Complete modernization of a ducted air conditioning system in a confined space, without interrupting operations
As part of a commercial HVAC retrofit project in Longueuil , our AirGreen team was tasked with replacing an old ducted air conditioning system housed in an exterior mechanical cage protected by a metal structure. The objective: to modernize the installation while ensuring business continuity for the tenant, an administrative services manager occupying several floors of the building.
Context of the mandate
The building in question, dating from the 1990s, was equipped with a central ducted direct expansion system, whose compressor and indoor unit had become obsolete. The client observed a significant drop in performance , excessive electricity consumption , and temperature regulation problems between zones.
The major constraints:
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Limited access to the equipment, installed behind a security grille fixed to the front.
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Restricted intervention windows to avoid any disruption to occupied offices.
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It is necessary to preserve the existing conduits, which are still in good condition.
Diagnosis and preliminary study
Before any intervention, our technicians carried out:
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A complete record of air flow rates and static pressures.
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A thermographic inspection to identify heat losses and condensation areas.
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A comparative energy analysis between the existing system and a modern VRF solution.
The results demonstrated a seasonal efficiency of less than 8 SEER — well below current ASHRAE 90.1 standards — justifying the complete replacement of the indoor unit and condenser.
Proposed technical solution
AirGreen has selected the installation of a 15-tonne Daikin VRF system , with a ducted medium-pressure module, offering:
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Load modulation from 10% to 100% , ensuring perfect thermal stability.
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Compatibility with existing ductwork and custom adaptation of plenums.
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Enhanced insulation of ducts and boxes to eliminate thermal bridges.
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Integration with the building's BMS via BACnet protocol, enabling real-time monitoring of temperatures, alerts and consumption.
A heat recovery system has also been added, allowing energy transfer between areas to be air-conditioned and heated, thus optimizing the TCO (Total Cost of Ownership).
Construction progress
The work took place over three days:
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Day 1: Dismantling of the old system and locking of the area.
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Day 2: Installation of the new ducted unit, reconnection of the ducts and sealing with aluminum tape and high-temperature insulating sealant.
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Day 3: Refrigeration connection, leak tests, vacuuming and probe calibration.
Our technicians operated on a staggered schedule (6 p.m. to 2 a.m.) to ensure zero interruption for the building's occupants.
Compliance and safety
The entire project was carried out in compliance with the standards:
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CSA C22.2 and ASHRAE 62.1 for ventilation and indoor air quality.
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RBQ and CNESST for safety at height and electrical work.
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Municipal permit for modification of outdoor equipment.
Guardrails and a security perimeter have been installed around the metal gate to secure access during the works.
Results and measured performance
After commissioning:
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Overall energy savings: +28%
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Reduction in indoor noise level: -6 dB(A)
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Thermal stability maintained at ±0.5 °C over 24 hours
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Elimination of recurring service calls due to summer overheating
The client also noted a significant improvement in occupant comfort and a reduction in annual maintenance costs .
Maintenance and monitoring
AirGreen now provides quarterly preventative maintenance for the system:
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Checking refrigeration pressures and temperatures
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Cleaning of filters, coils and sensors
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VRF controller firmware update
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Performance report automatically transmitted to the client's BMS
A 24/7 SLA contract guarantees intervention in less than 4 hours in the event of a critical failure.
ROI and subsidies
Thanks to the energy savings generated, the return on investment is estimated at 3.8 years , not including the Hydro-Québec subsidy for commercial energy efficiency , for which AirGreen managed the complete administrative file.
This project perfectly illustrates AirGreen's ability to design and execute complex HVAC retrofits in multi-constraint environments, while adhering to the strictest safety and energy efficiency standards.