Sustainability

Most people who have been nagging me to write this blog are interested in the idea of sustainable design and how we will be applying these principles. Our designers have worked to achieve a house that scores about 8.6 stars out of a possible ten. It is mandated that all houses will be six stars in our state. A ten star house is one that is entirely passive in its inputs and outputs and is constructed in a way to offset all the elements of the construction. It tends to be more of a theoretical concept because of the high costs of building. 

There are various features that will make the house passive:

1.   Thermal mass. Our house will be built on an insulated concrete slab. The north facing windows will allow winter sunlight to penetrate the full width of the building to warm the slab and it will retain heat through the day. The angle of the sun in summer will be sharper, so the interior of the house will not be heated in the same way. Blinds and a pergola will provide shade when it is required. The concrete in the slab is a more environmentally sustainable product with a percentage of flyash. We will have little need to heat or cool our house except after a run of very hot days where the temperature does not drop overnight. I will write more about heating and cooling at a later point. If you want a more expert explanation  of thermal mass and how it works, go to http://www.yourhome.gov.au/technical/fs49.html

2.    The house will be air tight to prevent heat loss or gain depending on the seasons. There is an airlock at the front and back doors to maintain the interior environment during extreme heat and cooler weather. The house will be heavily insulated with a wool-based product and there will be several other layers of insulation and still air in between. When cool changes come in summer, they usually come from the southwest. The house is positioned so all windows can be opened to catch the breezes and vent hot air out of the building. Three skylights will allow this to occur in the two bathrooms and the laundry as they do not have direct northerly windows.

3.   Windows are always the weakness in the fabric of a building in terms of heat loss and gain. We have some floor to ceiling windows in the living area, but most are not full height to maintain the integrity of the insulation. Our windows and skylights will be double-glazed which is unusual in Australia.

4.   We will collect all of our water and store it in two 37,000 litre rainwater tanks. We will be entirely dependent on an average rainfall of 500 millimetres per year. We also have a ten thousand litre tank for garden use which will collect water from the chicken coop roof. In addition to this, we will also have to provide another ten thousand litre tank for bush firefighting purposes.

5.   All of our black and grey water will be treated on our property with a worm farm system. http://www.wormfarm.com.au/domestic/ The water then drains into a holding tank and as it overflows, the filtered water runs though the swales and leaches down through the soil. This water will be odourless, and contain worm castings and eggs to benefit the soil.

6.   We will be investing in a large solar array that will run along the spine of the house. This will have a grid exchanger so we can send power to the electricity grid during the day and draw back in the evening when we might require it. This is not a cheap option and electricity companies are no longer paying a fair tariff for the excess electricity, however, there are more important reasons to set up the system than simply cost.

These factors, coupled with our intention to grow our own fruit, vegetables and keep chickens, should result in a smaller environmental footprint than we have at the moment. 

We also have to maintain good weed control to allow the native wild flowers to flourish in the poor soil. In this photo, I am hard at work with the mattock digging out blackberries, which are a curse in the bush because they are so invasive.