Low Energy Retrofit and Extension at Devonshire Mews West in Marylebone
Argal Farm Creative Studios Combine Strategically Retrofit and New Build

When We Build, Let Us Think that We Build Forever  1

Many of Woldon’s projects involve refurbishing existing buildings, finding new uses and giving them fresh life. As we pursue our vision, we find inspiration and narrative in their texture and grain. In tandem, reusing our existing buildings and their fabric is also key in addressing our carbon emissions.

The built environment contributes around 40% of the UK’s total carbon footprint. Approximately 75% of this comes from operational emissions (from energy used to heat, cool and light buildings) with the remaining 25% from embodied carbon emissions, that is associated with materials and construction throughout the whole building lifecycle. 2

New buildings tend to be more energy efficient, but demolition and rebuild is an energy-intensive process with significant upfront carbon emissions. The UK’s commitment to achieving a net zero-carbon status by 2050 has profound implications for architecture. 80% of the buildings that will exist in 2050 have already been built, so retrofitting and upgrading our existing building stock is critical in lowering carbon emissions.3 The RIBA has recently published an update to its 2030 Climate Challenge agenda which sets out building carbon emission targets for 2030, in order to have a realistic prospect of achieving net zero by 2050.

We look at three recent Woldon projects which approach retrofit and low energy refurbishment in different ways.

80% of the buildings that will exist in 2050 have already been built, so retrofitting and upgrading our existing building stock is critical in lowering carbon emissions. 3

An Opportunistic Approach

Devonshire Mews West is a late 19th century mews house in Marylebone that forms part of The Howard de Walden Estate.  The Estate is working towards net zero carbon emissions and as steward to over 200 Listed Buildings, the enhancement of sustainability credentials for period buildings is a key focus.  The brief was to refurbish the mews sustainably, improving the quality and size of the interior spaces while retaining its historic character. The design also needed to be robust, with a low maintenance strategy, which also minimizes unnecessary finishes and waste.

Behind retained masonry façades, the building has been reconfigured to improve circulation and a lightwell introduced through all floors to bring natural light to the basement. Most of the external masonry is retained and existing walls are insulated internally. A Mechanical Ventilation and Heat Recovery (MVHR) system together with airtightness provision maximises energy efficiency. The palette of finishes is robust and simple, with sustainable timbers and ceramics throughout. The party walls are in traditional London stock brick, eliminating an unnecessary layer of plasterboard and plaster which might only last until the next renovation. The exposed brick gives a sense of the history and texture of the mews.

There is no universal solution to improving the sustainability of existing buildings so it needs some strategic thinking and careful consideration of the issues. Laura Jockers, Head of Sustainability for the Howard de Walden Estate captures the challenge: “when you put [the] triad of planning, technical and conservation challenges together, you’d be forgiven for thinking improving the energy efficiency of period buildings is an impossible task: it is not. It just takes an opportunistic approach”. 4

Introducing Natural Light to the Basement at Devonshire Mews West
Argal Home Farm Creative Studios and Workshop

Being Strategic

At our Argal Farm project in rural Cornwall, Woldon encountered a different set of challenges. Our client,  furniture designer James Smith Designs, gave Woldon a brief to transform the former farmstead into an inspirational place to live and work, based on low energy principles. Proposals involved the conversi­­­­­­­­­­­on of a traditional stone barn into studios for local enterprises, and the creation of a new workshop facility for the client’s business. Where possible, existing structures and fabric were retained, with a strategic decision made to demolish a derelict stables that was of poor build quality and beyond repair. The principles of Passive House were followed, providing the workshop with exceptionally low embodied and operational carbon energy usage and, through the timber design, high levels of carbon sequestration. At the studios, 500mm thick granite walls were restored using lime mortars and provide significant natural thermal mass which was enhanced with further insulation internally.

A biomass boiler provides heat to the entire farm which is supplemented by photovoltaic panels integrated into the workshop roof. The biomass boiler is supplied from local sustainable Cornish woodland, minimizing road haulage.  The project has the potential to come close to achieving net zero energy.

Building Flexibility and Simplicity into the Design

Argal workshop is a robust and simple design. It uses a glulam timber frame, based on a repeating grid, with wide structural spans that allow for future partition and adaptation. Some feature such as the mechanical extraction are unique to the workshop brief, but flexibility is inherent in the design and the structure is adaptable for future change.  As an industrial building, the workshop is suited to simple finishes with ply covering many of the surfaces, but this approach can be applied to other building types. Traditional finishes like plaster are typically labour and maintenance intensive and not always necessary.

...of the 200 million tonnes of waste generated in Britain annually, 63 per cent is construction debris

Building for Deconstruction

Demolition and rebuild is typically an energy intense process. The Architects Journal reports how “[a]ccording to the Department for the Environment, Food and Rural Affairs (Defra),of the 200 million tonnes of waste generated in Britain annually, 63 per cent is construction debris” 5

Some building elements are suitable for direct extraction and reuse such as steel structure and this technique already has some traction. Nonetheless, it relies on deconstruction (the plan for taking the building apart at the end of its life) having been considered during design and construction, and materials being properly audited.  Retrieving materials more widely is possible but often entails downcycling to a lower grade product, rather than true recycling.

Argal’s thick granite walls were restored and provide significant natural thermal mass which was enhanced with breathable insulation internally.
Studio space in the refurbished granite barn at Argal Home Farm
Before RetrofitAfter Retrofit

Deep Refurbishment

In a recent report by Aecom, 60 per cent of embodied carbon emissions are associated with the sub structure, frame, upper floors and roof of a building. “A deep refurbishment should retain these elements, meaning on average, the carbon footprint of a refurbished building is half that of the newly-built replacement.” 6The frame and structure are also the elements with the longest life span, lasting in excess of 100 years. Laterally, this principle is well-established in a rural context, where Class Q and R Permitted Development rights have allowed for the change of use from agricultural buildings to dwellings and commercial uses respectively, and specifically require that the existing structure is retained. While not necessarily motivated by a low-carbon agenda, this policy has been widely adopted and lots of steel frame barns have been given a new life.

While permitted development rights which allow for change of use from commercial and retail to residential (Class MA) can be divisive, the results can be highly sustainable. On the South Coast, Woldon has recently developed a design for converting a redundant government back-office building to residential, reusing the existing concrete frame and recladding with winter gardens. The winter gardens increase the floor area and provide additional solar shading and insulation to the apartments. Redundant high street retail spaces are also in the spotlight and have huge scope for retrofit innovation and townscape reactivation.

Capital Commitment

A retrofit brief may focus on changing and upgrading a building’s specification like at Devonshire Mews or expand to include a change in use, like Argal Farm. Both routes have their own merits and scope for innovation in reducing energy consumption and carbon emissions. The motivation behind a capital investment in a retrofit project is, however, likely to involve a range of market factors beyond reducing energy consumption and carbon emissions, for example, improving comfort, convenience and place-making. For owners and managers of existing built assets, there will also be ongoing programmes for periodic maintenance and refurbishment for consideration. The extent and initiation of a retrofit project will be informed by progress through that cycle.

Legislation and Wider Environmental Change

In October 2021, the government published its Heat and Buildings Strategy which sets out how the UK will decarbonize its homes by 2050 and makes funds available to homeowners to switch to low-carbon heat systems like air source heat pumps. This is a significant policy, but for the wider adoption of retrofit strategies, further legislation is required. In general, refurbishment work incurs the full VAT rate. While there is a reduced VAT rate of 5% in some circumstances including conversion from commercial to residential dwelling, taxation currently favours new build which is typically zero rated. The London Plan has set out its Whole Life Carbon Assessment process and recently published its draft Circular Economy Statement which sets out some strong principles for ‘reducing waste….where materials are retained in use at their highest value for as long as possible and are then reused or recycled, leaving a minimum of residual waste”. But this is still a long way from recycling buildings.  Encouragingly, however, there is a growing body of resources and products available to assist designers and client with retrofit projects. For example LETI 7 published recently the valuable Climate Emergency Retrofit Guide which presents case studies on how to achieve effective low energy retrofit for different types of building.

An equally important factor, yet distinct from carbon reduction, is biodiversity. The policy of Biodiversity Net Gain (BNG) establishes the principle that planning permission should only be given if a new development project increases rather than reduces levels of biodiversity present on a site. This strategy is well-established with some Local Authorities but is now enshrined in the National Planning and Policy Framework (NPPF).

Longevity and the Culture of Reuse

The appetite for reuse and adaptation is not unique to buildings, as we become acutely aware of our finite resources. While there is a romanticism and cultural value in repurposing buildings that are 150 years old, it is the younger ones, 25 years old or less that should have just as much potential.  The words of 19th century art critic John Ruskin ‘…when we build, let us think that we build forever.’ 8 carry fresh meaning today as we think how our architecture facilitates adaptation and promotes reuse in the future.

[1] The Seven Lamps of Architecture, John Ruskin, Dover Publications 2000
[2]  World Green Building Council, www.worldgbc.org/
[3]  UK Green Building Council https://www.ukgbc.org/climate-change/
[4]  "Improving the energy efficiency of period buildings just takes an opportunistic approach" Laura Jockers E6 Estates Gazette 30th January 2021. pp.34
[5] https://www.architectsjournal.co.uk/news/introducing-retrofit-a-new-aj-campaign-championing-reuse-in-the-built-environment
[6] https://aecom.com/without-limits/article/refurbishment-vs-new-build-the-carbon-and-business-case/ by Dave Cheshire, Sustainability Director and Mike Burton, Director of Building Engineering, Aecom.
[7] LETI was originally founded as the London Energy Transformation initiative, https://www.leti.london/retrofit
[8] The Seven Lamps of Architecture, John Ruskin, Dover Publications 2000
Argal Workshop
Locally Sourced Wood Chip and Timber Waste from the Workshop, Supply the District Biomass System to Heat Sustainably, the Whole of Argal Farm