What is Retrofit?

Retrofit is simply the process of making changes to existing buildings so that energy consumption and emissions are reduced.  These changes should also provide the benefit of a healthier and more comfortable home with lower energy consumption., which also means lower bills.

Retrofit is not the same as renovation or refurbishment, which means upgrading a house but not necessarily reducing its energy use. 



solar panels on roofs houses with scaffold

By taking a fabric-first approach, which means focusing on reducing a home's heat loss, we can achieve a low carbon, sustainable home that is affordable to heat.  

Improvement works typically include:

  • insulation
  • highly efficient windows and doors
  • ventilation
  • heat pumps 
  • solar panels

In the UK we are facing two big problems, rising energy prices and the urgent need to reduce carbon emissions if we're to reach net-zero by 2050.  People are increasingly worried about how they can reduce energy use in their homes to not only save money but act in the fight against climate change.  Retrofit is the best solution to both these issues. 

To achieve these aims, works need to be carried out properly with a bespoke plan that is designed and installed by competent, skilled tradespeople who work to high standards of technical competence and customer service, with good trading practices. 

For more information visit the Trustmark website here -


The Process of Retrofit

To enable us to get the funding we carried out a desktop analysis to find the properties eligible for retrofit. 

These will all now require a full retrofit assessment site survey to confirm their suitability and figure out the most appropriate measures.  

Some factors may present barriers to certain properties such as planning and national grid Distribution Network Operator (DNO) approvals for installing heat pumps and solar panels, so these may affect which properties we can retrofit.

 If your home is identified –

A smart thermostat called a Switchee will be installed with your consent. This replaces your existing thermostat and works in the same way to control your heating and hot water and collects heating data. This enables us to assess the current energy performance of the property, and problems like damp.


The first stage of the retrofit process is to carry out a retrofit assessment on properties that have been identified, to work out the current level of energy efficiency, what ventilation is in place, and if there are any issues such as damp, mould, and condensation. The assessment will include collecting data and images of the current energy performance of your home.  Below is a checklist of the key stages of the process:

Retrofit Assessment & Condition Report

Full access to all rooms, including the loft space and All external elevations will be needed.

This assesses the suitability of the property for retrofit works. 

You will be contacted by Osmosis ACD to book in a retrofit assessment. An assessor will come to your home and conduct an internal and external property survey.

We will use the assessment to design and recommend the energy measures that will best make your home as energy efficient as possible …

Your home will receive the required works, installed by our approved contractor. 

You will be kept informed during all aspects of the process by our dedicated customer liaison officers.

What is a Switchee?

Switchee is a smart, connected thermostat for your heating and hot water which doesn't rely on your Wi-Fi network to function. We're piloting this technology to help us, and you, look after your home more effectively.

It's also part of our plans to reduce our carbon footprint. 


What does a Switchee do?

Easily manages your heating and hot water

Whatever suits you.  Over time, your Switchee will learn your daily routines and turn everything on/off automatically, according to your preferences. 

Control at your fingertips

If you have a smartphone you can download the Switchee app to manage your heating and hot water from your phone, whenever and wherever you need to.

Reduce your bills and carbon footprint

It can help you reduce your energy usage, and lower your bills by up to 15%.

Receive messages directly from us

Through your Swtichee, we can securely send you messages, schedule appointments, and ask you for feedback on repairs. 

Information gathered by the Switchee

Your Switchee gathers data and insights that help us look after your home effectively.  It is completely secure and can identify issues early. 

How does Switchee work?

Switchee has sensors that gather information about the energy efficiency of your home. 

It can highlight issues like condensation, suspected damp, and mould. 

If we complete any repairs in your home, it helps us measure how effective they are. 

With rising energy costs it’s more important than ever to use our heating systems as energy efficiently as possible, if you are interested Switchee can provide advice based on the information gathered from your home.


Switchee support

If you need help or support with your Switchee resident support can be contacted on Freephone 0800 133 7957 or email

Support hours are 9am - 6pm Monday to Friday. 

Learn more about Switchee at


When your home has been identified you will be contacted with further information and will receive the latest copy of the Retrofit newsletter.

Retrofit Newsletter Issue 1 March 2024


What types of measures will be used?

Works to the fabric of the building:

Cavity wall insulation

Cavity walls can be insulated by injecting insulation material into the cavity from the outside. 

A specialist company will drill holes in the outside walls, inject insulation through the holes, and then seal them with cement. 

The insulation material is usually polystyrene beads, but polyurethane foam may sometimes be used instead.

Cavity wall insulation being piped into building
External wall insulation with surveyors looking on

External wall insulation

If your home was built before the 1920s, its external walls are probably solid walls rather than cavity walls and can be insulated from the outside. This will cost more than insulating a standard cavity wall, but the savings on your heating bills will be bigger too. 

External wall insulation involves fixing a layer of insulation material to the wall and then covering it with a special type of render (plasterwork) or cladding.

Depending on local planning regulations the finish can be smooth, textured, painted, tiled, panelled, pebble-dashed, or finished with brick-effect tiles known as brick slips.

Loft insulation

A quarter of heat is lost through the roof in an uninsulated home. 

Insulating your loft, attic or flat roof is an effective way to reduce heat loss and reduce your heating bills.​​​​​​​

Rolls of mineral wool insulation are laid between the joists – the horizontal beams that make up the floor of the loft – then another layer is laid at right angles to cover the joists and make the insulation up to the required depth, currently recommended at 300mm.

Please remember you are not permitted to store belongings of any kind in the loft  area as noted in your tenancy agreement. 

Loft insulation being laid in roof space
air sourced heat pump single image

Heating systems:

Air sourced heat pump

Air source heat pumps (ASHPs) extract heat from the outside air to heat your home and hot water. They can still extract heat when air temperatures are as low as -15°C.

Air source heat pumps need electricity to run, but because they are extracting renewable heat from the environment, the heat output is greater than the electricity input. This makes them an energy efficient method of heating your home

Solar PV Panels

Solar PV cells generate electricity from the sun when light shines on the cells it creates a flow of electricity, 

Most PV systems are made up of panels that fit on top of your roof.

The solar panels provide free electricity during a bright or sunny day. An inverter is installed, usually in the loft space, to direct that electricity into your home.  Surplus electricity is returned to the national grid. When combined with a heat pump, surplus solar electricity is diverted to your hot water cylinder to help reduce your electricity bills. 

Solar PV panels on roof of bungalow
Ventilation system air vent on ceiling

Ventilation systems

Ventilation is important because, without it, the air in your home would become stale, damp, and generally unpleasant. Adequate ventilation ensures that the air inside your home changes often enough to avoid it getting stale and reduces moisture which can lead to mould growth

Regardless of whether you have a well-insulated home or not, if you’ve got draughts, they will ventilate your home, but they will also cool down your home making it harder to heat.