A roof installation designed for the Montreal climate, longevity and silence
At AirGreen , we have just installed a Sharp wall-mounted heat pump – ZU1 series (R-32) in a residential building in Rosemont–La Petite-Patrie . The outdoor condenser is installed on the gravelled flat roof , a configuration very popular in Montreal plexes to free up courtyard space and limit noise at the windows. This page details our approach: sizing , refrigeration path , supports , electrical , condensate management , roof waterproofing , commissioning and maintenance tips . The objective: four-season comfort with a clean, durable and easy-to-maintain HVAC system.
Why Sharp ZU1 series for this project
The Sharp ZU1 is one of the new generations using R-32 refrigerant , which is more efficient and has a lower GWP than R-410A. It offers:
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Inverter modulation to precisely adjust capacity according to thermal load.
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Extreme cold heating range (down to approx. −25/−30°C depending on configuration), suitable for Greater Montreal winters.
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Low noise levels on the indoor unit and condenser side, highly appreciated in urban environments.
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Common series capacities available (12k to 24k BTU), allowing fine adjustment to the volume to be treated.
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Filtration and dehumidification functions that improve comfort in summer.
In this home, the ZU1 has been sized for the main living area , with room for heat peaks. We always favor realistic sizing , which avoids short cycles, protects the compressor and optimizes operating costs.
Built context: flat roof, membrane and point loads
Plexiglas roofs in Rosemont–La Petite-Patrie combine membrane, gravel, and parapets . Successful installation takes into account:
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Load distribution : we use raised aluminum frames placed on anti-vibration pads and treated wooden beams . The weight is thus distributed, without punching the membrane.
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Expansions and vibrations : rubber inserts and controlled tightening to protect the structure and the coating.
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Air clearances : orientation and distance between condensers respected to guarantee free passage and heating performance (defrosting).
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Service access : easy movement for maintenance, clearance of the hood and electrical panel.
In this case, two condensers coexist in the same technical area. We have optimized the installation of the Sharp ZU1 to maintain standard clearances, suction and discharge, and facilitate any future intervention.
Refrigerated path: cleanliness, insulation and durability
From the interior head, the refrigerant lines rise to the roof via a technical duct . Our team has:
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Formed a service siphon and an anti-vibration loop to protect the connections.
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Used deoxidized copper brazed under nitrogen, then continuously insulated (high density cellular, UV-resistant).
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Cover the exposed sections on the facade with discreet capping , weatherproof and UV-resistant.
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Checked bend radii and internal cleanliness to preserve oil and compressor.
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Deep vacuum (< 500 microns) with stabilization, then weighting of refrigerant according to the total length.
The equivalent installation length on this type of building is often between 15 and 25 m . We systematically validate the pressure losses , the required refrigerant top-up and the recalibration of subcooling / superheating .
Electricity: security, compliance and scalability
For the Sharp ZU1, we have planned:
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Dedicated circuit from the electrical panel, sized to match the unit's MCA/MOCP.
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Disconnection box near the condenser, waterproof and accessible .
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Shielded/suitable control wiring between indoor and outdoor unit, chimney protected from mechanical and UV damage.
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Equipotential bonding and verification of polarity and grounding .
This treatment reduces parasites , prevents unwanted triggers and simplifies diagnosis in the event of subsequent intervention.
Condensate management: gravity when possible, pump when necessary
In the "head under roof" configuration, gravity evacuation is not always possible. We have:
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Favored gravity for front-mounted heads with direct output.
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Integrated a silent mini condensate pump when the slope does not allow it. The pipe is insulated and anti-siphon , with odor anti-return shield .
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Protect roof penetrations with membrane-compatible flashings and sealants to ensure watertightness.
Roof waterproofing: top priority
Each drilling is documented and sealed according to the rules of the art:
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Sleeves, flashings and additional membranes welded/adhered around penetrations.
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Mechanical protection under the rails to prevent gravel shearing on the membrane.
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Raised cable trays to prevent standing water and ice.
We perform a complete post-installation visual inspection and leave a penetration location report for the roofing contractor during future maintenance.
Commissioning: AirGreen quality control
Our commissioning steps include:
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Nitrogen leak test and electronic detector checks.
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Deep vacuum with documented vacuum holding .
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Setting the electronic card, ventilation modes, shutter orientation, airflow adjustment to avoid direct currents.
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Measurements (internal/external): ΔT, current, operating pressure, superheat and subcooling .
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Acoustic and vibration validation on the roof.
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Customer training : filters, seasonal instructions, diagnostic codes, best defrosting practices.
Expected results: comfort, silence and savings
The Sharp ZU1 wall-mounted head + roof-mounted condenser combination allows:
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Consistent comfort in living areas.
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A significant reduction in noise perceived from the facade and in the courtyard.
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Optimized energy bills thanks to the Inverter and R-32 .
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Minimalist visual integration inside and an orderly technical area on the roof.
Possible grants and eligibilities
Recent R-32 wall-mounted heat pumps that perform well in cold weather are generally eligible for assistance in several Quebec programs promoting energy efficiency. Eligibility depends on the capacity , performance indices and the building profile . We support our clients in Montreal, Laval, Longueuil, the North Shore and the South Shore for:
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Check the lists of qualified equipment ,
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Prepare technical documents ,
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Submit rebate requests, where applicable.
Good practices for use and maintenance
To get the most out of the heat pump :
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Clean filters every 4 to 8 weeks during peak season.
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Maintain 1.2 to 1.5 m of clearance around the rooftop condenser and clear snow in winter.
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Avoid operating in Auto mode during mid-seasons if alternating heating/cooling is not desired.
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Schedule annual HVAC maintenance : electrical inspection, tightening, pressure, coil/fan cleaning, condensate testing.
Common Mistakes…and How We Avoid Them
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Supports placed directly on the membrane : risk of punching. We use anti-vibration pads and beams to distribute the load.
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Insufficient clearances between two condensers: performance losses, icing. We respect the recommended skylights and flow orientation.
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Unprotected cables and lines : premature aging. Our UV-resistant covers and insulation guarantee longevity.
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Approximate roof waterproofing : medium-term leaks. Our flashings and sealants are carried out according to industry standards, with traceability.
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Approximate sizing : discomfort and overconsumption. We calculate the load and adjust the BTU capacity as needed.
What if you have a courtyard, balcony or brick facade?
We adapt the condenser installation: wall brackets , slab on the ground with snow guard, or roof structure . Each context (plex, condo, single-family home) receives a tailor-made solution to maximize durability , accessibility and discretion .
What you gain with AirGreen
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Independent technical advice on recent brands and series (Sharp, Gree, Fujitsu, Midea, etc.).
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Careful installation and complete documentation (diagrams, serial numbers, lengths, load).
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Local, responsive after-sales service with parts and expertise on wall-mounted , multi-zone and central heat pumps.
Our intervention in Rosemont–La Petite-Patrie illustrates an approach that respects the architecture of Montreal buildings while offering four-season comfort . The Sharp ZU1 rooftop unit delivers an ideal balance between performance, silence and visual sobriety—exactly what many households in Greater Montreal are looking for.
Quick Facts (technical summary of the installation)
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Machine type : Sharp ZU1 wall-mounted heat pump (R-32).
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Installation : condenser on flat roof , raised frame, anti-vibration bases, clearances respected.
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Route : technical duct up to the roof, UV-resistant insulated copper connections, clean capping on the facade.
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Condensate drainage : gravity when possible, silent mini-pump if necessary.
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Electrical : dedicated circuit, roof disconnection , grounding, protected control cable.
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Commissioning : deep vacuum , R-32 top-up according to length, ΔT, intensity, pressure, acoustic checks.
Are you considering a flat roof HVAC installation in Montreal, Laval, Longueuil, North Shore or South Shore ? We size, install and maintain Sharp ZU1 , Gree , Fujitsu , Midea and other recent series R-32 / R-454B systems for lasting comfort, winter and summer.