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Dolphin Square Foundation approached PDP London with a challenge - to provide a sustainable development that would house keyworkers on the busiest road in Westminster and on a site adjacent to a Grade 1 listed church. In October 2013, One Church Square was complete.

Once a series of derelict buildings and a disused car park along Vauxhall Bridge Road in London, the scheme provides 39 units over 5 storeys. Of the 39 homes, 31 are key worker accommodation on significantly reduced rents, with the remaining 8 being rented at open market values. The scheme with a GLA of approximately 2,400 sqm (excluding communal circulation) comprises of a range of studios, 1, 2 and 3 bed apartments.

The commission for Dolphin Square's first new build housing scheme was won by PDP in late 2012 through an invited competition based on both concept design and fee . This provided an exciting opportunity for the practice to work in an emerging sector and help establish a new standard in quality, design and environmental measures for affordable housing. Formed by an endowment from the Dolphin Square Trust, Dolphin Square Foundation is a charitable organisation that strives to provide high quality affordable homes for people working or living in central London. One Church Square provides this much sought after rental accommodation in the heart of Westminster at reduced rents.

Sustainability was integral to the evolution of the scheme design. Originally designed to achieve Code 5 of the Code for Sustainable Homes, the building generates its heating and hot water from CHP, a substitute for an earlier link to the district heating system, part of the reason to later procure the Design + Build scheme as Code 4. The building envelope is super-insulated and inherently airtight, employing mechanical ventilation with heat recovery. Fresh airflows into the shady courtyard by way of the double height entrance area and moves via stack effect up and out at roof level thus allowing fresh, tempered air to be mechanically distributed into each of the apartments via the MVHR systems.

It generates its own electricity by way of PV cells on the 5th floor roof. During the planning process, a challenging overheating brief was set by Westminster, which was dealt with by using passive measures such as intelligent facade/glazing, solar shading fins along with phase change board to increase the thermal mass.

A setting that provided a rich context and a strong palette of materials, led PDP London to produce a simple and contextual building which is essentially inward looking. Despite its obvious defensibility, it still addresses its context by way of carefully positioned openings and set backs referencing and paying deference to the adjacent listed buildings.

The concept of the scheme was to reinforce the connection with the public square in front of the church by drawing it into the proposal, taking advantage of an under utilised amenity. The building's entry is from the square, creating a calmer entrance courtyard space shielded from the heavy traffic of Vauxhall Bridge Road. This central courtyard has emerged as the heart of the building creating a sociable secure timber clad box. The ground level has been raised almost a metre and set back to form a perimeter planted edge design to protect inhabitants from the heavy traffic and pedestrian flow. This acted as defensible space for each of the lower floor occupants.

The scheme's two key areas contribute to a sense of community; the roof terrace is accessible to all tenants and consists of both paved and landscaped areas and the central , glass-covered courtyard, which generates the unique building form from which all apartments are accessed.

The flats meet Lifetime Homes standards and 10% of the apartments are wheelchair accessible. It is worth noting that PDP and DSF ensured a high-specification was achieved in each unit, whether affordable or of market value. Consequently, the only difference in the specification between the two is the inclusion of a dishwasher in the latter. In doing so, the notion of a new standard being reached in design and quality for affordable housing was reinforced.

PDP's Ciara Gormley explains: "A complex set of planning conditions, a site in a listed setting and an ambitious environmental agenda alongside the demands of a niche key-worker market has provided an interesting and challenging brief for the project."

Thanks to Dolphin Square Foundation's unique vision and commitment to setting a new standard in design, quality and sustainability for affordable housing in London, this scheme is undoubtedly one of the most significant projects of its type and reinforces PDP London's influential role in the future of London's residential developments.