Results Summary

Impact Area

Total CO2e

/ Year

/occupant

% Saved Against

Benchmark

eTool Medal
Embodied Carbon1,225 kgCO2eNo saving, increase of 20%No Medal small
Operational Carbon64 kgCO2e-98%etool_plat_medal
Total Carbon1,289 kgCO2e-69%etool_gold_medal

Project features

The key result of the whole of building Life Cycle Assessment is a figure of -2869 kg CO2-e per year per occupant. Please note LCA measures impact so a negative number is the ‘beneficial’ side of carbon performance, meaning the design will provide a carbon improvement over its life – Carbon Positive.

It is observed through the LCA modelling that the following areas have the greatest impact to the overall environmental footprint of the building:

Off-grid Functionality

This assessment is based on an estimated building life of 100 years of which an estimated 70 years will be completely off-grid. Off-grid was achieved by a combination of energy generation system water and energy storage system in combination with behavioural changes that will ensure off-grid systems will satisfy occupants energy and water demand over the period of time assessed in this LCA.

The current occupants do not intend to be using a generator but will instead further reduce consumption by closely monitoring energy use and by embracing behavioural change.  Furthermore, monitoring technologies, energy and water consumption reduction recommendations have also been adopted to incentivise reduction of consumptions and track energy and water used. Additionally, the current occupants are planning on installing a wind turbine to subside the absence of a diesel generator.

On site renewable electricity generation and storage 

For electricity generation, a 5kW Solar PV is employed. It is estimated the rooftop 5kW Solar PV system will get replaced three times over the period of assessment and a total of 4 times over the life of the building. For electricity storage, a 21kWh lithium battery bank is employed to store electricity produced by PV system when in excess, and to provide energy during hours of lover energy generation, the battery pack will also provide 3 days of electricity should the PV system fail. Solar PV size, battery pack size and energy utilisation have all been carefully assessed to provide enough electricity all year round. Additionally, heat pump was set up to act as an additional energy storage unit for excess PV electricity, heat pump will utilise timbers or relay switches to only activate when the PV is generating power, and ideally have higher thermostat set points to store more heat.

Efficiency operational energy use

Being this an off-grid house, efficient utilisation of operational energy is a driving design aspect which influenced the process of LCA to ensure a sustainable off-grid solution. Energy efficiency measures included a heat pump used an additional energy storage backup for the house, energy monitoring with comparative feedback, residential ceiling fans assisted cooling to reduce HVAC utilisation, ultra-efficient LED lights.

Efficiency operational water use

Water efficiency measures included a native garden with local flora which will reduce the need for watering and in general maintenance of the garden, low flow shower heads which will directly reduce water use and indirectly reduce energy by reducing hot water use. Finally, reduction of irrigation water and domestic water use will reduce water pump energy use.

Embodied Energy increase due to off-grid core services 

To allow the house to be off-grid, additional service equipment had to be added to ensure inhabitants would have enough ways to source energy and enough capacity to retain it in case of emergency. As mentioned before, the current occupants do not plan on installing a generator and will instead commit to reducing operational water and energy consumption by embracing behavioural change. Considering the LCA time span is 100 years, it is very likely that the next occupant will not be equally committed to such stringent behavioural changes therefore a more generous energy capacity must be allocated to account for such changes, this increases embodied impacts. Equipment such as water pump, generator (and associated diesel used), bigger-than-usual PV system, battery packs and tanks considerably increased the overall embodied energy associated with this built, hence the 20% increase of embodied impacts in comparison to the International residential benchmark.

This assessment was conducted by Leonardo Poli and certified by Fei Ngeow from eTool.