Having been involved in the sustainable housing industry for many years, Janine was keen to learn all about eTool LCA and use it to assess her newly finished home. After some software webinar training from Rich, Janine got to work and completed her assessment in her spare time in less than a week with Henrique certifying it shortly after.
The results from the LCA were very positive, with Janine at ease knowing her house will save an estimated 64% of the carbon emissions compared to an average Australian house. Janine is opening her house up as an educational opportunity for people to visit during Sustainable House Day 2012 and understand the benefits of the sustainable ‘best practices’ that were implemented.
The summarised results of this project:
|Total CO2e / Year / occupant (kg CO2e)||% Saved Against Benchmark||eTool|
|Embodied Carbon||489||41 %|
|Operational Carbon||988||69 %|
|Total Carbon||1,477||64 %|
The extended design life was a result of low redevelopment potential, due to the high quality design and its location in a semi rural area. It’s well known that design life is largely affected by redevelopment potential rather than structural integrity of the building.
The environmental impacts caused by the materials and their transportation, assembly and maintenance of the building will benefit more people during a longer period of time, contributing to a lower embodied carbon impact per year per occupant. Being a two story building also improved the embodied carbon since the constructed area of roof and foundations are optimised. On the other hand, the recurring carpet maintenance on a long last building represented 30% of the total internal finish carbon impact and highlighted an area of potential improvement.
Results achieved an eTool gold medal rating and represent a fantastic 69% saving when compared to a benchmark in the same climate zone. Taking advantage of natural ventilation and use of ceiling fans, Janine reduced the energy required for cooling the house. Located in a colder climate zone, most of the thermal control is associated with heating which is why a gas bayonet heater enhanced the performance and reduced carbon emissions when compared to standard reverse cycle air conditioners. Direct sun light is also part of the design to improve thermal control and make the house more comfortable.
Hot water system using solar thermal and gas boost is one of the largest savings in this design. When the system is not taking all necessary energy from the sun, the primary energy necessary to heat the water is minimised by burning gas at source of use (as opposed to electricity which experiences in the order of 70% heat losses at the generator). The instantaneous gas water heater also overcomes tank losses, only burning gas when required to boost water temperature. Instantaneous heaters are slightly less efficient at converting gas to water heat, however, the reduction in tank losses outweigh the efficiency losses.
Janine was also interested in learning about designing a refrigeration system to increase her savings; as a properly ventilated fridge can represent large savings in energy efficient houses. At eTool we’re always cautious about recommending highly rated energy efficient fridges, as the embodied energy of the food is likely to be at least 10 times more than the energy consumed by the fridge. Sometimes a fridge which is actually less efficient and uses a bit more power can extend the life of food quite considerably making it the more sustainable option! The ability to increase the efficiency of a fridge with well designed cabinetry and ventilation is not related to the fridge specification, however, so is something we can comfortably model in our LCAs.
After reducing the demand for electricity through energy efficiency measures, Janine was able to significantly reduce the remaining energy demand with a 2kW capacity solar PVsystem. Solar PV has a high embodied carbon component and without it, the design would have achieved a better “Embodied Energy” rating. However, the substantially reduced “Operational Impact” due to the renewable energy input offsets this increased “Embodied Impact” many times over during its design life. The main advantage of a solar system is that it offsets carbon intensive grid electricity.
Some of the inputs of operational energy such as entertainment appliances are based on an Australia average and may not be in accordance with occupant behaviour. The house is new and all operational inputs couldn;t be recorded, but as soon as we have more detailed information about occupant behaviour eTool will be able to customise the design accordingly and compare “as built” to “as designed” results.
One thing that LCA highlights to us everyday at eTool is that there isn’t a ‘one size fits all’ solution for sustainability. It’s really important to carefully consider the intended building function, suburb density, climate, distribution grid intensity, regionally available materials and local expertise to ensure the design decisions you make are the best for the environment.
If you have any questions regarding the sustainability features mentioned in this case study, would like some low carbon design training or a cost effective LCA, please contact us.
This assessment was conducted by Janine Strachan and certified by Henrique Mendonca.