An HVAC modernization designed for Montreal plexes
At AirGreen , we design HVAC systems that meet the architectural constraints of Greater Montreal's plexes while delivering reliable, four-season comfort. This project in Rosemont–La Petite-Patrie demonstrates the careful integration of a Gree Ultra Heat MultiZone heat pump on an existing flat roof , providing optimal performance for multiple indoor zones, even in extreme cold.
Building context and performance objectives
The building is a typical urban plex with membrane roofs, surrounded by masonry chimneys, low parapets, and drainage accessories. The client's needs can be summarized in three points:
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Stabilize the temperature in several interior areas, summer and winter, with minimal noise levels so as not to disturb nearby neighbors.
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Choose a machine that is resistant to Montreal winters (guaranteed starts and useful heat at low temperatures).
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Maintain the waterproofing and durability of the roof when drilling and passing conduits.
The Gree Ultra Heat meets these criteria perfectly: it is a multi-zone heat pump designed to maintain heating capacities at very low temperatures and provide efficient air conditioning during summer heat waves.
Design and execution of the installation: precision and durability
Support: a base that protects the membrane
We place the outdoor unit on a treated wooden structure resting on anti-vibration pads and distribution wedges to protect the roof membrane. This base:
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Diffuses loads (static weight + wind forces) to avoid punching.
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Reduces vibrations transmitted to the slab, limiting the propagation of noise towards the interior.
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Facilitates periodic inspection of the membrane and snow removal around the equipment.
Good to know: On flat roofs, we avoid unnecessary structural drilling. Proper sizing of the base, load distribution, and elastomeric pads are generally sufficient to meet wind and frost constraints.
Implementation and clearances
The unit is oriented with its back to the parapet, with free clearance on the exchanger front. This configuration guarantees:
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Smooth air circulation around the batteries.
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Convenient access to service panels for maintenance.
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Reduced risk of sucking in hot exhaust air (recirculation phenomenon).
Refrigeration and electrical routing
The refrigerant pipes follow a short, clear path on the roof, which is continuously insulated and sheathed for UV protection. Key points:
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High-density cold insulation covered with a UV-resistant sheath to prevent premature aging.
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Bend radius respected on elbows to preserve the flow of refrigerant.
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Base-mounted disconnect box in close proximity to the condenser for quick disconnection during service operations.
On the power supply side, the circuit is dedicated, sized according to the nominal intensity of the Gree Ultra Heat, with sealed conduits and cable glands adapted to the thermal cycles of the roof.
Roof penetrations and waterproofing
The penetrations (refrigeration, drain, supply) pass through a sealed roof sleeve , with membrane-compatible flashing and mastic. Our methodology:
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Controlled drilling at the shortest location from the inner heads.
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Raised technical sleeve/chimney to prevent potential water ingress.
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Cold waterproofing restoration according to the roofer's instructions.
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Expansion joints provided on exposed ducts to absorb seasonal thermal movements.
Result: the integrity of the roof is preserved , and the risk of infiltration is minimized .
Condensation management
Condensation mainly affects indoor units in air conditioning mode. We favor gravity drainage where possible, otherwise we integrate a silent lift pump with a float switch. On the roof, we provide local slopes and clearance around the base to prevent ice in winter.
Advantages of Gree Ultra Heat for Montreal and its winters
Low temperature performance
The Ultra Heat Series is designed to maintain stable heating capabilities when the thermometer drops. For a plex building, this means:
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Reliable starts in extreme cold.
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Reduced electrical backup , therefore lower operating costs .
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Consistent comfort in the areas served, with no cold spots near the windows.
Scalable multi-zone
The MultiZone configuration allows several indoor units (wall-mounted, console, cassette) to be powered with a single condenser. Advantages:
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Modularity : addition of later zones possible if rooms are renovated.
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Fine management : each zone has its own thermostat and setpoint , limiting waste.
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Aesthetics : fewer exterior units on the facade or courtyard.
Silence and urban comfort
The outdoor unit is low-noise , a crucial point in dense areas like Rosemont. Anti-vibration pads and the distance to the parapet further reduce noise transmission to neighbors and the interior.
AirGreen Execution Quality: What Makes the Difference
Sizing and verifications
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Linear length of lines marked from the design stage (roof route + downpipes). We aim for reasonable lengths to respect the refrigerant loads provided by the manufacturer and maintain nominal efficiency .
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Nitrogen leak testing and deep vacuum with micron control before commissioning.
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Setting up remote controls/controllers, synchronizing zones and checking defrosting in real conditions.
Durability and maintenance
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Permanent markers (UV labels): circuit identification, serial numbers, nominal currents.
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Optimized service access : the position of the condenser allows maintenance without scaffolding .
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Recommended maintenance plan : cleaning of internal filters, rinsing of exchangers, checking of electrical tightening and drain crawl space.
Security and Compliance
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Disconnect switch within easy reach, compliant wiring and rigorous earthing .
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Compliance with standard clearances around the condenser and roof access routes .
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Coordination with the roofer for all membrane repairs.
Concrete results for the client
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Four-season comfort in all service areas, without overheating or feeling drafty.
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Significant cost reduction compared to electric baseboards thanks to the high COP of the heat pump.
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Visual discretion : no equipment on the facade, the roof remaining the main technical area.
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Roof preservation : no unnecessary through-fixing, protected supports and anti-vibration device.
Grants and administrative support
In Greater Montreal (Montreal, Laval , Longueuil , North Shore , South Shore ), high-performance heat pumps may be eligible for assistance programs (e.g., LogisVert/energy efficiency based on certification criteria). Our team:
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Checks the configuration eligibility (model, low temperature heating performance).
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Prepares documentation (serial numbers, detailed invoices, installation photos).
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Advises on additional work that could improve the request (waterproofing, checks).
AirGreen Tips for a Successful Flat Roof Project
To do
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Provide access to the roof for maintenance (hatch, fixed ladder, safe schedule).
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Clear snow around the unit after major storms to prevent air recirculation.
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Plan annual maintenance before peak seasons (spring/fall).
To avoid
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Installing the unit too close to a parapet or projection that obstructs heat exchange.
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Undersizing lines or neglecting UV insulation: guaranteed performance losses.
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Pierce the membrane without coordinating with a roofer: waterproofing is a priority.
Conclusion
This Gree Ultra Heat MultiZone heat pump installation in Rosemont–La Petite-Patrie demonstrates the balance we seek between performance , silence , durability and respect for the building . On a Montreal flat roof, the key lies in a suitable support base , perfectly sealed penetrations and an exemplary refrigeration path . At AirGreen , we support our customers from design to after-sales service, for controlled comfort year after year.