Urban rooftop, four-season comfort: a neat Sharp installation on a flat roof, designed for Montreal's extreme cold
Context and objectives of the project
At AirGreen , we were asked to equip a condo located in Le Sud-Ouest (Griffintown) . The client was looking for a high-performance, quiet HVAC solution for the main living area, with a condenser placed on the roof to preserve the aesthetics of the balcony and limit noise pollution. Priorities: reliability in cold weather , controlled consumption , urban integration and easy maintenance .
We are choosing a Sharp wall-mounted heat pump – ZU1 series (R-32) in single zone , sized at 12,000 to 15,000 BTU depending on the calculated thermal load (orientation, insulation, glazing, internal inputs). This series is renowned for its high seasonal efficiency and its capacity maintenance in Quebec winters.
Keywords : heat pump , wall-mounted air conditioner , HVAC installation , HVAC maintenance , Montreal , Laval , Longueuil , North Shore , South Shore .
Why the Sharp ZU1 Series Meets the Need
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R-32 refrigerant : increased efficiency and reduced charge compared to R-410A.
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Extreme cold : reliable operation around −25°C to −30°C , ideal for Greater Montreal .
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Silence : low noise levels, compatible with co-ownerships.
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Air quality : Plasmacluster technology on the Sharp range to limit dust and odors in the indoor area.
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Compactness : a discreet interior design and a condenser that is easy to integrate on a flat roof.
Installation process — focus on “flat roof”
1) Installation and protection of the roof
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Raised steel support fixed on distribution pads and protective soles above the ballast (gravel).
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Distance measurement : compliance with clearances for suction and blowing, no obstacles (walls, parapets) in the air jet.
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Sufficient height to drain defrost water without obstruction in winter.
2) Refrigeration and electrical connections
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Short route from the technical column to the condenser to preserve efficiency .
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UV-resistant insulated refrigerant lines, flared couple fittings , anti-abrasion saddles .
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Shielded communication cable , dedicated power supply with compliant section and suitable circuit breaker .
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Disconnection box positioned near the outdoor unit for safe interventions.
3) Drainage and management of condensates
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The condo living room does not allow for a continuous gravity slope; we integrate a compact condensate pump (high level sensor with safety) on the interior side.
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On the roof, the installation leaves a free path for defrost water to avoid any accumulation under the unit in very cold weather.
4) Commissioning and checks
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Deep vacuum measured with a micron meter until stabilization; leak test .
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R-32 charge compensation based on actual lengths.
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Readings: intensity , supply/return temperature , delta T in cooling and heating, verification of the direction of rotation of the fan.
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Settings: automatic sweeping , blowing speed adapted to the open area, automatic restart after power cut.
What you see from the roof (and why it matters)
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Raised support : protects against accumulated snow and facilitates roof maintenance.
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Pads/soles : preserve the membrane ; no excessive point load.
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Insulated and sheathed connections : resistance to UV and freeze/thaw cycles; clean path to the technical path.
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Disconnection box : safety and electrical compliance, essential in co-ownership.
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Rear and front clearance : ensures airflow without recirculation, therefore a better real SCOP/SEER .
Result for the customer
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Even cooling in summer, rapid increase in comfort.
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Effective additional heating in autumn and spring, reducing the use of baseboards.
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Very low noise level in the living area and on the terrace.
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Aesthetics preserved: nothing on the facade or on the balcony.
Sizing: practical guidelines
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9,000 BTU : Bedroom/office up to 350 sq. ft.
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12,000–15,000 BTU : 400–700 sq ft open-plan living room (project case).
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18,000–24,000 BTU : large spaces, high ceilings or multiple openings.
A load calculation carried out by our AirGreen advisors remains the best guarantee of comfort and longevity (avoids over- or under-sizing).
HVAC Maintenance: Maintaining Performance
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Internal filters : clean every 4–8 weeks in season.
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Evaporator battery : gentle dusting; no corrosive products.
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Condenser : 30 cm minimum clearance, spring inspection of fan and fins.
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Condensate pump : test at the start of summer (float/threshold).
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Annual AirGreen visit : electrical check, microns/vacuum , pressure/load, delta T , condition of sheaths and tightening.
Subsidies and energy optimization
The Sharp ZU1 (R-32) wall-mounted heat pump may be eligible for assistance depending on the Energy Star configuration and cold weather performance criteria. We support our customers in Montreal , Laval , Longueuil , North Shore and South Shore for:
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Check the exact eligibility of the model;
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Assemble the file (invoices, serial numbers, installation photos);
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Optimize usage : stable instructions, intelligent auto mode, seasonal programming.
Common Flat Roof Mistakes — and How to Avoid Them
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Condenser too low in the gravel → air recirculation and ice under the chassis: we install a raised support .
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Lack of membrane protection → premature wear: we use dedicated pads/soles .
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Excessive connection lengths → pressure losses: we favor a short route via the technical duct.
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Fast commissioning without micronmeter → residual humidity: we aim for a controlled deep vacuum .
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Neglected indoor drainage → risk of water damage: pump sized and tested with safety shut-off.
Project sheet — The Southwest (summary)
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Type : single-zone wall-mounted heat pump
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Brand / Series : Sharp ZU1 (R-32)
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Capacity : 12,000–15,000 BTU (depending on load)
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Exterior installation : flat roof, raised support , protective pads
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Electricity : dedicated circuit, disconnection box on the roof
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Condensates : internal pump for secure evacuation
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Commissioning : deep vacuum, leak tests, delta T measurements
Need a comparable installation?
We cover the entire Greater Montreal area. Our team offers the study , HVAC installation and maintenance of wall-mounted and multi-zone heat pumps , ceiling cassettes and R-32/R-454B central systems . A technical visit is sufficient to validate the BTU power, the line routing and the drainage strategy adapted to your condominium.