A rooftop installation where choosing the location mattered just as much as choosing the heat pump
At Dollard-des-Ormeaux, we completed an installation that perfectly illustrates the level of planning required for a dual-zone heat pump installed on a residential roof. The selected system, a Fujitsu Aquila XLTH from the AIRSTAGE range, had to supply two separate indoor zones while integrating into an outdoor configuration with limited usable space, a parapet, a roof covering to protect, and a refrigerant route to be neatly directed into the building.
The photograph taken after the work shows the Fujitsu outdoor unit installed on a metal support near the parapet, without being placed directly on the roof membrane. The refrigerant lines leave the unit toward a raised finishing box, used to organize and protect their passage into the building. This configuration requires much more precision than a standard ground-level installation.
Our objective was not simply to place a machine on the roof. We needed to create a stable, accessible, and durable HVAC installation capable of withstanding conditions in Montreal’s West Island: wind, snow, freeze-thaw cycles, sunlight, wind-driven rain, and significant temperature variations.
Why a dual-zone heat pump was suitable for this property
The owner wanted to improve comfort in two areas with different needs. A single wall-mounted unit would have had difficulty distributing air evenly, while two independent systems would have required two outdoor units, more electrical connections, and additional roof space.
The Fujitsu multizone solution can power two indoor units from a single outdoor compressor. Each zone can be controlled separately, with its own set temperature and fan speed.
This independence is useful when a property includes, for example:
- an upper floor that is warmer in summer;
- a bedroom used primarily at night;
- an open-concept area exposed to sunlight;
- an office occupied during the day;
- two areas separated by a hallway or stairwell;
- an extension that responds differently to outdoor temperature changes.
In a home in Dollard-des-Ormeaux, heating and cooling loads can vary considerably depending on window orientation, ceiling height, insulation and wind exposure. Zoning therefore prevents a single general temperature from being imposed throughout the property.
Two independent zones, but one shared operating mode
It is important to understand how a multi-zone heat pump works. Each indoor unit can be controlled independently, but all zones connected to the same outdoor unit must operate in a compatible mode.
The system can provide heating or cooling, but it cannot heat one room while another simultaneously requires cooling. Fujitsu documentation specifies that AIRSTAGE multi-zone systems provide heating and cooling, but not both modes at the same time.
In most residences, this limitation causes few problems, since both zones generally require heating in winter and air conditioning in summer. Nevertheless, we explain it before the work begins so the homeowner understands exactly how the controls interact.
A Fujitsu product line designed for multi-zone applications
The Fujitsu Aquila H series offers several outdoor unit capacities, including 18,000, 24,000, 36,000 and 45,000 BTU/h. Depending on the selected model, one outdoor unit can accommodate two to five indoor units.
For a dual-zone system, selection should never be based solely on adding the capacities listed for the two wall-mounted units. Fujitsu authorizes various combinations, some of which nominally exceed 100% of the outdoor unit’s capacity. However, the manufacturer specifies that exceeding the combined capacity does not create additional power at the compressor.
For example, the documentation allows certain combinations of two indoor units whose total capacity exceeds the outdoor unit’s rated capacity. This flexibility may be appropriate when the two zones do not reach their peak demand at the same time. However, it must be validated through a technical analysis.
The photograph does not allow us to read the complete model number or the capacity listed on the nameplate with sufficient accuracy. We will therefore not present a BTU figure as though it were confirmed by the image. In a real project, this information is established based on heating and cooling loads, then verified using Fujitsu combination tables and selection tools.
Aquila XLTH: a suitable choice for cold-climate heating
The XLTH designation, associated with equipment designed for low temperatures, represents a significant advantage in Montreal’s climate. Documentation for the Aquila series indicates that cold-climate versions can provide heating down to an outdoor temperature of -26 °C.
This feature does not mean that the unit maintains exactly the same capacity at all temperatures. As with any heat pump, available capacity and efficiency change as the outdoor temperature decreases. A professional selection must therefore take into account the capacity actually delivered under winter conditions, rather than only the rated capacity advertised at a milder temperature.
We assess, in particular:
- the thermal load of each zone;
- heat loss through the building envelope;
- local design temperatures;
- the presence of an auxiliary heating system;
- the capacity of the electrical panel;
- the number and type of indoor units;
- the length of the refrigerant lines;
- the difference in height between the units.
This approach avoids two common mistakes: installing a system that is too small and runs continuously without reaching the setpoint, or choosing an oversized unit that performs excessively short cycles during milder periods.
The R32 refrigerant visible on the outdoor unit
The image clearly shows the identification R32 on the outdoor unit’s panel, as well as the safety marking associated with the A2L category.
R32 is a refrigerant used in several new generations of heat pumps. Its use requires appropriate practices, particularly for handling, connections, leak testing, and commissioning procedures.
For the homeowner, this label on the unit primarily serves as a reminder of the importance of entrusting any refrigeration-related work to a qualified technician. A heat pump should never be recharged simply because it appears to be performing less efficiently. Refrigerant loss generally indicates a leak that must be located and repaired before adjusting the charge.
The technical challenges of installing a Fujitsu system on a residential roof
Protect the membrane against unnecessary loads and punctures
A roof must not be treated like a concrete slab. Placing an outdoor unit directly on the roofing material can create pressure points, trap moisture, and complicate future repairs.
For this project, we used a raised metal support. The unit rests on horizontal rails that distribute its weight and keep its base above the roof surface.
This elevation serves several purposes:
- it protects the bottom of the unit from water;
- it facilitates drainage during defrost cycles;
- it limits contact with accumulated snow;
- it improves access to the connections;
- it reduces the risk of roof damage;
- it makes inspections and maintenance easier.
We also paid particular attention to the positioning of the supports. A rooftop installation must be compatible with the building structure and with the roofer’s recommendations when work affects the membrane or support components.
Maintaining adequate clearance from the parapet
The parapet visible in the photograph is both a protection and a constraint. It can reduce direct exposure to wind, but it can also disrupt airflow if the unit is installed too close.
A heat pump moves a significant volume of air through its fan. If this air immediately encounters a wall or flows back toward the heat exchanger, the unit may draw in the air it has just discharged. This recirculation can reduce performance, especially when the heat pump is operating at high capacity.
We therefore maintained enough space for:
- air intake through the heat exchanger;
- clear discharge in front of the fan;
- opening the service panels;
- safe technician access;
- future coil cleaning.
It is also important to prevent a homeowner from later adding a decorative fence or an enclosed cabinet around the unit. Although this modification makes the equipment less visible, it can seriously impair its operation.
Dealing with wind on a Dollard-des-Ormeaux roof
On a roof, a heat pump is more exposed to wind than it is on the ground. The force exerted on the unit, the support, and the pipes can become significant during a storm.
Mechanical stability must therefore be carefully checked. The pipes must also be supported so that they do not vibrate or rub against the parapet edge.
In the image, the refrigerant piping is grouped together and routed to a finishing enclosure. This arrangement reduces the number of loose elements on the roof and better protects the materials from wind-induced movement.
A protected and accessible roof penetration
The black enclosure visible near the parapet plays an important role in finishing the route. It allows the piping to be grouped together and protects the transition into the building.
An improperly made penetration can become a source of water infiltration. We therefore pay particular attention to:
- the location of the passage;
- mechanical support for the lines;
- protection of the insulation;
- leak-tightness;
- water drainage around the enclosure;
- accessibility for future inspection.
The lines must not be left unprotected against an abrasive edge. Movement caused by expansion, wind, or compressor operation can gradually damage the insulation.
The importance of refrigerant piping in a dual-zone system
A dual-zone heat pump has two connection circuits to the indoor units. Each circuit must comply with the diameters, lengths, and elevation differences permitted by Fujitsu.
A wiring error can have serious consequences. In particular, electrical and refrigerant connections between the zones must not be interchanged. If the piping for zone A is associated with the wiring for zone B, the controls and regulation will not operate correctly.
During commissioning, we therefore check each zone separately:
- activation of the first indoor unit;
- confirmation of the corresponding circuit;
- checking operation in heating mode;
- checking operation in cooling mode;
- verification of the second zone;
- testing with both units calling for operation;
- validation of the drains and remote controls.
Pressurization, leak testing, and evacuation
The quality of an installation cannot be assessed solely by its appearance. The invisible steps are often the most important.
After the connections are made, we must confirm the circuit is leak-free before releasing the refrigerant from the outdoor unit. A complete vacuum is then used to remove air and moisture from the lines.
Residual moisture can react with compressor oil, produce contaminants, and affect system reliability. A vacuum that is pulled too quickly or not verified is therefore poor practice, even if the equipment appears to operate during the initial startup.
Manage condensate from both indoor units
Each indoor unit produces water in cooling mode. The two drains must be designed independently and have an adequate slope.
We check in particular:
- the direction of flow;
- the absence of a reverse slope;
- the stability of the hose;
- the water outlet;
- the pan's watertightness;
- the absence of backflow.
In some properties, gravity drainage is impossible because of the indoor unit's position. A condensate pump may then be required. It must be installed in an accessible location because it contains moving parts and requires periodic maintenance.
Valuable flexibility for indoor units
The Fujitsu AIRSTAGE lineup is not limited to wall-mounted heads. The H series documentation presents several types of compatible units depending on the combinations: wall-mounted units, slim ducted units, compact cassettes, and medium-static-pressure units.
This flexibility makes it possible to adapt the installation to the architecture. In a room where a wall-mounted unit would be too visible, a concealed model may sometimes be selected. In another area, a wall-mounted head often remains the simplest and most effective solution.
However, the choice should not be based on appearance alone. A concealed unit requires space in the ceiling or attic, service access, and a properly sized duct network.
Rebates: eligibility must be confirmed for the exact combination
Some cold-climate heat pumps may qualify for financial assistance when they appear on lists recognized by the applicable program. Eligibility should never be assumed solely because the Fujitsu brand or the XLTH designation appears on the equipment.
You must confirm:
- exact outdoor unit number;
- exact indoor unit models;
- declared combination;
- applicable performance reference;
- program conditions at the time of installation;
- required documents.
A multi-zone combination may be treated differently from a single-zone system. The homeowner must keep the detailed invoice, model numbers, proof of payment, and required photographs.
Mistakes to avoid when installing on a roof
An installation like this can lose much of its value if certain details are overlooked.
Among the most important mistakes to avoid:
- place the unit directly on the membrane;
- install the compressor too close to the parapet;
- leave the lines unsupported;
- drill through the roof without coordinating with a roofer;
- place the unit in a difficult-to-access area;
- neglect condensate drainage;
- choose capacity based on floor area alone;
- confuse combined capacity with actual capacity;
- crossing the circuits of the two zones;
- ignoring exposure to wind;
- installing a cover that is too enclosed around the unit.
We also verify that the technician will be able to return to the roof safely. A heat pump must be maintained for many years, so access cannot be considered a minor detail.
Maintaining a Fujitsu heat pump installed on a roof
Routine maintenance remains simple for the homeowner, but a rooftop installation requires certain additional precautions.
Indoors, the filters of both units should be cleaned according to their usage. A heavily used area or one exposed to more dust may require more frequent cleaning.
Outdoors, we recommend a periodic inspection to check:
- the accumulation of leaves around the unit;
- the condition of the line insulation;
- the presence of abnormal ice buildup;
- the stability of the support;
- the condition of the protective components;
- the absence of objects blocking ventilation.
The homeowner should not walk unnecessarily on the membrane or attempt to clear the unit with a tool that could damage it. When the roof is difficult to access, the inspection should be entrusted to a professional.
The result achieved in Dollard-des-Ormeaux
This Fujitsu Aquila XLTH dual-zone heat pump installation now makes it possible to heat and cool two separate areas using a single outdoor unit.
The project brings together several essential elements:
- a Fujitsu AIRSTAGE unit suited to a multi-zone configuration;
- clearly identified R32 refrigerant;
- installation on a metal support;
- adequate roof protection;
- an organized line route;
- functional clearance near the parapet;
- sufficient service access;
- independent control of the two indoor zones.
At AirGreen, we carry out this type of HVAC installation in Dollard-des-Ormeaux, throughout the West Island, as well as in Montréal, Laval, Longueuil, on the North Shore and the South Shore. Each project requires a different analysis, particularly when a heat pump must be installed on a roof, terrace, balcony, or existing structure.
Final performance depends as much on the choice of equipment as on the quality of the support, the routing of the lines, drainage, refrigerant connections, and commissioning. It is this combination of technical decisions that turns a heat pump that performs well on paper into a comfortable and reliable system for the property.