A flat roof installation designed for Montreal's extreme cold
In Rosemont–La Petite-Patrie , we installed a Sharp ZU1 wall-mounted heat pump for a typical plex with flat roofs. The client wanted a four-season system combining efficient heating in winter and gentle cooling in summer, with clean and sustainable integration on the roof. Our intervention emphasizes three priorities: performance in extreme cold , longevity of the equipment and respect for the building envelope .
Building context and client objectives
The building, a modernized 1950s triplex, has a recent roof membrane and technical access via a hatch. The serviced apartment is located on the top floor, which reduces connection lengths by positioning the condenser directly on the roof. The mandate:
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ensure reliable heating even in the intense cold of the Montreal plateau;
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preserve the integrity of the membrane and limit vibrations transmitted to the structure;
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obtain a neat HVAC installation , accessible for maintenance, and compliant with the required clearances for snow and wind.
Equipment selection: Sharp, ZU1 range
Sharp's ZU1 range is renowned for its cold climate performance and the use of the more efficient R-32 refrigerant. Inverter modulation adapts power to actual needs, reducing on/off cycles and electricity consumption. For a flat roof exposed to gusts, the mechanical stability of the unit and frost management are essential: the housing design, the high-density fin exchanger and the defrost logic help maintain stable performance during snowfalls.
Key benefits for the customer
Heating and air conditioning with a single device ( heat pump ).
Silent operation inside thanks to modulation and external positioning away from the facades.
High seasonal efficiency , conducive to long-term energy savings.
Eligibility for current grant programs for high-efficiency equipment in Quebec (according to model and installation criteria).
Roof installation: structure, anchoring and protection of the membrane
We have chosen a raised aluminum support , equipped with anti-vibration pads and placed on distribution soles . The objective is twofold:
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Avoid any punching of the membrane by distributing the load;
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Elevate the condenser above accumulated snow and runoff areas to ensure free air intake and efficient defrosting.
The highlights of the implementation:
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Raising : sufficient height to take into account accumulations of snow and snowdrifts created by the wind.
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Orientation : suction and discharge grilles clear of obstacles (lines, vents, ballast guards) to limit recirculation of cold air during defrosting.
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Meltwater management : peripheral clearance for flow; no stagnation under the device.
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Safe paths : clear technical passages for the movement of maintenance technicians, even in winter.
Refrigeration connections and power supply: sobriety and serviceability
The refrigeration lines are routed along the shortest path to the wall of the accommodation. We used:
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UV insulation resistant to freeze/thaw cycles and radiation;
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rigid white capping at exposed points, for long-lasting mechanical protection;
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regularly spaced retaining collars , preventing buckling in the summer sun.
For the power supply, we installed a NEMA 3R disconnect box near the unit, in accordance with safety requirements. The connection is protected by a dedicated circuit breaker in the housing panel. We systematically document: circuit breaker rating, conductor rating, grounding , and compliance with clearances around the disconnect for future work.
Condensate and frost management
On roofs, frost generated during heating mode must be taken seriously. Our approach:
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Clearance under the unit for defrost water to flow freely to natural drainage areas;
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Absence of obstacle under the tray to avoid re-glazing around the supports;
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No external condensate pump required (risk of freezing), everything is managed by gravity and the raised installation.
Inside, the wall head has its gravity drain with controlled slope. We avoid pumps when the site configuration allows it in order to reduce noise and maintenance .
Execution details that make the difference
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Single sealed penetration with vapor barrier around the crossing.
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External service loop to avoid mechanical stress on flare fittings.
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Vacuum check and fluid weighing according to actual line length; load adjustment if required by manufacturer.
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Operational test on both modes, control of superheating and subcooling , and measurement of temperature differentials on the interior side.
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Recording of values in the report (pressure, intensity, voltage at load), useful for maintenance monitoring.
Result: stable comfort and controlled aesthetics
The client now benefits from rapid heating at the start of the day and pleasant air conditioning from the first warm days. The outdoor unit, discreet from the street thanks to its rooftop installation , does not disturb the aesthetics of the facade. The wall-mounted heat pump ensures uniform comfort in the main living area, with air diffusion optimized by the installation height of the indoor head.
HVAC Maintenance: Our Simple and Effective Plan
To maintain performance, we recommend:
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Clean the inner head filters every 4 to 6 weeks during use.
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Annual AirGreen inspection : pressure check, terminal tightening, defrost test, gentle washing of the exchanger.
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Autumn check : clearance around the condenser, visual inspection of the support, restart with heating test.
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Good winter practices : do not obstruct the grilles with stored objects; gently clear the blown snow if necessary (without aggressive tools).
Grants and Compliance
The ZU1 range is one of the most popular energy-efficient solutions in Montreal, Laval and Longueuil , as well as on the North Shore and South Shore . Depending on the configuration chosen (capacity, seasonal efficiency, nominal operating temperature), the installation may be eligible for provincial programs promoting energy efficiency. We assist our clients in producing supporting documents : model number, serial number, detailed invoice, photo evidence and installation diagrams.
Common mistakes… that we avoid
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Installing the condenser too low on the roof: risk of blockage by snow and recirculation of very cold air during defrosting.
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Direct anchoring in the membrane without distribution soles: source of infiltration and premature degradation.
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Insufficient bending radius of the connections and absence of expansion loop: leaks in the medium term.
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Poorly positioned or unprotected electrical disconnection : non-compliance and maintenance difficulties.
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Use of external condensate pumps in cold climates: recurring breakdowns.
Our AirGreen method eliminates these risks through design , verification and documentation .
Why AirGreen for your projects in Rosemont–La Petite-Patrie and Greater Montreal
Our team masters the specificities of flat roofs for Montreal plexes: access, security, snow, prevailing winds, technical traffic and neighborhood. Each project is treated as a whole : choice of material, respect for the building, aesthetics , acoustics, ease of maintenance and electrical compliance . We operate in Montreal, Laval, Longueuil, North Shore and South Shore , with controlled deadlines and consistent quality from the first diagnosis to commissioning.
AirGreen — your trusted partner for HVAC installation ** and maintenance of high-efficiency wall-mounted heat pumps in Montreal and surrounding areas.**