Two flat-roof units for reliable and discreet comfort — an AirGreen project designed for Montreal winters
In Rosemont–La Petite-Patrie , we installed two GREE wall-mounted heat pumps (recent R32 series) , with their outdoor condensers installed on a flat gravel roof . The objective: to provide efficient heating in very cold weather and stable cooling in the summer to two apartments in a low-emission building, while respecting the union's requirements and the integrity of the roof membrane.
Project context and roof constraints
The building is a typical Rosemont plex with a flat roof covered with gravel . The owner wanted:
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Minimize the visual impact on the facade;
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Avoid any vibration transmission to the housing;
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Preserve the existing bituminous membrane and the waterproofing of the upstands;
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Ensure easy access for maintenance without disturbing residents.
We therefore recommended installing the condensers on self-supporting frames on the roof, instead of wall mounting in the courtyard. This configuration avoids noise pollution on the courtyard side and simplifies the routing of connections to the interior heads.
Technical choice: GREE R32 series wall-mounted heat pumps
The selected units belong to GREE's R32 range , compatible with extreme cold and designed to optimize seasonal efficiency . Without setting a specific reference, the configuration is similar to the Livo/Vireo R32 families, which are very popular in Montreal.
Relevant highlights for this project:
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R-32 refrigerant : lower GWP than R-410A and better volumetric efficiency;
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Inverter compressor offering fine modulation, energy savings and soft starts;
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Reliable heating down to −25°C (depending on the size chosen), ideal for Montreal winters;
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Reduced sound levels, useful on roofs near skylights and vents;
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Compatibility with aid programs when effectiveness criteria are met.
Flat roof installation: AirGreen method
1) Supports and load distribution
We used galvanized frames placed on large-surface support soles , with non-slip EPDM mats to distribute the load and protect the membrane . The rails are oriented perpendicular to the slope to limit punching and resist prevailing winds.
2) Anti-vibration anchoring and alignment
Each condenser rests on anti-vibration mounts to cut off mechanical transmission. The alignment of the units ensures adequate clearances around the exchangers and facilitates maneuvers for technicians.
3) Routing of refrigerant connections
The insulated copper lines and communication cable run in UV ducts along a short path to the roof penetrations. Penetrations were made in flashing boxes with elastomeric sealant and fire collars where required, ensuring a durable seal.
4) Condensate management and defrosting
In heating mode, defrost water is freely discharged onto the gravel bed, away from risers and drains to prevent localized freezing. In summer, condensate from the indoor units is gravity-fed to indoor drain points; no pump was required, reducing maintenance.
5) Power supply and disconnection
Each condenser has a watertight roof- mounted disconnect box with UV-safe MC wiring . Circuits are run on cable trays attached to the ballast, all connected to dedicated circuit breakers in the main panel, in accordance with CSA C22.1 standards and RBQ requirements.
Construction site and safety coordination
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Secure roof access (lifeline, harness) and marking of work areas;
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Implementation plan validated with the owner to keep maintenance routes free (drains, vents);
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Checking the tightening torque of the flare fittings, placing under nitrogen , vacuum < 500 microns with recording;
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Commissioning by our certified technicians: compensation of refrigerant charge according to actual lengths, verification under load, mode setting.
Result: performance, silence and easy maintenance
Residents benefit from immediate cooling and stable heating in the mid-season; inverter modulation eliminates unpleasant temperature fluctuations. On the roof, noise levels remain low thanks to anti-vibration pads and the distance from the parapets. The clear driveway layout allows for:
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effective defrosting in winter (unobstructed airflow),
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rapid dusting of the exchangers if necessary,
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easy reading of nameplates and pressures.
Maintenance recommended by AirGreen
To maintain seasonal performance and lifespan :
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Spring : cleaning of external batteries, condensation test, inspection of insulation and UV trunking;
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Autumn : check heating pressures, inspect electrical connections, check snow clearances;
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Interior : Wash filters every 1 to 2 months during periods of intensive use.
Our maintenance visits include a measurement report (blowing/suction temperatures, compressor intensity, vacuum draw during any open intervention), which preserves the guarantees and reassures the union.
Best practices to remember for Montreal flat roofs
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Never anchor through the membrane without consulting a roofer; favor controlled ballast ;
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Anti-wind lift: choose frames sized and spaced in accordance with local wind speeds;
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Provide snow clearance and, if the site is exposed, the addition of a deflector ;
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Avoid excessively long connection routes: performance and loads depend on them;
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Always install a visible disconnect switch near the equipment.
What this installation changes for the owner
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Energy savings compared to electric convectors and window air conditioners;
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4-season comfort with a regular temperature in each accommodation;
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Low visual impact on the facade and reduced noise for the interior courtyard;
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Increased rental value thanks to recent equipment, R32 refrigerant and structured maintenance.
We also support our clients in verifying eligibility for subsidies (provincial and municipal programs when the required performance indices are met).
AirGreen, your HVAC partner in Montreal, Laval, North Shore and South Shore
Our teams operate every week in Montreal (Rosemont, Villeray, Le Sud-Ouest, Ville-Marie) , Laval and on the Rives to install wall-mounted and multi-zone heat pumps from recognized brands ( GREE, Fujitsu, Midea, Sharp , etc.). Our commitment: correct sizing , clean installation , responsive after-sales service .
Warning
Heat pump installation must be performed by a qualified contractor with an RBQ license . Any non-compliant modifications—particularly to roofing—may compromise the watertightness, manufacturer's warranty, and electrical safety.