Caroline Bowler of SIG Distribution explores how combining the right calculations with a fabric-first approach can yield the most efficient increase to thermal performance.

As winter draws in, the focus on how to efficiently heat a home becomes more apparent. For housing associations and local authorities this serves as a stark reminder of the amount of work needing to be done to existing homes to make them more thermally efficient. As the UK moves towards a net zero future and with domestic heating accounting for around 17% of the nation’s overall emissions, improving the overall efficiency of homes is vital if we are to achieve net zero by 2050.

To build on the momentum of the great retrofit challenge, there are a number of mechanisms and funds in place to help authorities and owners retrofit their housing stock for improved performance. One of the largest is the Warm Homes Social Housing Fund Wave 3 (WHSHF) which released £1.2 billion to help achieve an Energy Performance Rating of C or above for the millions of social homes in the UK which currently fall below this standard.

In order to access this funding, a business case must be put forward which demonstrates the estimated cost of the improvements and the benefits this would bring to occupiers. Therefore, doing the hard work up front to identify homes with the greatest potential as well as taking a commercial view on the most efficient way to achieve this, is vital.

An important factor to note in the funding is the requirement that the retrofit measures put in place cannot increase the energy costs for the householder. This places greater emphasis on ensuring the fabric of the building is addressed first. Installing an air source heat pump in a poorly insulated home would only result in increasing energy bills and therefore would put the Housing Association (HA) or Local Authority (LA) in breach of this regulation.

Understanding housing stock

To retrofit each home effectively, the measures put in place must work holistically to deliver improvements. Implementing retrofit activity without proper expert advice or planning can render those improvements ineffective.

Before any works commence, a full assessment of the current stock should be carried out ensuring all properties are in good structural condition. Many energy improvements are interdependent and rely on a baseline standard to be truly effective. There is no point insulating a property if it suffers from damp or has a leaky roof.

Once housing stock is in a decent condition, the next step is to understand what works need to be completed in order to achieve an Energy Performance Certificate (EPC) rating of C or above. A Standard Assessment Procedure (SAP) measures the energy efficiency and environmental performance of a building and is then used to create the EPC. The SAP considers construction materials, heating systems and how efficient they are, together with levels of thermal insulation amongst other indicators to provide an overall SAP calculation.

By calculating metrics like U-values to understand heat loss through walls, roofs, floors, and windows, Housing Association’s and Local Authorities can identify where insulation upgrades are best placed to reduce heat loss. In taking a holistic approach, SAP also assesses air leakage, revealing opportunities to improve air tightness through measures like draft-proofing.

As for the implementation of retrofit upgrades, there is a framework in place to help guide stakeholders. PAS 2035 is the British Standard for retrofitting dwellings and follows a fabric first approach to ensure the right measures are installed and deliver the intended improvement. Most government funded projects, including all those in England funded by the SHDF, are required to comply with the standard.

Insulation and heat retention should be the number one priority for Housing Association/Local Authorities. Reducing overall heat loss from the building’s fabric reduces the energy required for heating which can net some of the biggest improvements long term.

This was evident in the ‘Retrofit Revisit’ report from CIBSE where 10 homes with fabric energy improvements were visited 10 years after those updates were installed. The result demonstrated that ‘Fabric efficiency improvements have been shown to be very effective in the long run, with heat demand remaining very low compared to the national average.’

These results, however, are reliant on the proper application of the insulation for that property type. All elements of the building fabric should be taken into consideration as part of the retrofit strategy to avoid thermal bridges and the creation of cold spots where condensation can occur. This is where the first-stage calculations to understand the thermal performance of the house become so critical.

Accessing the right data

Upgrading the social housing sector is not straightforward. There are limits to both the capacity and technical knowledge of retrofit teams. Some Local Authorities and Housing Association’s also do not have an up-to-date understanding of their social housing stock and rely on outdated EPC’s which do not reflect the current state of the properties.

Older properties in particular can pose a challenge as they may require more specialist solutions – especially when dealing with solid external walls.

A lack of understanding has hindered some social housing projects along with inflation and council budget constraints. A combination of these challenges resulted in one council returning £6.4m earmarked for social housing decarbonisation. Other councils have reported delays in works commencing due to capacity challenges with many retrofit specialists competing for tenders.

This is where specialist product knowledge and technical advice from a distributor who has full access to the market can help. Distributors such as SIG are “product agnostic”, which means they have technical understanding of a range of products and systems from different manufacturers, plus a fully resourced technical team which can help with thermal calculations to help in the selection of the best solution.

Given their position in the market, they can also provide pricing guidelines on different solutions, saving retrofit teams either having to approach multiple manufacturers for different options or rely on costly consultants to provide the same information.

With expertise at every stage of the retrofit process, SIG can work with Local Authorities and Housing Association’s to get the most out of the funding available by understanding their social housing stock needs and matching these up with the most cost-effective and suitable energy efficient solutions.

Caroline Bowler is head of residential at SIG Distribution