Exceptional sustainability for a historic building in a conservation area
The Crown Estate is refurbishing the Quadrant 4 site in Soho, London as part of its estate management activities.
The building upper floors are currently occupied by a backpacker hostel and will be converted to high-end residential units. Although unlisted, the building is in the Soho Conservation Area and its primary elevations were considered to make a positive contribution to the area. This, and the consideration for materials efficiency, influenced the decision to retain the façade. The redevelopment involves the retention and upgrade of existing elements where possible and replacement of existing elements which have come to the end of their useful life; the ground and first floor are retained with minor changes, while the floor structure and one façade are retained on the second to sixth floors, with the other façades replaced and the internal partitions changed to accommodate individual apartments. The seventh and eighth floors are entirely new build with the exception of the seventh floor’s retained floor structure. New building services have been provided to meet exemplar residential sustainability standards.
Planning required the development to achieve a BREEAM “Very Good” rating; however, from the early stages of the project, the Crown Estate and project team aspired for the highest feasible percentage score. The project brief was to create a building that delivers and maintains an exceptional sustainability performance through design into occupation, whilst respecting the historic character of the area. Overall, it is the aspiration of The Crown Estate and project team to significantly improve the existing site and its immediate environment by providing an efficient, inclusive and climate-resilient residential development, and to exceed wherever possible current standards and industry norms.
The building achieved full credits in the Management section and scored at least 75% in the Health & Wellbeing, Energy and Waste sections.
Sustainability has been considered throughout the project, with the agenda set right from the client brief, which was to achieve a minimum of BREEAM “Excellent”, with the highest feasible percentage score. The design team, with the appointed BREEAM AP, set out to meet this objective by embedding sustainability into the design; from appointment at the end of the feasibility stage, roles and responsibilities were agreed for the whole of the project process. The BREEAM pre-assessment, during the concept design, showed that this target was achievable, although meeting both the expectations of high-end residential occupiers for high sanitary fitting flow rates and the BREEAM Wat 01 minimum standard for “Excellent” would prove challenging. Multiple BREEAM APs, each with different types of experience, have been involved in the project, across all the key project stages
The principal contractor has registered with the Considerate Constructors Scheme and has committed to achieving performance significantly beyond best practice, which will ensure the exemplary management of the construction site; this will involve maintaining a good relationship with the local community and minimising resource use, energy consumption, and pollution among other things. To encourage the minimisation of resource use and energy consumption, and demonstrate progress, targets will be set and data recorded and displayed by a relevant individual.
It has been confirmed that a Building User Guide will be produced that covers all functions and uses of the building, and this will be provided to all building users. This will assist building users in operating and maintaining the building efficiently and effectively.
A security consultant was engaged to meet with the design team during the concept design and provide input towards Secured by Design compliance. Measures have been incorporated into the design.
Land-Use and Ecology
As a well-connected and historic brownfield central London site with a large potential for improvement, Quadrant 4 is an ideal candidate for sustainable redevelopment. Ecological input was sought during the concept design stage, with a site visit and bat survey undertaken. The development was designated as being of negligible ecological value. Ecological enhancements were also recommended, including the creation of a biodiverse green roof. A management plan will be produced to maximise the ongoing ecological value of the site.
Health and Wellbeing
Daylight was maximised where possible, through glazing selection, the incorporation of an atrium, and best practice design of room layouts, although constraints in the structure and overshading from surrounding buildings limited the potential. However, internal finishes and energy efficient lighting have been designed to ensure adequate daylight is available to occupiers. Best practice sound insulation standards have been incorporated into the design, which improves on Part E standards by 3dB. Indoor air quality standards have been maintained by specifying low VOC fittings and finishes, to minimise the production of pollutants, and by providing ventilation to Part F standards in full, to ensure pollutants are removed from the apartments. Access provision to the development has been considered for all types of potential building users, and reasonable provision made to meet the standards in Lifetime Homes and Part M; this is particularly challenging for an existing building. Safety has been enhanced by providing fire alarms to properties in with best practice standards.
The energy strategy for the site involves enhancing retained existing elements as far as possible by adding insulation without compromising on room function, or increasing the summer overheating risk. Retained elements improve upon the minimum standards defined in Part L1B guidance, whilst new build elements meet and/or exceed Part L1A guidance. Lighting will primarily be LED with appropriate controls and consumption of on average <9watts/m2. Mechanical Ventilation with Heat Recovery provides best practice ventilation whilst retaining heat. Heating and cooling have been provided from the central energy centre in the adjacent Quadrant 3 development; this includes gas CHP, an innovative fuel cell CHP and backup boilers with low NOx emissions. A 16kWp Photovoltaic panel array has been included on the roof to provide renewable energy to the development, with a proportion of energy supplied from the development also considered renewable for BREEAM purposes.
Ene 01 credits have been limited by the reasonable pre-existing thermal performance, but full credits have been achieved for the post refurbishment energy efficiency (with energy efficiency ratings in the mid-80s) and levels of renewable energy (23%+ of primary energy demand) in place. The primary energy demand (Ene 03 also scores very highly.
Additionally, appropriate metering will be provided to each apartment and the landlord areas, allowing users to monitor their energy use in real time and view historical data. Highly energy efficient white goods have been provided to apartments. Meanwhile, many of the apartments have a room that meets BREEAM criteria for use as a home office, although some were limited by the constraints on the refurbishment; these facilities provide the occupants with the flexibility to easily and effectively work from home. Lighting for communal areas is categorised into specific areas, with controls set via a central processor in the FM office, and based on a combination of scene sets, daylight, presence and time clock sensors.
Excellent levels of cycle storage are provided for building occupants in a secure communal storage facility.
It is a challenge to meet both the expectations of high-end residential occupiers for high sanitary fitting flow rates and the BREEAM Wat 01 minimum standard for “Excellent”. However, this was achieved with careful consideration of the specification and the incorporation of low capacity dual flush toilets, low flow taps, moderate flow showers, moderate sized baths and water efficient white goods. This equates to a total internal water consumption of 106 litres/person/day. Water metering has been installed which allows building users to monitor their water use in real time and view historical data. The project has no significant unregulated water uses, and no requirements for irrigation; the green roof has been designed to avoid the need for irrigation.
The client decision to retain existing elements on this brownfield site, where not strictly necessary, instantly provides a large improvement to the materials efficiency of the project. Retained elements were enhanced in performance and the façade was also improved aesthetically, with new materials selections sympathetic to the context. This has limited the performance of new elements, in terms of minimising environmental impact, but the majority of elements still achieve A or A+ Green Guide ratings. Constructions are:
- External walls: Clay tile lightweight re-enforced concrete panel, extruded terracotta panel, cement board, metsec frame, timber veneered engineering panel, timber support frame.
- Windows: Powder coated aluminium window double glazing and PVC-U window with steel reinforcement, double glazing.
- Upper floors: Primary steel frame with new timber joist floors & areas of existing concrete floor slabs.
- Roof: Plywood board, waterproof layer, timber deck.
The contractor has committed to meet responsible sourcing requirements, which at the design stage are a minimum standard that may yet be exceeded. Timber will be sustainably sourced to PEFC or FSC standards and other products will be covered by relevant certification such as BES 6001 or ISO14001.
Insulation is of low embodied environmental impact, and responsibly sourced.
Apartments have been designed with appropriate internal waste and recycling storage to align with the local authority’s waste and recycling collection scheme. The communal waste store has also been sized to accommodate the local authority’s bins and designed with appropriate accessibility to allow all potential types of building users to access the facilities.
The contractor has committed to providing a Site Waste Management Plan and meeting exemplary standards for resource efficiency in construction and for diversion of waste from landfill.
Low NOx emission heating is supplied from the energy centre, which include CHPs and boilers with limited emissions.
The impermeable area of the development has not increased, and the provision of a green roof and enhancements to the drainage system will help reduce the surface water run-off from the development. A Flood Risk Assessment confirms that the site is in Flood Zone 1, and at low risk of flooding.
The project pursued exemplary performance credits in Man 02, Man 06, Hea 04, Ene 08 and Wst 02.
The Crown Estate monitor a variety of their own sustainability KPIs at regular intervals in the project process, which helps drive the design team towards sustainable outcomes.
The thorough approach to sustainable residential refurbishment is certainly exemplar, if not innovative. The opportunities for embedding sustainability into the designs have largely been taken.
The use of a fuel cell CHP in the energy centre is a particularly innovative low carbon feature.
- BREEAM rating: Excellent
- Score: 79.2%
- Size: 4800m2 (GIA of assessed residential element)
- Stage: Design
- BREEAM version: BREEAM Domestic Refurbishment 2012
- Client: The Crown Estate
- Architect: Allford Hall Monaghan Morris
- BREEAM Assessor: AECOM
- Contractor: Sir Robert McAlpine Ltd
- Building Services Engineer: AECOM
- Structural Engineer: Waterman
- Project Manager: M3 Consulting
- Ecologist: AECOM
- Acoustician: Clarke Saunders Associates