Two condensers on a flat roof, winter performance and careful finishing: the AirGreen signature
In Saint-Laurent , we completed a flat-roof HVAC installation designed to provide four-season comfort in a multi-unit residential building. The project included two Sharp Eco Inverter ZU1 series outdoor units mounted on raised supports with dedicated service paths. This configuration meets the constraints of a dense urban environment while maximizing heating reliability during Montreal's cold weather.
Why the Sharp ZU1 series for Saint-Laurent
In Greater Montreal, the ZU1 series wall-mounted heat pump stands out for its balance between energy efficiency , silence and air quality thanks to Plasmacluster Ion technology. For this project:
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The Eco Inverter compressor finely adjusts power and provides significant electricity savings .
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Stability in heating mode down to low temperatures responds to local cold peaks.
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The compact frame allows for discreet installation on a flat roof without encroaching on traffic areas.
We choose this model when the objective is to combine winter comfort , efficient air conditioning in summer and easy maintenance in an urban environment.
Building context and client objectives
The building has several apartments of varying sizes. The owners wanted:
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Standardize equipment to simplify maintenance and parts management.
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Avoid any encroachment on side walls visible from the street.
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Ensure safe access for maintenance without disturbing occupants.
The flat roof proved to be the best installation solution, with vertical passage of the refrigeration lines and the electrical supply in a central technical duct.
Technical architecture retained
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Device type: Sharp wall-mounted heat pump (ZU1 series), Eco Inverter outdoor units.
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Mounting: aluminum rails on mechanically fixed treated wooden runners , with anti-vibration pads under each support foot.
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Clearance under chassis: sufficient for the evacuation of defrost water and air circulation on gravel roofs.
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Refrigeration lines: vertical route by sealed piercing (vapor barrier + flashing), then UV capping towards the interior heads. Estimated cumulative length 12 to 18 m per system, continuously insulated.
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Power supply: dedicated 240 V circuits from the panel, with disconnect box near each condenser and grounding compliant with RBQ / Hydro-Québec .
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Internal condensate management: gravity with controlled slope; no pump required on this project.
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Service access: peripheral space respecting manufacturer clearances , rear and side clearance preserved for air flow .
Visible installation details and construction choices
On the roof, we favor modular aluminum supports : they resist corrosion and limit point loads. The treated wood pads distribute the load on the gravel and avoid any pressure points on the membrane. Anti-lift mechanical fasteners complete the protection against prevailing winds .
The refrigeration bundles and communication cables are connected and identified; they follow a short route to reduce pressure losses and facilitate future diagnostics. The exterior capping is chosen in a light gray shade to blend in with the roof relief and limit solar heating.
Interior integration and acoustic comfort
Each condenser serves a dedicated wall head per dwelling. Inside:
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The holes are made using a punch with vapor barrier packing to preserve the thermal envelope.
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The head mounts are lined with an anti-vibration gasket to reduce sound transmission to the walls.
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Airflow is adjusted room by room to avoid drafts in living areas.
The result: a very low noise level in automatic speed, perfect for rooms overlooking the courtyard.
Commissioning and quality controls
Our teams follow a constant protocol:
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Nitrogen test to confirm the tightness of the circuit.
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Deep vacuum with recorder, then stabilization .
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Power on and set seasonal modes.
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Verification of blown intensities and temperatures , with recording in the customer file .
This methodology guarantees increased compressor longevity and controlled consumption , both in winter and summer.
Results: constant comfort and savings
From the first week of operation, the occupants noted:
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Rapid temperature rise in cold weather thanks to inverter modulation.
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Consistent air conditioning during the hot July periods.
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An anticipated reduction in the bill thanks to the high coefficient of performance of the ZU1 series.
Annual HVAC maintenance remains simple: cleaning the interior filters, rinsing the exterior coils and checking the electrical tightenings.
Specifics of a flat roof installation in Montreal
Installing wall-mounted heat pumps on roofs requires special attention:
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Snow clearances : the elevation limits burial and facilitates the flow of defrosting water .
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Wind : orientation of the exchangers with their backs to the prevailing wind where possible, and suitable anchors .
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Waterproofing : all flashings are carried out with membrane repair and compatible mastic ; a vapor barrier is re-established after the conduits are installed.
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Maintenance : A clear technical aisle is maintained between the units for tool access and service measurements.
These points prevent unexpected shutdowns and extend the life of the devices.
Grants and Compliance
High-performance heat pumps like the Sharp ZU1 series may be eligible for certain assistance programs depending on the housing configuration and current criteria. We support our customers in the process and ensure compliance with RBQ , Hydro-Québec requirements and municipal regulations in Montreal, Laval, Longueuil, North Shore and South Shore .
AirGreen Tips for Owners and Managers
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Sizing : choose the BTU capacity according to the envelope and the actual use of the rooms.
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Short route : reduce line lengths to maintain seasonal yields .
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Raising : always use adjustable supports with anti-vibration mounts on flat roofs.
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Maintenance : Annual HVAC maintenance prevents efficiency losses and optimizes the warranty .
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Succession plan : in multi-unit housing, multiplying the units provides useful redundancy in the event of peak demand.
AirGreen, your HVAC reference in Greater Montreal
We design custom installations for Montreal , Laval , Longueuil , the South Shore and the North Shore . Our team understands the constraints of roofing and noise-sensitive interiors , and delivers clean, stable and easy-to-maintain systems. For a similar project in Saint-Laurent or elsewhere in Greater Montreal, we offer a technical visit and a detailed quote with implementation scenarios.