Optimizing the comfort of two dwellings in a dense urban environment, without encroaching on living space
At AirGreen , we design HVAC installations as a technical architecture project: respecting the building, preserving its aesthetics, and delivering reliable four-season comfort in Montreal. In this Rosemont–La Petite-Patrie plex, we installed two GREE FreeMatch R32 outdoor units on the flat roof to power several wall-mounted indoor units. This choice frees up balcony space, reduces sound transmission to occupants, and facilitates maintenance, while ensuring high efficiency in Montreal's extreme cold .
Context: a Rosemont plex, gravel roofs and limited access
The building has all the characteristics of a Montreal plex: flat gravel roof , narrow walkways and wooded surroundings. Since the balconies are used by the occupants, we chose to install the outdoor units on the roof in order to:
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keep balconies clear and safe;
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improve air circulation around the condensers;
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reduce the transfer of vibrations to housing;
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centralize maintenance points for our HVAC maintenance visits.
Equipment choice: GREE FreeMatch R32, flexible and scalable
The GREE FreeMatch R32 range is ideally suited to Montreal plexes. It allows several indoor heads (2 to 5 depending on capacity) to be connected to the same outdoor unit, with a low GWP R-32 refrigerant . We selected this solution for its modularity , its high seasonal efficiency , its low temperature heating operating range and the availability of parts on the local market.
Key technical assets:
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Fine modulation inverter for stable temperature;
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R-32 : better environmental performance than R-410A;
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Optimized winter operation (extreme cold configuration);
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Compatibility with several head formats (wall, console, cassette).
Preliminary study and execution plan
Before installation, our team carries out:
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Calculations of charges per dwelling (surface area, insulation, orientation, infiltration).
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Tracing of routes for refrigerant lines and electrical supply from each dwelling to the roof (technical risers, landings, sealed passages).
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Choice of roof locations based on clearances, prevailing winds and shade from neighboring trees.
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Structural verification : distribution of the load on the flat roof via rails and pads in order to protect the membrane.
Installation on roof: stability, drainage and silence
The two condensers are installed on galvanized steel frames placed on large white soles , themselves secured to treated wooden joists . This combination:
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distributes loads evenly;
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protects the membrane against punctures;
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mechanically separates the devices to limit vibrations ;
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maintains clearance above the gravel for better frost drainage.
We leave compliant service clearances around each machine to facilitate battery cleaning and interventions. The electrical boxes are mounted at working height, with connections under UV-sealed conduits .
Refrigeration path and sealing
From the apartments, the lines rise through the load-bearing walls to the roof. Our technicians:
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use high-density insulation resistant to UV and variations from −30°C to +40°C;
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protect roof penetrations with flashings and mastics compatible with the existing membrane;
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install protective covers over exposed sections for a clean and durable finish;
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carry out the vacuum draw and the nitrogen leak test according to the rules of the art.
Result: a perfectly sealed network, a guarantee of performance and reliability .
Power supply and protections
Each outdoor unit has its own disconnect switch in the immediate vicinity. The circuits are sized according to the nameplate, with circuit breakers dedicated to the housing electrical panel. The metal conduits and cables are:
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certified exterior ;
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fixed on corrosion-resistant supports;
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grouted to prevent any water infiltration.
This rigor guarantees safety and simplifies diagnosis during maintenance visits.
Noise management: neighborhood and comfort
Installing on the roof reduces the spread of noise to living areas. We add:
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anti-vibration pads under the chassis;
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an alignment which avoids reverberation on the acroterion;
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sufficient clearance for the fans to circulate undisturbed air.
Occupants thus benefit from discreet operation , in line with the expectations of a residential area like Rosemont.
Commissioning and fine-tuning
After the vacuum draw , we proceed with the commissioning :
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control of superheating and subcooling ;
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calibration of ventilation speeds of indoor heads;
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synchronization of modes (heating/air conditioning priority according to zones);
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configuration of remote controls and explanation of best practices to occupants (filters, adjustment range, defrosting).
These personalized settings ensure immediate comfort while optimizing consumption.
Installation Highlights (Technical Summary)
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Type of accommodation: plex in Rosemont–La Petite-Patrie
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Solution: 2 GREE FreeMatch R32 Multi-Zone heat pumps on a flat roof
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Supports: galvanized frames, wide soles and treated joists , anti-vibration pads
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Route: waterproof technical climbs, UV insulation , finishing hoods
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Electrical: proximity disconnectors, dedicated circuits, external conduits
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HVAC maintenance: easy access, peripheral clearances respected
Subsidies and economic benefits
New-generation heat pumps that run on R-32 or R-454B and perform well in cold weather are generally eligible for programs in Quebec. In projects like this, our advisors assist homeowners in preparing files (energy assessments, proof of purchase, photos, serial numbers) to maximize assistance and reduce the net cost of the project .
AirGreen Best Practices for Flat Roof Installations
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Load distribution : favor large-surface soles and avoid concentrated support points.
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Snow/frost clearances : raise units to prevent snow suction and facilitate defrosting .
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UV protection : UV-resistant insulation and sheaths on all exposed sections.
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Condensate management : provide gravity routes for the interior heads, and check the evacuation in cooling mode.
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Maintenance access : maintain aisles around the machines and indicate their location on building plans.
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Annual check : battery cleaning, leak test and recalibration of parameters to maintain seasonal performance .
Result: balanced comfort, clear facades, preserved building value
The occupants now benefit from efficient heating in winter and effective air conditioning in summer , without compressors on the balconies or visible ducts on the facades. The owner benefits from a reliable , scalable and easy-to-maintain system, perfectly adapted to the Montreal reality .
AirGreen, your HVAC partner in Montreal, Laval, Longueuil, North Shore and South Shore
Our team understands the constraints of plexes and condos in Greater Montreal . Whether installing wall-mounted heat pumps , multi-zone rooftop systems, or central systems, we deliver meticulous , efficient, and compliant projects, with HVAC maintenance monitoring that extends the lifespan of your equipment.