Two independent systems on a flat roof for four-season comfort in a Montreal plex
At AirGreen , we installed two Sharp ZU1 wall-mounted heat pumps on the flat roof of a plex located in Rosemont–La Petite-Patrie . The client's goal: to provide two separate dwellings with reliable heating in winter and efficient cooling in summer , while reducing energy bills and stabilizing indoor comfort despite the marked variations in Montreal's climate.
Architectural and climatic context
The building is a brick plex with a flat roof , typical of the area. The urban environment exposes the equipment to cold winds and significant snow accumulation . We therefore favored a raised frame configuration for each condenser, in order to:
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maintain optimal fan clearance ;
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avoid burial during blowing snow episodes;
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facilitate the flow of thawing drainage ;
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simplify winter HVAC maintenance .
Each galvanized aluminum support rests on anti-vibration pads , protecting the roof membrane and limiting the transmission of vibrations to the structure.
Choice of range: Sharp ZU1 in R-32
The Sharp ZU1 is a recent wall-mounted heat pump that runs on R-32 refrigerant . It meets current efficiency requirements and maintains a stable heating capacity down to -30°C , a decisive point for Greater Montreal. Among the concrete advantages for an apartment building:
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Inverter modulation : the machine adjusts its power to actual demand, which reduces ON/OFF cycles and improves comfort .
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High efficiencies (SEER/HSPF), conducive to eligibility for grant programs for efficient appliances.
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Low noise level , appreciable for immediate neighbors and roof occupancy.
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Multi-head compatibility in the Sharp family; here, we have chosen two separate systems for complete independence between homes.
For this project, we sized a 12,000 BTU for the more compact housing and an 18,000 BTU for the larger unit, after load calculations taking into account exposure, insulation and glazing.
Refrigeration path and power supply
On a flat roof, the route strategy determines winter reliability . Our teams have:
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Routed the refrigeration lines through sealed crossings in the roof, grouped near the technical chimneys to reduce wind resistance .
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Used UV resistant capping with continuous insulation to limit heat loss and ensure a clean finish.
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Position the disconnects within reach, on frost-resistant bases, for safe disconnection during maintenance.
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Provided gravity-fed condensate lines , protected against frost and guided to clear flow areas.
The total lengths of connections, of the order of 6 to 9 m per system , comply with the requirements of the ZU1 range and were laid on a slope to avoid oil pockets. The sheaths are mechanically fixed and sealed to the membrane according to the rules of the art, with bitumen/elastomer compatible sealing.
Snow management and clearances
The photos taken on the day of commissioning show a largely snow-covered roof. We therefore have:
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set a clearance height of approximately 40–45 cm under the condensers to minimize the risk of accumulation;
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respected peripheral clearances greater than the manufacturer's minimums to ensure adequate air sweeping in defrost mode;
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oriented the units so that the air discharges do not interfere with each other or with the vents;
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left a traffic corridor allowing for safe intervention in high season.
Interior coordination: wall heads and distribution
The wall-mounted interior heads are mounted in the main living areas, slightly off-center to optimize airflow and maintain aesthetics. The 65 mm holes include:
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vapor barrier sleeves to prevent internal condensation;
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outward slope on the drain;
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finishing plate for neat integration.
Each accommodation has its own independent thermostat/control , allowing for independent control of temperatures and schedules.
Deadlines, security and compliance
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Study and sizing : 1 visit.
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Installation : 1 full day with two teams (roof + interior).
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Commissioning : vacuum drawing, leak test , weighing and load adjustment according to actual lengths, electrical verification and calibration of probes.
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Compliance : work carried out under RBQ license, compliance with CSA requirements and current electrical codes .
Measured results
As soon as they are switched on, both accommodations benefit from:
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stable heating despite the negative temperature and wind at altitude;
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of low perceived noise on the roof and inside;
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controlled consumption thanks to the Inverter and correct sizing.
The owner gains operational flexibility : each tenant manages their own temperature, and maintenance is carried out without entering the accommodation for the exterior part.
Practical advice for apartment buildings in Montreal, Laval and Longueuil
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Favor raised and sturdy frames on flat roofs; avoid slabs laid directly on the surface.
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Plan winter access (walkways, anchor points) to simplify maintenance.
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Check the structure and membrane with a roofer when the cumulative equipment load increases.
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Plan the electricity supply for each dwelling for clear billing.
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Choose extreme cold ranges (−25°C to −30°C) eligible for provincial subsidies when efficiency criteria are met.
Why entrust your project to us?
We are experts in HVAC installations in the Montreal context: plexes , condos and houses on the North Shore and the South Shore . Our approach combines rigorous engineering , careful execution and administrative support for financial aid files. With the Sharp ZU1 , we deliver a balance between performance, silence and reliability , perfectly adapted to local winters.
Maintenance and longevity
Annual maintenance prevents performance loss: cleaning the coils, checking defrosting, tightening connections, and testing insulation. On flat roofs, we recommend clearing snow around the condensers after each major storm, following safety guidelines. An AirGreen maintenance program ensures continued performance and helps extend the manufacturer's warranty .
By delivering two Sharp ZU1 wall-mounted heat pumps on a flat roof in Rosemont–La Petite-Patrie, we offer the owner a reliable, efficient and scalable system, ready to face intense cold while reducing operating costs. This is a benchmark configuration for Montreal buildings looking for four-season comfort without compromising on aesthetics and durability.