Two condensers on a flat roof for 4-season comfort in a Montreal plex
At AirGreen , we are modernizing the comfort of a Rosemont–La Petite-Patrie plex with the installation of MultiZone GREE FreeMatch R32 heat pumps . The chosen configuration— two condensers installed on a flat roof , each serving several interior heads—meets a specific need: efficiently air conditioning and heating stacked dwellings, while freeing up the facades and preserving the roof membrane .
Context and objectives of the project
The building, typical of the area, has a masonry structure with a flat roof and technical access. The owners' priorities are clear:
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Improve summer and winter comfort.
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Reduce operating costs compared to electric supplementary heating.
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Centralize outdoor equipment on the roof to avoid clutter on the ground and disturbances in the yard.
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Guarantee a durable HVAC installation , compatible with Montreal winters.
Why the FreeMatch R32 range
The GREE FreeMatch R32 stands out for its MultiZone flexibility (2 to 5 zones) , its compatibility with wall-mounted, console or cassette heads, and the use of R-32 refrigerant , which is more efficient and has a lower GWP than R-410A. Main advantages for an urban plex:
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High heating and air conditioning efficiency , adapted to the temperature variations of Greater Montreal.
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Ability to power multiple rooms per system, ideal when each home has distinct requirements.
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Intelligent defrost management and low temperature blowing stability.
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Low noise levels, relevant for a dense residential environment.
Installation on a flat roof: method and precautions
We install the two condensers on an aluminum frame fixed to treated wood distribution soles placed on the membrane. This assembly:
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Diffuses the loads so as not to puncture the roof.
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Incorporates anti-vibration pads to absorb structural resonances.
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Ensures compliant service clearances (clear suction/discharge, maintenance passages).
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Facilitates snow removal and prevents ice buildup around appliances during defrosting periods.
An external disconnect switch is installed near each condenser for safety and maintenance. Refrigeration lines and communication cables run in a sealed technical box , with sealed and solidified penetrations to preserve the integrity of the membrane.
Refrigeration route and interior connections
From the roof, the connections descend into the technical columns to reach the interior wall heads . We favor:
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Short, insulated lines (UV/ozone insulation on the roof side and continuous vapor barrier on the interior side).
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A bending radius respected to avoid stress on copper.
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Gravity condensate drainage for indoor units when configuration allows; otherwise, silent mini-pump with vapor barrier and service point.
Electricity and protections
Each condenser has a dedicated circuit from the main panel: circuit breaker size, conductor size and GFCI when required, in accordance with the Canadian Electrical Code . Communication links are separated from the power to limit interference. On the roof, the ducts are UV-resistant and sealed against penetrations.
Rigorous commissioning
Our standard procedures ensure performance and longevity:
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Nitrogen leak tests (stabilized pressure, recorded readings).
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Deep vacuum draw down to less than 500 microns, hold and lift test.
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Fluid opening , load balancing according to actual lengths and number of evaporators.
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Setting control modes (thermistors, speed balancing, defrost curves).
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Reception with the owner : training in use, HVAC maintenance schedule, seasonal recommendations.
Winter management: details that make the difference
On a flat roof in Montreal, success depends on anticipation:
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Sufficient elevation of the condensers to avoid snow suction.
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Keep away from discharges from other appliances (hood, air exchanger, towers) in order to preserve air quality and avoid premature icing.
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Wind deflectors if the site is very exposed.
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Check defrost water drains to prevent ice patches from forming.
Concrete benefits for occupants
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Uniform comfort in key rooms (living rooms/kitchens/bedrooms), with no marked differences between floors.
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Silent operation : noise is relegated to the roof, the accommodation remains quiet.
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Significant energy savings compared to electric baseboard heaters or window air conditioners.
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Flexibility of use : each accommodation controls its own atmosphere room by room.
Preventive maintenance and durability
To maintain performance season after season, we recommend:
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Clean the filters of the inner heads every 4–6 weeks during use.
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Gentle washing of external batteries in spring (controlled pressure, counter-current).
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Annual inspection : tightening of terminals, insulation check, verification of supports, condensate test, reading of operating parameters.
Our teams provide HVAC maintenance throughout Greater Montreal, avoiding performance losses linked to clogging or small undetected leaks.
Grants and Eligibility
High-efficiency, cold-efficient heat pumps may be eligible for assistance under current programs. We guide homeowners through the prequalification process , taking into account installed capacity, seasonal performance, and required documentation. Our team compiles the necessary documents to facilitate the process in Montreal, Laval, Longueuil, the North Shore, and the South Shore .
What to remember for a flat roof installation
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Structure and membrane first : distribute loads, protect waterproofing, record interventions.
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Access and service : provide clearances and passages that can be maintained all year round.
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Clean paths : continuous insulation, anti-UV supports, controlled drainage slopes.
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Quality control : nitrogen testing, vacuum draw and documented commissioning measurements.
Result
The building now benefits from a discreet, efficient MultiZone R-32 system designed for Montreal's climate. Occupants enjoy temperate air in both summer and winter, with better controlled energy bills and integration that respects the area's architecture.
AirGreen, your local HVAC partner
We carry out custom HVAC installations throughout Greater Montreal. Whether your project involves a plex, a condo, or a house, we combine careful sizing , technical execution , and maintenance monitoring for lasting performance. Let's discuss your building in Montreal, Laval, Longueuil, the North Shore, or the South Shore : we will propose the most appropriate configuration at the best operating cost.