A cathedral staircase, consistent comfort: our HVAC solution for an urban duplex in the Southwest
In this project in the heart of Southwest Montreal – a renovated loft-style duplex with exposed brick walls and an open staircase – our team installed a Sharp ZU1 series wall-mounted heat pump ( R-32 refrigerant ). The goal: to provide stable comfort in both summer and winter in a space with high ceilings, while respecting the architectural signature of the space. The central stringer staircase created an ideal air shaft to distribute heat and air conditioning to both levels, provided the interior head was positioned in the right place and the condensate drainage was managed reliably and discreetly.
Customer context
The owner wanted:
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a compact , quiet and energy-efficient solution;
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a neat HVAC installation , without invasive ducts on brick surfaces;
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performance adapted to the Montreal climate and humid inter-seasons.
Why the Sharp ZU1 stands out in a vertical and open space
An inner head that “reads” space
The wall-mounted unit is located high in the stairwell , just below the ceiling drop. This position takes advantage of the natural draft: in air conditioning mode, fresh air flows to the ground floor by gravity, while in heating mode the forced air stratifies less thanks to the motorized shutters and the careful orientation of the slats. The result is faster thermal balancing between the upper floor and the main living level.
R-32: efficiency and reduced footprint
The Sharp ZU1 series uses R-32 , a new generation refrigerant that delivers improved seasonal efficiencies and lower GWP compared to previous generations. For an occupant, this translates into less energy consumed year-round and lower operating costs.
Acoustic comfort
The choice of the ZU1 is also due to its low noise level . In an open staircase, any vibration is propagated: we fix the plate to the load-bearing partition with anti-vibration spacers , check the tightening torque and validate the plumb to avoid resonances that can occur in vertical volumes.
Salient Installation Details (Southwest Project)
Refrigerated and electrical route
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Single hole behind the inner head, angle calculated to protect the insulation and maintain a continuous slope of condensates.
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Section hidden in the staircase partition; discreet capping on the exterior side only, in a neutral shade to blend in with the facade.
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Dedicated power supply from the electrical panel: circuit breaker compliant with ZU1 series requirements and shielded interconnection cable to limit interference.
Condensate management
The head being located above 4 m , direct gravity flow was not guaranteed. We integrate a compact lifting pump :
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anti-vibration and anti-foam tank to limit lapping noises;
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accessible purge line for annual HVAC maintenance ;
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safety cut-off in the event of an abnormal level (integrated float).
Exterior (condenser)
The condenser is mounted on sturdy wall brackets , with minimal clearance from blown snow. We plan:
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silent blocks to filter vibrations;
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rear clearance compliant to facilitate defrosting in winter;
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snow cutter if wind orientation requires it and drip gutter to direct water away from the siding.
Key steps: our HVAC installation method in residential environments
1) Technical visit and simplified load calculations
In a cathedral staircase, the thermal load is not linear. We take into account:
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of the air volume of the cage;
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exposed brick (inertia);
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solar gains from the living room.
The retained capacity of the Sharp ZU1 is sized to cover peaks without penalizing oversizing (short cycles, noise, consumption).
2) Implementation and tracing
We validate the clearances around the head (height, sides), trace the fixing crosspiece , and test the desired blowing angle towards the living room. The height facilitates diffusion on two levels and frees up the circulation walls.
3) Drillings, lines and soldering
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Drilling with core drill and vapor barrier sleeve .
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Installation of insulated refrigerant lines , nitrogen brazing and deep vacuum drawing .
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Leak test (pressure maintenance) before opening the fluid.
4) Power on and setup
We configure the vertical/horizontal sweep , validate presence detection if available, and configure the setpoint recovery after a power cut. Occupants receive a simple user guide : target temperatures per season, dehumidification mode for sticky days, and advice for managing open doors to better distribute the air beyond the staircase.
5) Finishing and site cleanliness
Wood and walls were protected during the work, carefully covered , cable ducts aligned with the architectural lines, and final cleaning was performed. The installation blends in with the loft's aesthetic without creating a visual clutter.
Results: comfort, energy bill and silence
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Consistent comfort between the upper and lower floors, despite the high ceilings.
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Cooling responsiveness : fresh air descends naturally through the stairs.
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Low noise level , even in the evening when the acoustics of the staircase are noticeable.
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Optimized consumption thanks to R-32 and adjusted sizing .
HVAC Maintenance: Maintaining Performance Year After Year
To keep your wall-mounted heat pump operating at its best:
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Clean the filters every 4 to 6 weeks during use.
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Annual inspection by our technicians: pressures, electrical connections, condensate pump , mechanical tightening, parameter check.
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Checking the flow (drain line) and the level of the plate.
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Outside: clear the condenser (leaves, snow), keep a free area for ventilation.
Regular HVAC maintenance protects the warranty , maintains performance and prevents the formation of odors due to stagnant water in the tanks.
Grants and eligibility (Montreal, Laval, Longueuil, North Shore, South Shore)
Recent R-32 wall-mounted heat pumps like the Sharp ZU1 are generally eligible when seasonal performance and cold weather operation criteria are met, particularly in current Quebec programs. Our team checks for you:
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eligibility based on installed capacity and published yields;
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the required documentation (serial numbers, invoices, photos);
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preparing the file to maximize the assistance available in Montreal, Laval, Longueuil, the North Shore and the South Shore .
Pro Tips for Stairs and Atriums
Choose the location carefully
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Higher than adjacent doors to prevent air short circuit.
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Aim for blowing towards the living area rather than only frontal and vertical.
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Provide secure access for maintenance (ladder, guardrail).
Controlled condensates
As soon as the natural slope is uncertain, the lifting pump is the most reliable solution: silent if it is detached from the structure and if the hoses are correctly embedded in flexible supports.
Invisible finishes
The capping must be continuous , without breaks or variations in color; the radii of curvature respect the insulation to avoid external condensation in summer.
Why AirGreen
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Local team that understands the constraints of Montreal plexes and lofts.
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On-site diagnosis , brand/model recommendations based on actual volumes and not just a surface area in m².
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HVAC installation with a straight line: brazing under nitrogen, deep vacuum , leak tests, configuration and commissioning .
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After-sales service and planned HVAC maintenance to keep your heat pump performing well for a long time.
Project Quick Facts
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Type : single-zone wall-mounted heat pump .
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Brand : Sharp .
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Series : ZU1 (R-32) .
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Context : duplex with open staircase, brick walls, height > 4 m.
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Special features : silent condensate pump , anti-vibration brackets, hidden path, discreet finishes.
For a similar project in Montreal , Laval , Longueuil , on the North Shore or the South Shore , our team will support you from study to maintenance, with the same requirement for quality and cleanliness of execution.