A flat roof construction site designed to last: quiet, clean and suitable for extreme cold
In the heart of Montreal , in a typical Rosemont–La Petite-Patrie plex, our team is installing two Gree R-32 condensers to power wall-mounted indoor units. The goal: to provide four-season comfort, a controlled energy bill, and exemplary integration on a residential flat roof without compromising watertightness. This project illustrates our expertise in urban HVAC installation : restricted access, membrane load management, optimized refrigeration path, and careful acoustic treatment to preserve the peace and quiet of the occupants—and the neighborhood.
Customer context and choice of solution
The co-owners wanted to replace old, disparate units with a homogeneous heat pump solution that was more efficient in cold weather and used a new-generation refrigerant. We recommended Gree R-32 for its performance in northern climates, its simple connectivity, and its high seasonal efficiency. Two outdoor units supply separate zones (day/night) to:
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modulate power according to occupancy;
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limit bond lengths;
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maintain very low noise levels, especially at night.
Expected result: a significant reduction in annual consumption while improving summer comfort ( wall-mounted air conditioner in cooling mode) and winter comfort ( heat pump in heating mode).
What makes the difference on this site
Installation on a flat roof: stability, waterproofing and maintenance
A successful HVAC installation on a flat roof requires respecting three principles: do not puncture the membrane, distribute the loads, and plan for future maintenance.
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Raised aluminum supports with anti-vibration pads : they isolate the machines from the roof, reduce the transmission of vibrations and facilitate water drainage.
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Distribution soles and joists made of treated wood : they diffuse the load and avoid pressure concentrations on the membrane.
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Service clearances respected: each condenser has peripheral clearances for optimal air sweeping and for access to service panels.
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Controlled routes : refrigeration connections and the electrical supply follow dedicated routes, fixed and protected to resist UV and freezing/thawing.
This approach guarantees a long lifespan for the equipment and a roof that remains healthy.
Refrigeration connections: performance and cleanliness
To preserve the seasonal performance of wall-mounted heat pumps , we are working on:
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Balanced lengths (approximately 12–18 m per zone) to limit pressure losses and comply with manufacturer specifications;
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Controlled bending and brazing under nitrogen to protect the interior of the copper tubes;
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High density, continuous, sheathed, UV-resistant insulation ;
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Nitrogen leak tests , then deep vacuum with a micron meter — a critical point too often overlooked.
The openings are grouped in a technical chimney with membrane-compatible flashing and caulking (mastic and collars), which makes the whole thing clean, inspectable and durable.
Noise and vibration management
In a dense environment like Montreal , discretion is a key to success. We combine:
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Anti-vibration pads under each foot;
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Tighten fasteners to the correct torque to avoid buzzing;
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Silent night mode can be activated from the remote controls;
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Direct air discharges away from neighboring windows when possible.
Neighbors thus benefit from intact acoustic comfort, even at high speeds during heat waves.
Electricity and control
Each unit has an external disconnect switch and a dedicated circuit from the main panel. Cables are capped and secured, protecting against water accumulation. Shielded communication cables connect condensers and wall-mounted heads for stable control, defrost management, and integration of smart functions.
Montreal Winter: Small Details, Big Effects
Installing a heat pump on a flat roof requires anticipating snow and frost :
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Sufficient clearance under the chassis to allow snow to circulate without blocking the lower grilles;
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Flatness and drainage checked to avoid frost pools;
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Defrost optimized by Gree logic to maintain efficiency and avoid persistent ice cubes.
If necessary, we add snow guards to protect the appliances from dripping from adjacent sloping roofs.
Simple interiors, clean comforts
On the housing side, compact wall-mounted heads serve the living room and bedrooms. Drillings are minimized and neatly capped . Condensate drains by gravity to the outside when the architecture allows; otherwise, we integrate a silent condensate pump with a safety tray. The filters can be removed without tools to simplify regular HVAC maintenance by the occupants.
Why the R-32 range today?
R-32 (or R-454B depending on the model) is used in new generations for three major reasons:
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Efficiency : better seasonal coefficients, therefore real savings in Montreal, Laval , Longueuil , North Shore and South Shore .
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Maintenance : lower refrigerant charge per kW returned; easier diagnostics.
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Regulatory future : alignment with HFC reduction trajectories.
The Gree brand , which is very popular in Quebec, offers XLTH (low temperature) machines compatible with local winters, with reliable start-ups right up to the coldest peaks. On this project, the R-32 range ensures stable heating and efficient cooling from the first warm spells, with a dehumidification mode that is appreciated in spring and fall.
Grants and Eligibility
Depending on the capacity chosen and the configuration, these R-32 wall-mounted heat pumps may be eligible for current Quebec programs (e.g., residential components focused on energy efficiency). Our team verifies the possible combination of assistance for each file, compiles the evidence ( AHRI numbers, detailed invoices, photos) and supports the application to maximize the financial return for customers.
What we deliver: an AirGreen method
1) Study and sizing
We analyze insulation, orientation, volumes to be treated and access constraints. Objective: to choose the BTU per zone which avoids undersizing (discomfort) as well as oversizing (short cycles, noise, wear).
2) Urban logistics
Secure roof access, time slots coordinated with the condominium, and protection of common areas. We work cleanly and quickly to limit the impact on the building's life.
3) Execution
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Supports and soles adjusted to the existing membrane ;
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Refrigeration connections brazed under nitrogen;
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Documented leak tests and vacuum draw ;
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Power up with electrical checks;
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Setting up remote controls (modes, flow rates, temperatures) and usage advice.
4) Delivery and tracking
Complete demonstration to the user, delivery of documents (warranties, maintenance sheets), then inspection visit after the first hot/cold sequence to fine-tune the setting if necessary.
Maintenance: the key to long-term performance
A high-performance heat pump remains so thanks to simple but regular HVAC maintenance :
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Clean the internal filters every 4 to 8 weeks during the season;
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Visually inspect the outdoor unit in spring and fall;
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Keep one meter clear around condensers;
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Plan an annual check (electrical checks, static pressure, condition of insulation, condensate test, parameter update).
AirGreen offers packages tailored to condominiums and multi-unit properties, with automated reminders so you don't forget anything.
Expected results for Rosemont–La Petite-Patrie
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Stable comfort : consistent temperatures, controlled humidity;
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Silence : anti-vibration mounts + night mode = minimal noise;
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Economy : high seasonal yield, especially in mid-season;
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Roof preserved : no unnecessary perforation, distributed loads, clean and inspectable routes;
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Real estate value : modern solution, in line with the energy expectations of buyers and tenants in the area.
Practical advice before you start
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Flat roof : require raised supports with pads, and a load distribution plan.
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Route : favor short, straight connections; avoid unnecessary “S”s.
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Electricity : a dedicated circuit per condenser and an accessible disconnect switch are non-negotiable.
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Service : Leave a maintenance lane . Poorly spaced machines are expensive to maintain.
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Documentation : Request AHRI numbers and a vacuum draw report. These are your performance guarantees.
AirGreen, your HVAC partner in Greater Montreal
We operate weekly in Montreal , Laval , Longueuil , the North Shore , and the South Shore . Our promise: clean construction sites, honest advice, careful installations, and responsive after-sales support. For your R-32 heat pump project— Gree , Fujitsu , Midea , Sharp , or other—we size, install, and maintain a solution that suits you, designed for winters here.