Preserving heritage and embracing sustainability: Decarbonising the UK's oldest buildings

Why decarbonising existing buildings is crucial for the UK's climate goals

Knock it down and start again - this has too often been the damaging default within our industry. With the construction industry's crucial role in achieving climate targets, we know we can’t build our way to Net Zero.

An essential step on this journey is to address the impact of existing buildings. The UK has the oldest building stock in Europe with 5.9 million buildings built more than 100 years ago, underscoring the scale and importance of the issue.[1] Many of these buildings represent a significant roadblock on our journey to meet important climate milestones whilst also being at risk of becoming a stranded asset. As knowledge and attention to energy reduction expands, the industry has turned its eye to spent carbon and whole life carbon as the key to unlock existing buildings re-use strategy.

What is whole life carbon?

Whole life carbon is essentially made up of two main aspects, operational carbon and embodied carbon. Operational carbon is used during the building’s operational lifetime for heating and powering the building. Embodied carbon is the energy and carbon used to extract, manufacture and transport the materials to the site and to construct the building.

Traditionally as an industry, the focus has been to reduce operational energy as this is more understood and the visible aspect of the energy consumption, and reducing it gives saves the general public money.  In contrast, there has been little onus or regulation placed on reducing embodied carbon. Despite this, the narrative towards this is shifting, with the industry having to think holistically about our carbon footprint. More needs to be done to focus on reducing the energy intensity of the materials extraction, processing and transportation.

But what does decarbonising mean?

Decarbonising refers to the reduction or removal of carbon dioxide from the environment. For the built environment, this relates to in-use energy and construction. Therefore, to decarbonise we must reduce both our energy use and our construction impacts. In order to achieve true decarbonisation within our sector, we must focus on decreasing this impact.

With Net Zero an increasingly fraught and important topic, we have to ask how do we decarbonise existing buildings? A common assumption is often that we should knock down existing buildings and start from scratch, which isn’t the case. As the climate crisis intensifies, we need to preserve our existing buildings wherever possible through retrofitting or decarbonising. Something we often see successful evidence of, specifically in Scotland as many churches, schools and older office buildings have undergone these modifications to better the building and make use of its existing structure.

However, it is vital that decarbonisation methods are better utilised and continue to be enforced. As part of the Scottish Government’s £20 million public sector heat decarbonisation fund, which launched last year, £11 million has been awarded to seven projects across Scotland, including Edinburgh University. This is evidence of a positive move in the right direction.

In a further bid to cut carbon emissions, the Scottish Government also introduced a £230 million fund late last year to improve the energy efficiency of public buildings which will be available to schools, hospitals, leisure centres and other public buildings. To date, 1,000 buildings are already receiving updates which has resulted in them saving thousands of pounds on energy bills.

In previous years, there has been a real lack of financial support for decarbonising buildings in the UK, so to see a fund for these buildings is hugely positive and is a step the engineering industry welcomes. However, we are still at risk of falling short of our Net Zero trajectory, the industry is crying out for further funding or financial incentives targeted towards developing the skills and infrastructure we need to decarbonise existing buildings at scale.

Decarbonization & Retrofitting Explained

In simple terms, retrofitting is modifying an existing building to reduce energy consumption. Doing this avoids the carbon emissions that come with demolition and building from scratch, in particular the large amount emitted from cement and steel produced by construction.

Decarbonising on the other hand means reducing the amount of carbon emissions across the entire building’s life cycle, from start to finish by reducing energy and materials used.

There are several ways to decarbonise existing building stock such as implementing fabric first, smart controls and renewable however no one size fits all, and should be assessed on a case-by-case basis through data gathering and informed decision making.

Having a fabric first approach is also essential when it comes to reducing energy demand. Considering the materials used in the early design stage will help identify how to conserve heat, this includes identifying what materials are used for the building structure such as walls, if the windows are triple glazed or double glazed and how the roof of the building will perform when conserving heat. Having a building fit to keep the heat in, will reduce the need for energy as most of it will be stored with less chance of it escaping.

Another key element to decarbonising our building stock is understanding the carbon spent to construct a building in the first instance and reducing it where possible. Engaging the right structural engineer early in the process is key to establishing the savings to the initial upfront carbon spent in the materials during construction. Early collaboration with the client and the design team can result in significant material savings, saving both costs and carbon.

We are currently working with the University of Edinburgh to refurbish 40 George Square Tower to minimise the energy demand during operation of the building, whilst also minimising embodied carbon required in the up-front construction process.

What’s holding us back?

The lack of workforce is a key challenge in the industry and our ability to achieve Net Zero. Recruitment across engineering is proving to be tough but with the introduction of this new Scottish Government fund, there may be an opportunity for both new jobs and training in green skills.

Obviously, not every single building can be decarbonised. Whilst there rightly should be a focus on older buildings, decarbonisation expands out to wider areas such schools, public and private sector buildings, which aren’t always decades or centuries old.

Additionally, legislation continues to develop as we are advancing industry knowledge on carbon emissions reduction technology and practice. The upcoming (expected Spring 2024) Net Zero Carbon Building Standard should play a pivotal role in pushing the whole life carbon agenda with regulators, which will hopefully drive retrofitting to the forefront of development.

To assist the upcoming regulations, many call for VAT relief on retrofitting to trigger the financial incentives. Under the current financial system, many pay the 20% VAT on retrofit but not on a new build which is a huge financial barrier to developments which results in developers feeling pushed to knock down old buildings and stat again. Whilst this is good for energy reducing operational energy, it has a detrimental effect on embodied carbon, as material used in the current building will go to waste, resulting in use of more carbon intensive materials to build new.   

Time to speed up

With the Scottish Government now rethinking its target of achieving 75% reduction greenhouse gas emissions by 2023, now is not the time to slow down. We should be accelerating. Achieving Net Zero is a major driver for most of us in the industry, however, we are seeing many shying away from environmental responsibility due to lack of knowledge or hesitation to move with the times. The news of this potential target change shouldn’t be a sign to put the brakes on but a catalyst of accelerated effort towards reaching Net Zero by 2045 in Scotland.

The engineering industry must push forward and drive decarbonisation throughout various buildings across the UK and debunk this ideology that we must knock down and start again. There are tried and testing methods to better our buildings to enable us to reach approaching climate timelines, but we need to take charge to adapt and utilise them.

As businesses are obliged to publicly declare their annual carbon emissions, we see more ESG lead demands to the built environment, which hopefully aligns and aides us to travel in the right direction towards Net Zero.

[1] https://www.propertymark.co.uk/resource/barriers-to-future-proofing-the-uk-s-historic-buildings.html