Discreet air conditioning: planning permission, no outdoor unit, listed and period homes

Do I need planning permission for an outdoor unit?

For most houses in England, no. Since May 2025 an air source heat pump — which is what an air conditioning outdoor unit is — can be fitted under permitted development rights. The old rule that the unit had to be at least one metre from the boundary has gone. The unit can be up to 1.5 cubic metres in size on a house, a detached house can have two, and the rules now include air to air units that cool as well as heat.

Permission is still needed in some cases: listed buildings, most properties in conservation areas, flats (one unit per block, and a smaller size limit), and where the council has removed permitted development rights. Every installation also has to meet the heat pump noise standard, which means we choose the position and the model so that the neighbours never hear it. We check all of this at the survey and tell you before you commit.

Can I have air conditioning without an outdoor unit?

Yes, and for a flat or a listed building it is often the only route. There are three ways. A through-wall unit sits inside the room and vents through two neat grilles in the outside wall, with nothing mounted outside. A water-cooled system moves the heat away through pipework instead of an outdoor fan unit. And where a small outdoor unit is allowed but must not be seen, we can put it behind a screen, in a lightwell, on a flat roof or in a plant area, with the pipework hidden. Each has trade-offs on capacity and cost, and we will tell you plainly which one suits the building.

Listed and period homes

We install in listed and period properties regularly. The rules of the job are simple: nothing that damages original fabric, pipework routed through existing voids, floors and cupboards rather than chased into walls, grilles chosen to match the room, and listed building consent obtained before work starts where it is needed. In a Victorian or Georgian house the usual answer is a ducted system in the loft or under the floor, with discreet grilles in the ceiling or skirting and no visible equipment in the rooms.

Hiding the indoor side

If you do not want a wall-mounted unit in the room, you do not have to have one. Ducted systems put the machinery in the loft, a cupboard or a ceiling void and deliver the air through slim linear grilles. Ceiling cassettes sit flush in a suspended ceiling. Floor-standing units can be built into joinery. For architects and designers we work from the drawings and agree the grille positions with you before anything is ordered.

Heating as well as cooling

Every system we fit is an air to air heat pump: it heats the room in winter as well as cooling it in summer. For a period house with cold rooms and no gas, that is often the reason people call us in the first place. Our air to air heat pumps page explains how it works.

What it costs

A discreet installation costs more than a standard wall-mounted system because of the design, the ducting and the making-good. We quote after a survey, and the quote is fixed.

How we work with architects and designers

Send us the drawings. We will mark up unit positions, duct routes, grille positions and the electrical requirement, and give you a specification you can put in the tender. We turn up when we say we will, we work to the site rules, and we do not put a photograph of your client's house on the internet.

Why people choose HT Cooling

Every engineer who works on refrigerant is F-Gas registered (certificate number 2004080). We hold Constructionline Gold, SMAS Worksafe and Acclaim accreditation, and our engineers are City & Guilds trained. We are rated 5.0 on Google from 50 reviews and have 66 reviews on Checkatrade, where we have been members since 2021. We are based in Lightwater, Surrey, and work across Surrey, Berkshire, Hampshire and London.

Questions people ask

Talk to an engineer, not a call centre

Call 03453 022 969 or send us a few details and we will come back to you the same working day.