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Home energy efficiency is about creating a home that stays warm, comfortable, and affordable – because the building and the technology inside it work together to minimise waste.

The physical structure and envelope of a building,  its walls, roof, floors, windows and doors. In the context of home energy efficiency, 'fabric' refers to how well these elements retain heat and resist heat loss. Improving the fabric (for example through insulation, draught- proofing or upgraded glazing) is often the starting point for reducing a home's energy demand.

In the context of home energy efficiency, energy refers to the total amount of gas or electricity a property uses over time. It is measured in kilowatt-hours (kWh) and is what households pay for on their energy bills.

Energy that is generated or stored on the property itself, typically via solar panels and battery storage and consumed directly without being drawn from the grid. "Behind the meter" generation reduces a household's exposure to wholesale energy prices and supplier volatility, because the energy never passes through the billing relationship with a supplier. It is distinct from energy exported back to the grid, for which households can receive payment through schemes such as the Smart Export Guarantee.

Neither term has a standardised definition in UK property valuation practice as individual valuers are not trained to apply them directly, and mortgage valuations are still primarily based on local comparable transaction data. Where a green premium is visible, it tends to emerge at a market aggregate level across large datasets rather than in individual property assessments. The practical implication: a client who has invested heavily in efficiency upgrades may not see those improvements reflected in their formal valuation, even if the broader market trend supports a price uplift.

A lending approach where a lender offers a borrower increased borrowing capacity, or applies a more favourable affordability assessment, on the basis that the property's energy efficiency will reduce running costs and therefore free up more income to service the mortgage. Not yet universal across the market, but a growing number of lenders have introduced enhanced affordability propositions for higher-rated EPC properties. This will be covered in more detail later in the programme.

Unlike fluvial (river) or tidal flooding, surface water flooding doesn't show up on standard flood risk maps. Properties can be flagged as "low risk" on a typical search and still be vulnerable. Separate surface water flood risk maps are available online, including through the Environment Agency, and give a more complete picture of a property's exposure.

Flood Re works by allowing insurers to pass the flood portion of a home insurance policy to the scheme at a price set by council tax band, which is what keeps premiums affordable for high-risk households. Two key limitations not always well understood are the scheme only applies to properties built before 1 January 2009; and when it closes in 2039, the intention is that the market will have moved to "risk-reflective pricing", meaning premiums for flood-risk properties could rise significantly.

The fund isn't accessed directly from government. It's administered through the homeowner's insurer as part of the claims settlement process. That means it's only available after a flood event, not as a preventive measure, and only through insurers who have signed up to the scheme. Worth flagging to landlord clients separately, as they are ineligible for Flood Re and would need to find alternative routes.

The UK Government's flagship programme to upgrade the nation's housing stock, combining public funding with private finance to support large-scale energy efficiency improvements at scale. The Plan commits to upgrading up to five million homes by 2030, and establishing a "universal offer", the idea that any household should be able to access a clear set of finance and support options to upgrade their home, regardless of tenure or income. GFI's role is specifically around scaling the private finance side of that offer, through the Strategic Partnership. 

New Future Homes and Buildings Standards will require new homes to use low-carbon heating and achieve higher energy efficiency standards. The Standard applies to England from 2028. Wales is introducing its own equivalent in 2026, while Scotland’s New Build Heat Standard has been in force since April 2024. For brokers advising on new-build purchases, there is currently a transitional period where some homes will meet interim standards, rather than the final Future Homes Standard.

The HEM is a new government calculation methodology designed to assess the energy performance of homes across the UK. It is designed to replace the current SAP methodology.One of the key issues with SAP is that it can undervalue the performance of heat pumps because it is primarily a cost-based metric rather than an efficiency- or carbon-based measure, and electricity has typically been more expensive than gas. HEM is designed to give a more accurate reflection of performance, which could affect EPC ratings and eligibility for green home finance products.

MEES (Minimum Energy Efficiency Standards) are UK regulations that set a minimum energy efficiency requirement for privately rented properties. In England and Wales, landlords must currently ensure properties meet at least EPC E before they can be legally let. Proposed reforms would tighten the standard to EPC C by October 1st 2030. There are exemptions, for example where the cost of upgrades exceeds a defined cap, but the direction of travel is clear. For broker clients with buy-to-let portfolios, this is potentially a significant financial planning issue.

Spark Gap is the price difference between electricity and natural gas. The gap exists partly because electricity bills carry a disproportionate share of environmental levies (such as those funding renewable energy subsidies), while gas bills carry fewer. This is a policy choice rather than a reflection of the underlying energy cost, which is why rebalancing is possible. Until it narrows, the financial case for heat pumps is strongest in well-insulated homes where the efficiency gains offset the higher electricity cost per unit.

Clean Power 2030 is the UK Government's mission to generate all of the country's electricity from clean sources, wind, solar and nuclear by 2030 and ending reliance on gas-fired power stations for electricity generation. The practical significance for home heating is as the grid gets cleaner, a heat pump's carbon footprint falls automatically, without any changes to the home itself. A heat pump running on today's grid is already significantly lower carbon than a gas boiler; and by 2030, on a clean grid, it would be close to zero. This is an important long-term framing point for clients weighing up the case for switching.

A voluntary industry framework launched by the Green Finance Institute and the Loan Market Association in September 2020 to provide a consistent definition of green home financing products. They are built around four core components: use of proceeds, process of evaluation and selection, management of proceeds, and reporting.

In the context of home energy efficiency, energy refers to the total amount of gas or electricity a property uses over time. It is measured in kilowatt-hours (kWh) and is what households pay for on their energy bills.

The Standard Assessment Procedure (SAP) is the methodology used to calculate an EPC rating, based on modelled energy use and running costs rather than actual household behaviour.

Neither term has a standardised definition in UK property valuation practice as individual valuers are not trained to apply them directly, and mortgage valuations are still primarily based on local comparable transaction data. Where a green premium is visible, it tends to emerge at a market aggregate level across large datasets rather than in individual property assessments. The practical implication: a client who has invested heavily in efficiency upgrades may not see those improvements reflected in their formal valuation, even if the broader market trend supports a price uplift.

A lending approach where a lender offers a borrower increased borrowing capacity, or applies a more favourable affordability assessment, on the basis that the property's energy efficiency will reduce running costs and therefore free up more income to service the mortgage. Not yet universal across the market, but a growing number of lenders have introduced enhanced affordability propositions for higher-rated EPC properties. This will be covered in more detail later in the programme.

See FCA Handbook definition / Anti-greenwashing rule guidance .

Technologies designed to reduce environmental impact by using energy and resources more efficiently, lowering emissions, or avoiding pollution.

How well a building retains heat, based on elements like insulation, windows, doors, floors, and draught‑proofing.

The UK Government's flagship programme to upgrade the nation's housing stock, combining public funding with private finance to support large-scale energy efficiency improvements at scale. The Plan commits to upgrading up to five million homes by 2030, and establishing a "universal offer", the idea that any household should be able to access a clear set of finance and support options to upgrade their home, regardless of tenure or income. GFI's role is specifically around scaling the private finance side of that offer, through the Strategic Partnership. 

New Future Homes and Buildings Standards will require new homes to use low-carbon heating and achieve higher energy efficiency standards. The Standard applies to England from 2028. Wales is introducing its own equivalent in 2026, while Scotland’s New Build Heat Standard has been in force since April 2024. For brokers advising on new-build purchases, there is currently a transitional period where some homes will meet interim standards, rather than the final Future Homes Standard.

The HEM is a new government calculation methodology designed to assess the energy performance of homes across the UK. It is designed to replace the current SAP methodology.One of the key issues with SAP is that it can undervalue the performance of heat pumps because it is primarily a cost-based metric rather than an efficiency- or carbon-based measure, and electricity has typically been more expensive than gas. HEM is designed to give a more accurate reflection of performance, which could affect EPC ratings and eligibility for green home finance products.

MEES (Minimum Energy Efficiency Standards) are UK regulations that set a minimum energy efficiency requirement for privately rented properties. In England and Wales, landlords must currently ensure properties meet at least EPC E before they can be legally let. Proposed reforms would tighten the standard to EPC C by October 1st 2030. There are exemptions, for example where the cost of upgrades exceeds a defined cap, but the direction of travel is clear. For broker clients with buy-to-let portfolios, this is potentially a significant financial planning issue.

Spark Gap is the price difference between electricity and natural gas. The gap exists partly because electricity bills carry a disproportionate share of environmental levies (such as those funding renewable energy subsidies), while gas bills carry fewer. This is a policy choice rather than a reflection of the underlying energy cost, which is why rebalancing is possible. Until it narrows, the financial case for heat pumps is strongest in well-insulated homes where the efficiency gains offset the higher electricity cost per unit.

Clean Power 2030 is the UK Government's mission to generate all of the country's electricity from clean sources, wind, solar and nuclear by 2030 and ending reliance on gas-fired power stations for electricity generation. The practical significance for home heating is as the grid gets cleaner, a heat pump's carbon footprint falls automatically, without any changes to the home itself. A heat pump running on today's grid is already significantly lower carbon than a gas boiler; and by 2030, on a clean grid, it would be close to zero. This is an important long-term framing point for clients weighing up the case for switching.

Sustainable finance covers green mortgages for homes that already meet sustainability criteria at the point the loan is taken out. The home is already 'green', and the mortgage recognises that - typically through rate discounts, enhanced borrowing, or specialist features.

Finance for low‑carbon and energy‑efficient home improvements that is not secured against the property. It is usually provided in two main forms:

Finance whose payment obligation is attached to the property rather than the person, so it stays with the home when the home is sold. Based on the US PACE (Property Assessed Clean Energy) model already deployed internationally.Three features define it. First, it runs with the land, helping overcome the payback‑period barrier, where financing terms can outlast expected occupancy. Second, it is non‑accelerating, meaning that missed payments do not trigger a demand to repay the whole outstanding balance early, which can make for a lower‑risk structure for the consumer. Third, it is not yet live in the UK, as it would require legislative change in England and Wales, and likely primary legislation in Scotland.

An arrangement where a service company decarbonises the home and recoups its outlay through an ongoing service or subscription fee. It is a performance‑based contract, typically long‑term, which removes the upfront capital cost entirely, making it well suited to debt‑averse or lower‑income households. A similar concept to the older 'pay as you save' principle where the customer pays for the outcome over time, rather than facing the whole bill at once. In future, it could be paired with property linked finance, so the home can be sold with the arrangement already in place.

A grant available in England, aimed primarily at lower‑income households, broadly those with a household income below around £36,000, and a low‑rated EPC. It can fund a range of energy efficiency measures. Less likely to come up with mortgaged clients, by virtue of the income threshold, but worth knowing about, and worth flagging that local authority programmes vary widely by area, so clients can use the gov.uk postcode‑based 'find your local council' tool to research what is available in their area.

A suitably qualified professional, in practice usually MCS‑certified, who assesses a property and recommends a schedule of retrofit works. Designing the retrofit project sits with the retrofit assessor, not the mortgage intermediary; the intermediary's role is to liaise with the assessor to understand the total cost breakdown and grant eligibility, so the residual financing need (and the impact of any lender incentives) can be identified accurately.

The total cost of borrowing, calculated as the total amount payable minus the original sum borrowed. Spreading borrowing over a longer term lowers the monthly cost but allows the cost of credit to stack up considerably. A practical implication for retrofit: if a measure is financed over a term longer than its expected lifespan, the customer risks paying for technology well past its natural life, storing up a future replacement cost on top.

The FCA's Consumer Duty, introduced by Policy Statement PS22/9 and in force since 31 July 2023, requires all FCA-authorised firms to act to deliver good outcomes for retail customers (Principle 12, PRIN 2A.1.1R). Unlike earlier rules-based regulation, it is outcomes-focused: firms must demonstrate that their processes, products and communications genuinely produce good results for customers, not simply that they have followed prescribed steps. It applies across all regulated financial products and services, including mortgages, and was extended to closed products on 31 July 2024.

A package of FCA rules and guidance published on 28 November 2023 (Policy Statement PS23/16) designed to improve the quality and consistency of sustainability-related information in financial services. The package includes the Anti-Greenwashing Rule, which applies to all FCA-authorised firms, and a set of product labels, naming restrictions and disclosure requirements that apply specifically to investment products. In the mortgage market, the relevant element is the Anti-Greenwashing Rule; the investment-focused labels do not apply to mortgage products.

Stands for Environmental, Social and Governance — a framework used to assess the sustainability and ethical credentials of a company or investment. In financial services, ESG is primarily associated with investment products and fund management. In the mortgage market, green mortgages are almost always assessed against the property's energy performance, not the lender's ESG credentials. A green mortgage is on a sustainable course (the property the loan is secured on), not necessarily from a sustainable source (the lender's wider activities).

A real estate interest granted above the roof of a property, governed by land and property law. In the context of solar panels, some companies offer installation at low or no upfront cost in exchange for an airspace lease, under which the company owns the panels and retains income from solar energy exported to the grid. An airspace lease is distinct from a financial lease (such as hire purchase) over the panels: a financial lease is governed by consumer credit rules and does not affect the property's title. An airspace lease can complicate title and affect the ability to sell, remortgage, or take a further advance.

The UK Government-endorsed quality scheme for work a consumer chooses to have carried out in or around their home. Established under a Master Licence Agreement and expanded following the Each Home Counts review (2016), TrustMark covers a broad range of trades including all those involved in energy efficiency and retrofit. Registered businesses must demonstrate technical competence, work to relevant standards including PAS 2035 and PAS 2030, and provide minimum two-year product and workmanship guarantees, rising to 25 years for certain insulation measures. TrustMark acts as the body of last resort for unresolved disputes. Registration is verifiable via the publicly searchable TrustMark register.

An independent review chaired by Peter Bonfield, published in December 2016, commissioned by the UK Government. The review found that the energy efficiency installation market suffered from serious fragmentation — different schemes, different quality standards, different certification bodies, and no single point of accountability. It recommended an all-encompassing quality mark for consumers, leading to the expansion of TrustMark's remit to cover all energy efficiency and retrofit trades. Often referred to as the Bonfield review.

The UK quality mark for small-scale renewable and low-carbon energy systems installed in homes and small businesses. MCS certifies along two axes: the products (solar PV, solar thermal, heat pumps, biomass, battery storage) and the installers who fit them. Installers must also belong to a Chartered Trading Standards Institute-approved consumer code (RECC or HIES). MCS is the only certification scheme accepted by governments for funding schemes including the Boiler Upgrade Scheme, Warm Homes Social Housing Fund and Local Grant, and the Clean Heat Market Mechanism. It is therefore typically a precondition for both grant funding and green lending. MCS is currently rolling out a redeveloped scheme with strengthened consumer protection, fully in place by spring 2027.

RECC (Renewable Energy Consumer Code) and HIES (Home Insulation and Energy Systems consumer code) are the two main Chartered Trading Standards Institute-approved consumer codes in the renewable energy and energy efficiency installation market. MCS-certified installers must belong to one of these codes as a condition of certification. The codes set conduct standards, dispute resolution processes, and customer redress routes — providing a layered model of protection alongside MCS's technical standards: technical quality through MCS, conduct and recourse through the consumer code.

Publicly Available Specification 2035, the UK standard for whole-house retrofit published by BSI (most recently updated 2023). PAS 2035 introduces whole-house thinking: properties are assessed as integrated systems, measures are planned and sequenced together, and the process is validated at completion. It structures retrofit work around six distinct roles — Retrofit Advisor, Retrofit Assessor, Retrofit Coordinator, Retrofit Designer, Retrofit Installer, and Retrofit Evaluator — with clear separation between assessment, design, installation and sign-off. PAS 2035 is mandatory for all publicly-funded retrofit work. PAS 2030 is the companion installation standard.

A qualified professional responsible for project-managing the whole retrofit journey under PAS 2035. Holds a Level 5 diploma in retrofit coordination and risk management and must be TrustMark-registered. Responsible for risk assessment, design review, project oversight, and final sign-off. The Retrofit Coordinator role did not exist in the pre-PAS world; its introduction addressed the absence of anyone thinking about a building as a whole system and managing the interaction between measures.

A Retrofit Assessor and a Domestic Energy Assessor (DEA) are different roles with different qualifications and outputs. A DEA produces an EPC using standardised SAP or RdSAP methodology - a regulatory rating designed for comparability. A Retrofit Assessor produces a detailed property report under PAS 2035, assessing energy performance, building condition, ventilation, occupancy patterns, and heritage or planning sensitivities. The Retrofit Assessor's report is the basis for project decisions; the DEA's EPC is a regulatory rating. They are often different people holding different qualifications.

A consumer protection mechanism providing financial assurance that remedial works will be carried out if an installer fails, goes out of business, or refuses to rectify defective work. Required under TrustMark for certain measure types, including 25-year guarantees for cavity wall, solid wall and certain insulation measures. Distinct from a product warranty (which covers defects in the product) and a workmanship guarantee (which covers installation quality).

A new government body announced in the Warm Homes Plan (January 2026), to be formed by bringing together functions from Salix Finance, parts of Ofgem, and relevant teams from the Department for Energy Security and Net Zero. The Agency is intended to be the front door for impartial home upgrade advice and is expected to begin delivering from 2027. It will act as a central coordination point connecting households to appropriate measures, funding, and finance.

A standardised document provided to mortgage customers as part of the advice process, setting out the key features of a mortgage product in a format designed for comparability. Produced by the lender and provided at the point of recommendation. In a green mortgage context, where an adviser produces their own contextual analysis alongside the lender's ESIS - for example, illustrating the enhanced affordability differential between properties of different EPC ratings - this helps the customer understand the full range of options available to them.

A green mortgage product has a product code, a rate, and specific criteria — it will typically appear in mortgage sourcing systems. A green mortgage proposition is a broader set of features or benefits a lender offers - for example, cashback available to all borrowers, enhanced affordability criteria applied across a product range, or retrofit funding contributions offered post-completion. Proposition-level features are often not attached to a product code and may not appear in product searches, meaning they need to be known and maintained separately as part of the adviser's market knowledge.

A suitably qualified professional, in practice usually MCS‑certified, who assesses a property and recommends a schedule of retrofit works. Designing the retrofit project sits with the retrofit assessor, not the mortgage intermediary; the intermediary's role is to liaise with the assessor to understand the total cost breakdown and grant eligibility, so the residual financing need (and the impact of any lender incentives) can be identified accurately.

A term describing a building that generates more clean energy than it consumes over a given period, resulting in a net negative carbon footprint. Distinct from carbon neutral (zero net emissions). In the context of a whole-house retrofit, this is typically achieved by combining solar PV, battery storage, and a heat pump to reduce consumption while increasing generation. Modelled figures are based on standard assumptions and actual performance will vary with occupancy patterns and energy use.