Why installing on a flat roof can be an asset
In Rosemont–La Petite-Patrie, many buildings have gravel roofs and stacked units. Placing the condenser of a wall-mounted heat pump on the roof frees up the courtyard and facades, protects occupants' privacy, and reduces noise pollution perceived at the windows. The Sharp ZU1 (R-32) is ideal for this context: compact, stable performance, and quiet. Here, we install it on a raised structure with damping supports to preserve the membrane and control vibrations.
Client context and objectives
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Brick triplex with gravel/elasto roof.
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Need air conditioning for the main living area and additional heating in winter.
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Requirement for discreet integration without cluttering the terrace and without multiple openings in the facade.
The Sharp ZU1: a recent wall-mounted unit with R-32 refrigerant
The Sharp ZU1 range is part of the recent R-32 generations, appreciated for:
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high energy efficiency in summer and winter thanks to the inverter ;
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quiet operation , relevant for shared roofs;
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a capacity range (12k to 24k BTU) covering an average size home;
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a compact footprint , facilitating regulatory clearances and maintenance.
Depending on the thermal load, we select the appropriate capacity based on a calculation taking into account the insulation, solar orientation and natural ventilation of the home.
Retained installation architecture: clean, stable and reversible
Support and anti-vibration
The condenser is fixed to an aluminum frame resting on shock-absorbing pads and rubber pads, themselves arranged on crosspieces in order to distribute the loads in the gravel without damaging the membrane. This assembly:
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isolates structural vibrations ;
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avoids punctual areas that could mark the seal;
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ensures adequate clearances for airflow and snow removal.
For roofs exposed to wind, we provide sized anchors or ballast in accordance with the installation manual and local uplift loads.
Refrigerated route and roof crossing
The refrigerant connections are grouped and UV-sheathed from the interior wall header to the roof. The crossing is made via a roof pass-through (gooseneck/flashing box) sealed with membrane-compatible mastic and, where appropriate, lined with an insulated sleeve. Inside, we limit the bends and ensure a continuous slope for the evacuation of condensate from the header.
Electricity and safety
An external disconnect switch is installed in the immediate vicinity of the condenser, powered by a dedicated circuit from the main panel. The cables follow the same route as the connections for clear visual reading and simplified maintenance. Tightenings are torque checked; grounding is verified.
Vacuum packaging, testing and finishing
We proceed to:
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a nitrogen pressure test ,
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a deep vacuum (vacuum gauge),
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weighing/adjusting the refrigerant if necessary according to the actual length,
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leak testing and load currents .
The capping is installed on the interior wall and at the base of the roof passage for a clean finish. On the roof, the curvature radii comply with the recommendations in order to preserve the insulation of the lines.
What the owner sees (and no longer sees)
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On the ground and on the facades: no clutter . The outdoor living areas remain free.
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On the roof: aligned units , each condenser on its own plate with dampers , tidy wiring, watertight roof passage and clear marking for maintenance.
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Inside: a simple wall head , minimal drilling and a discreet cover .
Comfort results measured after commissioning
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Rapid cooling of the main parts, uniformity of the air thanks to the oscillating flap of the head.
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Very low perceived noise level in the rooms located below the installation area, the vibrations being decorrelated by the pads.
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Stability in supplementary heating during cold periods; the ZU1 maintains a useful capacity without surges in consumption.
Best practices on flat roofs: our AirGreen method
Clearances and recirculation
We maintain a significant frontal clearance to avoid the recirculation of hot air in heating mode and we direct discharges away from air intakes (kitchens, bathrooms) visible on Montreal rooftops.
Snow and gravel management
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Sufficient height of the supports to allow the blown snow to pass through.
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Protective mat under the sleepers during installation to avoid scratching the membrane.
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Gravel guard cleaned around the supports to prevent abrasion by wind.
Drainage and condensates
The outdoor condenser does not produce water in air conditioning on the roof, but in winter defrosting mode, flows may appear: we ensure free flow without runoff near passages.
Access and maintenance
A service path is provided: clearance around the machines, accessible stainless steel nuts , covers not blocked by the support, marks on the lines and polarity . An intervention log notes lengths, quantities and commissioning measurements.
Common Pitfalls…and How We Avoid Them
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Improvised piercing of the membrane: we use compatible flashings and mastic, or even waterproofing/liner pockets depending on the membrane.
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Undersized supports : we select a structure certified for load and wind resistance, with suitable shock absorbers .
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Lines without UV protection : the insulation deteriorates; we cover/sheath the connections and respect the bending radii.
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Scattered cabling : we group power + communication in a single, attached and marked route.
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Recirculation under windbreaks or near extractors: we analyze the site's wind rose and visible obstacles to choose the orientation.
Grants and Compliance in Greater Montreal
Recent high-efficiency wall-mounted heat pumps such as the Sharp ZU1 (R-32) may be eligible for programs in effect in Quebec (depending on performance criteria, power and type of housing). We assist our clients in Montreal , Laval , Longueuil , on the North Shore and the South Shore to validate eligibility, prepare supporting documents (serial numbers, photos, proof of installation) and optimize the file.
HVAC Maintenance: Actions That Extend the Life of Equipment
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Clean the inner head filters every 4–8 weeks during use.
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Annual inspection : pressure/temperature, exchanger cleaning, tightening check, leak test, checking of silent blocks and condition of flashings .
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Clearance around roof units (no accumulation of objects).
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In winter, monitor possible ice floes around equipment after thaw/freeze.
Why entrust a flat roof to AirGreen?
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Mastery of roof penetrations and membrane compatibility.
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Calculated, cushioned and durable support .
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Instrumented commissioning (nitrogen, vacuum gauge, intensities) and complete documentation .
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Rapid intervention throughout Greater Montreal for heat pump , wall-mounted and multi-zone air conditioner projects.
Context keywords : heat pump , wall-mounted heat pump , Sharp ZU1 , HVAC installation , flat roof , Rosemont–La Petite-Patrie , Montreal , HVAC maintenance , R-32 , anti-vibration .