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July 4, 2022

Blog by

Emily Braham

Photo by

Melius Homes

Offsite construction – one piece of the puzzle for scaling up retrofit

Netherlands-based factories building parts for Energiesprong retrofits have improved the labour productivity of construction by 75% and reduced waste by 90%.

That’s why we propose that offsite construction is one of the key principles for scaling up deep retrofit in the UK by making it more cost-effective and quicker to install.

In the Energiesprong deep retrofit approach, homes are fully insulated using offsite manufactured wall and roof panels in conjunction with pre-assembled 'energy pods' - creating warmer, more desirable places to live that are financed by energy and maintenance savings.

The Energiesprong approach to deep retrofit

In fact, since starting to deliver Energiesprong retrofits in the UK six years ago, Melius Homes - one of our solution providers - has achieved significant productivity and performance gains in its factory with a typical installation period reduced by 60% and cost reduction of ~45%. You can read more about Melius Homes' factory in this recent piece by Building Magazine.

Currently there are 9.3 million UK homes suitable for offsite manufactured net-zero energy retrofit solutions - of which 2.1 million are in social ownership - found Innovate UK, so the opportunity is huge.

Offsite construction not the always the answer

We’re often asked: “what about these beautiful Victorian terraces?  How will an offsite solution work for these?”

Offsite construction won’t work for everything! It needs to, for now at least, be focused on the properties which are easiest to retrofit with standardised solutions – for example, homes without complex details or homes where there’s a significant volume of very similar properties.

Our overarching focus should always be on the big picture – the enormous challenge of retrofitting our ageing housing stock. And offsite construction is just one piece of the puzzle for building an industry for desirable, net-zero homes. There is no doubt that a huge scale-up of more traditional retrofit approaches is also needed with the labour force trained quickly in these skills.

What homes work best for offsite construction?

Properties most suited to offsite facades include those built after the war under the Emergency Factory Made Housing Programme. These properties are built from concrete - only meant to last 50 years, but still providing housing to 1000s households some 80 years later - are perfectly suited to a large offsite programme.  

These were built to standard patterns, have very little aesthetic quality and many need regeneration.  These are a focus for Energiesprong and our partners, and include Cross Walls, Timber Frames, Wimpey No Fines, and Concrete Panel properties.

In addition to these non-traditional properties, there’s also the large number of brick council houses which were built between the first and second world war. They were also built to standard patterns, and were often built without cavities or with very narrow cavities in the walls, meaning they are hard to insulate unless using an external solution.  

These include a large volume of fairly standard properties with minimal detailing. Often they've been rendered in the past - meaning they're already changed in appearance - so planning officers have less concern about them being insulated.

The Energiesprong approach to deep retrofit has been piloted on a number of cross wall properties by Nottingham City Homes and Melius Homes, pictured above before and after.

It’s time for action, not talk

By segmenting UK properties into the ones that suit offsite and the ones that require craft-based traditional approaches, we can grow both sectors rapidly. And once the industry is operating effectively and efficiently -  and costs are reducing for the simpler offsite solutions -  innovation in aesthetics and more complex bespoke solutions will follow.

At last year’s Royal Society conference on unlocking building sustainability, Adrian Joyce from EuroACE said "there is no silver bullet’ for retrofit", we need a range of solutions.

With millions of homes to retrofit, we can’t afford to spend any more time discussing the ‘best’ way forward – we need to draw on the solutions already out there, choosing the best for each situation and learning from one another along the way.

Our next part of this blog will explore the challenges we’ve discovered while testing approaches to offsite construction in the UK – as well as our proposed ways forward.

Photo credit: Melius Homes

Whole House Retrofit Nottingham is led by Nottingham City Homes, Nottingham City Council and Energiesprong UK. It’s funded by the Department for Business, Energy and Industrial Strategy.