Under the deck, behind a lattice: hiding an outdoor unit without cutting off its airflow
The request almost always comes the same way, and it is perfectly legitimate: “Can we put it back there so it won’t be visible from the terrace?”
In Sainte-Marie-Madeleine, in the agricultural corridor linking Mont-Saint-Hilaire and Saint-Hyacinthe, the desired location combined the two most common constraints in Quebec’s residential landscape: a decorative lattice on one side and a raised deck above.
We did not reject the location. We adapted it. Here is precisely what was modified, and why these adjustments matter far more than the choice of brand displayed on the cabinet.
The installed system
- Outdoor unit: GUD36W2/NhE-D(U)
- Indoor air handler cabinet: GUD36AH2/G-D(U)
- Cooling capacity: 34,000 BTU/h, modulation from 18,000 to 37,000 BTU/h
- Heating capacity: 34,000 BTU/h, modulation from 18,000 to 38,000 BTU/h
- SEER 2: 18.0 — HSPF 2: 10.0 — EER 2: 12.0 — COP at 8 °C: 3.20
- AHRI code: 217120760
- Airflow: 1,700 m³/h (1,000 CFM) at a nominal external static pressure of 125 Pa (0.5 in. w.c.)
- Sound level: 51 dB(A) indoors, 61 dB(A) outdoors
- R32 refrigerant, 2.9 kg (102.3 oz) charge
- Heating range: -30 °C to 24 °C — Cooling range: -15 °C to 54 °C
- 208-230 V / 60 Hz / 1 phase: outdoor MCA 27.7 A / MOP 30 A, indoor MCA 5.3 A / MOP 15 A
- Outdoor unit: 990 x 960 x 370 mm, 85 kg (187.4 lb)
- Two-stage, two-cylinder compressor, DC Inverter technology
- Integrated refrigerant leak detector, 24 VAC thermostat, and RS485 communication
What an outdoor unit actually requires around it
A central heat pump does not consume only electricity. It consumes air—very large quantities of it, continuously, throughout the year. A unit of this capacity moves a considerable volume of air during every hour of operation.
This air must be able to enter, pass through the coil, and then move away from the unit. Four separate clearances result, and they do not all serve the same purpose.
Airflow clearance
This is the most restrictive and least well-known clearance. Air enters through the finned sides. An obstruction pressed against these sides constricts the airflow well before blocking it completely, and the effect is gradual: capacity drops without anything seeming abnormal.
Discharge clearance
The discharged air must move away clearly. In cooling mode it is hot; in heating mode it is cold: in either case, if it returns toward the unit, the machine is working against itself.
Clearance above
This is the one people forget beneath a deck. A ceiling that is too low above the cabinet creates a layer of air that stagnates and recirculates.
Service clearance
A technician must be able to open the electrical panel, connect their instruments, access the service valves, and remove the grille. Without this access, every service visit becomes a disassembly—and difficult maintenance is maintenance that does not get done.
We follow the clearances specified in the manufacturer's installation manual, and they are consistently more generous than homeowners imagine. This is the conversation to have before fixing the location, not afterward.
Lattice: how to do it properly
Diamond-pattern wood lattice is the most common enclosure in Quebec. It is not forbidden. It must be designed properly.
The percentage of open area
A grille only makes sense if it allows air to pass through. A louvered panel with wide openings and a large free area barely slows the airflow. A panel of closely spaced slats, a fence made of adjoining boards, or a solid vinyl panel turns the enclosure into an airtight screen.
The practical rule we pass on is: if you cannot clearly see through it, the air cannot clearly pass through it either.
The distance
A very open grille placed two inches from the coil impairs performance more than a moderately open grille placed two feet away. Distance matters just as much as porosity because it gives the air time to redistribute before reaching the fins.
On this job, the existing panel was too close to the cabinet. It was moved back, and the unit was positioned so that its discharge face did not point toward it.
The removable panel
The enclosure must be removable without specialized tools, or at the very least without demolition. We favor panels mounted on hinges or hooks. An enclosure screwed into a permanent structure will sooner or later be torn off during a service call—and no one will reinstall it as neatly.
What should never be built
- A fully enclosed enclosure on all four sides, even if louvered.
- A roof over the equipment, including a simple decorative panel.
- A cedar hedge planted at what seems like the right distance in the year it is planted.
- A bench, storage chest, or planter pressed against the cabinet.
- A stone or masonry enclosure that becomes impossible to remove.
Beneath a gallery: four effects to address
Installing equipment beneath a raised structure deserves special attention because its drawbacks are seasonal and do not appear on the day of installation.
Water passing through the boards
An open-slatted gallery floor lets rain through. This water falls in concentrated streams in the same places and carries dust and treated-wood residue with it. On a coil, it leaves a film that binds dirt in place.
Ice in February
This is the most serious effect. Snow accumulated on the gallery partially melts during thaws, water passes through the boards, and falls onto the cabinet. It freezes there again. An appliance that is already producing defrost water then receives a second source of water from above, which it cannot drain away.
We address this situation by increasing the lateral clearance—moving the drip path out of line with the cabinet—or by installing a deflector beneath the structure, never placing it directly on the equipment.
Debris
Leaves, sweeping sand, conifer needles, and objects blown from the deck end up in the space beneath the gallery. This type of installation requires a more frequent maintenance schedule, and we tell the customer so from the time of the quote.
Recirculation under the ceiling
A covered, partially enclosed space traps the discharged air. Vertical clearance and directing the discharge toward the most open part of the space are the two factors that determine the outcome.
Commissioning: what an open cabinet reveals
On this job, the electrical compartment panel was open when the photo was taken. This is the step that determines everything that follows.
The micron gauge in the right place
The digital vacuum micron gauge is connected to the equipment, opposite the pump, never to the pump body. A reading taken at the pump indicates the pump's performance, not the condition of the circuit—and consistently gives a flattering value that means nothing.
After evacuation, the pump is isolated and the reading should stabilize. It is this stability, not the value reached, that confirms the circuit is dry and leak-free.
The 24 V terminal block and the thermostat
The open compartment provides access to the control terminal block. The UNIX R32 series accepts a standard 24 VAC wired thermostat, making it directly compatible with the vast majority of thermostats already installed in Quebec, and also supports RS485 communication for installations that require it.
The thermostat connection is where the most efficiency is lost. A misidentified backup wire, a reversed stage, or a delay left at the factory settings can make the unit operate—but not as it should.
Control board configuration
A modern unit is not ready for use as soon as it is powered on. The settings corresponding to the actual installation must be confirmed: fan configuration based on the measured ductwork, electric backup management, interlocks, and verification of the refrigerant leak detector and its safety shutdown mode.
These settings take about thirty minutes. They are invisible, do not appear in any photographs, and determine how the unit will perform for the next fifteen years.
Ultra Heat and the modulation range
The series advertises 100% heating capacity at -20 °C and stable operation down to -30 °C. Combined with the two-stage, twin-cylinder compressor, this feature provides a useful range of 18,000 to 38,000 BTU/h in heating.
Specifically, for a home in the Maskoutains RCM: the unit modulates instead of cycling for most of the season, maintains its full capacity during ordinary cold spells, and only gives way to electric backup during the most severe peaks.
It still needs to be able to breathe. A rated capacity maintained at -20 °C is worthless if the coil draws in the air it has just discharged against a wooden panel.
The most common mistakes when enclosing and concealing a unit
- Building the enclosure before installation, without consulting the HVAC contractor.
- Choosing a solid panel because it conceals the unit better.
- Placing the enclosure a few inches from the cabinet.
- Covering the unit with a decorative roof to “protect it from snow.”
- Enclosing all four sides, even with an openwork material.
- Planting vegetation too close and forgetting that it will grow.
- Wrapping the unit for winter. A heat pump operates year-round, unlike a central air conditioner.
- Making the service access impossible, compromising maintenance rather than immediate performance.
Subsidies
The GUD36W2/NhE-D(U) + GUD36AH2/G-D(U) match, under AHRI code 217120760, has a SEER 2 of 18.0 and an HSPF 2 of 10.0, placing it favorably within the grids for Quebec assistance programs for heat pumps, which are generally based on certified performance and low-temperature heating capacity.
We verify that the exact match is listed among the eligible equipment and prepare the application using the AHRI code for the actual pair being installed, before ordering the equipment. Amounts and conditions change from year to year.
What Sainte-Marie-Madeleine puts into perspective
There is nothing unreasonable about wanting to hide an outdoor unit. A yard is designed to be seen, and a gray cabinet has never improved a landscape design.
What costs money is treating screening as a decorating decision made afterward, with no connection to the HVAC system. A trellis set back twenty inches instead of two, a discharge direction chosen based on the open space, a hinged panel instead of a screwed-on one, a deflector beneath the deck: none of these decisions adds a significant cost to the project if made at the right time.
When taken after the patio has been built, they become demolition work.
Our coverage in Montérégie and Greater Montreal
At AirGreen, we design, install, and maintain central heat pumps, ductless wall-mounted heat pumps, air conditioners, VRF systems, and air exchangers in Montreal, Laval, Longueuil, on the North Shore, on the South Shore, and throughout Montérégie, including Sainte-Marie-Madeleine, Sainte-Madeleine, Saint-Damase, Saint-Jean-Baptiste, and Saint-Hyacinthe.
The question of screening comes up on practically every residential project, from a village bungalow to an urban triplex. We address it during the assessment visit, using deck plans when available.
Have your location assessed before building anything
If you are planning a HVAC installation and already have a precise idea of where you want to hide the unit, show it to us before the landscaping work begins. It is almost always possible to reconcile the two. What does not work is installing a unit in an already-built structure without any room for maneuver.
Contact AirGreen for an assessment of your home and property, a load calculation, and a detailed quote for a GREE UNIX R32 system. We will tell you what is possible in the location you have chosen and what would need to be adjusted to make it work.