What Is Residential Retrofit?

You may have heard of retrofitting insulation into a premises, but what happens during an insulation retrofit, and what is the purpose of completing one? If you wonder whether it’s something you could benefit from, keep reading to find out more.

What Is A Residential Retrofit?

A retrofit aims to improve a property’s energy efficiency, mainly by replacing the materials and improving the build of a property.

One of the most popular and most straightforward solutions is improving insulation. Retrofits help deal with problems such as mould and condensation, leading to lower energy bills and emissions.

You can do residential retrofits room by room or by doing an entire house at once. Studies show that the UK has the least energy-efficient housing stock in Europe, so it is time we took retrofitting more seriously. The UK has an aim to retrofit all homes to EPC band C standard by 2035.

The Aims of a Residential Retrofit

The main aim is to conserve energy before having to try to generate it! Insulating the building to the best standard is a crucial part of the process and ensures an efficient heating system. Where possible, renewable energy technologies should be considered and installed. As of July 2021, retrofits need to meet the requirements of the PAS 2035.

What Is The PAS 2035?

The PAS 2035 is a recently introduced set of guidelines in the UK for the retrofit process. It follows a review the government commissioned in 2015 called ‘Each Home Counts’. The study identified issues with properties, in particular, older buildings. It aims to create a process to introduce more energy-efficient measures.

The overall goal is for trained professionals to manage the retrofit process, all the way from initial inspection to the completion of improvement works. Any retrofits completed by private contractors must adhere to the PAS 2035 and any retrofits included in government schemes.

Make sure you always use an accredited assessor! This ensures you receive professional guidance and repair work that you can rely on.

What Does The Residential Retrofit Process Involve?

Possible renovations to come out of a retrofit include, but are not limited to:

  • Insulation
  • Ventilation
  • Heating and cooling systems
  • Water heating systems
  • Energy monitoring systems
  • Renewable technologies
  • Airtightness 

Retrofit Assessment

A qualified retrofit assessor must complete the retrofit assessment. They will have received training to ensure they have all the relevant knowledge and skills to complete the process correctly.

Choosing a suitably qualified assessor means you have confidence your retrofit will result in an energy-efficient property, prepared to stand the test of time. In the assessment, three documents are produced.

Energy Report

This report is based on your properties currency, energy usage, and the energy potential of the property.

Condition Report

This is not the same as a complete structural survey! It looks into the fabrics of the building, identifying any problems that could affect energy performance. The assessor will look for signs of damp and condensation and then work out the cause of these problems.

Occupancy Evaluation

This focuses on the use of the property, looking at previous energy bills and the daily energy usage in the building.

Insulation Options

One of the easiest and most effective ways to make a property more energy efficient is insulation. There are many types of insulation; the usage depends on the property, type of roof, etc. Wall insulation can be installed internally or externally.

For example, the appearance of a property may need to remain in compliance with appearance, especially for period properties. For properties where the appearance needs maintaining, internal insulation should be added to the front wall and external insulation to the rest.

Suppose a terraced house is refurbished as per a retrofit, but the joining properties haven’t been. In that case, the party walls need insulation to make the refurbishment effective.

Internal Vs External Insulation

Internal (Insulation Is Fitted to Inside of Wall)


  • Maintains external appearance of the building
  • Rooms are quicker to warm up


  • Reduces internal space, could compromise on decorative features in older properties.
  • Residents may have to re-locate during the work period.

External (Insulation Is Fitted to Outside of Wall)


  • Greater flexibility in the choices of insulation materials
  • Works will not inconvenience the residents


  • Could require planning permission
  • Replacing windows at a later date can prove challenging.

Pitched Roof Insulation

Additional pitched roof insulation will likely be required if the loft is used as a room, not just storage. Most pitched roofs are the ventilated type. These roofs are perfectly adequate, but there is the possibility of replacing the roof with an unventilated type, which performs better.

Ventilated Roof

A ventilated roof has an air space between the rafter insulation and the underside of the sarking felt. Any moisture is evaporated into this ventilated air space and then passed to the outside. The existing roof can be kept if:

  • The materials are in good condition.
  • There is sufficient depth or depth that can be added to install insulation.
  • Raising the roof height is undesirable.

Unventilated Roof

This is a relatively new type of roof, which has been developed over the past few decades. Unventilated roofs are growing in popularity thanks to the introduction of breathable insulations to the market. Breather membranes allow internally produced water vapour to pass through membranes.

The advantage of unventilated roof construction is the removed necessity to keep a ventilated cavity below the sarking. Insulation can be installed within the full depth of the roof rafters.

Floor Insulation

Without proper insulation, homes can lose up to 10% of their energy through their flooring! Floor insulation can be used directly over joists, creating an airtight seal underneath floorboards. It seals the gaps between floors and skirting boards, reducing draughts and lowering household energy bills!

What Happens Next?

A full report is created, including the energy report, condition report and occupancy evaluation. A timeline will be made for the necessary improvements to be completed. All the required installations will occur, and completing the retrofit process means your property is now more energy-efficient and cost-effective!

If you want to find out more about how insulation can reduce your bills, and make your home more energy-efficient, call us on 01636 556797 or email us.


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