A MIDEA35 installed on a flat roof: a configuration in which stability, clearance, and drainage become essential
In Saint-Urbain-Premier, we installed a MIDEA35 wall-mounted heat pump whose main distinctive feature is located outside the building. The project photograph shows the MIDEA outdoor unit installed directly on a flat gravel-covered roof, but most importantly significantly elevated by a metal structure designed to keep the unit away from the roof surface.
This type of configuration requires a very different approach from a traditional ground-level installation.
On a roof, we must consider the equipment’s weight, its stability, vibrations, wind, water drainage during defrost cycles, snow accumulation, airflow in front of and behind the unit, and accessibility for futureHVAC maintenance.
In this project in Saint-Urbain-Premier, so our objective was not simply to place the outdoor unit on the roof. We had to create an installation that fit coherently with the existing surroundings: a gravel roof surface, nearby equipment and roof outlets, the routing of the lines, and the space required around the heat pump.
The visible result in the photo is a MIDEA35 positioned well above the roof level, with its large, fully unobstructed side-discharge fan.
Why install a heat pump on the roof?
In some buildings, the roof is the best available location for the outdoor unit.
At ground level, several constraints can complicate an installation:
- lack of space around the building;
- frequently used walkways;
- terrace or landscaping;
- proximity to neighbours;
- windows or doors;
- need to keep the façade clear;
- long distance between the outdoor unit and the chosen location for the indoor unit.
A rooftop installation can help resolve several of these issues, but it comes with its own technical requirements.
MIDEA’s documentation specifically highlights the flexibility of its compact side-discharge outdoor units and indicates that they can suit different configurations, including roof, terrace, or balcony, depending on the installation conditions.
This flexibility is particularly appealing for a ductless heat pump, since the indoor unit and outdoor unit are connected mainly by refrigerant lines, wiring, and the drainage system.
A raised structure rather than a heat pump placed directly on the roof
The most obvious feature of our installation in Saint-Urbain-Premier is its support.
The MIDEA rests on a raised metal structure which keeps the underside of the unit well above the gravel. Beneath this structure, various distribution and support elements are visible on the roof.
This choice offers several practical advantages.
First, the underside of the heat pump remains accessible. This is important because a heat pump operating in heating mode must periodically perform a defrost cycle. Water may then drain beneath the unit.
In the middle of winter, this water may then freeze.
A unit installed too close to the roof may therefore gradually become surrounded by ice or snow. By raising it, we create more space for these accumulations to develop beneath the unit without immediately obstructing its components.
Winter clearance is particularly important in Saint-Urbain-Premier
The MIDEA35 is designed for more than just summer cooling.
MIDEA classifies this series as a cold-climate heat pump, using R-454B refrigerant, with a heating operating range extending down to -30 °C. The series can also reach up to 33.3 SEER2 in cooling and up to 22.0 HSPF2, depending on the selected capacity.
These winter capabilities make outdoor placement even more important.
A heat pump designed to continue heating when temperatures drop sharply must have an outdoor environment compatible with this use.
We must therefore anticipate:
- snow accumulated on the roof;
- ice produced by defrost cycles;
- snow being moved by the wind;
- clearance in front of the fan;
- access to the unit when service is required in winter.
A highly efficient low-temperature unit cannot deliver its best performance if it becomes buried or if its airflow is blocked.
The large front-mounted fan remains completely unobstructed
In the photograph, the fan occupies a large portion of the MIDEA unit’s front panel. Nothing is installed directly in front of it.
That is exactly what we are looking for.
A heat pump operates through a constant exchange of energy with the outdoor air. The fan must move a large volume of air through the heat exchanger.
An obstacle placed too close to the outlet can promote recirculation of discharged air and impair the unit’s operation.
On a roof, we therefore analyze not only the available space, but also the other structures present: mechanical outlets, parapet walls, ducts, equipment, chimneys, and vents.
In this project, the unit benefits from a wide-open front area, allowing the fan to operate without visible obstruction.
A raised installation that requires consideration of vibrations
A compressor and a fan necessarily generate some vibrations during operation.
At ground level, these can be absorbed by a slab or suitable support. On a roof, we must pay particular attention to how they are transmitted to the building structure.
In the photo, we can see that the unit is not placed directly on the membrane or gravel. It rests on its metal support, and intermediate contact points are visible beneath its feet.
The goal of a well-planned installation is to combine:
mechanical stability, leveling, and reduced transmission of unnecessary vibrations.
This consideration becomes particularly relevant when the equipment is located above occupied spaces.
A heat pump installed on a roof must remain accessible
Installing equipment in a difficult-to-access location without considering future maintenance is a mistake we seek to avoid.
A MIDEA35 heat pump may eventually need to be inspected, cleaned, or diagnosed.
A technician may need to access:
- to the electrical connections;
- to the service valves;
- to the refrigeration circuit;
- to the fan motor;
- to the outdoor heat exchanger;
- to the electronic control board;
- to the line-set connections.
In our Saint-Urbain-Premier project, the unit is installed on a clear section of the roof. Its elevation also facilitates access to certain lower parts of the unit.
MIDEA35: three capacities with different specifications
The MIDEA35 does not correspond to a single identical unit in every installation.
The MIDEA brochure presents three main configurations:
| MIDEA35 combination | Rated cooling | Rated heating | SEER2 | HSPF2 IV | AHRI reference |
|---|---|---|---|---|---|
| MSESU-H09B-2A / MO1SS-H09B-2A | 9,000 BTU/h | 12,000 BTU/h | 33,3 | 22,0 | 215471386 |
| MSESU-H12B-2A / MO1SS-H12B-2A | 12,000 BTU/h | 12,000 BTU/h | 29,4 | 14,5 | 215471387 |
| MSESU-H18B-2A / MO1SS-H18B-2A | 18,000 BTU/h | 20,000 BTU/h | 25,6 | 16,2 | 215471388 |
MIDEA indicates that the three configurations can operate in heating mode down to -30 °C.
However, the photograph of this installation in Saint-Urbain-Premier does not show the nameplate clearly enough to determine the exact installed capacity without ambiguity.
We therefore avoid arbitrarily assigning it 9,000, 12,000, or 18,000 BTU/h.
For a professional installation, these are the complete indoor and outdoor unit numbers, as well as the AHRI reference which confirm the exact performance.
Why precise sizing remains essential
Capacity selection should never come down to choosing the unit with the highest number of BTUs.
A wall-mounted heat pump must be suited to the space's heating and cooling requirements.
We take the following into account, among other factors:
- heated and cooled area;
- insulation;
- fenestration;
- building orientation;
- room layout;
- sun exposure;
- winter heat loss;
- how air can circulate between spaces.
An oversized heat pump does not automatically provide better comfort. In cooling mode, excessively short cycles can notably reduce dehumidification quality.
The MIDEA35 has variable-speed technology that allows the compressor to adjust its operation according to demand rather than operating only in full on-and-off cycles. MIDEA associates this modulation with a more stable indoor temperature and fewer fluctuations.
What this rooftop installation teaches us about a MIDEA35 heat pump suited to Quebec's climate
Refrigerant lines must be selected according to the exact model
A rooftop installation may require a very different line route from an installation where the condenser is located directly behind the indoor unit.
The MIDEA35 series offers some flexibility, but the limits depend on capacity.
For the 9,000 and 12,000 BTU/h, MIDEA specifies liquid and gas lines of 1/4 in and 3/8 in, with a stated maximum length of 82 ft.
For the 18,000 BTU/h, the dimensions increase to 3/8 in and 5/8 in, with a maximum length of up to 164 ft.
This information is particularly relevant on a roof.
There may be a significant height difference between the indoor and outdoor units. The documentation specifies a maximum height difference of 49.2 ft for the 9,000 and 12,000 BTU/h versions and up to 82 ft for the 18,000 BTU/h configuration.
We must therefore know the actual routing before definitively selecting the combination.
R-454B requires an installation corresponding to the new generation of equipment
The MIDEA35 operates on R-454B, an A2L refrigerant. MIDEA documentation also mentions an A2L refrigerant leak detection system for this product family.
For the owner, this does not change how they adjust their heat pump on a daily basis.
For our HVAC teams, however, the refrigerant is part of the technical data that determines the tools, practices, and checks required during installation and future service calls.
The electrical supply varies according to capacity
The electrical requirements must also be confirmed before installation.
For the 9,000 and 12,000 BTU/h MIDEA35 models, the manufacturer specifies a minimum allowable ampacity of 16 A and a maximum protection of 20 A.
For the 18,000 BTU/h version, the minimum ampacity increases to 24.9 A, with a maximum protection of 25 A.
The specified power supply is 208/230 V, single-phase, 60 Hz.
For a project with an outdoor unit on the roof, the electrical routing must also be planned before work begins to avoid an improvised installation around the building's other mechanical components.
The outdoor sound level deserves attention on a roof
The documented values for the outdoor unit are 57 dB(A) for the 9,000 and 12,000 BTU/h configurations at high speed and 61.5 dB(A) for the 18,000 BTU/h configuration.
An acoustic measurement does not, however, tell the whole story.
Where we install the equipment can strongly influence the noise perceived indoors.
On a roof, the structure, supports, and vibrations must be taken into consideration. That is why the quality of the base is almost as important as the sound level indicated in the technical specifications.
The roof visible in the photograph requires careful management of the refrigerant line route
The photograph also shows an insulated line leaving the unit and heading toward a roof structure on the right.
This is a good example of what distinguishes a rooftop HVAC installation a standard installation against an exterior wall.
We must plan the route to avoid:
- unnecessarily tight bends;
- excessive mechanical exposure;
- a route obstructing access to other equipment;
- poor line support;
- an unnecessarily long length.
The final result must be logical both for the heat pump and for people who may eventually need to move around on the roof.
The indoor features complement the work of the outdoor unit
Even though the photograph focuses on the condenser, the indoor section of the MIDEA35 offers several useful features for everyday comfort.
MIDEA indicates, among other things:
- ECO mode;
- Turbo;
- night mode;
- timer;
- function Follow Me;
- automatic cleaning;
- silent mode;
- heating at 8 °C;
- horizontal swing;
- vertical swing;
- gradual fan adjustment;
- humidity control;
- smart sensor.
The manufacturer also indicates up to 100 airflow-volume adjustment levels, as well as the option of control via the SmartHome app and Wi-Fi, depending on the selected configuration.
This allows the airflow to be adjusted more precisely to the space rather than being limited to a few fixed speeds.
LogisVert: the MIDEA35 series alone is not sufficient to announce an amount
The question of financial assistance comes up regularly when we install a heat pump in Saint-Urbain-Premier or elsewhere in Québec.
The MIDEA brochure provides specific AHRI references for the MIDEA35 and identifies it as a series Cold Climate V6.1.
For current installations, Hydro-Québec indicates that the LogisVert residential assistance is $50 per 1,000 BTU/h of heating capacity at -8 °C for an ENERGY STAR-certified heat pump, or $120 per 1,000 BTU/h at -8 °C when it is also a cold-climate model, when all program conditions are met. The applicable amount depends on the actual installation date.
Since November 26, 2025, Hydro-Québec has also required the certification ENERGY STAR for installations subject to the current rules.
We therefore cannot honestly announce the exact amount for this installation based solely on the photo or the MIDEA35 designation.
We always verify:
- the exact indoor unit model;
- the exact outdoor unit model;
- the AHRI number;
- the applicable ENERGY STAR certification;
- the cold-climate classification;
- the recognized capacity at -8 °C;
- the installation date;
- the other criteria specific to the dwelling and program.
In some eligible multi-unit residential buildings, Hydro-Québec has offered since June 15, 2026, an incentive that may bring the assistance to $220 per 1,000 BTU/h at -8 °C, when all specific conditions are met.
What a homeowner should avoid after a rooftop installation
Once the system has been installed, certain good practices help maintain proper operating conditions.
In particular, we recommend not intentionally accumulating objects or materials around the unit and periodically checking that its surroundings remain clear.
On a roof, particular attention should be paid to:
- significant accumulations of snow;
- ice beneath the unit;
- leaves or debris in the heat exchanger;
- objects blown by the wind;
- the apparent condition of the support;
- the lines that could be subjected to mechanical stress.
However, a technical intervention on the equipment must not be improvised. An anomaly, unusual noise, or significant accumulation must be evaluated using the proper methods.
Errors we seek to avoid with a heat pump installed on a roof
This Saint-Urbain-Premier project highlights several errors that can compromise a project:
- install the unit directly on a surface not intended for it;
- neglect the height required above winter snow accumulation;
- block the fan grille;
- forget about the water produced during defrosting;
- place the unit against a roof outlet or an obstacle;
- create an inadequately stable support;
- ignore vibrations that could be transmitted to the building;
- exceed the permitted line lengths or height differences;
- fail to plan for future access to the service panel;
- use a copper diameter that does not match the model;
- choose the electrical circuit based solely on BTUs;
- make the lines vulnerable to movement on the roof.
These installation details, often invisible in a commercial brochure, are frequently what determine long-term satisfaction.
A MIDEA35 installation adapted to the building rather than a standardized solution
This wall-mounted heat pump installation in Saint-Urbain-Premier is a good representation of our approach at AirGreen.
We do not decide in advance that an outdoor unit must necessarily be placed on a ground-level slab or on a support attached to a wall.
We analyze the building.
Here, the roof offered a configuration that made it possible to keep the equipment away from ground-level areas. Our job was then to make this location compatible with the heat pump’s actual requirements: height, stability, airflow, drainage, accessibility, and refrigerant line routing.
The photograph shows the final result: an outdoor MIDEA unit installed above the gravel on its own support, with a large clear area in front of its fan and sufficient space beneath the equipment to manage the demands of winter use.
It is this same attention to detail that we apply to our wall-mounted heat pumps and HVAC installation in Saint-Urbain-Premier as well as Montreal, Laval, Longueuil, on the South Shore and the North Shore.
A MIDEA35 has impressive technical specifications on paper. However, to truly benefit from it for several seasons, the unit must be installed in conditions that respect the manufacturer, the building, and the realities of Quebec’s climate.