Melbourne’s Monash University has just delivered a major first – Australia’s largest passive house building and the first multi-residential passive house structure to be constructed from cross laminated timber.
Gillies Hall student accommodation at its Peninsula Campus is a 150-bed building comprising one-bedroom studio apartments and common areas.
The focus on green building systems and energy-efficiency are part of the university’s broader plan to become net zero carbon by 2030.
It’s the first building to combine cross-laminated timber with passive house
It is currently the first major project in the country to combine the passive house design and construction approach with a cross-laminated timber structure.
Modelling suggests it will be three times more energy efficient than other university residential buildings.
Ryan Spittel, the University’s project manager for the development, says that the Monash guidelines for its new buildings require an internationally-recognised green building standard to be used.
The passive house standard used delivers comfortable healthy interior conditions for occupants, with the benefit of matching the University’s net zero emissions initiative.
The five key principles guiding the passive house approach
There are five key principles that guide the passive house approach which were used on the project:
- Continuous insulation
- High performance glazing
- Heat recovery ventilation
- A thermal bridge-free façade
Spittel says the use of CLT for the structure goes a “long way towards a bridge-free façade”.
As a material, it has inherent insulating properties and low thermal conductivity. It is also inherently an airtight product, he says, which de-risks achieving the required airtightness during construction.
Spittel says the ground floor of concrete, metal studs and precast took a much greater investment of time to achieve airtightness by comparison. They required significant quality assurance measures, and above all carried a large amount of risk when approaching the air-tightness testing.
The façade of the upper CLT levels comprises the CLT panels with a continuous moisture barrier, cladding of cement sheeting and shading structures.
Offsite prefabrication of the wall assemblies was investigated, but it was looking challenging to achieve the continuous moisture barrier, so the assemblies were built up on-site.
To verify the airtightness had been achieved, blower door testing was undertaken at the final stages.
This revealed some issues with airtightness when the test was first conducted, Spittel says.
Window seals were the source of the air leakage
Investigations into where the building was losing air located the problem in the seals around some of the windows on the ground (concrete) floor. Spittel says the combination of two window systems comprised of timber frames resulted in some settlement and movement following installation, so the sub-contractor was called back to site to rectify this.
A second test showed airtightness of 0.53 air changes per hour – meeting the passive house benchmarks comfortably.
Spittel says having the airtightness requirement and the goal of achieving passive house certification set down in the scope for the trade packages helped when it came to needing rectification following the first test.
There was also “continuous education” of the trades on the project that was carried out on-site during the project by the head contractor to ensure the passive house objectives were realised.
Rooftop solar, offsite wind and all-electric thermal plant make this 100 per cent renewable energy
In addition to the uber-efficient building envelope and passive design features, Gillies Hall has rooftop solar and an all-electric thermal plant.
Any energy required beyond that being supplied by the building energy systems will be supplied by the university’s power purchase agreement with Murra Warra Windfarm – making the residences powered 100 per cent by renewable energy.
Other sustainability features include a rainwater harvesting system and water sensitive urban design.
The individual studio apartments have operable windows, translucent blinds that reduce solar gain, blackout blinds and ceiling fans.
Continual fresh air is also supplied by a heat-recovery ventilation system.
Residents are supplied with information upon moving in that explains how to operate their apartment in both cool and warm seasons to use effectively the natural ventilation and passive heating and cooling.