There were plenty of incredible sights in Glasgow during COP26. But if you happened to be passing by the Kingston motorway bridge, you’d have seen one of the best innovations from the world of construction. Sitting on the grounds of a former petrol station was the COP house – a wooden cottage modelling a much more sustainable form of housing.
The wooden roof, floor and walls are designed to capture sunlight and body warmth – limiting the need for heating throughout the building’s lifecycle. And the structure itself can be unscrewed, enabling the building to be dismantled and moved whenever needed.
Housing is a crucial topic across Europe, where many countries are facing a housing crisis. In the Netherlands, it’s estimated that 850,000 extra houses will be needed by 2035. But the challenge will be balancing this demand with the growing climate crisis.
While creating new houses will be part of the solution, it’s often said that the most sustainable house is the one that’s already been built. In other words, it’s better to work with what we have through retrofitting, than to start from scratch.
So how can we retrofit Europe’s houses to make them more sustainable – and what are the challenges and opportunities along the way?
The benefits of retrofitting existing houses seem fairly clear on paper. On an individual level, older, inefficient homes can be extremely costly for owners and residents, potentially causing financial strain.
In Scotland, a large number of tenement houses were built a century ago in the wake of the first world war, before energy efficiency was a consideration. In 2019, 30% of the residents of these tenements were classed as fuel poor, meaning they pay more than 10% of their disposable income on heating. With the rising cost of fuel, leaky houses may be a key social issue.
From a sustainability perspective, countries will need to improve their housing stock to meet their targets for carbon emissions. Across the EU, buildings account for 25% of greenhouse gas emissions. As a result, there’s growing demand for retrofitting, with the European Commission calling for 3% of buildings to undergo deep renovations every year by 2030.
But to date, retrofitting has often been completed on a small scale. That means projects have frequently been piecemeal and reactive, tackling short-term needs: for example, repairing a leaking roof or draughty windows. And unfortunately, with projects often awarded to the lowest bidder, quality has not always been high – and there hasn’t been much incentive for companies to innovate.
To meet sustainability targets, retrofitting will need to be amplified across Europe. In the UK, meeting the national goal of a net zero economy by 2050 would mean retrofitting one million houses a year for the next three decades. But that in turn means tackling questions at the heart of retrofitting.
Retrofitting is a balancing act of benefits and costs – and projects often involve lots of considerations. One question is the importance of conservation. Although less energy efficient, older houses have lots of desirable attributes, from period features like large bow windows in the Glasgow tenements to central locations.
There’s also the impact of retrofitting for residents. On the one hand, large scale retrofitting projects often require occupants to move out – causing disruption and pushing up costs. But on the other hand, an upgraded home can improve quality of life for residents in the long-term, with accommodation that’s warmer, weatherproof and affordable, which is particularly important for vulnerable people in protected housing.
Perhaps the most significant consideration is the financial cost. For both individual owners and public and private sector landlords, it can be difficult to justify the upfront investment in upgrades for long-term cost savings. But innovations are already underway, such as the funding model created by the Energiesprong Foundation – where the costs and benefits are split between owners and tenants.
Planning retrofitting projects can be complicated by a lack of accurate information. Particularly for older buildings, plans might be incomplete, outdated or lack key detail on the structure as it stands today.
Creating accurate digital plans, such as a data-rich BIM models, can provide owners with the insight to plan retrofits more effectively – looking at multiple options, as well as enabling collaboration with specialists in sustainable technologies.
Digital plans can also open up benefits for the future, such as enabling facilities team to maintain building in a more cost-effective, energy efficient way. By accurately recording the materials used, owners can also lay the groundwork for any future renovations.
Modern methods of construction can help to overcome limitations of retrofitting – which can be costly and time-consuming or piecemeal and low quality. The Energiesprong Foundation has partnered with manufacturing to create a “whole-building” approach, using prefabricated parts.
Building facades are constructed in factories, including insulation “jackets”, windows, roofs and doors. Rather than tackling flaws like cracks or leaks one by one, the building is upgraded all at once. This approach is often quicker, minimising disruption for residents; moreover, prefabrication reduces variables – creating repeatable projects for public sector owners.
It can be difficult for owners to assess the full implications of retrofitting projects. As well as the actual impact on of improvements on carbon emissions, there’s factors like air quality, health in the home and impact on the local economy. When projects are complete, evaluating the cost/benefits and identifying improvements for the future is not straightforward.
To enable large scale retrofitting, collecting consistent, meaningful data will be critical. The Build Upon 2 (BU2) programme has been designed to measure multiple impacts of building retrofits, with a suit of measurable indicators that can be used at a city level. The framework is already being adopted by more than twenty cities, including Dublin, Padova and Leeds.
Making data analysis the norm will help to inform government policy and enable public sector owners to build a stronger business case for future projects, unlocking further finance. It will also help private sector owners to deliver projects that are more impactful and efficient.
Mistakes can significantly worsen the sustainability of a retrofit project, or any kind of build. Errors can be both costly and environmentally damaging, by wasting energy and extra materials. Worse still, errors while installing environmentally-friendly features mean they don’t work properly for years to come. Digital construction platforms can help teams to build right first time, by ensuring up to date information, such as BIM models, is always accessible.
Collaboration and knowledge sharing can also be particularly important on renovations, which might involve multiple specialists working together. The instant information sharing provided by collaboration platforms means everyone can access what they need, when they need it and work together in real-time.
Making existing homes more sustainable will be critical for governments – and housing industries – to meet their sustainability targets. In the UK for example, 85% of the homes that we'll live in by 2050 have already been built.
It’s clear that sustainability is quickly rising up the agenda of both owners and construction firms. On average, European construction companies are planning to invest €900,000 in becoming a more sustainable company over the next five years – and customers and clients are the main driving force (84%).
Retrofitting projects will always be a balancing act. But with better data, modern methods of construction and the right fundamentals, we can upscale retrofitting – creating more efficient homes, that are in turn better for the people who live in them.
Read more about what’s driving sustainability in the construction industry in our recent research.