When doing it yourself becomes a very bad idea in residential HVAC
At AirGreen, we’ve seen all kinds of failed installations, but this one—in a duplex in Montréal’s Rosemont neighbourhood—perfectly illustrates why installing a wall-mounted heat pump should never be left to a weekend handyman, no matter how motivated. This real-life case, far from unique, reflects a growing trend: the desire to do everything yourself, at the expense of performance, safety… and often, the budget.
The context: a client trying to save money… but poorly informed
The duplex owner, eager to cut down on heating and cooling bills, bought a 12,000 BTU Gree wall-mounted heat pump from an online retailer. Tempted by a 25% discount and the promise of fast shipping, he figured that with a few YouTube videos, he could manage the installation himself. The result? A series of poor decisions that led to a serious problem.
The mistakes made:
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Installed the indoor unit too close to the ceiling, blocking proper airflow
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Incorrectly sized condensate drain, causing a continuous leak onto the floor
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Drilled through the wall without considering slope for drainage
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Electrical connections not compliant with CSA code
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Skipped refrigerant pressure and leak testing altogether
Within three weeks, the heat pump was already showing signs of overheating, irregular start cycles, and worst of all… excessive humidity inside the walls, with mold starting to grow behind the drywall.
AirGreen steps in: restoring everything, one step at a time
Alerted by neighbours bothered by the noise of the outdoor unit, our client finally called us. Our team arrived on site and quickly saw the extent of the damage. The system was improperly installed, the lines poorly insulated, refrigerant levels too low, and the compressor already weakened from repeated short cycles.
Our action plan:
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Full removal of the uncertified unit
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Structural inspection of the exterior wall affected by moisture
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Recommendation of a new wall-mounted heat pump: Fujitsu KZAH 12,000 BTU, eligible for the LogisVert grant
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Professional installation with all required commissioning tests
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Complete explanation to the client on maintenance, operation, and routine checks
Final result: a high-performing, quiet system that complies with Quebec's electrical and mechanical standards, and most importantly, a safe, healthy, and comfortable home.
The real cost of a poorly executed project
The client thought he’d save money by avoiding professional installation. In the end, he paid twice as much as expected, not to mention the extra costs for mold removal and wall repairs.
Here’s a breakdown of avoidable expenses:
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Wall repair and mold remediation: $1,200
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Initial purchase of uncertified Gree heat pump: $1,450
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Safe removal of the DIY installation: $350
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New professional installation with Fujitsu KZAH: $4,100 (after grant)
Total: over $7,000, whereas a professional installation from the start would’ve cost around $4,500, grant included.
What we learned from this story
At AirGreen, we understand the desire to save money. But in HVAC, hiring qualified professionals isn’t a luxury—it’s a technical, regulatory, and health-related necessity.
A few key takeaways:
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A poorly installed wall-mounted heat pump uses more energy
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It wears out faster, shortening its lifespan by several years
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It can damage your home’s structure and affect occupants’ health
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It’s not eligible for grants if not installed by a certified company
The AirGreen approach: expertise, precision, and transparency
We don’t just install equipment. We advise, diagnose, correct, and guide our clients every step of the way. In this case, our transparency was greatly appreciated by the client, who admitted he should’ve come to us from the beginning.
We turned a project that started off wrong into a complete success, once again proving that hands-on experience, a solid grasp of Quebec’s regulations, and excellent service make all the difference.