On the rooftop terraces of Ville-Marie, HVAC systems face a unique reality: full sun, wind, fine dust, rapid temperature fluctuations… and sometimes less than ideal access. The photo clearly shows a Goodman outdoor unit installed on a roofing membrane, mounted on a raised base with anti-vibration pads/isolators and clearance near the parapet—a typical setup for serving a condo or an upper floor.
In this article, we present a recent intervention where we had to diagnose a loss of performance and restore the equipment to optimal condition, with a methodical and results-oriented approach.
The context: a Goodman heat pump in a “rooftop terrace” environment
The installation shown is a wall-mounted heat pump (mini-split) : a compact outdoor unit, usually connected to one (or more) wall-mounted indoor units. On a rooftop, this type of installation is common in condominiums, as it allows for unobstructed facades and reduces the space required on balconies.
Visible salient installation details:
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Goodman unit on a flat roof, near a guardrail/parapet
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Raised base with blocks/supports and anti-vibration dampers (reduction of noise transmitted to the structure)
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Implantation on membrane: a critical point where stability, drainage and protection against penetration are essential
The reported problem: unstable comfort and declining performance
The client contacted us because:
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the indoor temperature varied , despite a stable setpoint;
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the system seemed to run for longer than before;
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On some days, the cooling was less effective , especially during heat waves.
On a roof, these symptoms can come from several causes: fouling of the exchanger, ventilation problem, electrical fault (condenser/contactor), thermal overload, or even loss of refrigerant.
Our AirGreen diagnosis: check before you “guess”
We always proceed in the same order: measure, compare, confirm .
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On-site visual inspection
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Checking for clearances around the unit (condenser breathing)
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Condition of the grille and fins, presence of dust/pollen
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Stability of the supports and condition of the insulators (vibrations = accelerated wear)
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Electrical controls
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Supply voltage, tightness of connections (on the roof, hot/cold cycles can loosen some points)
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Checking the control components (contactor, capacitor depending on configuration)
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Operating measures
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Pressures, line temperatures, superheating/subcooling (depending on the circuit type)
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Outdoor unit fan behavior
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Validation of the startup and modulation logic
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Diagnostic result: we confirmed a set of factors typical of rooftop installations: degraded heat exchange (fouling and exposure), combined with an operational imbalance that prevented the Goodman unit from reaching its normal efficiency during peaks.
Repair steps: restoring the Goodman to its proper performance level
1) Technical cleaning of the condenser (without damaging the fins)
On the roof, fine dust accumulates and sticks to the fins. Even if the unit is "working", heat exchange decreases, pressures rise, and comfort becomes inconsistent.
We have achieved:
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controlled cleaning of the heat exchanger;
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slight straightening of affected fin areas (if necessary);
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fan rotation/balancing check.
2) Securing and cleaning the installation
A membrane unit must remain stable , well unobstructed, and transmit minimal vibration:
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seat adjustment and control of anti-vibration pads;
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checking the level and support points;
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validation of clearances on the suction/discharge side.
3) Performance checks and recommissioning
After the procedure:
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complete relaunch and stabilization of the regime;
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temperature measurements and validation of capacity return;
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monitoring of consumption and behavior under load.
The result: restored comfort, more stable operation, reassured customer
After repair and optimization:
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the Goodman heat pump has returned to a more consistent operating state;
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The walking time has normalized and the system responds better to weather variations;
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The client has regained reliable comfort, particularly important in a condo where sunlight can raise the temperature very quickly.
Why a rooftop unit requires special attention
On the roof, a heat pump is more exposed than on a sheltered side wall. To prevent breakdowns and preserve its lifespan:
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Regular maintenance of the condenser is crucial;
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the supports and insulators must be checked (noise, vibration, mechanical fatigue);
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Periodic inspection helps to anticipate performance losses before they become breakdowns.
At AirGreen, we work every week on systems installed at height in Montreal, particularly in Ville-Marie , and we know the sensitive points of membrane installations.