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What is a Retrofit Strategy? Why would I benefit?


One route that we recommend is starting with our Retrofit Strategy Reports.


Why retrofit?


Once we have your instruction to provide you with our Retrofit Strategy Pakage, we will help you to start by asking you questions, for example:

Do any of these statements apply to you?

-Your home is too hot.
-Your home is too cold.
-Your home is too damp and has mould.
-Your home is too draughty.
-Your home needs extending.
-Your family is expanding.
-Your kids are leaving home.
-Your elderly relatives are moving in.
-You are planning to replace your kitchen and/or bathrooms.
-Your home needs refurbishing.

Would you have guessed that these are all retrofit trigger points? – I didn’t before I studied retrofitting.


Why would, for example, replacing a kitchen or bathroom be a retrofit trigger point?


The question about the kitchen or bathroom centres around the retrofit strategy option you have chosen to insulate the walls. If you need to insulate internally, as is often the case for properties that are externally beautiful or in a conservation area, then you are likely to need to insulate some areas behind kitchen units or bathroom fittings. As such using the opportunity of a stripped-out space ready to take a new bathroom or kitchen is the ideal moment to review the possibilities for making your home fit for the future in that it is cosy, warm, draft-free and inexpensive to heat.


As such all the trigger points above might involve some work to your property and any refurbishment or opening-up of areas, or extensions all provide you with the potential to reach areas of your building that might otherwise be in a finished state and hard to get to. Specific reasons for retrofitting a property can vary enormously depending on your goals, priorities and the unique characteristics of your property.

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Image from Muswell Hill Low Carbon House kitchen with retrofitted walls having U-values of 0.15 W/(m2K) for the back wall and 0.30-0.32 W/(m2K) for the side wall. These walls were originally about 2W/(m2K) as is standard for solid masonry walls of period properties.

So how often do we do up our properties?

Well, the data I received from my course at the Retrofit Academy was that we typically do up our properties once every 30 years. For me, that means that every refurbishment carries importance in how it is done. As such, I ask myself:


-Will it be more economical to heat and cool?

-Will it be fit for the future and resilient to the danger of fuel price hikes?

-Will it have a lasting impact in a positive way?

-Will it contribute to our overall need as a country to reduce our use of fossil fuels?

Why is it important to review the condition of the building?

One of the first things needed for a retrofit project is to assess the original building for its age, construction type and general condition. A good retrofit starts by being ‘retrofit-ready’, this means that all necessary repairs are done to be able to add retrofit measures to the walls, floors, and roofs without the danger of leaks and disrepair damaging them. It is good to review the existing materials of the building to ensure we use insulation materials that work best with your building type. We look at the natural and mechanical ventilation that you have in place so we can assess how best to augment it. We place this in a report that forms part of your Retrofit Strategy.

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Image from Muswell Hill Low Carbon House showing view into new extension

What are the benefits of a retrofit assessment over a standard EPC report?


You are likely to be aware of energy efficiency ratings that you see on products that you buy, for example, whether a fridge has an efficiency rating of G or an A+++ is likely to influence your purchase of it. If you have bought/sold or rented a property since 2007 you will have come across an Energy Performance Certificate for your property. For a long time, people took little notice of them while buying or renting a property. As a retrofitter, I am all too aware of the difference the rating can make. The energy efficiency of our homes is now starting to make a difference, people are gaining awareness that:


-going up an EPC rating saves you money (£250/year per EPC rate increase on average)

-homes with higher ratings are starting to fetch a premium (Green Home Premium).

The EPC software assessments software however is a very blunt tool for something that is quite nuanced and specific, as such they can be a little misleading. A retrofit assessment while producing an EPC rating is much more specific by looking at things like:


-Existing occupancy and behavioural impacts.

-Existing temperature of your heating and amount of time set to be on.

-It considers the internal and external conditions

-Defects are noted

-Mechanical and natural ventilation is noted.

-Feasibility of any suggested measures in relation to local authority laws and regulations.

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Image from Muswell Hill Low Carbon House showing view into new extension.

How do I sequence a retrofit? Can I start by putting solar panels on or install an ASHP?


Money can easily be spent on a measure that may not be the most effective use of your funds. Solar Panels and ASHP often work best once your home has reduced the speed of heat loss by insulating the external surfaces such as your walls, floors, roof and windows. A Retrofit Strategy gives you a whole house plan and explores the measures for improvement and the best sequence of implementation specific to your home. For example, it can prevent retrofit blocking by ensuring insulation is installed behind a new kitchen or bathroom as they go in with the knowledge that having to return to these areas would be costly in the future.


Why do retrofit projects benefit from good coordination once the measures have been selected?


Retrofit measures seem simple enough in isolation however without a design or incorrect installation can cause unintended consequences. The sequence and quality of the design of junctions is key to the performance of the completed work. Once you have the overall design and perhaps have received local authority approval for any external insulation, we recommend the production of 1:5,1:10 scaled detail drawings. These form an exploration of the wall, floor and roof build-ups as well as the often of the complex junctions between the two. Retrofit designers aim to work out most junctions before the fast-paced on-site process. Relying on resolving all the junctions while on site is likely to require full-time site assistance and could cause delays to the contractor which can be costly. In addition the drawings, we produce a detailed schedule for costing that includes:


-The type of construction (vapour-sealed or vapour-balanced)

-The materials and products to be used.

-The systems to be installed

-Requirements for testing and commissioning

-The required standards of workmanship

-An air-tightness target

-Requirements for the handover of completed work

-Installers’ accreditation requirements

-Installation standards and sequences

What are the benefits of a whole house retrofit?

You can expect to enjoy:


-A home that is warm, cosy and draft-free with lowered bills.

-A home that is in a good state of repair.

-A home where mould and damp have been eliminated.

-A home that has good air quality and moisture control through good ventilation design.

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Image from Muswell Hill Low Carbon House showing 100mm thick Passive House door replica of the original door but fully airtight with a 0.84 W/(m2K) U-value.

So, what does a Retrofit Strategy provide you with?


By working closely with you, we’ll:


  • Help you to define your specific requirements and budget by asking you to fill out our questionnaire.

  • Visit you at your home to discuss your requirements in more detail.

  • Use the information we gather to help you to develop your exact brief.

  • Survey the internal and external conditions of your home: noting defects, building type/age, existing materials and existing ventilation provisions.

  • Take a measured survey and photographs to put together a report bespoke to you giving you drawn plans to show you where you can add certain measures on each floor.

  • Use our RD SAP assessment software to review the current performance of your home.

  • Use the software once more to explore the addition of improvement measures to optimise the effect on your home’s energy performance.

  • Provide you with a report that lists each measure and the cost involved to take your home up to higher EPC ratings*.

  • Give you an outline of the cost of measures and suggest the most effective sequence for their installation.

  • Give you an outline of our design and coordination costs to get your home retrofitted in a way that maximises the impact.

  • Meet with you to discuss and answer questions about our report findings and recommendations based on your initial brief and available budget.


*If you would prefer to aim for other accreditations such as Enerphit or AECB Retrofit Standard Level 1 or 2 etc. we can tailor this package to suit your specific requirements.


Do you want to chat about it?

This column is here to give you the benefit of some of the things we have learned over the years. If you have a project you would like to discuss in more detail, do get in touch or see our GETTING STARTED PACKAGE or our RETROFIT STRATEGY PACKAGE.

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Image from Muswell Hill Low Carbon House showing our fabulous collaborative team including Johanna Ahrberg-Jackson and Josephine Lecoufle-Vinet.

We work closely with our assessors who are TrustMark registered and comply with PAS2035:2019, a government-certifying body which lays out what is needed to conduct a retrofit successfully to a PAS2035 Standard and reach a high EPC rating. We also work with Passive House Planning Package (PHPP) assessors should you be interested in achieving Enerphit Certification for your retrofit.


To build responsibly for people and planet.

Designed for you, built fit for the future.

We retrofit and build with natural materials to:
- lower your energy consumption by 60-95%,
- improve your quality of life and well-being,
- give you greatly improved indoor air quality,
- for positive environmental impact.

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