Installation of a GREE FLEXX R32 ULTRA central heat pump (by Dettson) on wall brackets in Saint-Gérard-Majella, in the Pierre-De Saurel RCM

Three meters between two houses, a vegetable garden in full production, and a foundation that had to support the unit

The owner welcomed us one June morning in Saint-Gérard-Majella, a small parish municipality in the Pierre-De Saurel RCM crossed by Route 132, northeast of Sorel-Tracy. His request came down to one sentence: “I want central air conditioning, but I don't want to lose my garden.”

The only available location for the outdoor unit was the side passage between the owner's house and the neighbor's. A corridor about three meters wide, occupied on one side by a strip of pavers and on the other by cucumber and tomato garden beds growing on trellises. There was no worthwhile free ground space.

The solution was to get the unit off the ground: a GREE FLEXX R32 ULTRA central heat pump, distributed in Quebec by Dettson, mounted on steel brackets anchored to the concrete foundation. Here is why this solution worked in this case, and when it should be ruled out.

The selected equipment: 24,000 BTU/h, COP 3.6, 60 dB(A)

Two values in this table directly influenced the decision.

A COP of 3.6 and an EER2 of 12.5 are the best in the entire FLEXX lineup. This is no coincidence: on the same outdoor chassis, the least bulky combination operates with the most generous heat-exchange margin. The compressor does less work to deliver each BTU. In other words, the smallest unit in the family is also the most efficient, which runs counter to many homeowners' instincts.

The 60 dB(A) mattered just as much. In a narrow passage bordered by two walls, sound reflects and becomes concentrated. Three more decibels in the specifications are noticeably more pronounced than in an open area.

The load calculation: why 2 tons, and not 3

A homeowner's first instinct is to want “a little more, just to be sure.” It is the costliest instinct in the industry.

A unit that is too large for the home it serves behaves poorly in three ways:

• It short-cycles. It reaches the setpoint quickly, shuts off, and restarts. Each start-up is when mechanical and electrical stress is greatest.
• It dehumidifies poorly. Air drying occurs while the coil remains cold during steady-state operation. A unit that keeps shutting off never stays in that operating state long enough, and the house becomes cool but damp in July.
• It costs more twice over. When purchased, and then in operation.

The Saint-Gérard-Majella house, modest in size and already equipped with a network of ducts in good condition, was measured room by room: floor areas, orientation, windows, insulation, and air infiltration. The result placed its cooling load in the 2-ton range, with modulation capacity up to 30,000 BTU/h for heat-wave peaks. This calculation, not the gross floor area, determined the choice.

Wall-mounted units: when they are the right solution, and when they are not

We must be clear, because wall-mounted installation is used both appropriately and improperly.

A 187.5 lb unit suspended from the side of a building is acceptable only if four conditions are met simultaneously. If one is missing, the unit must be installed on the ground.

What the wall must be

The anchoring was done into the poured concrete foundation, below the siding level. This is the only portion of this wall capable of supporting a suspended load of this magnitude.

What is unsuitable, and what we refuse:

• Brick veneer. Brick veneer is not structural. It is held in place by ties and an air gap. A heavy unit fastened to veneer will eventually crack the joints and pull loose, sometimes years later.
• Vinyl siding over a wood frame, without direct attachment to the structural framing members.
• A hollow concrete block without a suitable through-anchor.

The rated capacity of the supports

The steel supports used have a rated capacity declared by their manufacturer. This capacity must exceed the unit's weight by a margin, not merely match it. A pair of supports salvaged from an old 80 lb wall-mounted air conditioner is not suitable for a unit weighing more than twice as much, even if it “looks sturdy.”

Anchoring and waterproofing

Every penetration through a foundation is a possible path for water. The anchors were installed with suitable sealant, oriented so that water could not travel inward, and the supports were leveled with a straightedge along both axes. A tilted unit does not drain its defrost water properly.

Vibration isolation

This is the step most often skipped, and the one that generates the most service calls six months later.

Vinyl siding over a wood frame is a sound box. The compressor produces low-frequency vibrations that, when transmitted directly to the structure, become a continuous hum in adjacent rooms—often a bedroom, because bedrooms almost always face the side yard.

Vibration isolation pads were installed between the unit's feet and the supports, and the assembly was mounted so that the cabinet would not come into direct contact with the cladding.

The narrow corridor: the recirculation effect

In a three-meter-wide passage bordered by two buildings, the warm air discharged by the unit in cooling mode does not disperse as it would in an open area. It swirls between the two walls, and some of it returns toward the air intake.

The unit then starts drawing its own discharged air back in. The temperature detected by the coil rises, condensing pressure increases, efficiency drops, and in extreme cases the control module triggers a high-pressure protection.

Three decisions resolved the situation:

1. Discharge orientation toward the most open part of the passage, toward the backyard, never toward the neighbor's wall.
2. Following the manufacturer's clearance requirements behind and beside the coil, without compromising them to gain a few extra inches of clearance.
3. Mounting height, which places the discharge above the area where air stagnates most near the ground.

Snow sliding off the roof

The unit is located beneath a roof overhang. This protects it from direct rain but poses a risk in February.

Snow and ice detaching from a sloped roof fall with considerable force. A sheet of ice weighing a few kilograms that falls one story onto a finned coil can disable it instantly.

We systematically check the fall line before finalizing a location: roof slope direction, the presence of snow guards, overhang width, and the accumulation history described by the owner. At Saint-Gérard-Majella, the selected position is protected by the geometry of the overhang, and we confirmed this with the client rather than leaving them to worry about it during the first thaw.

The vegetable garden: what we adjusted

That was the client's requirement, and it deserved better than a dismissive shrug.

A garden adjacent to an outdoor unit raises two very real questions:

• Coil fouling. Leaves, pollen, seeds, and soil lifted during watering are all drawn into the coil and stick to the fins. This is the leading cause of gradual efficiency loss that we identify during HVAC maintenance on units installed near a flower bed.
• The vegetation itself. A climbing plant that reaches the cabinet will eventually get inside it.

We established a clear zone around the unit with the owner, moved the cucumber trellis line out of that zone, and agreed that the nearest row would remain dedicated to low-growing crops. The mulch was held in place with an edging so it would not migrate toward the air intake. The garden was planted normally that year.

Defrost water above paving

In winter, the unit discharges several liters during each defrost cycle beneath its coil. Mounting it on wall brackets resolves much of the issue by raising the unit off the ground—the ice cannot rise as far as the fins.

The remaining issue is where that water lands. On paving, it freezes and creates an icy patch where people walk. The water was therefore directed toward the strip of soil rather than the pedestrian walkway, and the owner was warned that this area would remain icy at times.

The neighbor, noise, and municipal regulations

An outdoor unit in a side yard is, by definition, closer to the neighbor than to its owner.

Two checks are required even before deciding where to place it:

• Minimum distances from property lines, which vary from one municipality to another in Montérégie and often apply specifically to air-conditioning and heating units.
• Permissible noise levels, sometimes expressed in dB(A) at the property line, and sometimes according to separate daytime and nighttime periods.

Our office verifies these rules with the municipality before installation. A compliant, properly positioned unit costs infinitely less from the outset than one that has to be moved after a complaint.

What happens after installation: the LogisVert application, step by step

This is the part homeowners handle least well, and the one where a well-prepared application can be worth several hundred, or even several thousand, dollars.

Hydro-Québec's LogisVert program provides $50 per 1,000 BTU/h for an efficient heat pump, and $120 per 1,000 BTU/h for a cold-climate-rated unit, calculated based on the certified capacity at -8 °C. ENERGY STAR certification is mandatory for any installation completed since November 26, 2025.

The four required documents

1. The current year's municipal tax bill. The name and address must match those on the other documents exactly.
2. Hydro-Québec identifiers: the 9-digit customer number beginning with 1, and the 11- or 12-character meter number.
3. The purchase and installation invoice, which must include the company's name, its GST and QST numbers, the invoice number and date, the installation date, a description of the heat pump with its AHRI or ENERGY STAR number, the total cost with confirmation of full payment, and the contractor's RBQ licence number.
4. A photo of the outdoor unit's nameplate, on which the model and serial numbers must be perfectly legible.

The four most common reasons for rejection

• Incomplete or illegible documents.
• A mismatch between the name or address shown on the invoice, tax bill, and LogisVert profile.
• A missing AHRI number or RBQ licence number missing from the invoice.
• A blurry or missing nameplate photo.

Three of these four reasons are directly the contractor's responsibility, not the client's.

That's why our teams photograph the outdoor unit's nameplate before the equipment is permanently installed, while it's still accessible and well lit. On equipment mounted on wall brackets in a three-metre passageway, trying to take a readable photo of the nameplate six months later, with the unit in place and the garden in full growth, isn't a pleasant experience.

Our invoices consistently include the AHRI number for the installed combination and our RBQ licence number. This isn't a favor: it's what allows your application to be approved.

Five mistakes specific to side-yard installations

1. Reusing the supports from an old wall-mounted air conditioner without checking their rated capacity.
2. Anchoring into the cladding instead of the foundation or framing.
3. Compromising coil clearances to preserve a pedestrian passage.
4. Directing the discharge toward the neighbor's wall, causing both recirculation and noise disturbance.
5. Neglecting vibration pads on a wall with lightweight cladding.

Where we work

Our teams serve the Pierre-De Saurel RCM — Saint-Gérard-Majella, Sorel-Tracy, Sainte-Victoire-de-Sorel, Saint-Robert, Saint-Ours, Yamaska — as well as the entire Montérégie, from Saint-Hyacinthe to Contrecœur and Varennes.

We install the same support-mounted systems in the narrow side yards of Longueuil, Brossard, Saint-Hubert, and Boucherville, throughout the South Shore, in the dense neighborhoods of Montréal where the passageways between buildings are measured in centimeters, in Laval, and on the North Shore, from Terrebonne to Saint-Jérôme.

The homeowner in Saint-Gérard-Majella sent us a photo in August: his cucumbers had climbed to the top of the trellis, at a safe distance from the unit, and the house was air-conditioned. His LogisVert application had been approved without revisions.

Let's move on to your project

If your only available location is a side passage, if your property cannot accommodate a ground-level base, or if you simply want to know what capacity your home actually requires, the answer begins with a site survey and a load calculation.

At AirGreen, every HVAC installation project includes room-by-room load calculations, verification of the selected mounting system's load-bearing capacity, validation of applicable municipal regulations, and complete preparation of the financial assistance application. Contact us about your central heat pump project in Saint-Gérard-Majella, in the Pierre-De Saurel RCM, in Montérégie, on the South Shore, in Montréal, in Laval, in Longueuil, or on the North Shore.