Meeting carbon targets through retrofitting

Retrofitting insulation works for a whole host of reasons from saving money to carbon reduction. The Insulation Manufacturers' Association explores

It is widely accepted that the UK must embark upon a comprehensive retrofit programme of its existing housing stock, if it is to achieve net zero carbon by 2050 and the other stated targets to be achieved along the way.

The UK has some of the poorest performing housing stock in Western Europe as well as some of the oldest and IMA’s recent publication Insulation for Sustainability, produced by specialist low-carbon consultancy XCO2, explains the importance of installing high performing thermal insulation as a key part of the retrofit programme, that will cut emissions, reduce heating demand, curtail fuel poverty and maximise comfort and well-being.

With the government’s Heating and Buildings’ strategy, including its retrofit policy due to be published this year, there is no shortage of aspiration about what needs to be achieved. But the target ahead of us is daunting and will require a full commitment from government and other agencies. It must include a detailed programme of activity, coupled to the necessary legislative, financial and practicable frameworks to ensure the commitment is achieved in line with legal requirements

There remains increasing support for the retrofitting of good energy efficiency measures in the UK, as demonstrated by the interest shown for the recent Green Homes Grant scheme, even though this scheme was poorly prepared and prematurely withdrawn. There are currently some 29 million properties in the UK most of which will still be in use in 2050 and the majority of which will require some form of retrofitting to meet the UK’s net zero carbon target. This will be an enormous challenge for property owners to achieve the standards required but it will create many jobs in the construction sector and produce a great deal of economic activity.  

Generally, houses built from 1990 onwards have insulation fitted within the wall cavity to improve the thermal performance of the building. However, many homes built prior to this date may not have no wall insulation. Typically, houses built before 1920 are predominantly solid wall constructions with no cavity whereas residential properties built between 1920 and 1990 are most likely to have a wall cavity but with no insulation material.

A comprehensive retrofitting programme is therefore a valuable instrument in reducing heating demand, cutting CO₂ emissions, whilst addressing fuel poverty and improving comfort and well-being.

Design retrofit
There are specific design considerations when tackling a retrofit project, especially when targeting savings via a fabric first approach. The most common debate is centred around the best location to position auxiliary insulation. Generally, the most suitable location and insulation type for different building elements are:
•    Cavity wall – injection of loose fill or in-situ expanding insulation material;
•    Solid masonry wall – external/internal rigid insulation within a weatherproof/protective system;
•    Roof space (cold) – loose fill spray or fibrous insulation at roof joist level;
•    Roof space (warm) – rigid insulation boards or spray foam insulation at rafter level;
•    Solid floor – rigid board under screed or floating floor, and;
•    Timber floor – rigid board or quilted batting between floor joists.

Each Home Counts
Although produced in 2016, but still valid today, the Each Home Counts Report made the following sector specific recommendations for addressing insulation and fabric, in line with PAS2035/2030:2019 – Retrofitting dwellings for improved energy efficiency, specification and guidance.
•    All retrofit projects will have an appropriate design stage process which takes an holistic approach and adequately considers the home, its local environment, heritage, occupancy and the householders’ improvement objectives when determining suitable measures.
•    Put in place a process for gathering information and the design specification ahead of any installation of insulation or fabric measures; store this in a data log for future use and to facilitate continuous improvement; and load aftercare support and quality information into the data log following an installation.
•    Ensure that the Insulation and Fabric workstream feeds into the standards, skills and quality assurance development processes and that these reflect best practice and fully take account of the issues specific to the measures.

Fit for the future
Nevertheless, retrofitting must only be considered as a solution for existing and historic buildings and cannot be viewed as a panacea to be administered at a later date, for current new build homes. Developers must not be allowed to eschew the most appropriate building fabric/solutions available in favour of reducing expenditure – resulting in the responsibility of future-proofing the building to be transferred to the building owners.

The CCC report, UK Housing Fit for The Future?, assesses the cost associated with retrofitting a typical building to perform with a space heating demand of 15kWh/m2/yr. (considered a ‘deep retrofit’), illustrating that it is approximately five and a half times more expensive when compared to building a comparable building as a new build. Furthermore, the cost associated with retrofitting strategies to facilitate passive cooling, for example, are also seen to cost approximately four times as much as implementing the same strategies from the outset. This evidence illustrates the importance in considered design of new build developments from the start in order to avoid unnecessary costs and works further down the line.

Supplementary emission savings can be attained where the servicing strategy and supply-side improvements are implemented. This may include, where appropriate the replacement of traditional gas boilers by more efficient alternatives such as an air source heat pump system or connection to a district heat network.

Nevertheless, key considerations when evaluating the potential savings from retrofitting include practical, aesthetic and capital investment constraints, as well as supply side efficiency options being more applicable to new-build projects.

Health and well-being
The specification of insulation materials can also have substantial impacts on the lives of building users and occupants. The importance of thermal comfort, providing pleasant internal conditions during the winter and summer months, is a prime example. This factor is seen to influence performance and productivity as well as the physical and mental health of building users.

Another social benefit associated with enhanced levels of insulation is the reduction of fuel poverty. This issue is alleviated as a greater proportion of heat is retained more effectively in homes when incorporating superior fabric efficiencies. The provision of an enhanced building envelope results in a reduced overall fuel demand needed to achieve equivalent, sustained warmth over the winter months than for a building with lesser thermal performance.

Insulation strategy
Suitable for anyone looking to learn about the application of low-carbon strategies through a fabric-first approach, Insulation for Sustainability, highlights the issues associated with energy demand and the way enhanced insulation strategies play a crucial role in the built environment to help the UK meet its net-zero targets.

Retrofitting insulation works for a whole host of reasons from saving money to carbon reduction. Whether it is an internal or external insulation application, it is vitally important the UK’s housing stock is raised to an acceptable standard by making the fabric of the building as energy efficient as possible. Only then will we be able to provide a long-term asset that reduces energy usage and can be passed onto future generations.

The Insulation for Sustainability white paper can be accessed here.