UK-GBC ON SITE LEARNING CASE STUDY EBURY STREET

Transcription

1 UK-GBC ON SITE LEARNING CASE STUDY EBURY STREET INTRODUCTION In September 2016, the UK Green Building Council (UK-GBC) with Grosvenor and David Morley Architects, invited a group of members to 119 Ebury Street for an on-site learning tour. The Grade II listed building, located in Belgravia s Conservation Area, was originally a house and more recently a hotel. In 2013 Grosvenor Britain and Ireland was granted listed building consent to pilot a sustainable retrofit development of three highly sustainable apartments. The scheme is part of Grosvenor s Sustainable Retrofitting Programme which will produce 300 residential properties sustainably retrofitted across Mayfair and Belgravia. The tour provided an in-depth opportunity to understand the drivers behind the building design, construction methods, development features and sustainable technologies included in the Grade II listed building. This detailed case study, compiled with Grosvenor and David Morley Architects, aims to give professionals in the construction and property industry a deeper insight into the first listed residential building to achieve a BREEAM Outstanding rating at the design stage. PROJECT HIGHLIGHTS Anticipated to reduce the building s carbon emissions from 29 tonnes per year, to 6 tonnes, meeting the Government s 2050 target of an 80% reduction in emissions The project won the 2015 Best Global BREEAM Residential Refurbishment Award for its sustainable design The first listed residential building to be awarded BREEAM Refurbishment Outstanding rating at design stage A pilot project for Grosvenor to push the boundaries on sustainable retrofit in listed residential buildings 119 Ebury Street will be monitored to assess building performance over a two-year period. This will be compared against 125 Ebury Street, a similar property refurbished in 2012 Retained heritage features including; sash windows, the original staircase, cornices and mouldings, joinery, original fireplaces, wall and ceiling finishes 1

2 PROJECT DETAILS Location: 119 Ebury Street, Belgravia, London Ratings: BREEAM Refurbishment Outstanding at the design stage for a Grade II Listed Building Completed: 2016 Developer/client: Grosvenor Britain and Ireland Architect: David Morley Architects Contractor: Grangewood Builders Mechanical & Electrical: Edward Pearce Structural Engineer: Hurst Pearce and Malcolm Environmental Consultant: Eight Associates Monitoring Consultant: Rickaby Thompson BMS and controls: Perfect Integration Interior Designers: TH2 Designs THE DRIVERS FOR 119 EBURY STREET Grosvenor identified 119 Ebury Street as a pilot project to push the boundaries of sustainable development in listed residential buildings and monitor how occupiers interact with new sustainable technologies. Grosvenor were able to work alongside Westminster Council and Historic England to discuss their sustainability principles and are aiming to set a precedent for future planning policies on listed buildings. This is a particular challenge for Westminster Council that holds over 11,000 listed buildings and requires innovative methods for sustainable retrofit. The government s challenge to reduce carbon emissions by 80% by 2050, against 1990 levels, has driven Grosvenor to test themselves and respond by dramatically reducing carbon emissions. The reduction has been included in their listed building portfolio, which accounts for 25% of their total estate. Over the past 10 years, Grosvenor have produced a redevelopment strategy for Ebury Street which saw dilapidated buildings (listed and nonlisted) reinstated. However, to push their internal redevelopment plans to achieve more sustainable outcomes, a single building was targeted to see what level of sustainable design could be achieved.

3 KEY OBJECTIVES A crucial objective of this retrofit was to learn from the delivery of the three apartments and transfer the knowledge onto future projects. To deliver a successful project, Grosvenor set out the key objectives from the start to the project team: Investigate new sustainable technologies and materials that can be used on listed buildings. Collaborate with key stakeholders (Westminster Council and Historic England). Educate the existing team on sustainable building techniques to retain and transfer knowledge. Educate and engage with letting agents to promote understanding and ensure active marketing. Educate and engage the residential end user to understand what motivated them to live in a sustainable home and obtain relevant feedback. The objectives for the project team are directly informed by Grosvenor s sustainability strategy, Living Cities, whereby the business aims to make a lasting contribution to communities and the environment. The objectives to investigate, collaborate and educate on a project level, put into practice the overall aim to make a long term contribution to the success of London as a sustainable city. This is achieved through using creative design, high quality building methods and innovative environmental solutions, all demonstrated in 119 Ebury Street. PLANNING AND DESIGN In 2008, Grosvenor began considering the project for 119 Ebury Street and in 2010, the property was acquired. After a three-year planning period, the consent to retrofit the building was granted in June Westminster Council and Historic England required assurance that the heritage character of the original building would not be lost or damaged. To address this Grosvenor created a mock-up room with features of the new apartments. The glazing and insulation were primarily tested to demonstrate the sustainable features to the stakeholders, and as a result, Grosvenor were granted permission to trial a range of sustainable initiatives throughout the three apartments. The design brief set by Grosvenor ensured that innovative, sustainable technologies were fully integrated into the three functioning apartments that would be available to rent. Thermal imaging, air testing and performance modelling were all undertaken to fully understand the inefficiencies of the existing building and propose the appropriate retrofit solutions. CONSTRUCTION Construction took place from 2014 to 2016 and presented a steep learning curve for the construction team in using new materials and sustainable technologies. Challenges that arose during the construction phase included achieving: High quality of finish expected in Grosvenor properties with alternative new and traditional materials; and High levels of air tightness whilst retaining and working with the existing building fabric. The lessons learned on material selection and air tightness in this building will be applied to future projects aiming for the same standard. 3

4 DEVELOPMENT FEATURES AND SUSTAINABLE TECHNOLOGIES The principal features at 119 Ebury street include the existing heritage aspects and new integrated technologies. The key sustainable design improvements include: Reduction of unwanted air leakage through the building fabric Secondary vacuum glazing and triple glazing Rainwater harvesting and attenuation High performance thermal insulation Photovoltaic and solar thermal panels Phase change materials for temperature control Whole house ventilation and heat recovery Integrated smart home system with energy monitoring Responsibly sourced materials Low energy LED lighting Native planting A key feature of the development is retaining the form of the existing building, whilst adding to it with a new rear extension on the ground and lower floor, and a closet wing on the first floor level. The design of the retrofit kept the original layout of the listed structure and also retained the exposed brickwork to keep the original feel of the terrace properties along Ebury Street.

5 Construction materials and interior design finishes were selected based on their sustainable attributes. The same ethos was carried forward for the furnishings. TH2 Designs were appointed to complete the interior design with a brief to source from British manufacturers and suppliers. This method of sourcing reduced the number of miles from the suppliers to the development. The sustainable technologies include solar PV panels to provide renewable energy to the first floor apartment and solar thermal to the ground floor apartment. Triple and secondary glazing are used throughout. Brise soleil are also installed to shade one of the south facing windows. Grosvenor will assess the effectiveness of this method in preventing overheating. Phase change material is included in the middle and upper floor apartment, to help stabilise indoor temperatures. This is built into the ceiling and walls, and absorbs and delays heat build-up during the day throughout the summer. The heat is then released by ventilating the apartment with cooler air overnight. For internal walls, Fermocell board is used instead of traditional plasterboard dry lining. This is made of recycled gypsum, waste card and paper. By using a single board type that can be used for sound, fire and moisture-resisting applications, on-site wastage is reduced. The rainwater harvesting system provides three functions. Firstly, rainwater run-off from the front roof pitch is re-used for flushing the toilets in the three apartments. Secondly, rainwater runoff from the rear roof slopes is collected for irrigation of the garden and first floor terrace planting. Thirdly, any surplus runoff is held in an attenuation tank to reduce the risk of flooding due to overload on the local drainage network. Overall, the building is expected to use 32% less water (around 12,000 litres) than a similar property that has not been retrofitted. Other technologies include a smart home system for each apartment. The system controls lighting, room temperatures, window opening and can be set up to reflect the needs of the occupier. The system includes an energy monitor allowing occupiers to review their energy and water usage in the form of a traffic light system. A weather station is on the front of the property enabling the system to automatically close windows if they are open and it starts to rain. The system also prevents occupiers from turning the heating on if an external door or window is open in the same room. 5

6 Apartment one 3 bedroom / 1,672 sq ft Ground floor plan Reception Room 4.91m x 4.08m 16 1 x 13 5 Reception Room 3.60m x 3.54m x 11 7 Kitchen 6.58m x 5.41m 21 7 x 17 9 Void Garden 5.78m x 5.70m 19 0 x 18 8 Lower ground floor plan Bedroom 5.21m x 4.79m 17 1 x 15 9 Bedroom 4.81m x 3.35m 15 9 x 11 0 Bedroom 4.20m x 1.71m 13 9 x 5 7 Patio All furnishings sourced from British manufacturers and suppliers, by TH2 designs.

7 LESSONS LEARNED The completion of 119 Ebury Street has allowed Grosvenor and the design team to learn from the process of planning, designing, constructing and letting three BREEAM Outstanding apartments. The design features and sustainable technologies have challenged Grosvenor and the project team, but have also provided ample opportunity to learn from the experiences and successes. The means whereby challenges were addressed will be discussed in their imminent lessons learned workshops, with the feedback being taken forward onto future projects. In regards to leasing strategies, Grosvenor has taken lessons learned from previous sustainable developments that have shown occupiers do not appear to be motivated by sustainable initiatives. To address this, Grosvenor aimed to influence the opinion of occupiers at 119 Ebury Street and the way letting agents view and present sustainable projects. One way of achieving this was to engage and brief the agents, by undertaking a walking tour of the apartments and educating them on the sustainable features and their benefits for the end user. Grosvenor 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. POST OCCUPANCY EVALUATION The purpose of a post occupancy evaluation is to understand the in-use performance of the apartments and how the end user interacts with the sustainable features. The performance of 119 Ebury Street will be compared to 125 Ebury Street, which was recently upgraded to Grosvenor s minimum standards. This information will be used to build the business case for a more sustainable approach to retrofitting listed buildings. Grosvenor has commissioned a two-year monitoring program to cover: Energy, fuel and water consumption Internal comfort conditions Occupant satisfaction Effect of the insulation upgrade on the existing building fabric The monitoring strategy will include: A design review Occupant interviews Monitoring of fuel use, energy and water monitoring Temperature monitoring Fine tuning of design features the in early stages Regular reporting and an annual review Interstitial condensation monitoring Fault detection of features Regularly reviewing the energy display CONCLUSION The onsite learning tour at 119 Ebury Street has demonstrated that Grosvenor is willing to step out of its comfort zone and tackle the challenge of retrofitting a listed building. The successful refurbishment maintains the Grosvenor luxury look for all three apartments, makes significant environmental improvements, and commits to focussing on the future interaction of the occupiers and building performance. 7