A flat-roof compressor, designed for Montreal's extreme cold and quiet indoor diffusion
In a plex in the Le Sud-Ouest district of Montreal , we installed a Sharp wall-mounted heat pump (R-32 refrigerant) . The technical choice was dictated by two imperatives: preserving the aesthetics of the rear facade and ensuring reliable heating during the harshest cold spells. We therefore opted to install the outdoor unit on the flat roof , free from snow accumulations, while the indoor head serves the main living room.
Residential context and comfort objectives
The dwelling, typical of the area with a membrane roof and brick walls, required stable heating in winter and precise cooling in summer, without noise or unpleasant drafts. The installation aimed to:
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high efficiency in heating mode;
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reduced electricity consumption compared to existing baseboards;
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discreet integration despite the constraints of access to the roof and crossing the envelope.
Why a Sharp R-32 wall-mounted heat pump?
Sharp's recent R-32 range combines efficient inverter technology , compressors adapted to frequent defrost cycles in snowy climates and careful acoustics, ideal for plexes. R-32 allows for a reduced refrigerant charge with a lower global warming potential than older generations, while offering excellent seasonal efficiencies. In standard capacities of 9,000 to 24,000 BTU , this range covers the majority of rooms in Montreal homes.
Highlights of the flat roof installation
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Raised support structure : We have fixed the outdoor unit on an aluminum base providing substantial clearance above the snow cover. This choice reduces the risk of snow suction, coil icing and facilitates defrosting .
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Standardized clearances : the location ensures a free flow of air on all useful sides, essential to avoid loss of heating capacity.
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Short and protected refrigeration path : the passage hole was made with a drainage slope and vapor barrier , then sealed with a membrane compatible with the roof to maintain the integrity of the envelope.
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UV Capping : the refrigeration line and power supply were capped up to the roof entrance, which protects the insulation from UV, wind and water.
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Defrost management : The unit discharges defrost water directly onto the flat roof, away from traffic areas. We have provided a snow-cleared service road for winter maintenance.
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Anti-vibration and leveling : anti-vibration pads under the support legs limit the transmission of vibrations to the structure; fine leveling optimizes the flow of condensates.
Positioning of the inner head and air diffusion
The wall-mounted fan head is installed on a central wall, high under the ceiling, allowing the air jet to reach living areas without impacting sound comfort. The blower vanes are adjusted to sweep the room and maintain a uniform temperature, limiting short cycles and preserving efficiency.
Key stages of the project
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Technical survey : verification of the roof membrane, load zones and the shortest route to the interior room.
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Drilling and sealing : controlled coring, roof-compatible flashings and mastic for a waterproof and durable result.
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Brazing and vacuum drawing : assembly of copper connections, deep vacuum drawing then leak test before commissioning.
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Setting : configuration of priority heating mode , defrost control, blowing temperature test and electrical verification of the circuit dedicated to the interior panel.
Results obtained
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Rapid temperature rise thanks to the judicious positioning of the interior head.
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Low noise level inside and outside.
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Stability in extreme cold : regular defrosting, without persistent frost re-establishment.
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Neat aesthetics : discreet capping , neatly finished crossings, outdoor unit invisible from the street.
What you need to know for flat roof installation in Montreal
Installing a compressor on a flat roof requires special attention:
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Sufficient headroom to stay above the snow (we aim for generous clearance).
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Orientation and wind resistance : the clear surface prevents the recirculation of cold air during defrosting.
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Perfect sealing of the crossings, with materials compatible with the membrane in place.
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Planned maintenance access for spring condenser cleaning and seasonal checks.
HVAC Use and Maintenance Tips
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Maintain a snow-free perimeter around the outdoor unit to preserve heat exchange.
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Clean the inner head filters every 4 to 6 weeks during use.
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Schedule annual maintenance : pressure check, battery cleaning, electrical check.
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Use Auto/Heat modes with stable setpoint; avoid too frequent setpoint deviations to maintain optimal performance .
Grants and savings
The Sharp R-32 heat pump meets the efficiency requirements of current Quebec programs . In many cases, our eligible customers receive financial assistance when they replace or reduce the use of less efficient electric heating. We support our customers in Montreal, Laval, Longueuil, the North Shore, and the South Shore to optimize their project budget.
Pitfalls to avoid (AirGreen feedback)
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Support too low : snow suction and chronic icing. We always size the height for Montreal winters.
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Lack of clearance around the unit: loss of capacity, extended defrost cycles.
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Improvised roof penetration : possible leaks. We apply membranes and flashings according to best practice.
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Unnecessarily long refrigeration path : pressure losses, reduced efficiency. We favor short, neat lines .
Why entrust us with your HVAC installation in Greater Montreal?
At AirGreen , we combine local expertise , compliance with standards , and meticulous workmanship . Our teams, trained in R-32 heat pumps and the requirements of Montreal roofs, deliver reliable, durable installations ready for the most demanding winters. We operate weekly in Montreal , Laval , Longueuil , on the North Shore and the South Shore , with structured after-sales service and tailored HVAC maintenance contracts.
Conclusion
This installation of a Sharp R-32 wall-mounted heat pump with an outdoor unit on a flat roof in the Southwest illustrates our approach: rigorous analysis , clean implementation , and measurable performance in both heating and cooling. The result is four-season comfort and tangible energy savings , without compromising on aesthetics or reliability.