Surveyor Blog: Domestic Retrofit

Written by our Senior Regional Surveyor, Hugh Riley.


The UK is committed to the Climate Change Act and needs to reduce Green House Gas emissions by 80% by 2050. As 14% of the UK’s carbon emissions come from homes, improving energy efficiency in homes will be a large step forward in meeting this target.

Currently many homes are still poorly insulated with inefficient heating systems and controls and many homeowners are either unaware of energy waste or are reluctant to improve their property as the benefits may not be apparent to them. The UK has about 27.5 million homes of which 24 million could benefit from ‘whole-house’ retrofit making their homes low carbon, low energy and reducing their impact on climate change. Encouraging energy efficiency improvements has the added benefits of reducing fuel poverty, improving occupiers’ thermal comfort, improving property values, and increasing security of the national fuel supply.

As a result, there is now a target to improve the EPC ratings of all domestic property to Band C by 2035. Policies being developed to support this include a programme encouraging insulation installation, and an increased minimum EPC level for privately rented homes. There are also incentives to promote renewable energy with reduced VAT on energy efficiency measures.

New standards for domestic retrofit were introduced in 2019, the key documents being PAS 2035 which covers the assessment, design and evaluation of domestic retrofits from start to finish and the revised PAS 2030 which looks in depth into retrofit installations themselves.

Whole House Retrofit

‘Whole-house’ retrofit is a complete approach to making homes more energy efficient. A successful retrofit project starts with a full understanding of the property and how the occupants that live there use it. A ‘whole-house’ assessment will focus on the identification of the opportunities for any improvements to make the property more liveable and comfortable for the residents and the constraints that need to be considered.

Consideration will be given to the building fabric, moisture, airtightness, weather exposure, external insulation options and any unintended consequences of retrofit. Initial focus on the fabric of the house will include the walls, roof, floors, windows and doors, but this will expand to strategies for ventilation, heating efficiency and cooling in the summer months. Risks from cold bridging and thermal bypass will also need to be assessed as this is likely to lead to condensation, which, over time, will cause damp problems and potentially affect the health of occupants. Adding better glazing and draught-proofing can also increase condensation if suitable ventilation has not been provided for.

‘Whole-house’ retrofit is designed to deliver a set of outcomes that will provide tangible benefits to the consumer, so their homes are more comfortable, healthy, and economical to run.

Retrofit Survey

A retrofit is a specialist job, with tailored plan for each unique home. The process will start with a retrofit survey to give an understanding of the starting point and help to allocate budget to where it will have most benefit, and to set targets. A more detailed assessment may include an airtightness test or thermal imaging survey. A full retrofit plan will then be prepared and used to guide contractors on the work to be carried out. The details will be different for each house so each must be assessed on its own merit to produce a tailored specification of works. However, those in a row or block should share installation measures to make projects more cost-effective. A good plan is also important for being able to clearly communicate with contractors and suppliers to make known what needs to be achieved and how to measure it.

Energy Efficiency Measures

Following a ‘whole-house’ assessment a home may require individual or combined energy efficiency measures. Communication between all parties involved in the plan is key to delivering a successful outcome with customers understanding the options and benefits of each stage of the retrofit process. Consideration needs to be given to not only the home, but also environment, occupancy and the householders’ objectives and behaviours when determining the most suitable measures to install.

Possible renovations include, but are not limited to insulation, airtightness, ventilation, heating and cooling systems, renewable technologies, water heating systems, efficient lighting, energy monitoring systems, locally generated power that uses zero-carbon technologies.

Hot Water: hot water cylinder jacket, cylinder thermostat, waste-water heat recovery devices for showers and baths.

Lighting: low energy lamps.

Heating: heating controls (remotely controllable thermostats, zone controls, smart radiator valves), fan-assisted storage heaters, high efficiency circulation pump.

Insulation: cavity wall insulation, solid wall insulation, EWI external wall insulation, loft or roof insulation, under -floor insulation, party wall insulation, draught proofing.

Windows and Doors: energy efficiency glazing, energy efficiency doors.

Renewables: air source/ground source heat pumps, biomass boilers, micro wind generation, solar water heating, solar photovoltaic

Care should be taken in choice of improvements. It is worth noting that Spray Foam roof insulation may be a “false economy”, whilst it may offer some ‘whole-house’ energy efficiency saving, installation may contravene many mortgage lender’s policy, rendering the property unmortgageable.

Eco Retrofit

Reducing energy use within a building is the main focus of a retrofit project. An eco-retrofit would consider using natural fibre materials to ensure a lower manufactural impact than synthetic products. Natural fibres are also easier to recycle. Using natural building materials will therefore ensure a lower impact.

Materials made from natural fibres also offer the important additional benefit of ‘carbon sequestration’. This is because the growing plants absorbed carbon from the atmosphere, and this carbon then stays locked up for decades.
Another benefit of natural materials is their breathability, which affects how they deal with moisture. This is particularly important in older buildings, because they are designed to be open-to absorbing and releasing moisture. Cement render and nonbreathable insulation on an older home tends to cause damp problems. Using natural materials therefore helps to protect buildings from damage as well as leading to a low environmental impact.

Staged Retrofitting

Improvements should ideally be scalable allowing for the measures to be undertaken in one improvement or staged over time. A staged retrofit still needs to plan with the ‘whole-house’ in mind, set priorities and consider interactions of improvements over time with the building fabric to avoid possible risks. This will guide the choice of materials.

Later stages can be ‘futureproofed’ by adequate planning. For example, if changing a heating system, when improving the building fabric, the plumbing needed to prepare for a heat pump, biomass boiler, or solar water heating will need to be considered along with size and shape of radiators, and space for an appropriate type of hot water cylinder. If planning for future solar photovoltaic panels, and retrofit measures entail re-roofing, then this may be an opportunity for integrating the panels.


In future years there are significant opportunities for surveyors and contractors to retrofit UK property and play a vital role in the delivery of low carbon homes. This will, however, require education and encouragement of homeowners to think about energy efficiency measures and benefits. This is something the mortgage lending industry is also just waking up to with the introduction of favourable financing rates for better energy efficient homes. Such incentivisation, may drive such change forward for ‘whole-house’ retrofit to millions of homes across the UK.


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