How to improve your EPC rating (London homes, 2026)

The quickest way to lift a London home's EPC rating is to tackle the fabric first — loft and wall insulation and draught-proofing — then glazing, then the heating system, because that's the order of best return for the money spent. It matters most for landlords: the government has proposed an EPC C minimum for newly let private rentals by 2028, with all existing tenancies to follow. This guide ranks the improvements by cost-per-point, draws a clear line between what a builder does and what needs a specialist, and lists the grants available in 2026.

Why your EPC matters in 2026

An EPC rates a home from A to G on energy efficiency, and three things now hang on it. First, the proposed Minimum Energy Efficiency Standard would require an EPC of C or better to let a property in the private rented sector — phased in from 2028 on the current proposals. Second, a growing number of mortgage lenders price "green" mortgages off the EPC band. Third, energy bills track the rating directly. For a landlord, the 2028 direction of travel is the pressing reason to act now rather than in a rush later; for an owner-occupier, it's mostly about bills and comfort.

The quickest wins, ranked by cost-per-point

Spend in roughly this order — the early items return the most EPC points per pound:

• Loft insulation to 300 mm of mineral wool: about £400–£900 for an average three-bed, and one of the highest-value moves on the certificate.
• Draught-proofing around doors, windows, floorboards and the loft hatch: a few hundred pounds, and it lifts both the score and day-to-day comfort.
• Cavity wall insulation, if you have cavity walls: roughly £600–£1,500, and grant-eligible for many households.
• Insulating solid walls — the harder London case — covered below.

These fabric measures come first for a reason: the assessment rewards a well-sealed, well-insulated shell more than it rewards a new boiler, and they cut the heat demand that everything else then has to meet.

The London problem: solid walls and conservation areas

Much of London's housing is solid-wall Victorian and Edwardian stock with no cavity to fill, and that changes the job. Insulating a solid wall means either internal insulated plasterboard — which eats into each room, since you give up 45–55 mm off every insulated wall and then have to re-skim, re-run sockets and re-fit skirtings — or external insulation, which is rarely allowed on a street-facing elevation in a conservation area. On a whole-house renovation it's the efficient time to do internal wall insulation, because the walls are already being opened up.

Conservation-area and listed homes also constrain glazing. You often can't fit standard double glazing to a period front elevation, so the route is high-quality secondary glazing behind the existing sashes — around £300–£700 per window — which improves both the rating and the draughts without touching the protected exterior.

Glazing: the middle-cost win

After the fabric, glazing is the next lever. Replacing single glazing with modern double glazing lifts the score where the property allows it; new units must meet the Part L whole-unit U-value of 1.6 W/m²K. Where the building is protected, secondary glazing is the conservation-friendly alternative and is genuinely effective on draughty sashes. Triple glazing helps at the margins but rarely pays back on EPC points alone in a London terrace — spend the budget on walls and the loft first.

Heating: boiler vs heat pump, and the EPC effect

The heating system is the last big lever, and it's where the numbers need care. Replacing an old, inefficient boiler with a modern condensing one improves the score and the bills. Moving from a gas boiler to an air-source heat pump can add somewhere in the region of 5–15 EPC points, but a heat pump only performs well in a home that's already well insulated — which is exactly why the fabric work comes first. Fitting an air-source heat pump as a retrofit, with the radiators upsized to suit it, typically costs £8,000–£16,000 in London, and the Boiler Upgrade Scheme grant currently takes £7,500 off an air-source or ground-source installation in England.

A note on the work itself: gas and heat-pump installation is specialist, regulated work. PrimeCraft Surface Solutions handles the fabric side — insulation, glazing, plastering and making good — and coordinates the heating element with the right registered installer.

What a builder does vs what needs a specialist

Worth being clear on the split, because no single trade covers all of it:

• Builder's scope: loft and solid-wall insulation, draught-proofing, glazing replacement and secondary glazing, plastering and the making-good that every insulation job creates.
• Specialist scope: the heat pump or boiler (a registered heating engineer), mechanical ventilation with heat recovery where airtightness is pushed hard (an MVHR installer), and the EPC assessment itself (an accredited domestic energy assessor).

A good renovation builder coordinates the lot so the measures are sequenced sensibly — insulation before the heating is sized, ventilation considered once the shell is tightened — rather than bolted on one at a time.

A worked example: D to C

A common London target is moving a three-bed terrace from a D to a C. A realistic package: top up the loft to 300 mm, draught-proof throughout, insulate the solid walls internally on the coldest elevations, add secondary glazing to the worst sashes, and fit modern heating controls. The fabric measures do most of the lifting; the controls and any heating upgrade finish it. Costs vary widely with how much wall insulation is needed, so the only honest number comes from a survey — but the order above is what gets you there for the least outlay.

Grants available in 2026

Three schemes are worth checking before you pay full price:

• The Boiler Upgrade Scheme: £7,500 toward an air-source or ground-source heat pump in England.
• ECO4: support for insulation and heating measures for eligible households, running toward its current end date — confirm current eligibility and timing.
• The Great British Insulation Scheme: insulation support across a range of council-tax bands and EPC ratings.

Eligibility and end dates shift, so verify the current position on each before relying on it.

Closing CTA

PrimeCraft Surface Solutions handles the fabric upgrades that move an EPC — insulation, glazing, draught-proofing and the making-good — and coordinates the heating side with a registered installer, across London and the surrounding Home Counties. Whether you're a landlord planning for 2028 or an owner cutting bills, book a free site visit and we'll tell you which measures give you the most points for the money.