A rooftop installation where choosing the outdoor unit’s location matters just as much as the heat pump itself
In Saint-Bernard-de-Lacolle, installing a wall-mounted heat pump is not simply a matter of mounting an indoor unit on the wall and placing the outdoor unit in the first available spot. On this project completed by our AirGreen team, the building’s configuration led us directly to a flat roof, with a reality very different from a typical residential installation at ground level.
The job-site photo clearly shows the context: a gravel-covered roof, roof projections, skylights, vents, existing mechanical equipment, and mature vegetation nearby. In the middle of this environment, we installed a Fujitsu AIRSTAGE Altair 700, with its outdoor unit positioned high on a metal structure to maintain functional clearance around the equipment.
This is precisely the kind of situation where our experience with HVAC installation in Montréal, Laval, Longueuil, the North Shore, the South Shore, and Montérégie becomes important. A high-performance heat pump can lose some of its benefits if its location makes drainage, air circulation, maintenance, or operation during snowy periods more difficult.
Why install the outdoor unit high up on a flat roof?
The photo of this installation in Saint-Bernard-de-Lacolle shows that the outdoor unit does not rest directly on the gravel. It is installed on a raised metal support, which is itself distributed across support elements that help better manage contact with the roof.
This configuration provides several practical benefits.
- Better clearance beneath the heat pump, particularly for draining the water produced during defrost cycles.
- Reduced risk of finding the base of the unit surrounded by accumulated snow.
- More convenient access to the connections for future HVAC maintenance or diagnostics.
- Better separation between the equipment and the roofing gravel.
- Neater positioning of the refrigerant lines and wiring.
- Maintaining a reasonable amount of space around the outdoor heat exchanger to promote air circulation.
In a region such as Saint-Bernard-de-Lacolle, the winter management of an outdoor unit must be part of the planning from the time of installation. Wind, snow, and defrost water must not be treated as secondary details.
A rooftop with several visible constraints
The available space might have seemed substantial at first glance, but a mechanical rooftop must be analyzed as a whole.
We had to account for existing vents, roof edges, nearby trees, and equipment already in place. We also had to preserve sufficient working space around the heat pump.
A common mistake is choosing the location that simply minimizes piping length. At AirGreen, we also consider:
Outdoor unit airflow
The coils must be able to receive and discharge air without excessive obstruction. An installation too close to a wall, parapet, another machine, or a mechanical component can impair operation.
Accessibility
A heat pump will eventually need to be inspected, cleaned, or repaired. Positioning the service panels against an obstruction turns what should be a simple intervention into an unnecessarily complex operation.
Water management
A heat pump in heating mode periodically performs defrost cycles. The water produced must be able to drain away from the machine without creating significant ice buildup around its base.
Roof protection
Mechanical equipment should not be placed on a roof membrane or assembly without careful consideration. On this project, the visible structure distributes the support while keeping the outdoor unit above the gravel surface.
Fujitsu AIRSTAGE Altair 700: an R-32 wall-mounted heat pump designed for compact and efficient installation
The Fujitsu AIRSTAGE Altair 700 installed on this project belongs to Fujitsu’s H single-zone series. The manufacturer’s documentation lists two capacities in this family: 09KMAS1, with a nominal cooling capacity of 9,000 BTU/h, and 12KMAS1, with a nominal cooling capacity of 12,000 BTU/h. Since the nameplate is not legible in the provided construction-site photo, we do not claim to identify the exact capacity of this installation from the image alone.
This distinction is important. We prefer to provide verifiable technical information rather than arbitrarily assigning a capacity to a unit whose full model number is not visible.
Very impressive performance for a compact wall-mounted system
The Altair 700 series technical data sheet lists the following specifications:
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09KMAS1
- Nominal cooling capacity: 9,000 BTU/h;
- cooling range: 3,100 to 12,100 BTU/h;
- rated heating capacity: 12,000 BTU/h;
- heating range: 2,800 to 14,500 BTU/h;
- SEER2: 30,0;
- HSPF2, Region V: 9,9.
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12KMAS1
- rated cooling capacity: 12,000 BTU/h;
- cooling range: 3,100 to 13,800 BTU/h;
- rated heating capacity: 14,000 BTU/h;
- heating range: 2,800 to 15,000 BTU/h;
- SEER2: 27,5;
- HSPF2, Region V: 8,5.
These figures show why an inverter heat pump should not be evaluated solely based on the number of BTUs displayed on the label. Capacity varies according to demand, allowing the compressor to adjust its operation rather than operating only in on-off mode.
Heating down to -15 °C according to the Altair 700 technical sheet
For these two configurations, Fujitsu specifies a heating operating range of -15 °C to 24 °C, and a cooling operating range of -10 °C to 50 °C.
This is particularly important information for a homeowner comparing several wall-mounted heat pumps in Saint-Bernard-de-Lacolle.
A distinction must also be made between a unit’s minimum operating temperature and its actual ability to replace a building’s entire heating system during the coldest periods. System sizing, heat loss, insulation, air infiltration, and the presence of auxiliary heating must always be considered together.
R-32 refrigerant with lower global warming potential
This generation of the Altair 700 uses R-32. According to the Fujitsu documentation provided for this series, R-32 has a global warming potential of 675, compared with 2,088 for R-410A, which the manufacturer presents as an approximately 68% reduction in GWP.
For our HVAC installations, this change also requires compliance with the procedures and practices specific to equipment using next-generation refrigerants.
Compact 1/4 in. and 3/8 in. piping
Here is a particularly useful detail for homeowners, building managers, and installers planning the line-set routing:
liquid: 1/4 in.
gas: 3/8 in.
These dimensions apply to the 09KMAS1 and 12KMAS1 versions presented in the technical sheet.
The minimum indicated piping length is 10 feet, while Fujitsu allows up to 66 feet of piping, with a factory charge covering up to 49 feet. The maximum indicated vertical difference is also 49 feet.
On a project with an outdoor unit installed on the roof, like the one in Saint-Bernard-de-Lacolle, these figures are far from theoretical. The route between the indoor unit and the outdoor unit can be much more complex than a direct passage through an exterior wall.
Power supply: 208 to 230 V and a 15 A circuit breaker
The Altair 700 series operates on a 208 to 230 V, 60 Hz, single-phase power supply. The Fujitsu specifications call for a 15 A circuit breaker for both capacities presented.
For the 12,000 BTU version, the specified maximum current is 6.9 A in cooling mode and 9.4 A in heating mode. For the 9,000 BTU version, it reaches 6.4 A and 9.4 A, respectively.
This low electrical demand compared with many higher-capacity systems can be beneficial in buildings where available panel capacity must be carefully managed. However, it never replaces having the existing circuit inspected by a qualified professional before connection.
A truly compact outdoor unit
The outdoor unit listed in the documentation measures approximately:
31 7/16 in. wide
21 5/16 in. high
11 7/16 in. deep
It weighs approximately 71 lb.
This shallow depth helps make the Fujitsu Altair 700 appealing for spaces where every inch counts: a balcony, side passage, compact yard, or, as here, a rooftop with several mechanical units.
Indoor operation as low as 19 dB(A)
At the “quiet” speed, the indoor unit is rated at only 19 dB(A) in cooling mode and 21 dB(A) in heating mode.
For homeowners installing a heat pump in a bedroom, workspace, or living area where noise levels genuinely matter, this figure deserves as much consideration as energy performance.
The outdoor unit is also relatively discreet: Fujitsu specifies 44/47 dB(A) in cooling/heating mode for the 9,000 BTU version and 48/50 dB(A) for the 12,000 BTU version.
Integrated Wi-Fi and remote control
The Altair 700 series also includes integrated Wi-Fi connectivity, with remote monitoring and control through the AIRSTAGE mobile app.
For a building that is not occupied continuously, this function can be particularly practical. It makes it possible, among other things, to adjust the setpoint without having to physically go to the remote control.
Fujitsu also offers various integration options, including interfaces for 24 V thermostats and BACnet or Modbus communication capabilities with compatible accessories. This can be relevant in certain commercial or multi-unit residential projects where the heat pump needs to communicate with a more sophisticated control strategy.
An ENERGY STAR certified heat pump
The specification sheet classifies both models as ENERGY STAR, including the cold-climate designations displayed by Fujitsu.
For a subsidy application in Quebec, however, we always verify the exact model number, the indoor/outdoor combination, and the program criteria in effect when the project takes place. ENERGY STAR certification alone does not allow anyone to promise a specific amount of financial assistance.
This is a mistake homeowners should avoid when comparing quotes: a subsidy amount must be associated with an eligible equipment combination and the rules applicable at the time of the application.
What the Saint-Bernard-de-Lacolle photo reveals about a well-planned installation
The value of this installation lies not only in the figures on the Fujitsu specification sheet.
Several technical decisions are visible on the roof.
The unit is elevated. It has ample clearance around its heat exchanger. The connections reach the appliance without the machine being wedged against a building structure. The support keeps the equipment above the gravel layer and creates the necessary space beneath the chassis.
It is also worth noting that the project was carried out in an environment where other pipes, penetrations, and appliances are already located nearby. This type of roof requires more organization than a completely unobstructed façade.
Do not install a rooftop unit directly where snow will accumulate
One mistake we encounter in some existing installations is placing a heat pump too low.
When a significant amount of snow accumulates around the coil, the equipment has to operate under much less favorable conditions. The situation can be even more problematic when defrost water gradually freezes around the base.
The support should therefore be chosen based on the building and site conditions, not solely on its price.
Do not neglect future maintenance
An installation can be perfectly functional on the first day and become extremely unpleasant to maintain a few years later.
We therefore try to consider from the outset access to the panels, heat exchanger cleaning, connection checks, electrical measurements, and diagnostic work.
On a roof, this consideration is even more important because moving the equipment a few inches during installation can prevent many complications during future service calls.
The ProCore coil: an interesting detail of this Fujitsu generation
The Altair 700 documentation also indicates that the indoor unit uses highly corrosion-resistant copper ProCore coils.
In a market like Quebec, where a heat pump may operate for much of the year in cooling, heating, and dehumidification modes, the design of the heat exchanger is one of the factors we consider when comparing different units.
The series also includes several standard but useful features:
- economy mode;
- energy-saving mode;
- powerful mode;
- minimum heat mode;
- automatic defrosting;
- automatic restart;
- wireless remote control;
- automatic vertical airflow adjustment.
This project illustrates a rule we apply throughout the Greater Montreal area
Whether we are installing a wall-mounted heat pump in Montreal, a unit on a balcony in Laval, a rooftop system in Longueuil, an installation on the South Shore, on the North Shore, or a more remote project in Montérégie such as the one in Saint-Bernard-de-Lacolle, we always start with the building.
The heat pump model comes next.
An excellent unit that is poorly positioned can become noisy, difficult to service, or unnecessarily exposed to snow. Conversely, a well-planned installation improves system durability and makes operation easier for many years.
In this project, the Fujitsu AIRSTAGE Altair 700 was especially well suited thanks to its compact outdoor unit, its small 1/4 in and 3/8 in lines, and its ability to accommodate a line-set length of up to 66 feet according to the manufacturer's specifications.
Our AirGreen approach to rooftop HVAC installation
For this type of work, we pay particular attention to every detail that will remain invisible once the installation is complete.
We check the piping route, drainage location, future access, clearances around the unit, mechanical support, electrical requirements, and how the building will actually be used.
These are the decisions that make the difference between simply installing equipment and a heat pump installation properly integrated into the building.
The post-installation photo taken in Saint-Bernard-de-Lacolle clearly reflects this philosophy: a compact unit installed neatly on an existing roof, with a structure adapted to the setting rather than an improvised solution.
For homeowners evaluating a Fujitsu Altair 700, we recommend comparing more than just the equipment price. You should also compare how each contractor plans to install the outdoor unit, route the lines, protect the building, and maintain access for servicing.
This is particularly true for rooftop projects, where making the right decision before installation can prevent problems during every subsequent winter.