Harrow · cooling guide
How to cool a new build in Harrow
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 Harrow 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.
Harrow records just 23 EPC-certified new builds, a rarity in a borough where half the certified stock is flats. Rare or not, their lightweight post-2000 construction stores less heat-buffering mass than older homes, so a warm spell shows up indoors quickly, and many already run direct-electric heating, which shapes the right cooling choice.
Struggling to keep your Harrow new build cool once the heat sets in? You are far from the first to notice - and although new builds are a smaller share of the borough (about 23 homes, 0%), they overheat about as reliably as any home type here. On our overheating scale a typical Harrow new build lands near 53 out of 100 - "moderate" - meaning the fan-and-open-window routine stops coping once real heat arrives. This page gives you the property-specific answer instead: which cooling system suits your home, the real cost, and whether planning permission comes into it - before any installer visit.
Why new builds in Harrow overheat
A new build has the reverse problem to an old one. The tight, heavily insulated shell that holds winter warmth in is just as good at keeping summer heat from escaping, so once sun through large windows and everyday internal heat build up indoors, there is no easy way out. A single-aspect flat, with openings on one side only, cannot draw a cross-draught to shift it. The issue is common enough now that Part O of the Building Regulations sets overheating limits for new homes directly. More insulation would only make things worse; what a home like this needs is mechanical cooling, and a unit that cools in summer and heats efficiently in winter fits a new build that frequently has no gas connection at all. For a typical Harrow new build, the median floor area is around 79 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 Harrow: by the numbers
0% of Harrow homes are new builds
23 of 101,608
79 m²
median floor area
£238
median annual heating cost
EPC band distribution
23 new builds in Harrow 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 | 15 | 65% |
| C | 8 | 35% |
| D | 0 | 0% |
| E | 0 | 0% |
| F | 0 | 0% |
| G | 0 | 0% |
When these homes were built
Construction era of 11 new builds in Harrow
- pre-1919 0%
- 1919-1944 0%
- 1945-1999 0%
- 2000+ 100%
| Era | Homes | Share |
|---|---|---|
| pre-1919 | 0 | 0% |
| 1919-1944 | 0 | 0% |
| 1945-1999 | 0 | 0% |
| 2000+ | 11 | 100% |
Real EPC and property-intelligence data via HomePortfolio, aggregated for new builds in Harrow. Data as of 11 July 2026.
What those figures mean for your cooling is the real story: the fabric here is efficient, which trims winter bills but is exactly what seals summer heat inside, and these are predominantly modern-build stock, tight enough that once heat gets in it has nowhere to go - which is why the overheating bites harder here than the weather alone suggests. On the environment: air quality (PM2.5) averages about 5.6 µg/m³ and daytime noise around 51 dB, in a borough that is part of inner London's built-up heat island, where the city holds onto daytime warmth well into a summer evening - which is what tells you if free night cooling is realistic. This is historic ground, too: a small share of these homes sit inside a conservation area and some sit close to a listed building - 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 Harrow
The fabric itself decides a lot before any system is fitted. Across Harrow, new builds cluster at EPC band B - 65% of them sit there. That is an efficient rating on paper, yet it works against winter heat loss, not summer heat gain, so it barely touches the overheating problem. The full spread reads 65% at band B, 35% at band C, so the picture is a range, not a single rating. 100% were built since 2000, so this is mostly lightweight, airtight modern construction - fabric that traps heat as effectively as it keeps it in.
Can you cool this home by opening a window at night?
Before you commit to a system, it is worth knowing whether this home can be cooled for free by opening windows overnight. At around 51 dB it is borderline - fine on a quiet street, harder on a through-road where you would trade heat for traffic noise all night. Local PM2.5 air quality, around 5.6 µg/m³, is not the limiting factor.
How the planning numbers look in Harrow
For the planning side, not one of the 23 new builds profiled in Harrow falls inside a conservation area, which removes the commonest reason an outdoor unit gets refused. In conservation areas such as Little Common Conservation Area, Stanmore and The Grimsdyke Estate and Brookshill Conservation A, expect the external siting to draw more scrutiny.
A worked cooling plan for a typical new build
Worked example · a typical new build in Harrow
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 Harrow 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 Harrow new build runs around 79 sqm and already costs about £238 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 Harrow at around 79 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 Harrow 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 Harrow
Harrow's genuinely low conservation-area coverage works in your favour on planning. A house fitting an outdoor condenser usually clears permitted development without extra paperwork, though flats do not get the same automatic route and typically still need the London Borough of Harrow's permission for a front or side unit. In Harrow, conservation areas such as Little Common Conservation Area, Stanmore, The Grimsdyke Estate and Brookshill Conservation A and West Drive are where this bites hardest. Worth flagging a 2025 change: because an air-to-air heat pump heats as well as cools, a house can now often fit one under permitted development within set limits, while a cooling-only air conditioner cannot and needs planning permission outright. So your choice of system, not just the property itself, moves the planning answer. 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. Harrow carries genuinely low conservation-area coverage (about 4% of EPC-certified homes), which makes an external unit a lower-friction proposition here than in a heritage-dense borough for most addresses - a real advantage, not a workaround. It is very doable - the London Borough of Harrow approves plenty of these - but it is a step, not a formality, and it is exactly the kind of thing worth checking against your specific address before you commit. Treat this as indicative guidance, not legal advice.
0%
of new builds in Harrow sit inside a conservation area
35%
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 Harrow really overheat?
Yes - measurably. Our overheating model scores a typical Harrow new build around 53 out of 100 ("moderate"). Harrow holds around 23 homes of this type - 0% of the borough's certified stock - and the combination of roof heat gain, low thermal mass in older stock and the local heat-island effect means many of these homes are uncomfortable from late June onward, whatever the thermostat says.
What is the best cooling system for a new build in Harrow?
For most Harrow new builds the strongest option is an air-to-air heat pump, which cools in summer and heats in winter from the same near-silent, room-by-room unit. If you would rather keep your existing boiler and only add cooling, a single-split air conditioning unit is the usual private-pay choice. Our checker leans toward air-to-air heat pump for a typical home of this type, but your floor, aspect and heating decision move the answer - which is why it is worth checking your own address. These new builds average around 79 sqm. A typical Harrow new build already costs around £238 a year to heat.
Can I get the £2,500 grant for cooling my Harrow 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 Harrow new build already costs around £238 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 Harrow?
More often than for a house, yes. The permitted-development rights that cover a house fitting an outdoor unit do not extend to flats the same way, and with conservation-area coverage common across Harrow, especially around Little Common Conservation Area, Stanmore, a front or side condenser generally needs council consent. It is very achievable - a step to plan for rather than a given - and our checker shows the likely position for your exact address.
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 Harrow new build currently costs around £238 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 Harrow 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, cooling a new-build is not banned. The mix-up comes from Building Regs Part O (which makes new homes limit overheating by design) and from lease or managing-agent rules on external units. Neither outlaws air conditioning; they just mean an outdoor condenser may need permission. The checker shows where you stand for your Harrow address.
What is Part O and does my new-build flat need to comply?
Part O is the Building Regs standard limiting overheating in new homes, judged by the CIBSE TM59 method. It governs how new dwellings are designed and built, so it is the developer's responsibility, not a retrofit. If your new-build overheats anyway - common in airtight flats - active cooling is a separate, unregulated option open to you.
Do I need my management company's permission to fit air conditioning in a new-build flat?
Frequently, yes. A new-build flat usually has a lease and a managing agent whose permission is needed for external changes such as a condenser. Request the process in writing early - it takes time - and keep it distinct from planning permission. The checker handles 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 Harrow, that conservation-area exclusion bites hardest around places like Little Common Conservation Area, Stanmore.
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 Harrow new build already costs around £238 a year to heat, that saving is only available on the replace-your-heating route above.
Check your own Harrow 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 Harrow 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.
