A rooftop installation designed for Montreal's climate, by the AirGreen team
At AirGreen , we carried out a complete HVAC installation in a flat-roofed building in the Saint-Laurent district (Montreal): a Sharp ZU1 series wall-mounted heat pump with a condenser installed on the roof on raised supports. The client's objective was twofold: to benefit from four-season comfort for a large open-plan space, while preserving the aesthetics of the facades and freeing up the ground floor . The site presented a typical challenge for urban roofs: stagnant water after rain and numerous existing holes (ventilation, vents). We designed a robust, durable solution that complied with local standards, designed for Montreal winters and intense rain events.
Building context and implementation strategy
The building is a low-rise building surrounded by greenery and other technical roofs. The presence of water reflections on the membrane confirmed a temporary retention typical of bituminous/gravel roofs. In this context, we favored:
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Raising the condenser on anti-vibration H-stands , height calculated to stand above potential puddles and the winter snow line .
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Compact refrigerated path , protected by UV capping up to a waterproof roof passage (“gooseneck” cap and flashing).
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Dedicated electrical section with roof disconnect , UV-resistant reinforced wiring and secure routing.
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Condensate management : roof discharge with positive slope towards an evacuation point; heating cable option provided if the customer decides to operate in air conditioning mode at temperatures close to 0°C.
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Wind protection : orientation of the condenser with its back to the prevailing gusts on the site, clearances respected for optimal air flow and to avoid recirculation.
Inside, the Sharp wall-mounted unit is positioned high to take advantage of the Coanda effect and efficiently cover the work area. This configuration reduces on/off cycles and stabilizes the temperature, especially during afternoon heat waves .
Key steps in AirGreen installation
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Load study and electrical verification (circuit breaker, wire gauge, grounding).
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Structural identification : routing of lines without interfering with existing conduits or reinforcing steel; location of the drilling area with safety margin.
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Drilling and roof passage : collar + flashing, butyl mastic and polyurethane sealant; tar pocket avoided in favor of a modern mechanical assembly.
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Condenser mounting : H-stands placed on distribution pads (membrane protection), level checked; silent blocks to limit vibration transmission to the building.
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Copper lines : dynamometer flares, bending radii respected; class 1 UV-resistant insulation, taped joints and continuous cover .
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Nitrogen test (pressurization and bubble test), then deep vacuum drawing up to the validated micron threshold; vacuum holding checked.
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Commissioning : opening of valves, reading of currents, reference superheating/subcooling , indoor air flow test, calibration of gravity drain .
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Finishing touches : disconnect signaling, interior/exterior sealing , area cleaning, compliance photos for the customer file.
Why the Sharp ZU1 series for Saint-Laurent?
The Sharp ZU1 ( R-32 refrigerant) is a wall-mounted heat pump designed for extreme cold and urban buildings :
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High-precision inverter compressor : fine modulation, energy savings and reduced wear.
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High efficiencies (SEER/HSPF) and reliable low temperature heating , relevant for Montreal.
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Controlled acoustics : a major advantage on a flat roof close to other occupants.
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Simplified maintenance : direct access to the condenser, easy-to-remove panels, protected electronics.
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R-32 : lower charge and better volumetric efficiency compared to older fluids.
For this space, the 12,000–18,000 BTU range meets the needs after sizing (volumes, solar gains, envelope). The solution remains scalable if a future multi-zone proves relevant.
“Flat roof” specificities: what we put in place
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Water management : the slight stagnation visible after rain does not affect operation; the H-stands ensure ground clearance. We check the roof slope and the position of the drains to avoid any prolonged immersion of the supports.
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Snow clearances : the free height under the unit facilitates defrosting and limits snow banks around the fan.
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Anti-corrosion : galvanized/stainless steel hardware, protected anchor points, UV-resistant conduits and insulation.
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Noise/Vibration : flow direction and silent blocks to avoid transmitting vibrations to the occupants; sound control in forced operation.
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Safety & Access : Clear access path, disconnect within reach, clear labeling for future maintenance.
HVAC Use and Maintenance Tips
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Winter : stable setting (20–21°C), cleaning filters every 1–2 months; check that snow clearances on the roof remain clear.
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Summer : dehumidification mode on humid days; setpoint 23–24°C for a good comfort/economy compromise.
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Annual (by AirGreen): electrical inspection, pressure meter checks, exchanger cleaning, condensate drainage test, roof leak tightness check around the roof passage.
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Good to know : avoid forcing setpoint deviations too frequently; the Inverter works better on gentle slopes.
Grants, Compliance and Guarantees
High-efficiency wall-mounted heat pumps like the Sharp ZU1 are generally eligible for incentive programs in Quebec, subject to performance and configuration conditions. We support:
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eligibility verification ,
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preparation of the file (serial numbers, detailed invoices, before/after photos),
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submission and monitoring, in order to optimize return on investment .
The installation complies with RBQ and CSA standards, as well as the requirements of the co-owner /owner for any roofing work (access, PPE, schedules). Our work is covered by a clear labor warranty ; maintenance plans are offered to maintain the performance and longevity of the equipment.
Result: stable performance, contained noise, preserved roof
Upon commissioning, the treated room quickly reaches the setpoint ; the condenser switches to low speed with a discreet noise level, without resonance in the structure. The raised installation and the covered route protect the installation from hazards (rainwater, snow, UV), while facilitating access for future maintenance . The customer benefits from measurable comfort , improved air quality and a reduction in the energy bill compared to direct electric heating or a non-Inverter air conditioner.
AirGreen, your HVAC partner in Greater Montreal
We provide custom solutions for flat roofs, houses, plexes and condos in Montreal, Laval, Longueuil, on the South Shore and the North Shore . Our teams install and maintain wall-mounted heat pumps (Sharp, Gree , Midea , Fujitsu ), central systems and interior systems (cassette, ducted, console). Each project is delivered clean, compliant and documented .