A recent report from The Resolution Foundation has confirmed what’s been said for a long time - that the UK has the highest share of pre-war housing stock of any country in Europe. The report revealed that 38% of UK properties were built before 1946 putting the UK higher than any other country in Europe.

Up until the very early 20th century solid wall was the preferred method of construction. Solid wall (sometimes a called a massive wall) refers to a construction of a single primary material (primarily brick) in one layer, or different layered materials that make up a solid wall thickness.

There was a period in more recent history however when the construction industry looked a little different. After the First and, particularly the Second World War, the replacement and renewal of housing was a big issue. There was a housing shortage before WWII which was made worse by the fact that over half a million homes were destroyed in the war itself. Add to the fact that the building industry was seriously affected by a shortage of skilled labour and essential materials. The result was an acute housing shortage and the pressure to build new home quickly was greater than it had ever been.

Post war there was also a need to redeploy factories and work-forces that had been established to support the war effort, there was also a severe housing shortage and a lack of skilled labour and the traditional materials needed to build with – hence the emergence of non-traditional methods of construction.

As the name suggests, non trad methods of construction resulted in houses being built out of different materials to the traditional brick and block. Whilst literally hundreds of different types of non-traditional properties emerged and the actual materials used varied widely, they mostly fell into one of four main categories:

• Timber Frame: single storey timber framed panels that were externally clad and internally drylined.
• Metal Frame: Load bearing metal framework externally clad and internally faced.
• Insitu Concrete: Steel reinforcement added to formwork before concrete being poured on-site to create the framework. Often single skin and wet plastered internally.
• Pre-Cast Concrete (PRC): Factory made load bearing concrete columns and external concrete cladding infill panels transported to site and fixed together.

There is a fifth type which you should also be aware of – crosswall construction which consists of a timber frame construction between traditionally constructed gable end walls.

Non traditional houses were built quickly to resolve a specific housing issue. Speed was of the essence and there was little regard to thermal performance back then. The focus was solely on the short-term housing shortage. They weren’t designed to last with many having a design life of just 20 years or so. In spite of this people are still living in these properties to this very day!

Whilst these non-trads may not be officially classed as “solid wall” many (perhaps the majority) were built without a cavity of adequate dimensions to effectively insulate.

This means that much of the old housing stock can only be brought up to date by adding insulation to the external walls (external wall insulation - EWI) or the internal walls (internal wall insulation - IWI) and it's both of these measures which sit under the banner of solid wall insulation.

The challenge is substantial with Government figures for calendar year 2023 (2024 figures due out in March 2025) suggest there to be 8.5 million solid wall homes of which only 10% have been insulated.
 

The Effectiveness of SWI

New research led by Leeds Sustainability Institute (LSI) at Leeds Beckett University and in collaboration with University of Salford and Loughborough University has found that insulating the UK’s circa eight million solid walled homes has the potential to cut energy bills by up to 30 per cent and is essential to achieve the domestic energy efficiency targets.

The £3 million Demonstration of Energy Efficiency Potential (DEEP) project was commissioned by the Government’s Department for Energy Security and Net Zero. Investigating the retrofit (making energy improvements in homes) of solid walled homes, it is one of the largest research studies of its kind to have ever been attempted in the UK.

The Executive Summary begins with the following words:

Retrofitting solid walled homes is one of the greatest challenges for the UK in achieving its net zero ambitions. Solid walled homes have unique features, that require special consideration. They are among the least efficient in the UK, and their occupants are more likely to be in fuel poverty. They are also at elevated risk of surface condensation, excessive cold in winter and overheating in summer.

Retrofitting these homes is a cornerstone of UK policy to tackle fuel poverty and to facilitate the delivery of decarbonised electrified heat into homes

When looking at heat loss it was demonstrated that SWI alone could achieve between 19% and 55% reductions, equivalent to between a 7% and 38% fall in fuel bills.

Professor David Glew, Director of the LSI at Leeds Beckett University, said:
 

“Solid walled homes are among the least energy efficient – occupants are more likely to be in fuel poverty, and condensation, damp and mould problems can be common.
Our research found that insulating the solid walls of a home could save up to 30 per cent per year for some homes on their energy bills. It was by far the single most effective retrofit measure for solid walled homes – other types of retrofit couldn’t achieve the required improvement – and so this will be essential for tackling fuel poverty.”

Of course there are challenges and the report highlighted the cost of installing SWI and payback times along with the risks of unintended consequences especially when retrofits are installed in a ‘piecemeal’ way i.e., they did not consider how the retrofit measure affects risks of damp, inadequate ventilation, and overheating in homes – hence the adoption of the whole house approach in new technical standards for retrofit installers (PAS 20351) to ensure that all risks of retrofit measures were always considered.

That said, SWI was found to be “by far the single most effective retrofit measure for solid walled homes – other types of retrofit couldn’t achieve the required improvement – and so this will be essential for tackling fuel poverty.”
 

SWI - Fabric First!

At SWIGA we are strong supporters of a fabric first approach to retrofit which prioritises the energy efficiency of a building envelope over all other energy efficiency measures to maximise the positive impact of all current and future retrofit programmes to 2050.

• SWI as a Fabric First measure supported by renewable energy initiatives enables greatest bill savings and carbon reduction.
• SWI has the greatest cost saving impact on fuel bills of all energy efficiency measures (EEMs).
• SWI: delivers significant bill savings and carbon savings in comparison to all other insulation EEMs.
• SWI: Helps to deliver significant health benefits.

Clearly the Government has a focus on renewable energy and the installation of heat pumps which certainly have a major role to play but it’s got to be better to insulate the building itself and minimise heat loss before (or alongside) installing other such energy efficiency measures.

Even though they have removed a minimum requirement for insulation prior to heat pump installation Ofgem themselves still state:

"It is important that property owners understand that heat pumps perform best in a well-insulated property." 
 

Government Initiatives

On coming to power the Government unveiled a new national “Warm Homes Plan”.
 

Under this plan Prime Minister Sir Keir Starmer vowed that Labour would “upgrade every one of the 19 million homes below an EPC B and C over the course of the decade”, claiming that upgrading these poorly insulated homes across the country would save families around £500 per year on energy bills.

And at the pre-election Labour Party Conference Ed Miliband MP, the then Labour Shadow Secretary of State for Energy Security and Net Zero promised that: “with a Labour government, Britain will finally have what the Tories have refused for 13 years— a proper warm homes plan. Saving hundreds more off your bill. Creating tens of thousands of good jobs. Lifting millions out of fuel poverty. Insulating 19 million homes.”

This pledge was subsequently watered down somewhat – under the revised plans it was still intended to insulate some 5 million homes over the first five years of government though.

Around the same time Ed Miliband MP made a special visit to Maritime Court and Churchwood Court, to meet Housing Association Regenda Homes and see the impact of their newly insulated homes refurbished in partnership with Liverpool City Region funding and commented:
 

"Visiting these homes today brings home the reality of what having proper insulation can do - it saves money off people's bills but it also improves their quality of life.”
 

Why We Need SWI - Conclusion

So, the old housing stock means the demand is there, both EWI and IWI are needed to insulate these solid wall properties, as a measure solid wall insulation is proven to be highly effective and a well insulated building will optimise the impact of other energy efficiency measures.

The Government seem to recognise this need and the benefits that all forms on insulation provide so we need to overcome any hurdles in order that we can deliver on the demand, help get families out of fuel poverty and really make a difference economically as well as positively impacting both socially and environmentally.