A detached house can have more room for an outdoor unit than a terrace, and a narrow side passage is still a poor default. Passages fail boundary limits, choke the coil, and bounce noise at bedroom windows. Measure the width and the gap to the boundary, then read the Planning Portal conditions in England before you assume permitted development. If the passage cannot give the coil its air and an engineer a path, use a rear wall or a garden stand. The circuit needs an F-gas certified company.
A bin route that is already under a metre
Side passages on detached houses are often a bin route: under a metre of clear width once the wall, the fence and a downpipe are counted. An outdoor unit with its service clearance may not fit, and what fits on paper may sit inside the boundary distance the Planning Portal conditions describe. Measure to the boundary, not to where you wish the fence was. Measure clear width and distance to the boundary. Leave intake, discharge and a service side.
Detached houses are treated more generously than terraces on unit counts in the current Planning Portal summary, and only if every other limit is met. A passage that fails those other limits is still an application, or a different wall. A slimmer unit sometimes fits the width and still fails the air gaps or the boundary limit. Ask for clearances, not only the cabinet depth.
Recycled air, reflected noise and the bins
A passage recycles discharge air back into the coil, especially when a fence closes the far end. The unit then runs hot, loud and iced in cold weather. Noise reflects between two hard surfaces and travels to the rooms whose windows open onto the passage, yours and next door's. Do not face the discharge at a bedroom window. Ask for sound power, the night figure, and mounts. Anti-vibration feet do not fix a coil that cannot breathe. If the only way to fit the unit is to delete the manufacturer's gaps, the passage is the wrong place.
Engineers have to remove the front panel, and you have to get bins past the unit for years. A condenser that blocks the only side door is a daily argument. Condensate in heating mode must not sheet across the path and freeze. Pipework from a passage to the rooms can be long. That is acceptable when it is insulated and reachable. F-gas commissioning is the same wherever the outdoor unit stands. Energy Saving Trust's air-to-air notes describe heating and cooling, not passage geometry. A rear wall or a garden stand may be the lawful spot. The rear garden is often simpler if a stand or a rear wall keeps the unit off windows and off the boundary.
Frequently asked questions
Can a detached house put the outdoor unit in the side passage?
Only when the width, the boundary and the airflow all work. Many passages fail at least one. Measure, then read the Planning Portal conditions.
Will a slimmer unit solve a tight passage?
Sometimes it fits the width and still fails the air gaps or the boundary limit. Ask for clearances, not only the cabinet depth.
Is the rear garden simpler?
Often yes, if a stand or a rear wall keeps the unit off windows and off the boundary. Say if the passage is your only idea so they can price the alternative.
Core buying guides
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How this guide was prepared
This guide was written by the Local AC Installers Editorial Team. We compare official guidance, legislation and established consumer information, separate general information from project-specific advice, and show publication dates and sources. We do not accept installer accreditation claims at face value.