Midea PortaSplit at a Roof Window: Installing in Attic Conversions

Attic conversions are among the hottest rooms in any European house during summer: the roof surface absorbs solar radiation all day and re-radiates it into the living space through the insulation layer above. Residents of attic rooms frequently report temperatures 6–10 °C above the floors below, making cooling not a comfort preference but a genuine sleep-quality necessity. The only external opening available in most attic conversions is a roof window or skylight, which creates a specific set of challenges for positioning a portable split's outdoor unit and routing its refrigerant hoses.

What types of roof windows are compatible with a Midea PortaSplit installation?

The three common European skylight types have different implications for hose routing and outdoor unit placement. Top-hung Velux-style windows (which hinge at the top and open outward, pivoting to expose a triangular gap at the bottom) are the most practical for a portable split because the opening gap at the lower frame is large enough for a custom foam panel carrying the refrigerant hoses. Centre-pivot windows (which rotate 180° for cleaning) can be used but require the panel to be fitted at mid-opening. Fixed skylights are not usable without cutting a supplementary aperture.

How do you fabricate a hose panel for an open roof window?

A top-hung Velux-style skylight opened to approximately 25–30 degrees creates a triangular lower gap typically 150–250 mm deep across the full window width. A custom foam panel fills this triangular void: cut rigid foam insulation board (25–30 mm Kingspan or Celotex) to the trapezoid shape of the open gap — the sill width at the bottom and the narrower window pane width at the top edge where the frame meets — with two 40 mm hole-saw cutouts for the individual refrigerant hoses at a convenient position. EPDM foam tape seals the panel against the window sill, lower frame, and the angled glass pane face.

The hoses exit the panel on the exterior face and must be immediately protected with a split-foam sleeve to prevent abrasion against the roof tile, felt, or flashing at the window surround. Velux and other skylight manufacturers fit a flashing collar around the window base; the hoses should exit over this flashing, not under it, to prevent water ingress along the hose path. A dab of clear silicone sealant around the hose-panel exit points completes the weatherproof seal without permanently bonding the panel in position.

Where can the outdoor unit of a PortaSplit be positioned on a pitched roof?

The outdoor unit cannot be placed directly on a pitched roof surface without a purpose-made bracket, both because the unit must sit level for proper compressor lubrication and because the weight of 14–16 kg concentrated on a small footprint risks damaging roof tiles or membrane. Three locations work well for attic conversions: a flat-roof section or dormer ledge if one exists adjacent to or below the skylight, the top of a flat-roof extension abutting the main building, and a wall bracket fixed to the dormer's vertical masonry face below the skylight.

A dormer wall bracket is the most common solution for converted attic rooms: the dormer's vertical masonry face (typically 215 mm or 325 mm brick) provides a solid substrate for standard masonry anchors, and a 300 mm standoff bracket positions the outdoor unit beside or below the skylight within the refrigerant hose reach of most portable split kits (3–4 metres of pre-charged hose on most Midea PortaSplit models). The bracket installation on a dormer wall is identical to a standard house-wall installation — two 10 mm masonry anchors, torqued to 35–40 Nm, with the bracket positioned at least 200 mm above the flat roof or gutter line to avoid standing water.

The condensate drainage edge case: why rooftop outdoor units drain differently from ground-level installations

Condensate (liquid water drawn from the humid outdoor air as it passes over the cold condenser and chilled refrigerant lines) accumulates in the outdoor unit's drip tray during high-humidity operation and must drain away without pooling. On a ground-level installation, condensate simply drains through a weep hole in the base and soaks away. On a rooftop or dormer bracket installation, the drain path must be considered: condensate dripping onto a flat roof will evaporate harmlessly in most conditions, but if it drains toward a blocked gutter or pooling area, it can contribute to moss growth or water ingress at the roofing membrane edge. Route a 10 mm silicone tube from the outdoor unit's drain port to the edge of the flat roof or to a gutter downpipe as a precaution — a £3 investment that prevents a £300 roofing problem.

How much cooling capacity does a portable split need for a hot attic room?

Attic rooms have a substantially higher cooling load per square metre than conventional rooms because of roof solar gain. A well-insulated modern attic room (200 mm mineral wool between rafters, U-value approximately 0.18 W/m²K) may need 30–40 W of cooling per square metre in a southern European summer. An older, poorly insulated attic (50 mm insulation, U-value approximately 0.45 W/m²K) can require 50–70 W per square metre when the roof surface reaches 55–65 °C under direct sun. For a 20 m² attic room, this means a cooling load of 1,000–1,400 W — well within the 2,640 W capacity of a 9,000 BTU Midea PortaSplit, but the unit will run at higher duty cycles than in a well-insulated ground-floor room.

Adding external shading — a reflective foil on the roof exterior, an awning over a flat roof section, or dense deciduous planting on the sun-facing elevation — can reduce the effective cooling load by 20–40% and make a meaningful difference to both the unit's duty cycle and the attic room's peak temperature before the split starts. Passive measures and active cooling work better together than either does alone in an attic environment.

In home improvement communities, attic conversion owners who have successfully installed portable splits describe the planning stage — particularly working out where the outdoor unit can go given the lack of conventional wall space — as the most time-consuming part of the project, with the actual installation being straightforward once the bracket position and hose routing are decided.

Do attic conversion portable split installations require planning permission?

In England and Wales, fitting an air conditioner outdoor unit on a roof or dormer wall generally falls within permitted development rights for domestic properties, provided the unit is not on a principal elevation facing a highway and its installation does not result in the unit projecting above the highest part of the roof. A dormer wall bracket below the ridge satisfies both conditions on most attic conversions. Listed buildings and properties in conservation areas are exempt from permitted development and require prior approval; checking with the local planning authority before installation avoids retrospective enforcement notices.

• Standard domestic attic conversions in England and Wales: outdoor unit on a dormer wall or flat roof section is generally permitted development if below the roof ridge and not on a principal highway-facing elevation.
• Scotland and Northern Ireland apply different permitted development rules; the local authority's building standards department is the definitive reference.
• Conservation areas and listed buildings: always seek prior approval regardless of unit size or position — enforcement action can require removal and reinstatement at the owner's cost.
• Flat or communal roofs in apartment buildings: obtain written landlord or management company consent before any outdoor unit installation, as roof access rights are usually held by the freeholder rather than the individual leaseholder.

Because attic rooms are among the most uncomfortable spaces in a European heatwave and the least well-served by conventional cooling solutions, demand for Midea PortaSplit-class mobile splits spikes sharply when summer temperatures rise — often clearing stock within 24 to 48 hours of a heatwave forecast.