Two raised units, designed for Montreal's extreme cold: performance, silence and maintenance access
At AirGreen , we design every HVAC installation to withstand Montreal winters without compromise. This project in Rosemont–La Petite-Patrie illustrates our approach: two Sharp wall-mounted heat pump units (ZU1 series, R-32 refrigerant) , installed on a flat roof , carefully raised above the snow level and cleared to ensure optimal airflow even in extreme cold.
Building context and objectives
The brick building houses several apartments. The occupants wanted an energy-efficient and reliable heating solution down to sustained sub-zero temperatures, without transmission of vibrations inside and with safe maintenance access to the roof. We selected the Sharp ZU1 , an R-32 (A2L) wall-mounted heat pump , renowned for its stable operation in cold weather and excellent seasonal efficiency.
Key objectives:
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Reliable low-temperature heating and quiet summer air conditioning .
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Clean, durable roof integration that complies with clearances.
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Easy HVAC maintenance , with accessible components and clean pathways.
Details of the roof installation
Support and clearances
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Each condenser rests on a galvanized steel trestle fixed to Unistrut rails with anti-vibration pads .
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Significant clearance under the frames: the base of the units remains well above the visible accumulation of snow , limiting the risk of blockage of the exchangers and facilitating defrosting.
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Rear and side clearance respected for optimal airflow: no immediate obstruction around the grilles.
Refrigerant and electrical paths
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The refrigeration lines are continuously insulated and UV-sheathed (visible black sheath) to protect the insulation from sun, ice and friction.
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Power and communication cables follow the same protected path, with controlled bend radii to preserve conduit integrity.
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Service/disconnect boxes located within technical reach (near roof access), reducing intervention time.
Condensate management in heating mode
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The height under the units and the release from below allow the natural flow of defrost water, avoiding the formation of ice stalagmites in contact with the frame.
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Drip trays remain clear; seasonal maintenance checks the condition of the drains.
Device and expected performance
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Brand / range: Sharp ZU1 (R-32)
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Type: wall-mounted heat pump (mini-split)
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Use: main supplementary heating in cold weather, efficient air conditioning in summer
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Key features: inverter technology, high-efficiency compressor, optimized defrost function , low noise levels, high efficiency even in negative temperatures common in Montreal.
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Energy efficient: R-32 refrigerant, reduced charge and better GWP than older generations, eligible for grant programs when combined with cooling performance criteria.
Winter constraints and solutions implemented
Snow, wind, ice:
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Significant elevation of the units to maintain free air intake .
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Orientation designed to avoid recirculation of hot air in defrost mode.
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Galvanized fasteners and stainless hardware: increased corrosion resistance.
Vibrations and noise:
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Anti-vibration pads and rigid frame ensure minimal transmission to roof elements.
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Alignment of the fans and tightening of the fasteners to the correct torque to limit any parasitic noise.
Waterproofing and building envelope:
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The crossings towards the technical columns are flashed and the vapor barrier restored to preserve the envelope.
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Slopes and elevations respected so as not to create water retention islands under the supports.
Result: four-season comfort and simplified maintenance
This two-unit rooftop configuration ticks all the boxes:
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Uniform comfort for separate accommodations, each supervised by its own interior head.
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Controlled aesthetics : no influence on the facades or balconies.
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Quick maintenance : direct access to service valves , electronics and filtration without moving the devices.
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Durability : materials suitable for freeze/thaw cycles, protected parts and long-lasting UV insulation .
AirGreen Best Practices for Rooftop Heat Pumps (Montreal, Laval, Longueuil, North Shore, South Shore)
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Minimum height : Aim for 30–45 cm of free air below the units for effective defrosting.
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Short and compact paths : reduce refrigerant pressure losses and facilitate leak detection.
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UV/frost protection of insulation: sheath and attach at regular intervals.
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Standard clearances : respect the manufacturer's distances around the grilles.
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Electrical : dedicated circuit breaker, accessible disconnection , cables secured and protected.
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HVAC maintenance : cleaning of batteries, checking of pressure switches , checking of refrigerant charge and tightness each season.
What the occupants earn
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Energy savings thanks to the inverter and R-32 .
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Quiet and stable in winter heating mode.
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Flexibility of use: each accommodation controls its own zone, precise and rapid temperature.
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Increased real estate value through a clean , documented and compliant installation.
Our commitment
Throughout Greater Montreal — Montreal , Laval , Longueuil , North Shore , South Shore — we deliver rigorous installations, designed to last and optimized for the Quebec climate . This project in Rosemont–La Petite-Patrie is a demonstration: two Sharp wall-mounted heat pumps (ZU1, R-32) , raised on a flat roof, ready to provide four-season comfort with easy maintenance.