A tiny 5m x 4m sustainable building experiment, modelled on a minimal life-cycle energy and One Planet Living approach, promises to yield big results for the green building industry and set the precedent for sustainable small apartment living in Australian cities.

The ‘5x4 Hayes Lane Project’ earns its name from its diminutive site which hides in an East Melbourne back alley on a five by four metre plot.  Nestled between existing buildings, the prefabricated residential dwelling will house two people and rise three stories.

The project comes from a team that includes Arkit architects, as well as GHD and Felicetti engineers and university researchers who endeavour to create the yardstick sustainable apartment design for a future that will undoubtedly require us to live in smaller and smaller spaces.


The project incorporates a few materials that will be recognisable to most, but calls on others that some would have never heard of.

The building envelope is prefabricated offsite and incorporates two recent insulation innovations that allow for a lightweight, thermally excellent wall construction that has similar thermal performance to a concrete wall.

The first is an integrated aerogel based product that has extremely low thermal conductivity (typically a K-value of around 13.9W/mK at 23°C) and can achieve R-values of between 4–6 in unusually thin wall assemblies. It was originally developed by NASA but has been used by the 5x4 team to achieve their goal of creating a lightweight panellised system that behaves like a heavyweight wall and can be assembled easily.

A dual-skin staircase acts as a climatic buffer from thermal gains, and allows diffuse light into the bedroom.

The second innovation has seen recent use in sustainability buildings across Australia, particularly in the recent 2014 Sustainability Awards. Phase-change material was also incorporated into the 5x4 building fabric because of its heat-of-fusion property. The material will melt and solidify at certain temperatures and absorb or release heat when it changes from solid to liquid and vice versa.

GHD’s Tai Hollingsbee, a member of the design team, notes that their phase-change material was essential to creating an internal environment suitable to Melbourne’s thermal range.

“The product used for this project has been “tuned” to useful temperatures for human comfort, melting at temperatures above 23°C – absorbing heat as the temperature rises and releasing it slowly as it melts,” she said in a journal article for the Australian Institute of Refrigeration, Airconditiong and Heating.  

“This combination of high-performance thermal insulation and a phase-change material allows for a lightweight, thermally excellent wall construction that has similar thermal admittance to a concrete wall, without the weight, construction time and quality issues associated with traditional construction methods.”

Thermally broken frames with high-performance double glazing has lower embodied carbon than a triple-glazed system over the life of the building.

The building is can be well sealed and insulated when needed or opened for passive comfort. A whole house energy-recovery ventilation system from Zehnder Systems provides outdoor air, with tempering during peak conditions. Additionally a ground-coupled heat pump system can provide heating, hot water and supplementary conditioning of the supply airstream when needed (see below diagram).


Two core design strategies that seem the most pertinent to the design team are firstly to minimise the building’s life-cycle and embodied energy, and secondly to emphasise the role of occupant behaviour on a building’s performance.

Hollingsbee notes that the building’s materials faced a stringent selection process which considered both its predicted operational energy demand, as well as initial and recurrent embodied energy over a period of 100 years.

She said that this design approach minimises the building’s life-cycle energy demand and ensured appropriate, low-embodied energy content materials and processes were selected.

The behaviour and lifestyle of the building’s inhabitants was also an integral design focus and the 5x4 team called on the BioRegional’s One Planet Living approach to guide the design, construction and operation of the house.

In terms of design, using the One Planet Living approach involves a commitment from the architect to enable the building occupants to monitor their ecological footprint and adapt their behaviour to yield better results.

The occupant’s carbon emissions are monitored and publicly shared on a BIM system by Zoo Automation. More importantly they are also offered a behavioural adaptation program which encourages and guides occupants to better such a performance.  The short video below shows how the building’s facilities and appliances can be controlled by the system.

The 5x4 project has since been approved for construction and its construction process can be monitored at the design team’s online journal.

Images: 5x4 website and the AIRAH.