Using CLT to make a more sustainable apartment building

752 High St is a building with a vision. The design team set out to explore and demonstrate an environmentally sustainable, low carbon footprint approach to multi-residential projects. Mass Timber was therefore a perfect fit. Prefabricated Cross Laminated Timber (CLT) takes the place of concrete or steel as the primary structural system of the apartments. The final design is 5 storeys, with retail and parking at ground level. 13 apartments with 1-3 bedrooms fill the floors above, topped by a communal rooftop garden. Each apartment is different, optimising the space according to its orientation and size. The High St CLT apartments achieve an average environmental star rating of 8.2, far above the 6 stars currently required.

Project Data

Number of CLT panels used: 337

Volume of CLT: 564.4m³

Mass of CLT: 282.2 tonnes

Equivalent CO₂ sequestered: 455.3 tonnes

Collaboration is key

As we discuss in our Technical Sessions, Mass Timber must be approached with a specialised project structure for the best possible results. In particular, the early and close involvement of consultants and contractors is key. A Mass Timber project that is carefully considered through the design and planning can not only be superior sustainably but also commercially. Gardiner Architects, Sinjen Builders, XLam, and Vistek Engineers worked together to develop an approach using CLT that met the client’s vision and budget, as well as the requirements of the site. The final cost of this building using CLT worked out about 8% cheaper than a conventional build by leveraging off the fast construction time and reduced waste.

Key features of the design

The CLT provides multiple benefits to project. The Mass Timber embeds sustainability into the very structure of the building accounting, sequestering C02. CLT is lighter than equivalent concrete and steel systems. As a result the foundation requirements are reduced, which in turn reduces materials and labour. CLT’s lightweight nature made the construction much easier to execute onsite. The prefabrication process for the CLT is millimetre-precise, with minimum wastage and a very airtight build. This leads to excellent thermal and acoustic performance. Combined with the building’s air exchange system, a constant fresh air supply without leaks is achieved. This has significant health benefits for occupants.