Designing envelopes for Passivhaus townhouses

Architect Gavin Finnan describes the design of Passivhaus townhouses in a south London regeneration project, focusing on how their external envelope was fundamental to performance

360 new homes. A total of 15 townhouses within South Gardens have been designed as ‘future homes’, i.e. aspiring to a raft of sustainable innovations which include Passivhaus standards, use of CLT (cross laminated timber), green roofs, additional renewables and local community initiatives.

S The townhouses are composed of three- and four-bed house

types, forming part of a terrace. The primary aim is to make homes in the best tradition of London architecture that allow inhabitation in a clearly defined manner. It is also important that the materials age gracefully and are low maintenance, in order to ensure that the area will continue to look better over time.

The design of the terrace has been informed by the architecture of the traditional Victorian era housing which is found within the nearby conservation area. The new townhouses have projecting bay windows and their materials will sit comfortably with the existing buildings.

The simple brick terraces have elegant, vertically proportioned windows with vertical opening casements recessed behind a brickwork facade. All external rainwater goods are attached to the rear of the terraces to provide a clean, crisp, uncluttered facade to the street. Recessed timber lined entrances and projecting bay windows break up the elevation at lower level, and give a scale and rhythm to the street. Front doors have fixed glazed panels to the sides, and in some case have a glazed light above. The structure of the townhouses is formed from cross-laminated timber (CLT), a highly sustainable material as trees absorb carbon dioxide while growing. In addition, the CLT panels can be re-used at the end of a building’s life. Walls, floors and roofs have been constructed from pre-fabricated panels. Off-site production has meant less on-site waste, a shorter build programme, and whole-life cost savings. A lighter frame and reduced weight has ensured a lighter building and smaller foundations. The ultra-low energy buildings require very little energy for space heating or cooling, thus reducing their ecological footprint.

Passivhaus standards are rigorous and result in ultra-low energy buildings that require little energy input in use. A range

SOUTH GARDENS The terraces mimic the style of a traditional Victorian terrace

outh Gardens is the first phase of Elephant Park, a major regeneration project that sits on the site of the former Heygate Estate in Southwark, which when complete, will deliver



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