A flat roof installation designed for durability, service access and 4-season comfort
At AirGreen , we adapt each HVAC installation to the real constraints of Montreal buildings. On this Plateau-Mont-Royal plex, we installed a Gree wall-mounted heat pump (R32 series) with a condenser installed on a flat roof . The objective: to guarantee impeccable air flow , facilitate HVAC maintenance and protect the building envelope, while preserving the roof's watertightness.
Building context and choice of location
The building has a gravel roof with a brick parapet topped with a metal flashing. We chose to install it set back from the parapet , on a galvanized structure placed on wooden pads and distribution plates in order to:
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protect the membrane against punctures;
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create clearance under the unit for summer runoff and freezing events;
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allow clear access to service panels for annual inspections.
This position limits the recirculation of hot air in summer and preserves heating capacity in cold weather.
Refrigeration path: clean, short and airtight
The connection route leaves the apartment, crosses the parapet under a metal cap and then heads towards the condenser in a rigid white capping . We have:
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cored at the most favorable point between joist and flashing;
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installed a vapor barrier and a membrane-compatible sealing piece ;
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reinforced UV insulation on refrigeration lines;
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large curvature radius to preserve insulation and mechanical strength.
The total visible length is approximately 6 to 8 meters , optimized to remain within the refrigerant charge range intended by the manufacturer.
Structure and anti-vibration: silence and stability
On roofs, wind resistance and resonances can affect the comfort of neighbors. Our solution:
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Anti-vibration bases under the crosspieces;
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Tighten to the torque prescribed on the stainless steel hardware;
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Checking clearances (rear, sides and ventilated facade) to avoid any air recycling;
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No perforation of the slab: the load is distributed by the soles and the plates.
The result is quiet and stable operation, even during defrost cycles.
Why the Gree R32 series for an urban plex?
Gree's R32 range meets current performance and maintenance criteria in urban environments:
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R-32 refrigerant : better volumetric efficiency and reduced impact compared to R-410A;
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Inverter technology : fine modulation, energy savings and stable temperature;
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Low noise level , ideal on roofs close to residential units;
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Accessible components for quick HVAC maintenance .
In practice, this translates into consistent comfort in summer and winter, controlled energy bills and increased equipment longevity .
Condensate and defrost management
Even on a flat roof, drainage must be considered:
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natural slope of the platform to direct water away from technical passage areas;
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route to an identified evacuation point in order to avoid stagnation;
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clearance under the unit to avoid creating an ice island in winter.
These measures protect the membrane , limit the risk of ice and facilitate maintenance.
Key steps in an AirGreen commissioning
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Nitrogen test and deep vacuum (controlled microns).
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Checking the load according to the actual length of the lines.
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Control of electrical parameters and communication between units.
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Load tests: pressure stability , superheating/subcooling , and validation of defrost mode .
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Delivery of a maintenance guide to the owner: cleaning of interior filters, visual inspection of capping, seasonal verification of clearances.
Site constraints and technical responses
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Gravel roof : distribution plates + wooden soles to distribute the loads and protect the membrane.
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Brick parapet : waterproof crossing under metal cap, without water bridges.
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Wind exposure : set back from the edge and orientation of the condenser to evacuate hot air on the free side.
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Service access : frontal clearance maintained and sufficient height under the base.
Every decision aims to protect the envelope , simplify maintenance and make performance more reliable .
Operating Tips for the Owner
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Keep the area around the condenser clear (no storage).
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Prioritize annual maintenance : washing the fins, checking the connections, testing the pressures.
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After strong winds, quick visual inspection of the soles and capping.
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In winter, check that no snow accumulation is blocking the suction or discharge.
Grants and Eligibility
Several Quebec programs can support the purchase of a high-efficiency wall-mounted heat pump . Eligibility depends on the home's energy profile and the exact specifications of the machine (cold operating range, seasonal performance). We support our clients in Montreal , Laval , Longueuil , the North Shore , and the South Shore to prepare applications when the criteria are met.
What AirGreen delivers on a flat roof project
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Building diagnosis and shortest refrigeration route;
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Roof protection (load distribution, rigorous waterproofing);
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Performance verified in real conditions;
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Clear documentation for maintenance and warranty.
Conclusion — This installation of a Gree wall-mounted heat pump (R32 series) on a flat roof in Plateau-Mont-Royal illustrates our approach: a careful design, a stable structure, exemplary waterproofing and a system calibrated to deliver comfort all year round . This is the AirGreen promise: sustainable, clean and efficient HVAC installations in Montreal and throughout Greater Montreal.