A cathedral staircase finally tempered: comfort, silence and energy sobriety in a Montreal loft
At AirGreen , we are working on a cathedral ceiling loft located in the South-West district. The open stairwell created a marked stratification : too hot upstairs, too cool downstairs. The owner wanted a discreet , quiet and efficient solution to stabilize temperatures all year round, without major work or visible ducts. We selected a Sharp ZU1 wall-mounted heat pump ( R-32 refrigerant), positioned high above the staircase, to take full advantage of the airflow and break the thermal cushion under the skylight.
Why the Sharp ZU1 in an open stairwell?
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Large air throw : the geometry of the ZU1 projects fresh/hot air beyond the mezzanine, which homogenizes the volume without creating air currents in the process.
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High seasonal efficiency : the heat pump covers the majority of off-season heating at low cost, complementing existing systems.
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Operation in Quebec cold : performance maintained at low temperatures, useful during winter episodes in Greater Montreal .
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Controlled acoustics : the sound level of the interior head remains discreet in a reverberant space, an essential asset for an open living room.
Installed device: characteristics and configuration
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Brand / range : Sharp ZU1 , new generation R-32 .
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Type : single-zone wall-mounted heat pump .
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Capacity : sizing around 12,000 to 15,000 BTU depending on the peak loads calculated for the cathedral volume and the solar gains of the skylight .
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Control : IR remote control + Wi-Fi option for time scenarios (night lowering, return from work).
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Filtration and comfort : multi-axis motorized shutters to direct the jet under the mezzanine and along the staircase, reducing stratification.
Our technical approach step by step
1) Targeted thermal study
We establish a load calculation integrating: air volume, orientation of the glazing, contributions from the skylight , infiltration rate, daily use of the staircase. This step guarantees a capacity that is neither oversized nor insufficient , a key condition for the performance and longevity of the compressor.
2) Installation of the wall head
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Installation height : installation at the top of the wall to benefit from the maximum airflow and capture the hot air bubble accumulated under the ceiling.
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Anchors : plate screwed into the structural uprights; check with detector to avoid metal networks and reinforcements.
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Orientation of the shutters : vertical sweep adjustment to force mixing; horizontal angle directed towards the stairwell to supply the ground floor.
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Accessibility : sufficient space around the hood for maintenance (opening, cleaning filters, checking cards).
3) Refrigeration and aesthetic route
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Route : clean crossing of the load-bearing wall towards the technical area, then exit to the outside via the shortest route; minimal white capping on visible sections for integration with the painted walls.
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Lengths : compact connections to preserve pressure losses and maintain the COP provided by the manufacturer.
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Protection : high-density closed insulation, anti-UV tape, and vapor-tight seals to prevent parasitic condensation in the wall.
4) Condensate management
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Priority gravity with continuous slope ; when the configuration requires lifting (passing over a beam or long distance to discharge), we integrate a silent condensate pump with anti-overflow tray and discreet service hatch .
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Protected external discharge : non-return elbow and section outside the frost zone, essential in Montreal winters .
5) Power supply and communication
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Dedicated 240V circuit with calibrated circuit breaker; Low-Voltage communication cable separated from the powers, clearly marked on the panel.
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Compliant external disconnect switch , facilitating maintenance.
6) Commissioning and checks
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Nitrogen leak test , vacuum < 500 microns, additional weighing of the refrigerant according to the line length.
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Functional checks : supply/return temperature differences, intensity, defrost sequence, residual noise in the stairwell.
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Settings : fan speeds adapted to break stratification without excess noise, anti-over-humidification setting in summer.
Construction site challenges and AirGreen solutions
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Working height : approximately 16–18 ft . We use secure floor scaffolding and positioning lanyards for certified and careful installation.
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Skylights : Rapid temperature fluctuations in direct sunlight. We program time scenarios and an I-Feel mode (remote sensor via remote control) to stabilize comfort.
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Staircase acoustics : hard walls, metal railings, possible reverberation. Fine-tuned speed adjustments and silent mode in the evening to maintain peace and quiet.
Results measured after commissioning
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Thermal homogeneity found between the bottom and top of the staircase (difference < 1.5°C in steady state).
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Responsiveness : rapid temperature rise upon waking, without overheating the mezzanine.
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Reduced consumption observed in mid-season compared to the old electrical backup.
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Acoustic comfort : minimal perceived noise on the landing; conversations do not echo.
Best practices for use in a stairwell
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Orient the shutters slightly downwards for heating, more horizontal for air conditioning to rinse the volume.
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Stable settings (21–22°C winter, 23–24°C summer): avoid sudden variations which encourage short cycles.
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Interior doors : leave ajar to encourage recirculation to adjacent rooms.
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Dehumidification mode during humid episodes, useful for protecting the wood of the steps.
Recommended HVAC maintenance
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Clean filters every 8 to 12 weeks during periods of heavy use.
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Annual inspection by us: heat exchange, fan, condensate tray, possible pump, electrical tightening, superheating/subcooling control.
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Exterior clearances cleared of snow and leaves; review of the disconnector and silent blocks .
Grants and Eligibility
Recent R-32 wall-mounted heat pumps generally meet Quebec's assistance criteria when approved and installed by a licensed contractor. We assist our clients in Montreal, Laval, Longueuil, the North Shore, and the South Shore with model verification, document compilation, and application submission .
Common mistakes to avoid in this type of project
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Undersizing capacity by neglecting volume and skylight .
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Ignoring stratification : installing the shutters too low or with the wrong orientation allows heat to stagnate at the top.
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Unnecessarily long refrigeration journey : pressure losses, reduced performance, increased consumption.
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Condensates without slope : risks of overflow or freezing; always favor a clear gravity and purge points.
Why entrust your project to AirGreen?
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Local expertise : daily installations in Greater Montreal , including lofts, plexes and condos with architectural constraints.
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Quality of finish : discreet capping , clean crossings, careful retouching.
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Technical rigor : preliminary studies, commissioning reports, settings geared towards real comfort and savings.
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Follow-up : HVAC maintenance plans and priority assistance during peak periods.
Balance sheet
The Sharp ZU1 installed in this stairwell in Le Sud-Ouest transforms a difficult volume into a comfortable space in summer and winter. The refined integration, mastery of stratification and energy sobriety meet the expectations of a modern Montreal loft. We put the same requirement at the service of your projects, whether you are in Montreal , Laval , Longueuil , on the North Shore or the South Shore .
Service keywords : heat pump , wall-mounted air conditioner , HVAC installation , HVAC maintenance , Montreal , Laval , Longueuil , North Shore , South Shore .
Do you have a cathedral staircase, a mezzanine, or a loft with laminate flooring? Our team will size and install the most suitable Sharp , Gree , Fujitsu , or Midea solution, with a clean and durable route.