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Tasmanian project kickstarts prefab timber industry

Inveresk Residences
Inveresk Residences

A student accommodation project for the University of Tasmania has kickstarted a new prefabricated modular timber construction industry in Launceston.

James Morrison, director of Morrison and Breytenbach Architects, said the catalyst project, Inveresk Residences, is also the state’s first timber-framed multistorey residential project and that it will hopefully inspire a new sustainable direction for the local timber industry.

The Inveresk Residences comprises 120 apartments plus common areas across two three-storey buildings. The project is piloting the Green Building Council of Australia’s new Green Star Design and As Built tool, with a 5 Star Green Star rating targeted and potentially a 6 Star rating achievable, Morrison says.

James Morrison

James Morrison

Morrison told The Fifth Estate there were two reasons timber was chosen for construction. The first was the nature of the site itself, which is riverside mudflats. The boggy ground conditions made the expense of conventional foundations cost-prohibitive, so lightweight construction was decided on.

The second motivation was a desire on the part of the architects to contribute in a positive way to further development of a sustainable local timber industry.

A new sustainable direction mapped out

The design team, comprising a collaboration between Morrison and Breytenbach, Robert Morris Nunn & Associates, and Birrelli Architects, approached local manufacturers, trades and construction firms. With the assistance of technical expertise from UTAS’ Centre for Sustainable Architecture from Wood and the project team’s structural engineers, the design team were able to spearhead the development of a prefabrication enterprise within 100 metres of the project site.

The fabrication facility is based in a warehouse, with tracks – similar to railroad tracks – along which the modules move from workstation to workstation as the various trades complete their part of the construction process.

“It’s not rocket science,” Morrison says.

Now the factory is established, Morrison says the next step is for the new manufacturer to grow the timber prefabricated construction sector with further projects, including the potential to develop an export market.

Morrison says the university had originally been considering importing prefabricated modules from China, but the design team said “no, we can do this locally, and we can do it better’.

Inveresk Residences unit interior

Inveresk Residences unit interior

Phase change materials, solar and other good green initiatives

In addition to the use of certified local timber, the project’s sustainability features include the use of phase change materials to insulate the apartments. These are an Australian-made PCM in the form of pockets of paraffin-derived material inside flexible sheeting Morrison described as “a bit like bubble wrap”. This was used between the external timber panels and the interior plasterboard.

The buildings have solar photovoltaics to reduce mains energy use and rainwater capture and re-use systems.

Low- or no-VOC sealants, adhesives, paints and finishes were used, and PVC minimised. All windows are double glazed, and every apartment has a northerly aspect for passive solar heating and natural light.

“[As architects] we tend to try and push ESD as far as we can – we are always finding ways to improve,” Morrison says.

Sun + mass + insulation = energy efficiency

Morrison says an energy efficient building basically comes down to good solar access, good insulation and good mass. In the Inveresk project, it is the PCM that adds the thermal mass to the lightweight timber. Designing for single-stack apartments has also ensured solar access for all the units.

Operable windows and a design that minimises direct thermal gain in summer means the project has no mechanical ventilation and cooling, and heating is provided by electric panel heaters. Morrison says that while these are not particularly energy-efficient, the experience in the two prior projects is that the combination of mass, insulation and winter sun means they are rarely turned on, even in the middle of winter.

A lifecycle assessment of the project by eTool established a NatHERS energy rating for the apartments of eight stars, and a 60 per cent saving on global warming potential compared to the Green Star benchmark.

The modular construction also means that all the parts of the building can be removed from the site and repurposed at end-of-life, and the timber pile foundations mean there will have been minimal disruption to the underlying land. The apartments also have no parking, and are located close to cycle paths, pedestrian pathways and public transport.

Dramatic bill reductions shows green pays off

Inveresk is the third student accommodation project Morrison’s practice has done for the university. He says the bottom-line performance of one of the prior projects, where a combination of pre-cast concrete panels for thermal mass, solar orientation and external insulation resulted in power bills for student residences that were a third of previous bills, convinced UTAS that the green approach pays off.

“When we have saved them two-thirds off their power bills, it really makes them sit up and take notice,” Morrison says.

A similar energy-efficient approach was applied to two child and family centres the practice designed as part of an 11-centre rollout for the Tasmanian government.

Morrison says the centres each have an operational budget of $70,000 annually for running costs and equipment. The majority of the centres have power bills of about $35,000 a year, whereas the two his firm designed have bills ranging from $11,000 down to $8,000 per year. This means those centres have more to spend on programs and equipment for their clients.

“People are seeing real benefits from sustainability,” Morrison says.

Recycling on a grand scale – the SLC

Another recent project, the Sustainability Learning Centre at Mount Nelson, is targeting a 6 Star Green Star rating with a building constructed largely from recycled or re-used materials.

The SLC is a Department of Education project that provides learning opportunities for a number of schools and also office space for the CSIRO and Greening Australia.

Sustainability Learning Centre

Sustainability Learning Centre

The recycled materials came from another project the practice was working on in Hobart for the Department of Housing. The Brisbane Street site has an existing warehouse and whaler’s cottage that needed to be demolished before construction of a multi-apartment affordable housing project could commence.

Resource Work Cooperative, a social enterprise that provides training and employment opportunities for unemployed persons and also operates the South Hobart Tipshop, were contracted to undertake the deconstruction. A labour-intensive approach was utilised to ensure minimal damage to materials including convict-era bricks, an entire hardwood staircase, hardwood floorboards, copper wiring, heritage pit-sawn timbers, plumbing fixtures, roofing iron, steel I-beams and a 5m steel staircase.

The crew was able to repurpose, redistribute or recycle 98 per cent of both buildings, with the majority of materials going to the SLC site for re-use. The project also generated 12 jobs, and what RWC in its report said was a “healthy profit”.

The SLC’s sustainability features include the use of recycled cooking oil for heating, solar photovoltaic capacity that generates more power than the building needs, rainwater capture and re-use, a blackwater system to recycle water for toilet flushing, and full natural ventilation.

No concrete was used for a ground slab; instead Morrison says the building is floored with stone pavers directly laid on the ground, “like one of those old cathedrals in Europe”.

Between the stone slabs and the ground a hydronic heating and cooling system was installed. In cooling mode, water is sprayed on the roof at night to cool the water and then it is recaptured and pumped through the hydronic system.

The plasterboard used in the interior was also from a recycled source. Morrison says they made contact with a new CSR plasterboard factory in Victoria that had been doing pre-runs and was intending to send the test products to landfill. Instead, they were procured for the SLC.

“Sustainability is an ethical stand [for us],” Morrison says. “And we try to get ahead of the game.”

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