What is the fabric-first approach?

Fabric-first means improving the building fabric (walls, roof, floor, windows, draughts) before upgrading the heating system. If you insulate first, you reduce the amount of heat your home loses — which means the heat pump you install can be smaller and cheaper, and will run more efficiently. Skipping insulation and fitting a large heat pump to compensate is less efficient and more expensive.

How much does a whole house retrofit cost in 2026?

A complete East Anglia retrofit — insulation, heat pump, solar panels, battery storage, underfloor heating, MVHR, and EV charger — typically costs £35,000–£65,000 depending on the property size and starting point. Available grants and incentives (£7,500 BUS grant, Warm Homes Local Grant up to £15,000 for eligible households, 0% VAT on energy measures) can reduce this significantly. Most customers phase the work over 2–5 years, spreading the cost.

What is the PAS 2035 standard?

PAS 2035 is the British Standards Institution's framework for whole house retrofit. It requires a qualified Retrofit Assessor to assess the property and produce a Whole House Plan before any work starts. A Retrofit Coordinator then oversees the work to ensure it is carried out safely and in the right order. PAS 2035 compliance is required for government-funded retrofit schemes (ECO4, Warm Homes Plan) and protects homeowners from costly mistakes.

How long does a whole house retrofit take?

A complete retrofit is usually phased over 1–3 years to manage disruption and cost. Individual measures take from 1 day (EV charger) to 5 days (heat pump installation) to 1–2 weeks (external wall insulation on a semi-detached). Most of our customers start with the measures that provide the quickest return — solar panels and a battery — then phase in the heat pump and insulation as budgets allow.

Can I get free whole house retrofit in East Anglia?

Fully-funded retrofits are available for eligible households through the Warm Homes Local Grant. In 2026, households in East Anglia earning under £36,000/year (or on means-tested benefits) with a property rated EPC D–G can receive up to £15,000 for energy efficiency measures (insulation, windows) and up to £15,000 for low-carbon heating — potentially £30,000 of free work. Contact us or your local council to check eligibility.

Do I need planning permission for a whole house retrofit?

Most whole house retrofit measures are permitted development: solar panels, battery storage, external wall insulation, heat pumps (under the 42 dB limit), MVHR, and EV chargers typically do not require planning permission for standard residential properties. Listed buildings and conservation area properties have additional requirements — we assess this during your free survey.

What EPC rating will my home be after a whole house retrofit?

A full retrofit on a typical East Anglia 3-bed semi (starting at EPC D or E) can achieve EPC B or high C. The measures with the biggest EPC impact are: solid wall insulation (+15–25 SAP points), loft insulation (+8–12 points), air source heat pump (replaces inefficient boiler, +10–20 points), and solar panels (+3–8 points depending on system size).

Retrofit Guide | Updated March 2026 | 9 min read

Whole House Retrofit: The East Anglia Guide [2026]

Q: What is whole house retrofit?

Whole house retrofit is a coordinated programme of energy efficiency improvements to an existing home, carried out together or in planned phases. It typically includes: improving the building fabric (insulation, draught-proofing, windows), upgrading the heating system (usually to a heat pump), improving ventilation (MVHR), and adding renewable generation (solar panels, battery storage). The goal is a highly efficient, low-carbon home with significantly reduced energy bills.

A whole house retrofit joins every energy improvement into a coordinated plan — insulation, heat pump, solar, battery, MVHR, underfloor heating — so each measure works harder because of the others. This is the guide to doing it right.

At a Glance

£35k–£65k

Typical total cost

Up to £30k

Max available grants

E/F → B/C

EPC improvement

60–80%

Energy bill reduction

70–90%

Carbon reduction

Yes, 1–5 years

Phasing possible

What Is Whole House Retrofit?

Whole house retrofit means treating your home as a system. Rather than replacing your boiler when it breaks, or adding solar panels independently, you plan all the improvements together — so each measure is sized correctly for the improved home, and you avoid costly mistakes like fitting an oversized heat pump to an under-insulated house.

In East Anglia, most homes were built before modern energy efficiency standards. Victorian and Edwardian terraces in Cambridge and Norwich, post-war semis in Peterborough and Ipswich, 1970s bungalows in Norfolk villages, and agricultural cottages across Suffolk all share the same challenge: they leak heat, rely on expensive fossil fuels, and have untapped potential for dramatic improvement.

The Fabric-First Principle

The single most important principle in whole house retrofit is insulate before you upgrade the heating. Every unit of heat demand you eliminate through insulation reduces the size of heat pump you need — and a smaller, better-matched heat pump is more efficient, quieter, and cheaper.

10–12 kW heat pump needed

Without insulation first

6–8 kW heat pump needed

With loft + wall insulation

4–6 kW heat pump needed

Full fabric improvement

Based on a typical 3-bed East Anglia semi-detached. Smaller pump = lower upfront cost, higher COP efficiency, lower running costs.

The Retrofit Measures

External Wall Insulation

1–2 weeks

Up to 70% heat loss reduction

Warm Homes Local Grant

Air Source Heat Pump

3–5 days

COP 3.5–4.5 (350–450% efficient)

£7,500 BUS grant

MVHR Ventilation

3–5 days

85–92% heat recovery from exhaust air

0% VAT

Underfloor Heating

2–4 days per floor

Ideal for heat pump — 35°C operation

0% VAT

Solar Panels

1–2 days

Up to 80% self-consumption with storage

0% VAT until March 2027

Battery Storage

1 day

Evening out solar generation

0% VAT

EV Charger

4–6 hours

Near-free charging from solar

EV chargepoint grant (£350)

The Retrofit Process: Step by Step

Whole House Assessment

A qualified Retrofit Assessor visits your property to calculate heat loss, assess current insulation and ventilation, review the heating system, and identify the most cost-effective improvements. This produces a Whole House Plan — the roadmap for your retrofit.

Improve the Building Fabric

Insulation is addressed first. For older East Anglia properties this typically means external wall insulation (solid-walled homes), loft insulation, floor insulation, and draught-proofing. This reduces heat demand so the heating system can be smaller.

Upgrade Ventilation

As insulation makes the building more airtight, controlled ventilation becomes essential. MVHR (Mechanical Ventilation with Heat Recovery) provides fresh air while retaining 85–92% of the heat that would otherwise be lost through ventilation.

Replace the Heating System

With insulation in place, an air source heat pump can be correctly sized. The £7,500 BUS grant applies. Underfloor heating or upgraded radiators distribute heat efficiently at the low flow temperatures heat pumps deliver best.

Add Renewable Generation

Solar panels generate free electricity to power the heat pump, EV charger, and home appliances. Battery storage captures surplus generation for use overnight or during cloudy days.

Complete Smart Controls

Smart energy management — heat pump controllers, battery management systems, smart EV chargers — ties the system together and maximises self-consumption. Octopus Agile or Flux tariffs can add further savings.

Costs and Phasing Options

Measure	Typical Cost	Grant Available	Net Cost
External Wall Insulation	£8,000–£20,000	Warm Homes Local (up to £15k)	£0–£5,000+
Air Source Heat Pump	£8,000–£13,000	£7,500 BUS grant	£500–£5,500
Underfloor Heating	£3,000–£8,000	0% VAT	£2,800–£7,500
MVHR System	£5,000–£10,000	0% VAT	£4,700–£9,300
Solar Panels (4kW)	£5,500–£7,500	0% VAT	£5,200–£7,100
Battery Storage (9.5kWh)	£3,500–£5,500	0% VAT	£3,300–£5,200
EV Charger	£700–£1,200	OZEV grant £350	£350–£850

Prices for typical 3-bed semi in East Anglia, 2026. Warm Homes Local Grant eligibility depends on income (under £36,000/year) and EPC rating (D–G).

Phasing Your Retrofit

You do not need to do everything at once. A typical phased approach for an East Anglia home:

Phase 1 — Quick wins

£9,000–£13,000

Solar panels + battery storage

Highest immediate return. Generates bill savings from day one, funds future phases. Zero disruption to daily life.

Phase 2 — Fabric

£8,000–£20,000 (grants available)

External wall insulation + loft insulation + draught-proofing

Reduces heat demand before upgrading heating. Makes the heat pump cheaper and more efficient.

Phase 3 — Heating

Net £3,000–£10,000 after grants

Air source heat pump + underfloor heating or radiator upgrades

Now properly sized for the insulated home. £7,500 BUS grant applies.

Phase 4 — Ventilation and transport

£5,700–£11,200

MVHR + EV charger

Completes the whole-house system. EV charger enables near-free motoring from solar.

Available Grants in East Anglia (2026)

Warm Homes Local Grant

Up to £30,000

Income under £36,000/year or means-tested benefits, EPC D–G

Applications open now

Boiler Upgrade Scheme

£7,500

Any homeowner replacing fossil fuel heating with heat pump

Running to at least March 2028

0% VAT — Energy Measures

Saves £500–£5,000

All residential energy-saving materials

Until at least March 2027

Smart Export Guarantee

Up to 20p/kWh exported

Any solar panel system

Ongoing, no end date

OZEV EV Chargepoint Grant

£350

Homeowners with off-road parking

Running until March 2026

ECO4 Scheme

Variable

Low-income households on benefits

Transitioning to new scheme March 2026

Why Green Hat Renewables?

Unlike single-technology installers, we install every measure in a whole house retrofit — solar panels, battery storage, heat pumps, underfloor heating, MVHR, insulation, and EV chargers. This means one point of contact, one coordinated installation programme, and no conflicts between contractors.

We carry out free whole-home energy surveys across Cambridgeshire, Norfolk, and Suffolk. Our surveys assess your current EPC rating, calculate heat loss, identify the optimal improvement sequence, and provide a clear whole-house plan with costs and available grants.

Book a Free Whole-Home Survey Whole House Retrofit Service

Frequently Asked Questions

Heat Pump Installation Insulation Solar Panels Battery Storage MVHR EPC Guide Warm Homes Plan BUS Grant Guide

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