»Existing building fabric
The existing load-bearing brick external envelope is retained. Openings in the external envelope are retained in current positions where possible. The external envelope is uninsulated. Due to space restrictions and cold bridging the designers consider an external insulation system preferable.

The existing roof finish is assumed to be a clay tile. In order to insulate the roof efficiently it is proposed to remove the tiles to create a layer of insulation above and between the roof structure to superinsulate the roof up to an ideal level of 350 mm.
The existing fireplaces and chimneys have been superseded by the gas fires. The designers look to remove these elements and make use of the valuable space that they occupied.

»Context
The orientation of the block is north-south along the long axis, which for the purpose of generating energy from solar panels is not as efficient as an east-west orientation. The block is overshadowed nominally on the south end by the adjacent dwelling, but is otherwise not overshadowed by surrounding buildings. The designers are assuming that the masterplan described in the Southwick Phase 3 design and access statement is the accepted context in terms of the proposed pedestrianisation of Shakespeare Street. The designers are assuming that the parking and refuse strategy is as shown on the masterplan.

The key consideration for the designers was deciding what to retain and what to replace or enhance of the existing building. This involved a process of analyzing the quality and condition of the accommodation and the fabric to assess how effectively it would perform in the new dwelling. The existing accommodation does not meet current space standards in some instances, and requires considerable updating to facilitate inhabitation by older users, wheelchair users and extended families.

»Design proposal
The proposal looks at how the existing block can be reconceived as a way of accommodating different sizes and make-up of families together. The existing block comprises four two-storey units. The proposal develops four types of unit that can be combined in six different ways within the block.

The unit 'types' are designed to cater for a large family with dependants, old or young, through to couples on their own and individuals. All units are accessible directly from the ground floor and are double aspect. Flush thresholds are created by integrating access ramps into the front gardens.

The plan matrix demonstrates how the plan develops from a single person unit (type 1) to the extended family dwelling (type 4). The space standards are taken from the London Housing Design Guide.

The layout aims to reconcile the conventional layout of the existing block with the new roof fins to create an exciting series of spaces/lightwells on the first floor level and within the new roof fins themselves.
The existing roof is enhanced by the addition of four roof fins that face due south in order to generate energy more efficiently and to allow more daylight into the interior spaces.

»Energy efficient retrofit
The proposal aims to achieve the Passivhaus standard, as follows:

• Annual energy consumption for space heating of less than or equal to 15kWh/m2yr
• A primary energy requirement of less than 120kWh/m2yr
• An air leakage of less than less than or equal to 0.6 air changes per hour at 50 Pa when tested in accordance with EN 13829.

»Low energy features are to:

• Reduce heat loss through installation of external render system with minimum 150 mm phenolic foam insulation with acrylic finish to existing brickwork
• Reduce heat loss through installation of minimum 350 mm phenolic foam insulation above and between the roof joist
• Prevent overheating by super insulating and enhanced mechanical ventilation/heat pump
• Maximize daylight through allowing increased amounts of light through roof/energy efficient lighting
• Strategic mechanical/natural ventilation
• User-friendly radiant heat panels with thermostatic radiator valves or underfloor heating where appropriate.

»Low carbon features are:

• Renewable energy generation through use of 9-12 m2 high efficiency photovoltaic panels to each roof fin
• Air source heat pump to be used in combination with photovoltaics and underfloor heating system/radiant panels
• Reduce material miles/travel distances by looking to specify as locally as possible
• Recycle and reuse the external fabric, existing openings and roof/floor joists as much as possible
• Sustainably sourced aluminium clad double glazed timber windows, eg, NorDan.

»Water conservation features are:

• Collect and reuse rainwater within the garden
• Water saving appliances. Baths retained due to requirement by young and elderly.

»Low toxicity features include

• Natural materials for interior finish, such as bamboo and rubber

Zero formaldehyde MDF/Smartply for joinery items.

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