Lewisham · cooling guide
How to cool a new build in Lewisham
Written by Solomon Amos.
Sources: CIBSE TM59, Building Regs Part O, gov.uk Boiler Upgrade Scheme, and MCS (the certification scheme for registered installers) - see methodology
Last checked against current grant rules on 14 August 2026
Quick answer
Overheating risk for the typical Lewisham new build is moderate, so the usual fix is air-to-air heat pump, about £2,800-£3,220 installed. An air-to-air heat pump replacing qualifying fossil-fuel or electric heating can attract a grant through an accredited installer; kept alongside your boiler it is private-pay. Check your address for the exact verdict.
Lewisham's post-2000 stock is small, just 174 EPC-certified new builds, but at a median of 95 square metres these are decent-sized homes with a specific weakness: lightweight construction and low thermal mass mean they heat up faster than the older stock around them. Many also run direct-electric heating, which shapes the cooling choice.
If your Lewisham new build gets uncomfortably hot the moment summer arrives, you are not the only one - and although new builds are a smaller share of the borough (about 174 homes, 0.1%), they overheat about as reliably as any home type here. On our overheating scale a typical Lewisham new build lands near 53 out of 100 - "moderate" - meaning the fan-and-open-window routine stops coping once real heat arrives. Here is the property-specific answer: the right cooling system for your home, what it realistically costs, and whether you need planning permission - before you speak to a single installer.
Why new builds in Lewisham overheat
A new build overheats for the opposite reason to an old one. The airtightness and heavy insulation that keep winter warmth in also stop summer heat getting out: once solar gain through large glazed areas and everyday internal heat build up inside, the fabric has no easy route to shed it. Single-aspect flats, with windows on one side only, cannot cross-ventilate at all. It is a recognised enough problem that Part O of the Building Regulations now governs overheating in new homes directly. Since the fabric is already doing its job, the answer here is mechanical cooling rather than more insulation, and a system that can both cool in summer and provide efficient heat in winter suits a home that often has no gas supply to begin with. For a typical Lewisham new build, the median floor area is around 95 sqm - over that footprint of sealed, airtight construction, the trapped heat described above has nowhere to go once the windows are shut.
New builds in Lewisham: by the numbers
0% of Lewisham homes are new builds
174 of 168,750
95 m²
median floor area
£242
median annual heating cost
EPC band distribution
174 new builds in Lewisham with an EPC on record
Greener bands are more energy-efficient; red bands (E-G) are poorer-fabric homes that trap summer heat.
| EPC band | Homes | Share |
|---|---|---|
| A | 0 | 0% |
| B | 140 | 80% |
| C | 29 | 17% |
| D | 5 | 3% |
| E | 0 | 0% |
| F | 0 | 0% |
| G | 0 | 0% |
When these homes were built
Construction era of 114 new builds in Lewisham
- pre-1919 0%
- 1919-1944 0%
- 1945-1999 1%
- 2000+ 99%
| Era | Homes | Share |
|---|---|---|
| pre-1919 | 0 | 0% |
| 1919-1944 | 0 | 0% |
| 1945-1999 | 1 | 1% |
| 2000+ | 113 | 99% |
Real EPC and property-intelligence data via HomePortfolio, aggregated for new builds in Lewisham. Data as of 11 July 2026.
Read past the chart to what it implies: the fabric is on the efficient side, great for heating costs yet quick to trap warmth once a heatwave sets in, and these are predominantly modern-build stock, tight enough that once heat gets in it has nowhere to go, so the heat that gets in does not leave easily. Set against that, Lewisham is part of inner London's built-up heat island, where the city holds onto daytime warmth well into a summer evening, and air quality (PM2.5) averages about 5.2 µg/m³ and daytime noise around 51 dB - together these decide whether night ventilation is a real option here. This is historic ground, too: a small share of these homes sit inside a conservation area - which is why the planning route for an outdoor unit needs more care here than the approval rate alone suggests. Being near a listed building is not the same as your home being listed.
What the data says about new builds in Lewisham
Look past the address at what the stock is actually made of. In Lewisham, 80% of these homes carry an EPC band of B. That is a reasonably efficient profile, which keeps winter bills down - but efficiency is about stopping heat escaping, not stopping it getting in, so on its own it does little for summer overheating. The full spread reads 80% at band B, 17% at band C, 3% at band D, so the picture is a range, not a single rating. With 99% built since 2000, this is largely modern, airtight construction that seals summer heat in as readily as winter warmth.
Can you cool this home by opening a window at night?
It is worth testing whether you even need active cooling, or whether night ventilation would carry the load. At about 51 dB it is marginal: workable on a side street, awkward near a main road with the windows open overnight. Local PM2.5 air quality, around 5.2 µg/m³, is not the limiting factor.
How the planning numbers look in Lewisham
When it comes to permission, only 1 of the 174 new builds we profile in Lewisham sit inside a conservation area, around 1%, so most homes of this type here are outside one. The London Borough of Lewisham waves through the large majority of recent planning applications around this stock, though each still turns on the siting. In conservation areas such as Brookmill Road and Halifax, expect the external siting to draw more scrutiny.
A worked cooling plan for a typical new build
Worked example · a typical new build in Lewisham
Recommended system
Air-to-air heat pump
Cools in summer and heats in winter - the only cooling system the £2,500 grant can fund.
Replacing your direct-electric heating with an air-to-air heat pump cools in summer and heats in winter, and qualifies for the £2,500 Boiler Upgrade Scheme grant when installed by an MCS-certified installer.
Boiler Upgrade Scheme
£0 grant - eligible
Eligible: replacing your direct-electric heating with an air-to-air heat pump via an MCS-certified installer qualifies for the £2,500 Boiler Upgrade Scheme grant.
Not claimable yet
The grant itself is law and your eligibility is real, but no air-to-air product has reached the MCS Product Directory yet, so no installer can issue a Boiler Upgrade Scheme voucher today. Air-to-air enters MCS scheme scope on 5 December 2026, and vouchers follow once certified products list. Get quotes now, but treat the grant as pending rather than banked.
- Installed by an MCS-certified installer
- Residential property only
- Existing qualifying heating system is decommissioned, not retained alongside the new system
- Not combined with another government heating grant for the same install
- Air-to-air products must be listed on the MCS Product Directory before a voucher can be issued - not yet the case
Indicative cost
- Typical install
- £2,800–£3,220
- Less grant
- −£2,500
- You pay
- £300–£720
- Indicative UK install cost, sourced from 2026 trade guides - actual quotes vary by property and installer.
- Net cost shown after the £2,500 Boiler Upgrade Scheme grant.
Planning permission likely needed
- The permitted-development right for a heat pump sits with the whole building, not the individual flat - you will usually need freeholder/management-company consent, and in practice that means a full planning application in most cases.
- External condenser units must meet permitted-development noise limits regardless of planning route.
- This is an indicative assessment only - always confirm the final position with your Local Planning Authority (LPA) before installing.
- Listed-building status was not confirmed - if this building is also listed, listed-building consent will additionally be required.
Illustrative only. Your own floor, aspect, heating and conservation status change the result - check your specific address below.
The right system, and the £2,500 grant honestly
For most Lewisham new builds, the strongest option is an air-to-air heat pump - a modern high-wall or ceiling unit, the same hardware people loosely call "air conditioning", except it heats as well as cools. It is near-silent, controllable room by room, and because it does both jobs it can replace your existing heating entirely. There are two honest ways this plays out, and which one applies to you turns on a single decision: whether you replace your heating or keep it. For context, a typical Lewisham new build runs around 95 sqm and already costs about £242 a year to heat - the baseline the figures below are measured against.
Branch 1 - replace your direct-electric heating, and the £2,500 grant is in play. The £2,500 air-to-air grant (Boiler Upgrade Scheme) only pays when the heat pump replaces your fossil-fuel or electric heating and is fitted by an MCS-certified installer. So if you take out your existing system and let the air-to-air heat pump handle your heating as well as your cooling, a job costing around £2,800-£3,220 installed can come down to roughly £300-£720 net. Eligibility is per-property and depends on your current heating and the installer's accreditation - our checker confirms it against your address. (Grant rules as of August 2026 and subject to change.)
Branch 2 - keep your boiler and simply add cooling, and the grant does not apply. If you want to keep your existing heating and only add cooling, that is a private-pay job - a cooling-only add-on that keeps your boiler is not eligible for the £2,500 grant, whatever your heating type. The sensible choice here is usually a single-split air conditioning unit (around £1,500-£3,000 installed), carried out by an F-Gas / REFCOM-registered engineer - not MCS, which applies only to the grant-eligible heat-pump route above.
We match you to the right accreditation for whichever path fits your home: MCS for the grant-eligible heat pump, F-Gas / REFCOM for a pure cooling install. For a typical new build in Lewisham at around 95 sqm, sized to that footprint, our checker leans toward air-to-air heat pump, but your own floor, aspect and heating decision move the answer - which is the whole point of checking your specific address.
What cooling costs in Lewisham in 2026
| Air-to-air heat pump | Single-split AC | |
|---|---|---|
| What it does | Cools in summer and heats in winter | Cools only |
| Typical install cost | £2,800 - £3,220 | £1,500 - £3,000 |
| The £2,500 grant | If you replace fossil-fuel or electric heating, via an MCS installer | Not eligible |
| Cost after grant | £300 - £720 (if eligible) | £1,500 - £3,000 |
| Installer accreditation | MCS | F-Gas / REFCOM |
Planning permission in Lewisham
Planning permission is more straightforward here than in a lot of the country. Lewisham has relatively low conservation-area coverage, so most houses can fit an outdoor condenser under permitted development without a fresh application - flats are still the exception, and a front or side unit there will usually need planning permission from the London Borough of Lewisham. In Lewisham, conservation areas such as Brookmill Road, Halifax and St Stephens are where this bites hardest. One recent rule change matters here. As of May 2025 an air-to-air heat pump counts as a heat pump for planning, so a house can often install one under permitted development within the size and siting limits - whereas a pure cooling unit, which only cools, still needs a full planning application. Which system fits your home therefore decides which planning route you are on. For a typical new build here, our checker's read is: planning permission is likely required. External condenser units must meet permitted-development noise limits regardless of planning route. This is an indicative assessment only - always confirm the final position with your Local Planning Authority (LPA) before installing. Listed-building status was not confirmed - if this building is also listed, listed-building consent will additionally be required. For context, the London Borough of Lewisham waves through the large majority of recent planning applications around this stock, though each still turns on the siting. Roughly 17% of Lewisham's EPC-certified homes fall inside a conservation area, concentrated in areas like Brookmill Road, Halifax, St Stephens - most addresses are outside one, but the boundary check is worth doing before committing to a wall-mounted unit. None of this is a dealbreaker - approvals happen for homes like this all the time - but it is a step to plan for rather than a given, and one worth confirming for your specific address before you commit. This is indicative guidance, not legal advice.
100%
of recent Lewisham planning applications approved
1%
of new builds in Lewisham sit inside a conservation area
0%
within 30 metres of a listed building
Conservation-area and listed-building status both tighten the planning route for an outdoor unit. Sitting near a listed building does not by itself make a home listed, so the checker confirms your property individually.
Conservation-area and listed-building records © Historic England 2026, via planning.data.gov.uk, used under the Open Government Licence v3.0. Data as of July 2026. See all data sources.
Permitted development, or a planning application?
Air-to-air heat pump (heats and cools)
Can be permitted development
Can be permitted development on a house under Class G, within size, siting and noise limits, because since 29 May 2025 a unit that also heats is no longer excluded for cooling.
Pure air conditioning (cooling only)
Needs planning permission
Not permitted development - a cooling-only condenser fails the Class G "not solely for cooling" condition and there is no other PD class for it, so it needs a full planning application.
| Air-to-air heat pump | Cooling-only AC | |
|---|---|---|
| Does the permitted-development route apply? | Yes on a house, within the Class G limits below (it heats as well as cools). | No - a cooling-only unit needs full planning permission. |
| Property type | Houses get the Class G right directly. For a flat the right sits with the whole building (one unit for the block) and needs freeholder consent, so in practice a flat almost always needs permission. | Planning permission required either way. |
| Maximum outdoor-unit size | Up to 1.5 cubic metres on a house (0.6 cubic metres for a block of flats). | Not applicable - planning permission required. |
| Number of units | Up to two on a detached house; otherwise one. | Not applicable - planning permission required. |
| Where it can go | Not on a pitched roof; on a flat roof it must sit at least 1 metre from the edge; not on a wall above ground-floor level that faces a highway. | Set by the planning application. |
| Conservation area | Stricter - it must not go on any wall or roof that faces a highway, and an Article 4 direction can remove the right entirely. | Planning permission required. |
| Listed building | Excluded from permitted development; listed-building consent is needed regardless. | Excluded from permitted development; listed-building consent is needed regardless. |
| Noise | Must pass the MCS Planning Standards (MCS 020) sound test, measured at the nearest neighbour's door or window. | Any planning permission will set its own noise conditions. |
England only, as of 29 May 2025 (reflects the 29 May 2025 Class G change, SI 2025/560). Sources: GPDO 2015, Schedule 2, Part 14, Class G (air source heat pumps); SI 2025/560 (the 2025 amendment).
This is an indicative summary of England permitted-development rules for outdoor units, not legal advice. Rules change and vary locally - confirm the final position with your Local Planning Authority before installing.
Common questions about cooling a new build
Does a top-floor or new build in Lewisham really overheat?
Yes, and we can put a number on it: our model scores a typical Lewisham new build at about 53 out of 100 ("moderate"). Lewisham holds around 174 homes of this type - 0.1% of the borough's certified stock - and between roof heat gain, low thermal mass in older stock and the local heat-island effect, homes like this are routinely uncomfortable from late June, whatever the thermostat reads.
What is the best cooling system for a new build in Lewisham?
An air-to-air heat pump is usually the best answer for a Lewisham new build: one near-silent, room-by-room unit that cools in summer and heats in winter. Prefer to keep your boiler and simply add cooling? A single-split air conditioning unit is the usual private-pay route. For a typical home of this type our checker leans toward air-to-air heat pump, though your floor, aspect and heating decision shift it - which is exactly why checking your own address is worth it. These new builds average around 95 sqm. A typical Lewisham new build already costs around £242 a year to heat.
Can I get the £2,500 grant for cooling my Lewisham home?
Only in one specific case, and it is worth being precise. You are eligible for the £2,500 air-to-air grant (Boiler Upgrade Scheme) only when an air-to-air heat pump replaces your fossil-fuel or electric heating and is fitted by an MCS-certified installer. If you keep your boiler and add cooling as an extra, that is a cooling-only add-on and it is not eligible for the £2,500 grant, whatever your heating type. Eligibility is per-property, so our checker confirms it against your address. (Grant rules as of August 2026 and subject to change.) Given a typical Lewisham new build already costs around £242 a year to heat, replacing that heating as part of this route is usually where most of the saving comes from.
Do I need planning permission for air conditioning in Lewisham?
Usually more than a house would, yes. Permitted development lets a house add an outdoor unit, but flats are treated differently, and conservation-area coverage is widespread enough in Lewisham, especially around Brookmill Road that a front or side condenser will typically need the council's sign-off. It is far from impossible - a planned step rather than an afterthought - and our checker gives the likely position for your exact address. For context, the London Borough of Lewisham approves the great majority of recent applications around this stock, provided the unit is sensibly placed.
How much does it cost to cool a new build?
On 2026 UK trade prices as a rough guide: fitting an air-to-air heat pump here is around £2,800-£3,220, falling to roughly £300-£720 net when it replaces your heating and qualifies for the grant. A single-split air conditioning unit that leaves your boiler in place is about £1,500-£3,000 installed with no grant. Final quotes shift with access, unit size and pipe runs. A typical Lewisham new build currently costs around £242 a year to heat. That heating bill sits alongside the cooling cost above, not instead of it.
MCS or F-Gas - which installer do I actually need?
It depends on the route, and getting it wrong is a common trap. The grant-eligible air-to-air heat pump route needs an MCS-certified installer - that accreditation is what the grant requires. A pure cooling install (a single-split, multi-split, ducted or portable unit that keeps your existing heating) needs an F-Gas / REFCOM-registered engineer, not MCS. We match you to the right accreditation for whichever path fits your home. This is a separate question from planning permission - the London Borough of Lewisham handles that side, and accreditation is ours to get right.
If I use the checker, will you cold-call me?
No. The free cooling check shows your full plan on screen straightaway, with no phone call and no waiting. If you would like us to email your plan, or to have a single vetted local installer contact you about a survey, you choose that at the end - we only get in touch if you ask, and you are never sold to five companies at once.
Is air conditioning banned in new-build homes?
No - there is no ban on cooling a new-build. The confusion comes from Building Regulations Part O, which requires new homes to limit overheating by design, and from management-company or lease rules that control external units. None of that bans air conditioning; it just means you may need permission for an outdoor condenser. The checker shows where you stand for your Lewisham address.
What is Part O and does my new-build flat need to comply?
Part O is the Building Regulations standard that limits overheating in new homes, assessed with the CIBSE TM59 method. It applies to the design and construction of new dwellings, so compliance is the developer's job, not something you retrofit. If your new-build still overheats in practice - as many airtight flats do - active cooling is a separate, unregulated choice you are free to make.
Do I need my management company's permission to fit air conditioning in a new-build flat?
Very often, yes. New-build flats usually come with a lease and a managing agent whose consent is required for external alterations, including an outdoor condenser. Ask for the process in writing early, since it can take time, and treat it as separate from any planning permission. The checker covers the planning side for your address.
What size outdoor unit can I fit under permitted development?
It depends on the system. Since 29 May 2025 (SI 2025/560), an air-to-air heat pump - which heats as well as cools - can be permitted development on a house: broadly a unit no larger than 1.5 cubic metres (0.6 cubic metres for a block of flats), and not on a wall above ground-floor level facing a highway, as long as you are not in a conservation area. A pure, cooling-only air conditioning unit does not get that route - it needs a full planning application whatever its size. Flats and conservation areas usually fall outside the permitted-development rights either way, so a unit there typically needs permission. The checker applies this to your address. In Lewisham, that conservation-area exclusion bites hardest around places like Brookmill Road.
Does the air-to-air grant still apply if I add air conditioning but keep my gas boiler?
No. You are eligible for the £2,500 air-to-air grant (Boiler Upgrade Scheme) only when an air-to-air heat pump replaces your fossil-fuel or electric heating and is fitted by an MCS-certified installer. If you keep your boiler and add cooling as an extra, that cooling-only add-on is not eligible for the £2,500 grant, whatever your heating type - it is an F-Gas / REFCOM job instead. (Grant rules as of August 2026 and subject to change.) Given a typical Lewisham new build already costs around £242 a year to heat, that saving is only available on the replace-your-heating route above.
Check your own Lewisham home
Pre-scoped to a new build - enter your address for a plan specific to your property.
- Address
- Confirm
- Questions
- Plan
Let's look at your home
We use property data to pre-fill the boring bits - no long forms, and we never cold-call you.
Every home is different - your floor, aspect, EPC, heating type and conservation status all move the answer. Our free cooling checker pre-fills your home from public property data (EPC and UPRN records) and gives you a property-specific verdict on screen, straightaway: your overheating score, the right system, your real grant eligibility, the planning position and a net cost. No phone call, no waiting.
Check my Lewisham homeYou will see your full cooling plan instantly. If you would like us to email it to you, or to have a single vetted local installer contact you about a free survey, you choose that at the end - we only get in touch if you ask.
Every figure above - overheating scores, costs, grant rules and planning positions - follows our published methodology.
