Bridport House case study, Willmott Dixon

Overview Bridport House is an eight-storey residential tower built for the London
Borough of Hackney. It is the first phase of the regeneration of the local
authority’s Colville Estate. The brief was for 41 socially-rented affordable
homes - the first wave of council housing to be built in Hackney for 45 years
The 1,576m³ building has two main entrances and eight front doors to
the family sized four bedroom maisonettes at ground and first floor. Above
there are 33 one, two and three-bedroom apartments, many of which are
double aspect with generous flat areas, large storage and multiple balconies
and terraces; exceeding GLA space standards.
Bridport was entirely constructed from cross-laminated timber (CLT), making
it one of the tallest residential wooden structures in the world and UK’s first
multi-storey to be entirely built of the material – including the ground floor.
The team chose CLT because of its lighter weight: a survey revealed a large
Victorian storm sewer under the site and building around a reinforced
concrete (RC) or structural steel frame would have required significant
extra reinforcement of the foundations to create a building of the
same height. Constructing with CLT was also quicker, taking just 12 weeks
on site, six weeks less than a traditional frame solution. Willmott Dixon is
probably the leading main contractor delivering CLT projects, having recently
started our eleventh of this type.
The Research Project Willmott Dixon worked with the Cambridge University Engineering
Department (CUED) Centre for Sustainable Development to calculate
the structure’s embodied energy. The team carried out a comparison of the
materials between CLT and RC frame with available data from manufacturers
and the Inventory of Carbon and Energy (ICE) database.
They found that, had the building been of conventional RC frame, an
additional 892 tonnes of carbon would have been embodied in it. This is
equivalent to 12 years’ worth of energy required to heat and light all
dwellings. When the sequestered carbon was added to the carbon avoided,
the total figure was 2,113 tonnes, provided the timber is reused. This is
equivalent to 29 years of operational energy.
Equipped with this data, the design team successfully negotiated with
Hackney Planning Department to reduce the requirement for onsite
renewable energy provision from 20% to 10%.
Experts have welcomed our research since there is a shortage of credible
information on embodied carbon. As thermal efficiency standards improve
and buildings produce less carbon in operation, embodied carbon becomes
relatively more important.