In practice: Grosvenor’s highly sustainable redevelopment of a heritage building

Grosvenor Britain & Ireland's building project at 119 Ebury Street, Belgravia, is the UK's first listed building to achieve BREEAM 'Outstanding', utilising a range of low-carbon technologies that significantly reduce the site's environmental footprint.

The challenge

Grosvenor chose the project to investigate the extent to which listed, heritage buildings can be made more environmentally sustainable. 119 Ebury Street – winner of the Green Buildings category at edie’s 2017 Sustainability Leaders Awards – forms part of the company’s wider sustainability strategy which seeks to reduce carbon emissions across its London estate by 50% by 2030, against a 2012 baseline. The goal is made more challenging by the fact that 25% of properties on the estate are listed.

Making a significant energy savings in listed properties is challenging given planning constraints which limit the type and scale of changes required. Originally, 119 Ebury Street was a hotel in very poor condition, requiring substantial retrofit. Meanwhile, close collaboration was required with Westminster City Council and Historic England to convey the message that the heritage features of the original building would not be lost or damaged.

Challenges that arose during the construction phase included achieving high quality of finish expected in Grosvenor developments whilst trialling new and innovative materials, alongside high levels of air tightness whilst retaining and working with the existing building fabric.

The solution

Construction took place from 2014 to 2016 and saw the property refurbished from an old hotel into three residential apartments (two duplexes and a triplex)The development aimed to go beyond existing good practice and was designed to reduce carbon emissions by more than 75% from the property’s pre-development stage. This target is 34 years ahead of the national 80% emissions reduction target established for 2050.

The complexity of retrofitting a listed building has seen Grosvenor balance new technologies with existing period features, which have been preserved and enhanced. The building now incorporates a rainwater harvesting system which stores water at the front of the building, to be pumped into the three apartments.

High levels of insulation and use of triple and secondary-glazing contribute to the energy efficiency of the building. The use of phase change material allows the building to retain heat during the day and release it at night.  The scheme also incorporates photovoltaic panels on the roof and mechanical heat ventilation and recovery (MVHR) systems. A fully integrated building management system has been installed to enable the residents to monitor their energy usage, whilst encouraging energy efficient behaviour, for example shutting off the heating system if a window is opened.

Sustainability workshops were held throughout the development process to ensure the project was progressing in line with Grosvenor’s sustainability aims. These workshops, alongside tours with leading industry organisations including the Better Buildings Partnership, UK Green Building Council and the Urban Land Institute.

The benefits

The apartments offer a number of benefits to residents including lower energy bills, improved indoor air quality and better sound-proofing.

The property now offers tenants a 46% lower energy bill per annum and a 58% reduced carbon footprint. The building’s carbon emissions have been reduced from 29 tonnes per year, to 6 tonnes.

A new mansard roof and a rear extension to the ground and lower floors have increased the overall floor space of the building. Pollinator-friendly planting on the balconies and terraces in the garden have also enhanced the biodiversity of the project. An upgraded ventilation systems also provide tenants with improved comfort and health with continuous access to fresh air, while zero toxic materials such as low VOC paints were used during the retrofit.

Due to its role as a research initiative, costs were 30% above the basic specification, with the overall construction costs estimated at around £2.6m. However, the trial aspect of the project has enabled Grosvenor to demonstrate that sustainable technologies can be successfully used in historic buildings.

The future

The building was initially selected by Grosvenor to be a research and development project due to the similarities it shares with the nearby 125 Ebury Street building.

It will now be subjected to a two-year monitoring period against 125 Ebury Street using real-time data, allowing Grosvenor to obtain and better understand the cost-saving benefits. Grosvenor hopes the research will give other developers the confidence and insights to implement sustainable elements of the project at other listed buildings.

Grosvenor has selected specific waste contractors to arrange twice-weekly food waste collections, which the company hopes to rollout across its estate in the future. The property developer intends to let the apartments to occupiers that appreciate the sustainable features and are willing to take part in an ongoing monitoring programme of the building performance.

Over the next couple of months, Grosvenor will seek to gain feedback on occupier engagement over the sustainability features of the building.

Ebury Street is a crucial project for the future of Grosvenor’s overarching sustainability strategy. The completion of 119 Ebury Street follows Grosvenor’s delivery of other sustainably retrofitted properties across the estate, including London’s first properties to achieve ‘EnerPHit Passivhaus’ accolade. Grosvenor hopes to build upon the 300 homes retrofitted since 2013, which have already saved 1,932 tonnes of carbon equivalent.

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George Ogleby & Luke Nicholls

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