and exterior vapor barrier with continuous tape. A vapor barrier left open around an exterior-air duct produces condensation in the closet during winter.

On this project, the two exterior branches pass through the ceiling into a service cavity, then exit through the side wall. We chose the shortest route, even if that meant drilling where the finish would be more difficult to restore.

Suspending above a water heater: what must be preserved

The unit is suspended by anti-vibration chains and isolators anchored to the ceiling joists, never placed on a shelf or mounted flat against the wall. Suspension isolates vibrations and allows the unit to be leveled during installation.

Three requirements for this type of location:

• The 14-inch front clearance must remain unobstructed at all times; otherwise, the annual core rinse becomes a disassembly job.
• The electrical outlet must remain accessible. The FLEX is supplied with a power cord and plug; the outlet must therefore be reachable without tools and preferably reserved for the unit.
• The water heater must remain replaceable. A unit suspended too low or too far forward turns a two-hour water-heater replacement into a half-day job. We systematically check the vertical clearance above the tank before securing the anchors.

The ceiling penetration: a detail that becomes costly later

Every ceiling penetration into an unconditioned space must be sealed around its perimeter, both for airtightness and vapor-barrier continuity. An unsealed penetration allows humid air from the dwelling to migrate into the service cavity, where it condenses on the cold side in January.

Acoustic sealant or low-expansion foam applied around the duct solves the problem in ten minutes. If postponed, it becomes a water stain on the ceiling three winters later.

The most common deficiencies with this type of installation

• Deliver the system without measuring the pressures at ports A and B. Without readings, there is no balancing, only an estimate.
• Install a flexible duct that is too long. This is the most common and costly mistake in terms of efficiency.
• Block the core removal clearance with improvised storage.
• Choose a unit that is too powerful for the available space, then install it crookedly because there is not enough room.
• Neglect to seal the penetration.
• Balance at a single speed.
• Do not check the water heater's accessibility.

Rénoclimat and eligibility for this type of project

The Rénoclimat program provides $500 for the installation or replacement of a heat recovery ventilator (HRV) or energy recovery ventilator (ERV), subject to two conditions: the unit must be listed in section 3 of the Home Ventilating Institute (HVI) certified products directory—the FLEX 100H ES is certified there—and the EnerGuide rating must improve between the initial and final assessments.

An important point for a multigenerational dwelling: when the two units share spaces that allow air circulation, the energy assessment covers the entire building, not just the added dwelling. The project must therefore be considered on the scale of the complete building, and the initial assessment must be carried out before opening the first ceiling.

Maintaining an Aluminum Core

The core is removed from the front and rinsed with lukewarm water once a year, without harsh detergent that could damage the aluminum. The washable indoor filters are rinsed every three months. The outdoor hoods are checked in the spring. And in a rental or multigenerational dwelling, we recommend assigning these three tasks to the same person for the entire building—the only way to ensure they are actually done.

How We Work in the West Island

Senneville, Baie-D'Urfé, Sainte-Anne-de-Bellevue, and Beaconsfield combine large properties, recent basement renovations, and tiny mechanical closets. We regularly install ventilation systems there in spaces where the first instinct would be to say that nothing will fit.

The method does not change according to the size of the project: airflow calculations before the quote, equipment selection dictated by the actual space rather than the catalog, manometer balancing at all three speeds, and a report provided. We apply the same discipline throughout Greater Montreal, in Laval, Longueuil, on the North Shore, and on the South Shore, for both a complete HVAC installation and annual HVAC maintenance.

To have the ventilation of an added dwelling, a finished basement, or an entire house assessed, contact us at (514) 316-2973 or sales@airgreen.ca. RBQ 5645-9605-01.