Conversion mortgage

If you’re inspired to design and convert a non-residential building into an energy-efficient home, our award-winning conversion mortgage has been designed with you in mind.

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Your home may be repossessed if you do not keep up repayments on your mortgage


Trusted since 1981

Pioneers in providing energy-efficient conversion mortgages


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Experts in specialist mortgages

We’ve lent to over 4,500 unique properties and projects


Flexible decision making

We take a case-by-case approach to every project


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Discounts for energy efficiency

Our C-Change discounts reward you for creating an energy-efficient home


Flexible stage payments

We offer flexible stage payments during the conversion


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Open to the unusual

We’ll consider a wide range of non-standard construction types

We are experts in providing mortgages for conversions of derelict and non-residential buildings into homes that meet specific energy ratings when converted.

We don’t have a ‘tick box’ approach to assessing projects – in many instances, we’ll welcome projects that standard lenders may not accept.

What buildings qualify?

At Ecology, we are not put off by non-standard projects; if we can see your conversion will result in a sustainable energy efficient home and, where possible, use locally sourced materials, we’ll consider lending.

We’ll look at:

  • Derelict barns, cow sheds
  • Redundant garages
  • Windmills
  • Water towers
  • Churches and chapels
  • Oast Houses
  • Redundant pubs (public houses).

Our mortgages are available throughout the UK (England, Scotland, Wales and Northern Ireland).

How does the mortgage work?

We’ll lend money to support the purchase of the plot and the costs of your conversion project if you are aiming for an energy performance of anywhere from an EPC B (SAP rating 85+) to EnerPHit standard.

Outline planning permission, including Class Q, or listed building consent needs to be in place to apply for the mortgage, and detailed planning needs to be granted before any mortgage funds are released.

We’ll release up to 80% of the plot purchase price or value of the property if you already own the land and subsequently, the money required to cover the build costs. As your conversion progresses, staged payments of up to 80% of your increased property value will be released in arrears – this will help you keep tabs on your budget and planning.

This type of mortgage may be suitable if you are able to make a 20% deposit for your plot and further funds to commence the early stages of the conversion. We normally recommend you begin your project with 20% of your total build budget.

Once your conversion is complete and you achieve the appropriate energy certificate, we can lower your interest rate through our C-Change discounts.

Our conversion mortgage product is on a Standard Variable Rate and our discounts are applied from the date we receive evidence that the conversion works have been completed and the energy rating required has been achieved.

Our standard of service

We’re committed to always giving you the best service that we can, with over 94% of Ecology borrowers rating us as very good or excellent.

You can speak directly to our dedicated team of specialist mortgage advisers who are experts in conversion mortgage finance. We consider every project on a case-by-case basis and have extensive experience in non-standard properties and ecologically sound building practices.

The Financial Conduct Authority (FCA) has laid down detailed rules about the service we must offer on regulated residential mortgages. Under these rules, we will provide you with advice and a recommendation on which of the Society’s products is most suitable for you, based on your needs, preferences and affordability.

Conversion Mortgage

6.29% interest rate
6.6% APRC overall cost for comparison
£799 application fee
80% maximum loan-to-value
  • Energy-efficient conversions rewarded through our C-Change discounts from 0.50% to 1.50%.
  • Ability to overpay by up to 10% per annum within the first two years. Any amount above 10% will incur an early repayment charge.
  • Borrow up to 80% of the property’s value on a repayment basis, or up to 75% interest-only (or part repayment and part interest-only).
  • All conversion projects must show they will achieve a minimum SAP rating of 85.

Representative example

This is an illustration of a typical mortgage and its total cost. It looks at a mortgage of £225,700, paid over 25 years on a variable rate of 6.29%. This mortgage would need 1 monthly payment of £2,546.67 and 298 monthly payments of £1,496.52 to pay off. The total amount paid would be £449,933.63. This includes the loan amount (£225,700), interest (£222,809.63), a mortgage application fee (£799) and a valuation fee (£625). This illustration assumes the cost of the property is £350,000.

The overall cost for comparison is 6.6% APRC representative.

APRC (Annual Percentage Rate of Change) shows you, as a percentage, the annual cost of a secured loan or mortgage. It brings together all charges (such as fees and other costs), calculated as if you kept your secured loan or mortgage for the full term without changing it.


  • We’ll consider lending up to four times joint or sole income subject to loan-to-value and an affordability assessment
  • Borrowers must be aged 18 or over.  This mortgage is only available to UK residents.
  • A maximum mortgage term of 30 years is available (subject to eligibility).
  • Mortgages are available on a repayment, interest-only or part (repayment) and part (interest-only) basis, subject to eligibility.
  • If your project requires planning permission or listed building consent, this will need to be in place before we lend any mortgage funds.

Fees and charges

  • An early repayment charge may be payable if you repay all or part of your mortgage within the first two years.
  • A non-refundable mortgage application fee of £300 is payable in addition to a mortgage valuation fee.
  • Read our full list of fees and charges for more information.

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Download our mortgage brochures

Heat Pump Cashback

Thinking about undertaking an energy efficient restoration project where you are upgrading the heating system to the property? If you are planning to install an air or ground source heat pump, you can claim for a £500 or £1000 cashback when you apply for a new mortgage at Ecology.

detailed info

Full details of the offer

We offer a cashback for eligible residential mortgage applications for projects including installation of a heat pump. If you qualify, you can claim:

  • £500 for when you install an air source heat pump
  • £1,000 cashback for when you install a ground source heat pump

To be eligible:

  • Make sure that your installer is MCS accredited
  • This offer applies to our self-build, renovation, conversion and shared ownership mortgages.
  • Your property must have loft and cavity wall insulation

How to obtain the cashback

The process is simple and part of the mortgage process.

  • When speaking to your appointed mortgage broker or one of our mortgage advisors, they will check your eligibility for the cashback.
  • The cashback value and installers accreditation requirements and how to claim will be shown in your personalised illustration and any Offer of Loan.
  • The cashback is payable within 18 months of completing your mortgage (i.e. when you receive your first stage release/advance) and with the production of an MCS installer certificate.
  • The cashback will be paid when we receive a completion certificate confirming that the heat pump has been installed by an approved installer.  If you qualify, your cashback will be paid into the account you use to make your monthly mortgage payments.

Other important information

Please be aware that Ecology is not responsible for ensuring the quality of the work carried out and the costs provided.  You should carry out your own checks to ensure the costs and the supplier is suitable. If you find that you are not happy with the work carried out, you should speak to your supplier in the first instance. If the work carried out is covered under a scheme provider (e.g. MCS) you should also contact the appropriate provider.

Our awards

Good With Money Good Egg award - 2021/2022

NaCSBA Gold Partner - 2022

Best Buy Mortgages & Savings - 2021/22

Benefit from our energy-efficiency discounts

94% of our residential mortgage customers are eligible for one of our C-Change discounts, which are designed to reward you for improving your home’s energy efficiency. So, not only can you enjoy reduced energy bills while shrinking your carbon footprint, you can get a lower rate on your mortgage, too.

Learn more about C-Change

1 Take out your mortgage with Ecology

2 Convert a building that doesn’t yet have residential status

3 Confirm your new energy rating and we'll calculate your discounted rate

Mortgage calculator

Work out how much you could borrow and compare monthly payments for our Conversion mortgages. You'll also be able to see how much you could save if you're eligible for our C-Change discount.

Our mortgage calculator is for illustrative purposes only and is designed to give an indication of the amount that we may be able to lend. The actual amount that we may be able to lend will depend on a full assessment of affordability, the property value and the size of your deposit.

Find out how much you could borrow

Your home may be repossessed if you do not keep up repayments on your mortgage

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C-Change FAQs

C-Change discounts explained

As a building society with a unique mission to build a greener society, we lend on projects and properties that support our aims through their reduced impact on our environment. Making your home energy efficient is a major way you can support tackling climate change – while saving on your energy bills.

We reward borrowers whose properties are energy efficient (therefore have lower carbon emissions) with our C-Change discounts off our Variable Rate which helps them save money on their mortgage. We call our discounts ‘C-Change discounts’ simply because we’re aiming to make a ‘sea-change’ of difference to our climate with each property or project we fund.

The level of our C-Change sustainable homes or C-Change retrofit discount that applies is based on the Energy Standard rating achieved on the self-build, off-site build, renovation or conversion when the work is completed. Our C-Change energy improvements discount is based on the qualifying energy measures being installed. The discount is applied from the date we receive evidence that the work has been completed and if applicable the Energy Standard rating required has been achieved.

For new builds and existing energy efficient homes: C-Change sustainable homes discount

Our C-Change sustainable homes discount applies to new and existing energy efficient homes and extensive retrofits using the Passivhaus EnerPHit methodology. Once your build is complete, you need to provide an Energy Standard certificate and Architect/Building Control certificate for us to apply the Sustainable C-Change discount. The discount is applied from the date we receive all the required documentation and is based on the Energy Standard rating the property achieves.


Energy StandardRatingsSVR (Standard Variable Rate)Discount %Variable Mortgage Rate
PassivhausPassivhaus6.29%1.50%4.79%. The overall cost for comparison is 5.00% APRC
PassivhausPHPP Modelled6.29%0.75%5.54%. The overall cost for comparison is 5.80% APRC
Energy Performance Certificate (EPC)A (SAP rating 110+) (++)6.29%1.25%5.04%. The overall cost for comparison is 5.20% APRC
Energy Performance Certificate (EPC)A (SAP rating 100-109) (+)6.29%1.00%5.29%. The overall cost for comparison is 5.50% APRC
Energy Performance Certificate (EPC)A (SAP rating 92-99)6.29%0.75%5.54%. The overall cost for comparison is 5.80% APRC
Energy Performance Certificate (EPC)B (SAP rating 88-91)6.29%0.50%5.79%. The overall cost for comparison is 6.00% APRC
Association for Environment Conscious Building (AECB)AECB CarbonLite Building Standard6.29%1.00%5.29%. The overall cost for comparison is 5.50% APRC

Mortgage FAQs

Conversion FAQs

Does Ecology require planning permission for my conversion project?

Yes. We need at least outline planning permission to start the application process and detailed planning permission before the mortgage is released.

What information do I need to progress a mortgage application?

You’ll need to have a specific property conversion in mind which needs to be supported by detailed plans, including a breakdown of material and labour costs and an indication of the Energy Standard you are converting to. We’re currently focusing on conversions that are aiming for Passivhaus or EPC B (SAP rating 85+) or above.

What deposit do I need for my conversion project?

You need a 20% minimum deposit to buy the property and a further 15% – 20% of total conversion costs to start your project.

Do I still need a deposit for my conversion if I already own the property and have planning permission?

No, you don’t always need a deposit; we can lend based on the value of your property to start the conversion, providing you already own the property and it’s mortgage-free. Also, we can help you repay any outstanding finance on the property if you need it.

Do borrowers who are planning to convert their property need to show how they plan to improve the property’s energy efficiency?

Any project we support needs to show planning details of the proposed conversion with an indication of the Energy Standard you are converting to, and how the project costs are expected to be funded with savings and mortgage finance. We don’t just lend to purchase the property.

How long do I have to complete the conversion?

Subject to planning constraints, we allow a maximum of 2 years for you to complete the conversion, although we encourage you to complete earlier to benefit from our C-Change discount (C-Change sustainable homes or C-change energy improvement). The applicable discount is applied to our Standard Variable Rate when we receive evidence that the work has been completed and the Energy Standard rating required has been achieved.

Do you offer stage payments for a conversion?

Yes, although the Ecology conversion mortgage does not release payments at set construction milestone stages. We release funds as and when the conversion progresses and release up to a percentage of the increased value of the property.

Can I have an interest-only mortgage during the conversion phase?

We offer an interest-only mortgage only when you have a qualifying repayment vehicle to support this for example an established ISA, endowment policies or Pension Plan.

Does Ecology require a particular build warranty on completion of my conversion?

A build warranty is not a mandatory lending requirement of our mortgage and we are happy with a Building Regulation Completion Certificate. However, if you wish to take out a build warranty for the completion of the property then this is acceptable to the Society.

Does the conversion property have to be my main residence?

Yes, although we do offer a buy-to-let mortgage. Please bear in mind that we don’t offer mortgages for second homes, holiday homes or homes classed as mobile planning.