Installation of a Midea (R-454B range) wall-mounted heat pump in Lachine
Midea R-454B wall-mounted heat pump installed on a roof in Lachine: distribution rails, UV ducting, snow clearance, optimized commissioning. AirGreen, HVAC installation experts in Montreal and the surrounding area.
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On a condo rooftop terrace: a clean, safe HVAC integration ready for our winters
At AirGreen , we regularly work in Montreal condominiums where floor space is scarce and facades are protected. This project, carried out in a contemporary building in the Lachine sector, illustrates a rooftop HVAC installation : a Midea wall-mounted heat pump – R-454B extreme cold range designed to provide stable comfort year-round, while respecting the roof membrane and condominium standards.
The technical choice: Midea R-454B for efficiency and extreme cold
Here we are choosing a Midea wall-mounted heat pump of the new generation using R-454B , a refrigerant with low GWP and excellent seasonal efficiency. This cutting-edge technology is essential for three major reasons:
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Low temperature heating performance : the inverter compressor and defrost electronics provide sustained power in negative temperatures, ideal for the exposed shores of Greater Montreal .
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High energy efficiency (SEER/HSPF higher than previous generation R-410A), meaning savings on bills and a reduced carbon footprint.
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Eligibility for municipal and provincial support programs when efficiency criteria are met — a real asset for co-owners in Montreal, Laval, Longueuil, North Shore and South Shore .
We size the capacity (9,000 to 18,000 BTU depending on common cases in condos) from a load calculation taking into account the orientation, the glazed surface, air infiltration and the insulation of the roof slab.
Context: co-ownership, shared spaces, TPO/EPDM membrane to be protected
Flat condo roofs impose strict rules: no uncontrolled penetration, protection of the membrane , respect for access and clearances. Our mission is to deliver an HVAC installation that heats and cools efficiently without compromising the building envelope .
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Refrigerated path : short and direct route to the technical column of the accommodation, under black UV sheathing to protect the refrigerated insulation (Armaflex) from rays and freeze/thaw cycles.
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Slope and snow management : the equipment is placed away from prevailing gusts of wind, with a clearance of 30–40 cm under the chassis to allow air circulation and facilitate the evacuation of ice during defrost cycles.
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Maintenance access : positioned near the access hatch, in a safe area, without obstructing drains or roof vents.
Roof support: stability, load distribution and zero perforation
To preserve the membrane, we use a raised aluminum support placed on distribution soles . Here we distinguish:
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Treated wooden rails resting on high-density foam distribution pads : they diffuse the condenser load and protect the TPO/EPDM membrane.
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Adjustable feet with anti-vibration pads : they limit the transmission of vibrations to the structure and allow precise leveling of the device, essential for the flow of condensates.
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No perforation : the mechanical fixing is not anchored to the slab; stability results from load distribution and frame bracing — a solution recommended by most condominium associations.
This system is complemented by a cleared road surface for our technicians, to ensure safe work in both winter and summer.
Condensate and frost management: avoiding ice patches
Wall-mounted heat pumps in heating mode periodically generate frost on the outdoor heat exchanger. We anticipate:
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A clear clearance under the unit so that water flows towards the natural drainage areas of the roof, away from the drains to avoid icicles around the grilles.
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A discreet deflector under the housing (when required) which channels runoff from defrosting.
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A controlled inclination of the chassis (a few millimeters) to promote flow, verified electronically during commissioning.
Electricity and compliance: safety first
On roofs, exposure to the elements requires impeccable execution:
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External disconnection in a waterproof, accessible and visible box.
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Metal conduits and cables rated for outdoor use, compressed joints and sealed edges.
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Checking the currents and adjusting the circuit breaker according to the nameplate; checking the direction of rotation of the fan and the defrost sequence .
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Compliance with RBQ and building engineering requirements; grounding and insulation testing before charging.
Refrigeration: vacuum, charge and fineness of connections
We install new refrigeration lines (annealed copper), insulated and sleeved against UV rays. The key steps:
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Nitrogen brazing (or flared fittings calibrated according to the Midea technical data sheet) with visual inspection and nitrogen pressure test.
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Deep vacuum < 300 microns, resistance test and validation by sensors.
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Opening the circuit and adjusting the additional load if the length exceeds the factory load.
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Control of subcooling and superheating , temperature/pressure readings in cold and hot mode, then acoustic verification (bearing, turbine, parasitic vibrations).
Challenges of this project… and our solutions
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Snow on the ground and meltwater : we planned the intervention during a stable weather window and secured the work area with non-slip mats ; the distribution rails on skids protect the membrane from freezing/thawing punctures.
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Visible route on the roof : the technical ducting groups together the connections (refrigerator + communication + power supply), reduces the visual footprint and simplifies maintenance .
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Old equipment nearby (condenser of a previous brand seen on the roof): disconnection and clean decommissioning , avoiding any interference with the new device.
Measured results: comfort, silence and savings
After commissioning , the readings show:
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In negative temperature heating mode, remarkable blowing stability and short defrost cycles, imperceptible on the housing side.
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In air conditioning mode, a contained exterior noise level (important for the peace and quiet of the neighbors) and fine modulation adapted to the partial loads of summer evenings along the Lachine Canal .
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Reduced electricity consumption compared to the old system, thanks to R-454B and the inverter, with predictable savings over the season.
AirGreen Best Practices for a Rooftop Heat Pump
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Always distribute the load on suitable rails/pads, never directly on the membrane.
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Allow 12–18 inches of clearance under the base for snow and ice.
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Position the rear of the unit away from prevailing winds; limit recirculation near guardrails.
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Protect connections from UV and shocks; inspect collars and seals annually.
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Schedule HVAC maintenance before winter: cleaning the coil, checking the fans, updating the firmware if necessary, and validating the defrost sequence .
Grants and administrative support
Depending on the chosen configuration and performance, the installation may be eligible for energy efficiency grants . Our team assists co-owners in preparing files and validating criteria (power, efficiency, cold climate). Whether you are in Montreal, Laval, Longueuil, on the North Shore or the South Shore , we guide you from the thermal assessment to claiming grants when eligible.
Why entrust your project to AirGreen?
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Specialists in HVAC installation on flat roofs, balconies, backyards and tight spaces.
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Mastery of reference brands , including Midea in R-454B extreme cold.
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Quality procedure : load calculation, route study, documented vacuum draw, test sheets and maintenance booklet given to the client/union.
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Local after-sales service , rapid response and stock of common parts for peak season.
And now, time for your comfort
This Midea wall-mounted heat pump installation in Lachine combines performance, energy efficiency, and roof protection . The result: a comfortable four-season home, a reassured condominium, and a sustainable solution, ready to face our winters.
Are you considering a wall-mounted heat pump on your roof, balcony, or slab? Our team operates throughout Greater Montreal . Contact AirGreen : we analyze your building, recommend the right capacity (BTU) , and deliver a clean, compliant, and sustainable installation .
The job tools
Two quick checks with real numbers: what heat costs, and what your current heaters add up to in BTU/h.
Conversion: 1 W = 3.412 BTU/h. An indication, not a load calculation: baseboards and furnaces are often stronger than the real need, and they can stay as backup. AirGreen confirms the capacity on site.
How the job unfolds
The main steps of this kind of job at AirGreen. Every house has its quirks: the estimate brings them out.
We look at the room, the outside wall, the line route and where the outdoor unit will go. That is where the capacity gets chosen.
Model, capacity and price, in writing. We also check whether the model qualifies for assistance programs.
Floors and furniture protected, wall plate position marked level, wall opening located.
A single opening, with the slope the drain needs to flow outside.
Set on a stand raised above the snow, with the clearances the manufacturer requires.
Connected, insulated and protected. The opening is then sealed against water, cold air and insects.
A dedicated circuit and an accessible disconnect near the outdoor unit.
Leak test, vacuum, then start-up and a check of heating and cooling.
Remote, modes, filters: we show you the essentials before we leave.
- The on-site estimateWe look at the room, the outside wall, the line route and where the outdoor unit will go. That is where the capacity gets chosen.
- The quoteModel, capacity and price, in writing. We also check whether the model qualifies for assistance programs.
- Getting readyFloors and furniture protected, wall plate position marked level, wall opening located.
- The wall openingA single opening, with the slope the drain needs to flow outside.
- The outdoor unitSet on a stand raised above the snow, with the clearances the manufacturer requires.
- Lines, cable and drainConnected, insulated and protected. The opening is then sealed against water, cold air and insects.
- The electrical workA dedicated circuit and an accessible disconnect near the outdoor unit.
- Tests and start-upLeak test, vacuum, then start-up and a check of heating and cooling.
- The walkthroughRemote, modes, filters: we show you the essentials before we leave.
What we check on a job like this one
Each number is a point we check on site. Switch between summer and winter to watch air and heat move.
In summer, the outdoor unit rejects the house's heat outside.
Generic illustration of this type of installation, not a survey of this job site. Tap a number.
Mounted level on a wall plate, high enough for the air to reach the whole room, with enough space around it to slide the filters out easily.
The refrigerant lines, the communication cable and the drain go through the wall in a single opening, sealed against water, cold air and insects.
Two insulated copper pipes connect the two units. Outside, a line cover can protect them from sun, knocks and weather.
A shut-off switch near the outdoor unit isolates it safely for service. It must stay accessible at all times.
The compressor and the fan. In heating mode it captures heat from the outdoor air, even in winter, and moves it inside.
On the ground or on the wall, it keeps the unit above accumulated snow. The unit stays clear and defrost water can drain away.
The fan needs to blow freely. Storage, a fence or a wall too close, and efficiency drops while noise goes up.
Is your home ready?
Check what applies at your place. A "no" is not a refusal: it is what we sort out during the estimate.
Good habits, once the unit is in place
Six simple habits that keep the unit going. Your list stays on this device.
What to do, season by season
Three habits per season for this unit. They take a few minutes and prevent many calls.
- Clean the indoor unit's filters.
- Clear leaves and debris left on the outdoor unit by winter.
- Test cooling before the first hot days.
- Clean the filters more often when the unit runs a lot.
- Keep plants away from the outdoor unit.
- Check that no water drips from the indoor unit.
- Rake the leaves around the outdoor unit.
- Test heating before the first cold days.
- Book periodic maintenance before winter.
- Keep snow away from the stand and the front of the unit.
- Let the unit defrost: it is normal.
- Never hit the ice on the fins; call us if the unit stays iced up.
The right pages, at the right time
Four statements: true or false?
It all comes down to details you have just seen.
1. In heating mode, the outdoor unit can produce water.
During defrost cycles. That water must drain away without forming ice.
2. You pick the capacity with a simple square-footage rule.
Windows, insulation, orientation and how the room is used all count. Capacity is chosen on site.
3. A multi-zone connects several indoor heads to a single condenser.
One head per room, all on the same condenser. Each room keeps its own temperature.
4. The disconnect can sit behind the patio furniture.
It must stay accessible: it is what shuts the unit off for service.
0 / 4 right answers
What people ask us about this kind of work
Does a wall-mounted heat pump heat in winter?
Wall-mounted or multi-zone: how do I choose?
Where does the outdoor unit go?
Are there grants?
Do I need a permit?
How cold can it heat?
How much can I save?
How is the LogisVert assistance calculated?
Is it noisy?
The outdoor unit is covered in ice: is that normal?
Does AirGreen hold the required licences?
Is the estimate free?
No question matches. Write to us: we answer.
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Text and photo: a real AirGreen Climatisation & Chauffage job. The diagrams are generic illustrations of the type of installation, not a survey of this job site. Sources of the added figures: airgreen.ca product pages (NEEP / AHRI performance), Hydro-Québec (Heat pumps page, LogisVert, read on 13 October 2026), Régie de l’énergie (rate D as of 1 April 2026).