An exemplar sustainable housing refurbishment in a London conservation area
31 -35 Craven Hill Gardens is located to the north of Hyde Park, within the Bayswater Conservation Area in central London.
The property is located to the north of the main square, overlooking the garden in the centre. The building is of late 19th Century origin and comprises five stucco-fronted townhouses with seven floor levels including the basement and mansard roof. The development involved the transformation of the existing buildings 31 – 35 Craven Hill Gardens, previously used as a hotel, into a residential complex with 18 apartments in a mix of unit sizes, ranging from studio flats to four-bedroom dwellings.
Sustainable development is a key value of Bouygues UK, which is the appointed contractor on this project, and is firmly embedded in its driving principles. BREEAM certification and reducing the operational impact on the environment, as well as managing the environmental impacts of site activities during construction, has always been a Bouygues UK priority and this was illustrated throughout this project.
The design brief clearly stated all requirements to be met for the project from design stage to post construction stage. The aim of the project was to target sustainability throughout the lifetime of the building. In particular, energy and water efficiency measures to be integral to the building’s design and specification. The building was designed to prevent overheating and avoid excessive requirements for heating and cooling; thus making it pleasant for users and efficient to run. Achieving BREEAM rating ‘Excellent’ was also one of the Planning Conditions set by Westminster City Council. The Craven Hill Gardens project exceeds the high standards of sustainability beyond the London Plan and City of Westminster planning policy.
The project is shortlisted in the BREEAM Awards 2017
- BREEAM version: Domestic Refurbishment 2012
- BREEAM rating: Excellent
- Score: 82.52%
- Stage: Post-Construction
- Size: Total GIA 3,603 m2
External walls were improved with a layer of internal high thermal performance insulation and the existing windows replaced with improved high performance double glazing, achieving a Building Regulations compliant standard and improving the overall efficiency of the development. The development has achieved a reduction of 111.5 tonnes CO2/ year when compared to performance of the existing building fabric and services efficiency.
This level of CO2 reduction is a 77.9% improvement over pre-refurbished building emissions.
The CHP and 38 mono-crystalline silicon midrange photovoltaic panels fitted in the roof of the development deliver a significant proportion of the overall saving, resulting in 10.9% of the Regulated CO2 savings.
Further energy efficiency measures were applied to the space heating and hot water generation utilizing 95% efficient gas boilers for domestic hot water and space heating. Additional heating system control features were also included such as zone controls, boiler interlocks and thermostatic radiators valves.
The energy results achieved are the result of provision and improvement of fabric to high energy efficiency standards, combined with the specification of photovoltaic (PV) panels, high efficient community CHP, supported by a communal high efficiency gas fired boilers and A-rated variable speed compressors for comfort cooling.
The potential overheating during the summer was addressed through a combination of high levels of fabric performance and insulation and energy efficient design, resulting in low u- values.
All existing non-original windows were removed and replaced with double glazed timber windows, and full height and width double glazed aluminium casement doors/ windows added to the rear lightwells to maximise daylight and sunlight, reducing the need for artificial lighting during the daytime hours or heating during the winter months.
- Energy efficiency measures were incorporated into the design, along with high-quality construction standards, better u-values for windows, high levels of insulation, a communal CHP engine (with backup communal gas boiler) and photovoltaics (PV) panels.
- The design maximizes the use of natural systems by allowing passive solar gain and maximizing the use of natural ventilation, to minimize the resource use and maximize the comfort of the users over the lifetime of the development.
- The above measures have resulted in a 77.9% reduction over the pre-refurbished building emissions.
- 100% of credits in the BREEAM management section were achieved.
- The site met Considerate Constructors Scheme standards beyond compliance, achieving a score of 43/50. Risk to air quality, noise or nuisance to the neighbours were considered and best practices with respect to nuisance to neighbours and local fauna were adopted in line with Man 03 requirements.
- The development achieved 100% of credits for Mat 02 Responsible Sourcing of Materials. This meant careful planning and selection of construction materials to ensure all materials manufacturers held a high level of responsible sourcing certification.
- 100% of the timber used in this development was FSC certified and legally harvested
Health and Wellbeing
- The comfort of prospective occupants of the building was extremely important for this project, as such the comfort of the rooms was carefully considered and only quality fittings were specified. Only inert or low VOC emission finishes, construction materials, carpets and furnishes were specified.
- High quality sound insulation, in line with requirement Hea 02, contributed to the indoor comfort of the occupants by reducing the likeliness of nuisance due to noise transmission.
- A pre-demolition audit in line with best practice standards was undertaken in order to determine methods for the refurbishment and reuse of demolition material and ensure waste was diverted from landfill. This resulted in just 9.3m3/100k of construction waste generated and 99.6% of demolition waste being diverted from landfill.
- Although demolition of the existing building was required, the extent of the demolition was limited to those parts of the building that prevented the optimal design for the dwellings. The façade of the building was retained in order to maintain the heritage value of the site, which also helped in reducing demolition waste.
- Water consumption has been reduced in the range of 96 to <107 litres per person per day, by the incorporation of water efficient fixtures and flow control fittings throughout the proposed residential units, in line with BREEAM requirements. Additionally, water consumption is individually metred per dwelling.
- NOx emissions arising from the operation and hot water systems in the dwellings are less than 40 mg/kWh.
- The flat roofed areas to the rear of the property at first floor mezzanine level have sedum laid on them. The sedum roof has increased the ecological credentials and the biodiversity of the property, adding an area for a natural habitat. In additional the sedum reduces storm water runoff, making a neutral impact on the surface run-off due to the development.