Sustainable Building The Key To The Future
As global warming and water shortages become more a part of all our lives, then increasingly it is becoming beholden on us to act in an environmentally responsible manner. If you are planning on building a new home, then you have the opportunity to play a key role in correcting these major problems. The New South Wales government has recently introduced a water and energy efficiency housing policy called BASIX, and meeting it’s compulsory minimum performance standards is a good start. Other options are available such as grey water recycling, solar voltaics and solar water heating etc.
Case study – New house at Bayview
In what may be a first in Pittwater, the owners of this house which is currently under construction at Bayview, are aiming to be self sufficient in water and energy consumption.
Under BASIX (refer to www.basix.com.au), all new houses are required to meet minimum consumption reduction targets compared to the existing housing stock. For both water and energy consumption, that minimum is 40 %.
Typically, a rainwater tank of about 5000 L is required to pass BASIX, with the water being re-used in the laundry, toilets and garden, and it is also necessary to specify low water use fittings and appliances (eg dishwasher) throughout the house.
For this project, a water consultant was engaged to calculate the necessary tank size for self sufficiency, and the results indicated that a 20,000 L tank would result in a 95% probability of never running out of water, and that going to a 30,000 L tank would only increase that to 98%, so the smaller of these 2 options was chosen.
The relatively high rain fall in the Northern Beaches area, combined with large blocks (and hence large roof areas) makes water self efficiency easier to achieve compared to the inland areas of Sydney. The Penrith area for example receives approximately half of the yearly rainfall that occurs at the coast.The water consultant also assisted in the selection of the pump, and all the household fittings and appliances as these items have to be compatible with each other in terms of pressure and flow rates. Additionally, he provided a schematic diagram to assist the plumber with installation.
It was decided that the increased complexity and costs associated with grey and waste water recycling was unwarranted given the easy availability of the existing sewer system, and the abundance of rainwater.
The first step in this process is to make the house to be as energy efficient as possible, using passive solar design principals. North facing windows, particularly in the living areas, appropriate eaves overhangs, thermal mass (in this case concrete floors), cross flow ventilation and insulation to the walls and roof all play their part in this equation. Low “E” glazing was specified to all windows and doors as it approximately twice as efficient as standard clear glass at preventing heat loss in winter.
Thus the amount of energy needed to heat the house in winter is minimised, and, as is typical of all new houses that comply with BASIX, air conditioning is simply a waste of money.
The second step is to select low energy usage appliances as this plays a major role in reducing energy consumption, as does solar assisted gas boosted hot water heating.
All of the above will achieve the compulsory decrease in energy consumption.
In order to go from a 40% reduction to 100%, solar panels are necessary. The biggest issue with solar generated electricity is storing the energy as it only available during the day, whereas peak demand is obviously at night. The solution to this is to use the existing grid as a “battery” by feeding power into it during the day (the meter runs backwards during this process), and then drawing on the grid at night, in which case the meter then runs forwards. The desired outcome is come out even overall, or even be a nett exporter.
For this project, the hot water and pool are both solar heated.