Two condensers on a flat roof, raised structure and optimized refrigeration path: an urban construction site designed for four-season reliability, silence and easy access to maintenance.
Context: urban co-ownership, fragmented comfort and roof access
In a condominium building in the Southwest (flat roof, elastomeric membranes, technical access via an interior ladder), the occupants complained of unequal comfort between the units: strong sunlight on the south side, cooler rear rooms, and limited installation constraints on the facade. The union wanted a sustainable HVAC solution, not very visible from the street , capable of covering several areas without multiplying the visible openings.
Our recommendation: a GREE FreeMatch R-32 MultiZone heat pump to serve the main rooms, supplemented by a single-zone R-32 condenser dedicated to a high-load space (glass office). The two machines are grouped on the roof , with a raised structure and short refrigeration paths to the technical columns.
Choice of devices: performance, flexibility and compatibility with extreme cold
We are choosing the FreeMatch R-32 range (2 to 5 zones) for three main reasons:
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Precise inverter modulation and high efficiency with R-32 refrigerant (better volumetric efficiency and lower GWP than R-410A).
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Flexibility of indoor unit combinations (wall heads, consoles, cassettes) which allows you to adapt the air diffusion to each room.
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Reliable cold weather performance typical of recent generations, with optimized defrost management.
The second outdoor unit (single-zone R-32) supplies a space with a high sensitive load (bay windows). This division avoids oversizing and guarantees fine regulation in each zone.
Flat roof installation: structure, clearances and longevity
The roof, made of clear elastomeric membrane , imposes strict rules in order to protect the envelope and maintain air releases from the condensers:
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Aluminum elevation : a modular frame made of anodized profiles supports the main condenser. The height is calculated to remain above winter snow and to facilitate water runoff during defrost cycles.
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Treated wooden bed bases : laid flat on non-slip protective strips, they distribute the loads and prevent punching. Through fixings are prohibited in the active roof area; we respect non-penetration to preserve the membrane warranty.
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Anti-vibration pads under each foot**: they limit structural transmission and solid-borne noise perceived in apartments.
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Suction/discharge clearances : the machines are oriented back to back , each with its own free zone to avoid recycling of hot air in summer and premature frosting in winter.
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Management of defrost condensate : free discharge onto the membrane with deflector to direct flow away from flashings and drains ; natural roof slope respected.
Refrigerated routes and crossings: short, protected, watertight
To reduce pressure losses and simplify maintenance, we have favored refrigeration lines :
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Optimized length thanks to the location close to the technical columns ; each route follows a secure cable path .
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High density insulation (UV sheathing) on liquid and gas, connections tied and protected in a technical conduit from the roof entrance.
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Waterproof penetrations : dedicated sleeves, metal flashings and polyurethane sealing; continuity of the air barrier and vapor barrier maintained.
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Wiring grouped together (power supply, communication, heated drain if required) in UV-stabilized gutters.
This care on the courses guarantees the stability of overheating/undercooling and facilitates any future intervention.
Electricity and compliance: dedicated circuits and local cut-offs
Each condenser has its own dedicated circuit to the main panel (rating according to the nameplate), a suitable circuit breaker and a metal disconnect box installed within easy reach on the roof. The cables are UV-resistant , laid on risers to prevent water stagnation. Grounding and labeling comply with the Canadian Electrical Code and the municipal requirements of Greater Montreal .
Commissioning: deep vacuum, checks and fine adjustments
Our standard procedure includes:
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Vacuum draw < 500 microns , stabilization and ascent test (micro-leak detection).
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Electronic detector check on all flared and brazed fittings.
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Weighing and adjustment of the additional load according to the actual lengths.
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Measurement of temperature differentials and operating pressures to validate the target enthalpy diagram .
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Setting of blowing curves and time scenes by zone to limit power demand during peak hours .
Result: quiet operation , long cycles at low RPM and smoothed consumption .
Climate management: snow, wind and sun
A Montreal roof requires planning ahead:
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Snow : The elevation maintains a guard above accumulations; modular snow guards are still provided if vortices make a corner more loaded.
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Wind : the frames are braced and secured according to the site category; the spacing limits aeraulic interactions .
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Sun : the orientation respects the expansion of the lines and the UV protection of the ducts; summer tests confirm controlled discharge temperatures .
Interior diffusion: discreet comfort, independent zones
Inside, the MultiZone FreeMatch R-32 powers two wall-mounted units in the living areas and a compact cassette near the hallway, while the single-zone unit serves the office. Advantages:
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True zoning : each space sets its own instructions and flow rate .
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Silence : Low/Quiet speeds at night, adapted sweep to avoid direct breath.
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Homogeneity : no more 2–3°C differences between opposing facades.
HVAC maintenance: preserving efficiency and acoustic discretion
We offer an annual program including:
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Cleaning and disinfection of evaporators (filters, trays, fins),
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Control of currents , voltage and communications ,
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Inspection of the structure (tightening, pads, bed bases, gutters),
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Checking defrosting flows and sealing of crossings,
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Update scenes (summer/winter, presence/absence) to optimize savings .
Careful maintenance keeps the actual COP close to the nominal values and extends the service life .
Key design points to remember for flat roofs (Montreal, Laval, Longueuil, North Shore, South Shore)
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Raise the condensers: snow clearance, defrost drain, maintenance access .
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No drilling into the active surface of the membrane; favor weighted supports and protected paths .
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Move machines apart to avoid air recycling .
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Short refrigerated paths , UV insulated, sealed crossings.
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Dedicated electrical circuits with proximity disconnection .
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Zoning adapted to the actual use of the occupants.
Grants and Eligibility
Recent R-32 heat pumps with high efficiency and good performance in extreme cold may be eligible for Quebec programs. We support customers to document the criteria (capacity at –25/–30 °C, seasonal performance indices) and maximize the assistance available in Montreal , Laval , Longueuil , North Shore and South Shore .
Conclusion: aesthetics, robustness and four-season comfort
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Urban discretion : nothing on the facade, everything is on the roof, clean and accessible .
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Robustness : aluminum chassis, anti-vibration pads, protected paths.
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Controlled comfort : MultiZone FreeMatch R-32 + dedicated single zone = fine regulation without overconsumption.
Are you planning a flat roof project? We size, raise, secure and commission your heat pumps with the same high standards, for a durable , quiet and easy-to-maintain result.