Entrant:
Emma O'Neill / PTL Structural & Fire
Category:
8. Sustainable development award
Photographed by:
Crispin Schurr
Overview
Kohinga - St. Albans Community Centre
Kohinga, the St. Albans Community Centre, is an exciting new timber structure which provides the Christchurch suburb of St. Albans with a home for educational, cultural, and recreational activities. The single storey building features a large hall, three meeting rooms, a kitchen, and a timber deck. The structure includes European spruce in CLT walls, roof, floors, and glulam beams, and New Zealand radiata pine in LVL bearers, driven timber piles, and exposed timber cladding.
The 293 cubic metres of timber in this building sequester carbon equivalent to 179 tonnes of CO2 emissions. As a comparison, the Naylor Love carbon calculator shows that for a concrete alternative design, the net carbon balance for the structural materials would have been emissions equivalent to 4,400 tonnes of CO2 . The use of timber rather than heavier steel or concrete allowed a subfloor structure of CLT floor panels on LVL bearers and driven timber piles, which was critical considering the poor soil conditions of the site. This has allowed the floor level to be raised to meet flood zone requirements, and to be re-levelled if a major earthquake causes any liquefaction damage.
Kohinga is the first project that Christchurch City Council has commissioned that is carbon neutral and is seen as a precedent for the future performance of buildings for the council as it aims to achieve carbon neutrality by 2045. Kohinga is celebrated by the trust that operates it, who are helping spread the word to visitors that low carbon design can be affordable, beautiful, and durable.
There are many sustainable design benefits contributing to all stages of the Life cycle Assessment (LCA):
Product and Construction:
The materials chosen were timber where possible to sequester carbon and reduce emissions. On-site and off-site wastage was minimised with an optimised prefabricated structure arriving on-site ready for installation. Clever detailing reduced the amount of materials in the building: CLT walls support glulam beams directly without the use of columns, and exposed structural elements eliminate internal linings, reducing material usage, wastage, and embodied energy, with very low maintenance over the life of the structure.
Use:
The building has low operational lifetime energy use as the CLT walls and roof-ceiling are externally insulated and cavity-ventilated, to ensure that the building breathes with a comfortable indoor environment. The CLT panels provide an additional R1.0-R1.2 of insulation. A building physics study has shown the moisture content of the timber will not exceed 18% throughout the expected range of environmental conditions, ensuring long-term durability well beyond the requirements of the NZ Building Code.
End of Life:
At the end-of-life of the building, construction details allow the timber to be disassembled and re-used or recycled into a new building. If the untreated spruce becomes no longer fit for purpose, the wood can be burned for bio-energy, or composted.
In conclusion, the mass timber building with timber cladding provides an attractive, durable and sustainable building which will provide a long-term cost-effective solution for the local community, meeting a full range of LCA objectives.