Having achieved the first BREEAM Outstanding for a healthcare building, Willmott Dixon has pushed the boundaries of construction by delivering Bridport House, the largest solid timber residential development in the UK. Also one of the tallest timber buildings constructed, Bridport House was commissioned by Hackney Council to replace an original 1950s block with 41 new homes in two joined blocks, one eight storeys high and the other five storeys. Wilmott Dixon was able to effectively offset the carbon emissions resulting from the construction process as timber acts as a carbon sink. Each of the 41 homes contains approximately 30-40m³ of timber which is equivalent to over 30 tonnes of CO2. Benefits include:
There are several reasons CLT (Cross Laminated Timber) was specified. It is considerably lighter than alternative structural materials of reinforced concrete or structural steel. This was important at Bridport House, where a large Victorian storm relief sewer runs beneath the surface and it was necessary to avoid a heavy frame structure. The structure was designed so that the load bearing CLT panels are placed in a variety of positions on each floor, thus spreading the load. Speed of construction was another benefit; constructing the CLT took 12 weeks on site, six weeks less than a traditional frame solution. Engineering was completed by timber contractor Eurban, a company Willmott Dixon has worked with extensively on education projects. The CLT boards were made from PEFC-4,300 certified spruce trees from within 100km of Stora Enso Wood Products' factory and integrated sawmill in Austria - 94 minutes after felling the trees, replacement timber would have grown back! Integration of factory and sawmill means raw material selection is greatly improved and CO2 emissions reduced as the factory uses all its waste for energy driving the machinery. And there is no material transportation between sawmill and factory. After manufacture, boards are transported to the UK. The accuracy of construction with CLT aids air tightness as elements such as windows fit exactly. The CLT boards are also edge glued, further increasing air tightness and ensuring the five layer CLT boards achieve the same air tightness as non-edge glued five layer boards. As a result, the air tightness of Bridport House, at 3m3/m2.hr @50 pa is three times better than minimum Building Regulations.
Carbon saving CLT is becoming more popular owing to the carbon benefits within the structures. Willmott Dixon's in-house sustainability consultancy Re-Thinking worked with the Centre for Sustainable Development at the University of Cambridge to calculate the embodied carbon of Bridport House. They found that, had the building been of conventional reinforced concrete frame, the materials required would have incurred an additional 892 tonnes of carbon. This is equivalent to 12 years of operational energy required to heat and light all the dwellings at Bridport House. Additionally, when the sequestered carbon locked up in this 1,576m³ timber structure is added to the carbon avoided, the total figure is 2,113 tonnes of carbon saved provided the timber is reused - equivalent to 29 years of operational energy.
Project facts: Name: Bridport House Local authority: Hackney Council ALMO: Hackney Homes Architect: Karakusevic Carson Architects Contractor: Willmott Dixon Value: £6 million For further information, please contact: Andrew Geldard, Group Communications, Willmott Dixon Tel: (01462) 671852 Email:andrew.geldard@willmottdixon.co.uk Website: www.willmottdixon.co.uk