Optimizing the energy performance of an industrial building by replacing an aging rooftop unit
In Montreal East 's industrial district, a building owner leasing several spaces to manufacturing companies was facing a recurring problem: an old, noisy, energy-inefficient, and outdated rooftop heating system . Maintenance costs were increasing year after year, and maintaining a stable temperature inside the workshops was becoming difficult.
The AirGreen team was mandated to design and execute a complete retrofit of the rooftop HVAC system , while ensuring continuity of production operations inside the building.
Project context and objectives
The building, constructed in the 1980s, was equipped with a York brand monobloc natural gas system , providing both heating and air conditioning. After a detailed inspection, our technicians noted:
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a thermal efficiency of less than 65% ;
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unbalanced blower fans , causing vibrations and noise;
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advanced corrosion on heat exchangers and cooling coils;
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and an incompatibility of the existing control system with the new building automation management standards.
The client's main objective was twofold:
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Reduce the building's energy consumption ;
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Improve reliability and thermal comfort for tenants without interrupting industrial activities.
Site constraints and planning
The project presented several logistical and technical constraints :
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Limited access to the roof , requiring a crane with temporary closure of the rear alley;
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Weight of units : the old installations totaled more than 500 kg each, requiring a structural check of the roof by an engineer;
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Gas and electricity supply to be rerouted to adapt to the new connections;
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Limited intervention window : 24 hours per unit in order not to disrupt tenants' activities.
Thanks to rigorous coordination between the AirGreen teams, structural engineers and the electrical department, the replacement was able to be planned in two phases.
Proposed technical solution
Following a thermal load study and consumption analysis, AirGreen recommended the installation of two new Trane Voyager 15-tonne rooftop units , with the following characteristics:
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Variable speed scroll compressor technology ;
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Integrated economizer to maximize the supply of fresh air in temperate conditions;
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Condensing burner with an efficiency greater than 90%;
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R410A refrigerant , compliant with current environmental standards;
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BMS (Building Management System) control via BACnet protocol, enabling centralized building management.
These units were chosen for their high energy efficiency (SEER 17) and simplified maintenance , ideal for multi-tenant buildings.
Construction progress
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Safe decommissioning of existing units: disconnection of gas, electricity and pipes.
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Regulatory removal and disposal of end-of-life equipment, including refrigerant recovery.
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Structural inspection and addition of galvanized steel plates to reinforce the roof.
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Installation by crane of the new Trane Voyager units on adaptation curbs.
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Complete connection : conduits, gas lines, power supply, BMS control.
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Functional testing and calibration of static pressures and air flow rates.
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Acoustic verification and network balancing.
The entire project was completed in four working days , without any interruption of production inside the building.
Results and Key Performance Indicators (KPIs)
Post-installation measurements have demonstrated:
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35% reduction in annual electricity consumption ;
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42% savings on natural gas , thanks to integrated condensation;
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Noise level reduced by 9 dB(A) on the roof;
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Improved stability of indoor temperature (variation ≤ 1 °C);
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60% reduction in unplanned maintenance calls within 12 months of commissioning.
The client also noted improved indoor air quality (IAQ) perceived by employees, linked to MERV 13 filtration installed in the new units.
Maintenance and remote monitoring
AirGreen has integrated the new system into a building management system (BMS) remote monitoring platform , enabling:
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monitoring of pressures, temperatures and fan speeds ;
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automatic alerts in case of performance discrepancies;
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remote access for rapid diagnosis;
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and dynamic preventive maintenance planning .
A Service Level Agreement (SLA) has been signed with the client, guaranteeing:
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Full semi-annual inspection ,
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Cleaning of coils and filters ,
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24/7 breakdown service with a guaranteed 4-hour response time .
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Critical stock of spare parts on site to ensure continuity.
Compliance and safety
The intervention was carried out according to the standards:
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CSA B52 and B149.1 (refrigeration and natural gas);
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ASHRAE 62.1 and 90.1 (air quality and energy efficiency);
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and the Quebec Building Code for mechanical installations on roofs.
The required municipal permits were obtained before work began, and a full compliance report was given to the owner upon project delivery.
Return on investment and subsidies
The project received support from the Quebec Ministry of the Environment's EcoPerformance program, covering 20% of equipment costs .
The return on investment (ROI) is estimated at 3.8 years , primarily due to:
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to energy savings (electricity and gas),
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to the reduction of maintenance costs,
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and to the increased longevity of the new system.
Over ten years, the modernization of the HVAC system will allow a reduction of more than 120 tonnes of CO₂ equivalent.
AirGreen Expertise: Performance, Compliance, and Peace of Mind
This project perfectly illustrates AirGreen 's ability to work on complex commercial HVAC systems , while respecting the operational constraints of industrial clients.
Our approach combines technical analysis, regulatory compliance and energy optimization to deliver sustainable and measurable long-term performance .
Whether it's for a rooftop retrofit, preventive maintenance or a design-build project , our teams serve all of Greater Montreal — from Laval to Longueuil, including the North Shore and the South Shore — with the same rigor and excellence.