Can You Install Air Conditioning in a Listed Building?

Can You Actually Install Air Conditioning in a Listed Building?

Short answer: yes. Longer answer: yes, but you need to think about it properly, and most people who tell you it can’t be done haven’t actually tried.

I’ve been installing air conditioning and ventilation systems across Sussex for over 20 years. A decent chunk of that work has been in listed buildings and conservation areas — Grade II listed flint cottages on the South Downs, Regency townhouses in Brighton and Hove, Victorian shopfronts in Lewes, and timber-framed medieval buildings in Steyning.

Every one of those jobs got done. Every one is still running. But every one required a different approach, because old buildings aren’t standardised — they’re individual, and the solutions have to be individual too.

This is everything I know about installing AC in heritage buildings. It’s long, because the subject deserves it. There’s no shortcut to understanding why these buildings matter, what the rules actually say, what can go wrong if you get it wrong, and how to get it right.

Why Would You Want AC in an Old Building?

This might seem obvious — because it’s hot — but there’s more to it than comfort. The reasons people come to us about AC in listed buildings have shifted dramatically in the last decade.

Climate Change Has Changed the Conversation

When I started in this trade in the early 2000s, air conditioning in homes was a luxury. Something for conservatories that overheated and the odd home office. But British summers have changed. The Met Office now records temperatures above 30°C regularly in the South East. The 2022 heatwave hit 40.3°C — the highest temperature ever recorded in the UK. Brighton recorded 37°C. Even the most stoic “we don’t need AC in Britain” types were reconsidering.

Old buildings, especially those with thick stone or brick walls, are actually excellent at staying cool in moderate heat — those massive walls have huge thermal mass that absorbs heat slowly. But once the temperature stays high for several days, the walls absorb so much heat that the interior becomes unbearable, and there’s no way to shed it quickly. Opening windows in a Regency terrace in Brighton when it’s 35°C outside just lets the hot air in.

Humidity Is the Real Enemy

This is the one most people don’t think about, and it’s arguably more important than temperature.

Old buildings and moisture have a complicated relationship. Historic construction — lime mortar, breathable renders, timber frames, lath and plaster — was designed to manage moisture by absorbing it and releasing it slowly. The building “breathes.” This works brilliantly in a temperate maritime climate like ours, where humidity fluctuates but rarely stays extreme for long.

The problem comes when internal humidity stays too high for too long. A family living in a listed building generates the same 10–14 litres of moisture per day as anyone else — breathing, cooking, bathing, drying clothes. In a modern home, you might run the extractor fan and open a window. In a listed building with single-glazed sash windows and no trickle vents, the moisture either condenses on cold surfaces (causing mould, rotten timber, and damaged plaster) or absorbs into the historic fabric (causing salt migration, efflorescence, and long-term decay).

Air conditioning doesn’t just cool air — it dehumidifies it. Every AC system removes moisture from the air as part of the cooling process. In a listed building, this dehumidification function is often more valuable than the cooling itself. Controlling internal humidity between 45–60% RH protects timber, plaster, paintings, furnishings, and the building fabric in ways that no amount of window-opening can match.

I’ve had conservation officers who initially resisted AC installation change their minds once they understood the humidity control benefits for the building’s preservation.

In some heritage buildings where full air conditioning isn’t the right fit, a dedicated ventilation system or heat recovery unit can provide essential humidity control without the cooling function — we explore these options in detail in our guide to MVHR, MEV, and PIV ventilation systems.

The Home Office Revolution

COVID changed how people use their homes. We saw a surge in enquiries from people working in bedrooms, spare rooms, and attic conversions in listed buildings — spaces that were designed for sleeping, not for sitting at a desk for eight hours with a laptop generating heat. Several of our heritage installations were driven specifically by the need to create a comfortable working environment in rooms that had never been designed for daytime occupation.

Protecting Valuable Contents

Many listed building owners have collections — art, antiques, books, musical instruments — that are sensitive to temperature and humidity fluctuations. A piano in a room that swings between 15°C and 30°C with humidity anywhere from 40% to 85% won’t stay in tune and will eventually develop cracks. Art on walls that sweat with condensation deteriorates. AC provides stable conditions that protect both the building and its contents.

A Brief History: Why We Protect These Buildings

Understanding why listed buildings have the rules they do helps when you’re trying to work within those rules. It’s not arbitrary bureaucracy — there’s a logic to it, even if it doesn’t always feel like it when you’re trying to get consent for a condenser bracket.

The Blitz and the Birth of Listing

Britain’s building protection system grew directly from the Second World War. As bombs destroyed irreplaceable buildings across London, Coventry, Bath, and other cities, there was a growing recognition that historic architecture needed formal protection. The architect Sir John Summerson was among those who argued that what survived the war deserved protection from the peace — from the post-war development boom that was already threatening to demolish what the Luftwaffe had missed.

The Town and Country Planning Act 1947 introduced the first statutory listing process. Buildings of “special architectural or historic interest” were to be identified and listed, giving them legal protection against demolition or unsympathetic alteration. The system was refined through subsequent legislation, culminating in the Planning (Listed Buildings and Conservation Areas) Act 1990, which still governs today.

The Grades

There are roughly 500,000 listed buildings in England. They’re graded by significance:

• Grade I (2.5% of all listed buildings): Of exceptional interest. Think cathedrals, great country houses, iconic public buildings. Lancing College Chapel — that Gothic masterpiece on the hill above the A27 — is Grade I.

• Grade II* (5.8%): Particularly important buildings of more than special interest. Many significant churches, manor houses, and public buildings across Sussex fall into this category.

• Grade II (91.7%): Of special interest, warranting every effort to preserve them. This is where most residential listed buildings sit. The Georgian terraces in Brighton’s Kemp Town, the flint cottages in Rottingdean, the brick-and-tile-hung houses in Steyning — all typically Grade II.

The grade affects how closely your plans will be scrutinised, but the fundamental rule is the same for all grades: you need Listed Building Consent for any works that affect the building’s character or appearance. There’s no permitted development shortcut for listed buildings.

Conservation Areas

Conservation areas are different. Introduced by the Civic Amenities Act 1967, they protect the character of an area rather than individual buildings. There are over 10,000 conservation areas in England. Brighton and Hove alone has 34 — covering everything from the seafront terraces to the North Laine streets.

In a conservation area, your property might not be listed, but your permitted development rights are more restricted than normal. Specifically, equipment on front elevations, visible external changes, and anything that affects the area’s character can require planning permission. The key word is “visible” — work to the rear, behind walls, or below roof lines is usually far simpler.

Article 4 Directions

Some conservation areas go further with Article 4 Directions, which remove additional permitted development rights. Brighton’s Round Hill conservation area, for example, has an Article 4 Direction that means even replacing your front door or windows needs planning permission. If your property is subject to an Article 4 Direction, assume that any visible external change needs consent.

The Regulations: What You Actually Need

Right, let’s get specific. The rules depend entirely on whether your building is listed, in a conservation area, both, or neither.

If Your Building Is Listed

You need Listed Building Consent (LBC) for any works that affect the building’s character. This is separate from (and in addition to) planning permission. The test isn’t whether the work is visible from outside — it’s whether it affects the character of the building. This includes:

• Drilling through external walls for refrigerant pipework
• Drilling through internal walls if they’re part of the historic fabric
• Mounting equipment on walls (internally or externally)
• Running trunking or pipework across visible surfaces
• Installing grilles or vents in walls, ceilings, or floors
• Any work that might affect decorative features — cornices, mouldings, panelling, plasterwork

The word “character” is deliberately broad. A bracket hole in a modern plasterboard wall inside a listed building probably doesn’t need LBC. A bracket hole in an original lime plaster wall with horse-hair binding absolutely does.

Who decides? Your local planning authority — specifically, their conservation officer. These are the people who will assess whether your proposed installation affects the building’s character. They vary enormously in approach. Some are pragmatic and supportive; others are cautious. The best conservation officers understand that buildings need to be used to survive, and that sympathetic modern interventions can actually help preserve a building rather than harm it.

If Your Building Is in a Conservation Area (But Not Listed)

For non-listed buildings in conservation areas, external AC equipment falls under Class G of the General Permitted Development Order (GPDO) — but with conservation area restrictions.

Permitted development allows:

• Equipment on the rear or side of a building (not fronting a highway or principal elevation)
• Equipment that doesn’t protrude more than 1 metre from the wall surface
• No single piece of equipment larger than specified dimensions

A typical split-system outdoor condenser protrudes about 300–350mm from the wall, well within the 1-metre limit. So a condenser on your back wall or in your garden is usually fine without any planning application — even in a conservation area.

However, if you want equipment on the front elevation, visible from a highway, or if an Article 4 Direction applies, you’ll likely need planning permission.

At a Glance: What Do You Need?

Your Property	Listed Building Consent?	Planning Permission?	Bat Survey?	Typical Timeline
Listed + Conservation Area	Yes — always	Likely for external equipment	Recommended	4–6 months
Listed only	Yes — always	Only if condenser on front elevation	Recommended	3–5 months
Conservation Area only (not listed)	No	Only if condenser on front/visible elevation	Only if old building with loft work	1–3 months
Neither listed nor conservation	No	Usually permitted development	Unlikely needed	2–4 weeks

Ecclesiastical Exemption

Here’s one most people don’t know about. Churches and other places of worship that are in regular use for worship are exempt from listed building controls — they have their own separate consent system (Faculty Jurisdiction for Church of England buildings, or denominational equivalents for others). If you’re installing AC in a church, chapel, or similar, the rules are completely different. We’ve done a few of these and the process goes through the Diocese rather than the local council.

The Bat Question

This catches people out. If you’re working on a building that’s old enough to be listed, there’s a reasonable chance it houses bats. And bats are extremely well-protected in the UK.

Why Bats Matter for AC Installation

All bat species in the UK are protected under the Wildlife and Countryside Act 1981 and the Conservation of Habitats and Species Regulations 2017. It’s a criminal offence to:

• Deliberately kill, injure, or capture a bat
• Deliberately disturb bats (including during hibernation)
• Damage or destroy a bat roost — even if bats are not present at the time

That last point is critical. A bat roost is protected whether or not bats are actually there. Bats are creatures of habit — they return to the same roosts year after year. A loft space that a colony of pipistrelles used last August is legally protected even in January when they’re hibernating elsewhere.

What This Means in Practice

If your AC installation involves:

• Work in a loft or roof space
• Drilling through external walls where bats might access the building
• External work near eaves, soffits, or roof lines where bats roost
• Work on any building where bats have been seen entering or leaving

…then you may need a bat survey before work can begin. This is typically a two-stage process:

1. Preliminary Roost Assessment (PRA): A qualified ecologist inspects the building for signs of bat use — droppings, staining, scratch marks, feeding remains. They assess the building’s potential to support bats. Cost: typically £200–£400.

2. Emergence/Re-entry Surveys: If the PRA finds evidence or potential, follow-up surveys involve watching the building at dusk and dawn to count bats entering and leaving. These can only be done during the bat active season (May to September), which has obvious implications for project timing.

If bats are confirmed, you’ll need a European Protected Species Mitigation Licence from Natural England before work can proceed. This sets out conditions — timing restrictions, alternative roost provision, method statements for the work.

For AC installations specifically, the risk is usually lower than for major building works. A couple of 60mm core-drilled holes through an external wall for pipework are unlikely to disturb a bat roost — but if those holes are near known roost entry points, or if loft work is required to route pipework, the risk increases. The safe approach is to commission a PRA if there’s any doubt. It’s a few hundred pounds and it keeps you legal.

Timing Around Bats

If bats are present, work restrictions typically mean:

• No work disturbing roosts during the maternity season (June–August) when females are raising pups
• No work during hibernation (November–March) in or near hibernation sites
• Optimal window: April–May and September–October, when bats are active but not breeding or hibernating

This can affect your installation timeline significantly. If a bat survey in May reveals a maternity roost, you might not be able to start work until September. Plan ahead.

Humidity, Weather, and the Sussex Climate Challenge

Why Sussex Is Tough on Old Buildings

Sussex sits in what building scientists consider one of the most demanding climate zones for historic buildings in the UK. We don’t get Scandinavian cold (where buildings are bone-dry inside all winter) or Mediterranean warmth (where moisture evaporates quickly). We get:

Mild, damp winters. Average winter temperatures of 4–7°C and relative humidity regularly above 85%. The air itself is sodden. Single-glazed windows on a listed building will stream with condensation on any cold morning. That water runs down into timber sills, lime plaster reveals, and original joinery — doing cumulative damage year after year.

Marine air along the coast. Brighton, Hove, Worthing, Shoreham, Lancing, Southwick, Portslade — all within a few miles of the sea, with salt-laden, high-humidity air driven inland by the prevailing south-westerlies. Salt is hygroscopic — it attracts moisture. Salt deposits on historic masonry accelerate damp penetration and can cause devastating spalling and decay.

The “shoulder season” trap. October and March are when most moisture damage occurs in old buildings. It’s cold enough for condensation but not cold enough that anyone’s running the heating consistently. People stop opening windows because it’s chilly, but moisture from daily life has nowhere to go. A few weeks of this and you’ve got black mould behind the Victorian chest of drawers on the north wall.

Summer overheating. When we get extended hot spells, listed buildings with thick walls absorb heat during the day and radiate it back at night — the building never fully cools. South-facing rooms with large Georgian sash windows become unbearable. The temptation is to open everything up, but that lets humidity in too, and if your building has sensitive plasterwork, panelling, or paintings, uncontrolled humidity is worse than the heat.

How AC Addresses These Problems

A properly specified AC system in a listed building does three things simultaneously:

1. Temperature control — obvious, but important for comfort and for preventing thermal stress on historic materials. Sudden temperature swings cause timber to expand and contract, plaster to crack, and paint to flake. AC provides gentle, consistent temperature management.

2. Humidity control — every AC system dehumidifies as it cools. A well-set system maintains 45–60% RH year-round, which is the sweet spot for most historic materials. Too dry (below 40%) and timber shrinks, cracks, and joints open up. Too humid (above 65%) and you get mould, mildew, corrosion, and decay.

3. Air circulation — AC units move air through the room, preventing the stagnant pockets that develop in corners, behind furniture, and in alcoves where moisture accumulates and mould thrives. Old buildings with thick walls and deep window reveals are particularly prone to dead air spots.

The Preservation Argument

Here’s something I’ve used successfully in Listed Building Consent applications: a well-designed AC system can actually protect a listed building better than leaving it uncontrolled.

Historic England’s own guidance acknowledges that climate control can be essential for the long-term preservation of building fabric and contents. Museums, galleries, archives, and historic houses routinely use sophisticated climate control to protect collections — there’s no reason a listed dwelling can’t benefit from the same principle on a domestic scale.

When framing a planning application, emphasising the preservation benefits of humidity and temperature control — alongside the comfort benefits — can help conservation officers see the installation as a positive intervention rather than a threat.

Which AC System Works Best in a Listed Building?

Not all AC systems are equal when it comes to heritage buildings. The right choice depends on the building, the rooms, the level of preservation required, and what the planning authority will accept.

Wall-Mounted Split Systems

The most common type of domestic AC. One indoor unit on the wall, one outdoor condenser, connected by refrigerant pipes through the wall.

Pros for listed buildings:

• Simple installation — minimal disruption
• Small wall penetration (typically 60–65mm core drill)
• Quiet operation (19–22 dB on low speed)
• Heating and cooling in one unit
• Affordable (£1,500–£3,000 installed per room)

Cons for listed buildings:

• Indoor unit is visible on the wall — not always acceptable in rooms with significant features
• Wall penetration goes through the historic fabric
• Outdoor condenser needs to be mounted or placed somewhere acceptable

Best for: Bedrooms, home offices, and rooms where the wall unit can be positioned discreetly — above a door, in an alcove, or on a wall without significant features.

Ducted Systems

A concealed indoor unit sits in a ceiling void, loft space, or cupboard. Cooled air is distributed through small ducts to grilles in the ceiling or low on the wall. Only the grilles are visible in the room.

Pros for listed buildings:

• Nothing visible on the walls — only discreet ceiling or wall grilles
• Can serve multiple rooms from one indoor unit
• All equipment is hidden
• Superior humidity control due to larger coil size

Cons for listed buildings:

• Needs a ceiling void deep enough for the unit and ducts (minimum 250–300mm)
• More invasive installation — ceiling work required
• Higher cost (£4,000–£10,000 depending on scope)
• Not feasible if original ceiling plasterwork must be preserved

Best for: Properties where wall-mounting is unacceptable, rooms with significant wall features, and situations where the ceiling is already modern (a plasterboard ceiling in a listed building is fair game — an original ornamental plaster ceiling is not).

Floor-Standing Console Units

Compact units that sit on the floor against the wall, similar in appearance to a small radiator.

Pros for listed buildings:

• No wall mounting — no fixings into historic walls
• No ceiling work required
• Easy to remove without trace (fully reversible)
• Some models are genuinely attractive

Cons for listed buildings:

• Takes up floor space
• Still needs a wall penetration for the pipework
• Less common, fewer model choices

Best for: Situations where reversibility is the primary concern — where the planning authority wants assurance that the installation leaves no permanent mark on the walls or ceiling.

Ceiling Cassettes

A square unit recessed into the ceiling, blowing air in up to four directions.

Pros for listed buildings:

• Powerful and effective for large rooms
• Good for high-ceilinged rooms (Georgian, Victorian) where wall units would look out of proportion

Cons for listed buildings:

• Needs a significant ceiling opening
• Visible in the ceiling — a modern intrusion
• Not suitable where original ceilings must be preserved

Best for: Heritage properties where the ceiling has already been replaced with modern plasterboard — restaurants, offices, shops in listed buildings where the original ceiling is long gone.

Condenser-Free Solutions

In some heritage situations, no outdoor condenser is acceptable — anywhere. This is rare but it happens, particularly in dense urban conservation areas or on prominent listed buildings where every elevation is visible.

Options here include water-cooled systems (where heat is rejected to a water loop rather than outdoor air) and specialist units designed to reject condenser heat through louvred openings integrated into existing features — window panels, existing ventilation grilles, or purpose-made openings that blend with the building’s character.

These systems cost more and run less efficiently than conventional splits, but they solve the problem when a planning authority says no external equipment. We’ve used this approach on Grade II listed properties in central London where every wall was in a conservation area and no condenser would have been acceptable anywhere.

Quick Comparison: AC Systems for Listed Buildings

System	Visibility	Heritage Cost	Best For	Reversibility
Wall-mounted split	Unit visible on wall	£2,500–£4,000 per room	Bedrooms, offices, rooms without significant wall features	Good — small wall penetration, unit removes cleanly
Ducted system	Only ceiling grilles visible	£6,000–£15,000	Rooms with significant wall features, multi-room coverage	Moderate — ceiling work needed, but grilles are small
Floor console	Unit on floor against wall	£2,000–£3,500 per room	Where full reversibility is required by planning	Excellent — no wall fixings, leaves no trace
Ceiling cassette	Square unit in ceiling	£3,000–£5,000 per unit	High-ceilinged rooms, commercial heritage spaces	Moderate — needs ceiling opening
Condenser-free	Nothing external	£5,000–£10,000+	Where no outdoor equipment is acceptable	Good — all internal

For more details on air conditioning systems and how they work, see our service page.

The Planning Process: Step by Step

Before You Apply

1. Check whether you actually need consent. If your building isn’t listed and the condenser goes on the rear wall, you may not need to apply for anything. If your building IS listed, you need consent regardless.

2. Talk to your local conservation officer. This is the single most valuable thing you can do. Conservation officers are usually happy to have an informal conversation before you submit anything. They’ll tell you what they’re likely to accept and what they’ll push back on. This saves time, money, and frustration.

Brighton & Hove offers formal pre-application advice for £60–£120. Worth every penny. Other Sussex councils offer similar services.

3. Commission a bat survey if needed. If there’s any possibility of bats, get this done first. A bat issue discovered during the application process will delay everything by months.

4. Get your installer involved early. A good AC installer who understands heritage buildings can help design an installation that’s both technically effective and planning-friendly. We regularly attend pre-application meetings with conservation officers to explain proposed installations and answer technical questions.

What to Include in Your Application

A Listed Building Consent application for AC installation should include:

Heritage Impact Assessment. How the installation affects the building’s significance. This doesn’t need to be a 50-page document — for a straightforward domestic AC installation, a clear written statement covering what’s proposed, where, why, and what the impact is should suffice. For more complex or sensitive buildings, a heritage consultant may be needed.

Detailed drawings. Show exactly where equipment goes — indoor unit locations, outdoor condenser position, pipework routes, any penetrations through walls or ceilings. Include dimensions and distances from significant features.

Photographs. Existing condition of the building, proposed equipment locations, and the relationship between proposed equipment and the building’s significant features.

Technical specifications. Unit dimensions, weight, noise levels, and appearance. Conservation officers want to know what they’re approving.

Method statement. How the work will be done without damaging historic fabric. This might include: core drilling through mortar joints rather than stone or brick; using non-destructive fixings; protecting adjacent surfaces during installation.

Reversibility statement. Demonstrating that the installation can be removed in future without permanent damage to the building. This is often the key that unlocks consent — if the conservation officer knows it can all be undone, they’re more likely to approve.

Typical Timeline

• Pre-application enquiry: 2–4 weeks for a response
• Bat survey (if needed): Can only be done May–September; results in 2–4 weeks
• Listed Building Consent application: 8–13 weeks determination (statutory target is 8 weeks, complex cases take longer)
• From consent to installation: 1–4 weeks depending on equipment availability

Total realistic timeline: 3–6 months from first enquiry to installation. Plan ahead — don’t wait until June to start thinking about AC for the summer.

What Gets Approved and What Doesn’t

Based on our experience across dozens of heritage installations:

Usually approved without difficulty:

• Condensers in rear gardens, behind walls, or in courtyards — not visible from public areas
• Small wall-mounted units in rooms without significant features
• Ducted systems where the ceiling is already modern
• Pipework routed internally through non-significant spaces

Approved with conditions:

• Condensers on side elevations with screening conditions
• Equipment in rooms with some historic features — with specific conditions about fixings and positioning
• Installations that require wall penetrations — with conditions about drilling through mortar joints and making good

Usually refused:

• Condensers on principal (front) elevations of listed buildings
• Large equipment on prominent elevations in conservation areas
• Installations that require removing or damaging significant architectural features
• Systems that would be highly visible and out of character

The trump card: Precedent. If similar buildings nearby already have AC installed, reference this in your application. Conservation officers are pragmatic — if the building next door already has a condenser on the back wall and the world didn’t end, your application is much harder to refuse.

Good Practice: Doing It Right

Respect the Fabric

Drill through mortar, not masonry. When core-drilling for pipework, always go through a mortar joint rather than through stone or brick. Mortar is sacrificial and repairable — original brickwork or stonework is not. A skilled installer will mark the drilling position to hit a mortar course, even if it means a slightly longer pipe run.

Use appropriate fixings. Stainless steel fixings in masonry. Avoid resin anchors in lime mortar — they don’t bond properly and can cause cracking. If fixing into timber, use screws not nails, and consider whether the timber is original or replaceable.

Protect adjacent surfaces. When working near plasterwork, panelling, or decorative features, mask and protect them. Dust from core drilling is the enemy of everything — it gets into paint, stains fabrics, and clogs decorative carving.

Make good properly. When a pipe penetration goes through an external wall, seal it with appropriate materials. Lime mortar for lime-mortared walls, not cement. The repair should match the existing as closely as possible. A neat, invisible repair is not just aesthetically important — it’s often a condition of the Listed Building Consent.

Route Pipework Thoughtfully

The pipework between indoor and outdoor units is often the most visible part of an installation. In heritage buildings, the default should be to conceal it wherever possible:

• Internal routing through wall cavities, floor voids, or ceiling spaces rather than running trunking on external walls
• Existing service routes — chimney flues that are no longer in use, redundant pipe runs, and existing cable routes can often accommodate AC pipework
• Through cupboards and built-in furniture — a pipe run behind a fitted bookcase or through the back of a wardrobe is invisible
• Where external trunking is unavoidable, match it to the building — painted to match the wall colour, routed along existing lines (following a rainwater pipe, for instance)

Choose Equipment Carefully

Colour matters. Most AC units come in white, which looks fine on a white wall but jarring on anything else. Several manufacturers offer units in black, silver, or custom colours. Matte black finishes work particularly well in period interiors with darker walls or wood panelling.

Size matters. A compact unit that fits neatly in an alcove or above a door is far less visually intrusive than an oversized unit dominating a wall.

Noise matters. In quiet residential conservation areas, a noisy outdoor condenser will generate neighbour complaints and potentially a noise nuisance claim. Modern condensers are remarkably quiet — 45–48 dB at 1 metre for most domestic units, dropping to 30–35 dB at the property boundary. But check the specifications and position the unit away from bedrooms (yours and your neighbours’).

Best Months for Installation

Spring (March–May) is ideal — the weather is dry enough for external work, bats are emerging but not yet breeding, and you’re ready for summer. Autumn (September–October) is also good — the summer rush has passed, equipment is readily available, and you can also use the system for heating through winter.

Avoid June–August if you can. This is peak demand — every AC company in the country is flat out, lead times stretch, and if your building has bats, you may face restrictions during the maternity season.

Avoid November–February for installation. Cold weather makes external work harder (sealants don’t cure properly below 5°C), bat hibernation sites may be disturbed, and core drilling in freezing conditions risks cracking masonry due to trapped moisture expanding.

Plan around consent timescales. If you want AC installed by June, start the planning process in November. Get your bat survey booked for May, submit your LBC application in January, and allow 8–12 weeks for determination. That gives you an April/May installation window.

Common Mistakes We See with Heritage AC Projects

After 20+ years of installing AC in listed buildings across Sussex, these are the mistakes that cause the most problems — and they’re all avoidable.

Mistake 1: Skipping the Conservation Officer Conversation

The single biggest mistake is treating planning consent as a hurdle to clear rather than a conversation to have. People spend weeks researching systems, getting quotes, and planning their installation — then submit an application cold, without ever speaking to the conservation officer. The application gets refused on a technicality that a five-minute phone call would have resolved.

The fix: Call the conservation officer before you do anything else. They’ll tell you what they’re likely to accept. This costs nothing and saves months.

Mistake 2: Starting Too Late

Every May we get calls from people who want AC installed “before summer.” For a non-listed property, that’s feasible — we can often install within 2–3 weeks. For a listed building needing LBC, you’re looking at 3–6 months minimum. Starting in May means you’re getting AC for autumn, not summer.

The fix: Start the process in November for a spring/summer installation. Book bat surveys for the following May. Submit applications in January.

Mistake 3: Using Cement on Lime Mortar

This one makes us wince. A general builder or less experienced installer drills through an old wall for pipework and makes good with cement mortar. On a lime-mortared wall, cement is a disaster — it’s too hard, it doesn’t breathe, it traps moisture, and it eventually causes the surrounding historic mortar and masonry to crack and decay. It’s also a sure way to fail a Listed Building Consent condition.

The fix: Always use lime mortar on lime-mortared walls. Make sure your installer understands heritage materials — not all do.

Mistake 4: Choosing the Wrong Condenser Location

A condenser on the front elevation of a listed building will be refused. Every time. But people still try, and it wastes everyone’s time. Even on non-principal elevations, a poorly positioned condenser — too high, too prominent, or in an architecturally sensitive spot — will face pushback.

The fix: Default to rear gardens, courtyards, or concealed locations. If that’s not possible, discuss screening options (timber enclosures, planting, purpose-built housing) with the conservation officer before applying.

Mistake 5: Ignoring the Bat Survey

Bats and old buildings go together. Ignoring the possibility because “I’ve never seen any” is both illegal and risky. If bats are discovered during installation, work must stop immediately. You’ll need an emergency licence, the project will be delayed by months, and you may face prosecution.

The fix: Commission a Preliminary Roost Assessment (£200–£400) before starting any work on a pre-1900 building. It’s cheap insurance.

Things Most People Don’t Know About Listed Buildings and Climate

The National Trust spends millions on climate control. Historic houses like Petworth House and Uppark (both in West Sussex) use sophisticated environmental monitoring and control systems. The lessons learned from managing humidity in a 17th-century state room apply directly to managing it in a listed townhouse.

Medieval churches face the same problems you do. The huge stone interiors of Sussex’s medieval churches create exactly the same challenges as listed homes — thermal mass, humidity, condensation — but on a cathedral scale. The Diocese of Chichester has been trialling heat pump and air source systems in historic churches for years. If they can climate-control a 12th-century nave, your Georgian terrace is solvable.

Brighton’s Regency terraces were never designed for year-round living. The grand terraces along the seafront — Brunswick Terrace, Adelaide Crescent, Lewes Crescent — were built as fashionable seasonal residences. Many were only occupied in summer. The idea that you’d live in one year-round, with central heating, modern bathrooms, and a family producing moisture every day, would have baffled their Georgian architects. These buildings need modern climate control precisely because we now use them in ways their designers never intended.

Humidity has destroyed more historic interiors than fire. This is a heritage truism that’s essentially accurate. Long-term humidity damage — mould, timber rot, salt efflorescence, paint flaking, plaster decay — is slow, insidious, and cumulative. By the time it’s visible, years of damage have already occurred. A house fire is catastrophic but sudden; humidity damage is catastrophic but gradual.

The 1990 Act has no de minimis threshold. Unlike planning permission, which has a range of permitted development rights for minor works, Listed Building Consent has no formal “small works” exemption. Technically, even drilling a single hole in a listed wall requires consent. In practice, councils use common sense — no one’s going to prosecute you for hanging a picture — but for AC installation, which involves multiple penetrations and permanently fixed equipment, consent is always needed.

Frequently Asked Questions

Can I install AC in a Grade I listed building?

Yes, but expect more scrutiny. Grade I buildings are of exceptional interest and any application will be examined carefully, potentially involving Historic England as a statutory consultee. The principles are the same — discreet, reversible, sympathetic — but the bar is higher.

Do I need planning permission AND Listed Building Consent?

Potentially both. LBC covers the impact on the building’s character. Planning permission covers the development itself (external equipment, etc.). For a simple split system with a rear condenser, you might need LBC but not planning permission (if the condenser is permitted development). Your local authority will advise.

What if I install AC without consent?

It’s a criminal offence to carry out works to a listed building without LBC. The local authority can require you to reverse the work at your expense. Prosecution can result in fines or (theoretically) imprisonment. Insurance may also be affected. Don’t risk it.

How much does AC cost in a listed building?

Expect to pay 20–40% more than a standard installation due to the additional care required — heritage-appropriate making good, careful routing, potentially longer pipe runs, and the time spent on planning and consent. A single-room split system might cost £2,500–£4,000 installed. A multi-room ducted system: £6,000–£15,000 depending on complexity.

Cost Element	Standard Home	Listed Building	Why the Difference
Single-room split system	£1,500–£2,500	£2,500–£4,000	Heritage-grade making good, careful routing, longer pipe runs
Multi-room ducted system	£4,000–£8,000	£6,000–£15,000	Concealment requirements, working around historic features
Pre-application advice	N/A	£60–£120	Conservation officer consultation
Bat survey (if needed)	N/A	£200–£400+	Preliminary Roost Assessment; emergence surveys extra
Planning application fee	N/A	£0–£234	LBC applications are free; planning permission has a fee
Running costs (per room/year)	£30–£60	£30–£60	Same once installed

Will AC damage my building?

A professional installation, properly planned and executed, should cause no damage. Every penetration is sealed and made good. Every fixing is appropriate for the material. The system is fully reversible — if removed in 20 years, the building should be indistinguishable from its pre-installation state.

Can I use AC for heating too?

Yes. Modern split systems are heat pumps — they cool in summer and heat in winter. This can be particularly valuable in listed buildings where installing radiators or underfloor heating would be disruptive. A wall-mounted AC unit providing 3.5kW of heating is far less invasive than running new central heating pipework through a Grade II townhouse.

What about the running costs?

A typical single-room split system costs £30–£60 per year in electricity for cooling and around the same for heating. For comparison, a 2kW portable electric heater running 4 hours a day costs about £300 per year. AC heat pumps are roughly 3–4 times more efficient than direct electric heating.

What if my listed building has original decorative ceilings?

Original decorative ceilings — ornamental plasterwork, cornices, ceiling roses, or painted surfaces — rule out ducted systems and ceiling cassettes, which would require cutting into the ceiling. The best options are wall-mounted split systems (positioned on walls without significant features) or floor-standing console units that need no ceiling work at all. A console unit is often the ideal choice for rooms with important ceilings — it sits on the floor, needs only a small pipe penetration through the wall, and can be removed without any trace.

Can I install AC alongside MVHR or ventilation?

Absolutely — they complement each other well. Air conditioning handles temperature and active dehumidification, while a mechanical ventilation system or MVHR system provides continuous fresh air exchange and helps manage background humidity levels. In a listed building, combining both gives you the best of both worlds: comfortable temperatures in summer, efficient heating in winter, and year-round humidity control that protects the building fabric. We cover the different ventilation options in our MVHR vs MEV vs PIV guide.

How We Can Help

If you own a listed building or live in a conservation area anywhere across Sussex and want air conditioning, we can help at every stage:

1. Survey your property and assess what’s feasible given the building’s constraints and significance
2. Advise on planning requirements — whether you need LBC, planning permission, a bat survey, or none of the above
3. Design a discreet installation that works with the building rather than against it
4. Liaise with conservation officers on your behalf — we’ve built good relationships with local authorities across Sussex through years of heritage work
5. Prepare the planning application if needed — heritage impact assessments, method statements, and technical specifications
6. Install the system with the care and respect the building deserves
7. Maintain it with annual servicing to keep everything running quietly and efficiently

Every building is different, but we’ve yet to find a listed building or conservation area where AC was genuinely impossible — just ones where it took more thought than usual.

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