Grosvenor’s Sustainable Retrofit at 119 Ebury Street

31/07/2015

119 Ebury Street in Belgravia is the UK’s first listed building to achieve BREEAM Outstanding for its proposed design, the highest possible rating. Grosvenor worked closely with Historic England and Westminster City Council to design a scheme that both protects the historically significant fabric of the residential property and achieves leading sustainability standards. The building’s improved appearance, healthy, high quality environment and strong sustainability credentials are all expected to enhance its appeal to occupiers and may increase the property’s rental yield, at the same time as reducing environmental impacts.

BREEAM Global Residential Award 2015

86% lower CO2 emissions

Healthy and high quality environment

Significantly reduced running costs

Strong sustainability credentials

Enhanced occupier appeal

Situation

Grosvenor is a privately-owned property group, which aims to use resources responsibly and create high-quality places for people to enjoy.

At 119 Ebury Street, Grosvenor is creating three highly sustainable duplex apartments. The Grade II listed building was previously a hotel and originally a single family home. The scheme is part of Grosvenor’s Sustainable Retrofitting Programme, which will improve 300 residential properties across Mayfair and Belgravia.

When the BREEAM Domestic Refurbishment rating was launched in 2012, Grosvenor’s development team wanted to test the feasibility of achieving the highest level of certification in a listed building. BREEAM Domestic Refurbishment assesses not only energy and water consumption, but also the health and wellbeing of future occupants, the type of materials used, the management of waste and the extent of sustainability innovation.

Grosvenor chose 119 Ebury Street as the pilot for BREEAM Outstanding in a heritage context, aiming to:

  • Achieve an exemplar sustainable retrofit project that aspires to meet the Government’s 2050 national carbon reduction target of 80%
  • Investigate the effectiveness of new sustainable technologies suitable for retrofitting historic buildings
  • Work collaboratively with Westminster City Council and Historic England to explore the planning constraints on sustainable refurbishment of a listed building
  • Engage with residential end users to understand how to motivate them to choose to live in a sustainable property and how they interact with the sustainable initiatives provided
  • Assess the relationship between the cost and value of implementing sustainable initiatives.

Grosvenor received Planning and Listed Building Consent for 119 Ebury Street in May 2013. The project team includes David Morley Architects, Edward Pearce (mechanical and electrical engineers), Hurst Peirce + Malcolm (structural engineers), Eight Associates (sustainability consultant), Rickaby Thompson Associates (building performance engineers) and Grangewood (contractor).

Actions

Key sustainability features at 119 Ebury Street include:

  • Vapour-permeable solid internal wall insulation for retained walls, sensitive to the building’s heritage features, whilst minimising the risk of interstitial condensation and improving U-values (reducing heat loss)
  • Lowest possible U-values targeted for new walls (0.15W/m2K), new flooring (0.20W/m2K) and the new mansard roof (0.15W/m2K)
  • Air tightness target of 3m3/hr/m2 to minimise heat loss and provide a pleasant internal environment, through a strategy of tapes and membranes, as well as secondary vacuum glazing on most retained windows and triple-glazed timber frame windows on the new extensions
  • Automated window shading
  • Whole house ventilation and heat recovery, with carefully considered design to integrate the ductwork into the listed fabric
  • Healthy internal environment through the constant supply of pre-warmed fresh air and the specification of low VOC fittings and finishes throughout
  • Photovoltaic and solar thermal panels to generate electricity and hot water
  • High efficiency boilers with heat recovery
  • Rainwater attenuation to reduce local flood risk
  • Rainwater harvesting to provide year round water for toilet flushing and garden watering
  • Low-flow toilets, taps and showers to minimise mains water consumption
  • Integrated building management system, to optimise efficiency, monitor consumption and provide user-friendly occupant controls, with remote control over heating and lighting
  • Materials strategy including high levels of recycled content and sourcing from local suppliers where possible.

Once 119 Ebury Street is completed in 2016, the scheme will undergo a two-year post-occupancy monitoring programme led by Rickaby Thompson Associates. This will benchmark the building’s actual performance against a standard Grosvenor refurbishment.

Benefits

  • 86% reduction in forecast operational CO2 emissions, exceeding the Government’s 2050 target, well before it may become a statutory requirement
  • 19% reduction in operational water consumption
  • Healthy, high quality environment for occupants, designed with their comfort and convenience in mind
  • Strong sustainability credentials, minimising environmental impacts and significantly reducing running costs
  • Enhanced appeal to occupiers, which may increase the property’s rental yield
  • Recognition for Grosvenor, Historic England and Westminster City Council, leading the market for sustainable retrofit of historic buildings
  • Improved understanding of the relationship between the cost and value of sustainability initiatives, through the post-occupancy study.

Financials

  • 30% projected capital investment premium versus Grosvenor standard refurbishments
  • 76% forecast reduction in utility bills for occupiers
  • £6.2 million property value
  • £208,000 annual rental value.

Challenges & Achievements

 

START EARLY

 

How to achieve the highest sustainability standards?

At 119 Ebury Street, strong sustainability aspirations from the outset have been key. Grosvenor appointed Eight Associates during the pre-planning phase to advise on the BREEAM and energy strategies. Together, Eight Associates and Grosvenor carried out an occupant profiling study to understand the expectations of occupants and identify opportunities to optimise the design.

 

PLANNING

 

How to achieve planning consent for sustainability improvements in a listed building?

Grosvenor’s London estate includes 1,500 listed buildings, a quarter of its London portfolio. The planning constraints for altering listed buildings mean significant energy saving improvements are challenging. At 119 Ebury Street, Grosvenor worked closely with English Heritage and Westminster City Council to explore a range of smart technological enhancements, considering their potential and appropriateness within a heritage building. 119 Ebury Street is a pilot that Grosvenor hopes will bring about clearer guidance for the sustainable redevelopment of heritage properties.

 

RETROFITTING

 

How to balance preservation of historic fabric alongside cutting edge sustainability initiatives?

At 119 Ebury Street, the team is trialling some previously untested technologies and building methods, which can bring challenges. For instance, they are exploring alternatives for the innovative solar slates originally specified, as these are no longer in production. It also continues to be challenging to achieve the required air tightness levels of 3m3/hr/m2, when working around retained historic building fabric. Initiatives at 119 Ebury Street will inform Grosvenor’s future approach to reducing the environmental impact of heritage buildings whilst conserving the character of the company’s London estate.

Find out more

E: sustainability@grosvenor.com

T: + 44 (0) 20 7408 0988

http://www.grosvenor.com

 

Relevant links

“119 Ebury Street sets a benchmark for the sustainable retrofit of listed buildings in the UK. Through the hard work of a close-knit design team and the co-operation of a forward-looking council, a scheme has been produced that demonstrates how much the environmental impact of a listed building can be reduced, whilst preserving historically significant urban fabric.”

Judges at the 2015 BRE Awards