Up until December 2006, our family lived in a large brick and colourbond house in Shenton Park.
We built the house in 2004 before we had become truly aware of the climate change issue. While the house was a beautiful design and was built to a high standard by my brother, it didn't really incapsulate all of the elements of solar passive design that we are now looking to install in our new house in Piesse Brook.
The house was about 350m2, predominantly on one level, with a guest bedroom and ensuite as a small second story. The house ran east-west and faced onto a verandah looking over a lap pool on the north side. Wide bi-fold doors giving onto the terrace could be opened for ventilation and to improve access.
The size of the house required us to install a ducted reverse cycle air conditioning system which was so large that it had two large compressor units on the south side of the house. During our first summer in the house, I would guess that we used the airconditioning on about 45 days. Our electricity bill for 66 days from 7 December 2004 to 11 February 2005 was $1,528 based on average daily consumption of 87Kwh/day!!!
After choking on this bill, and efter becoming better educated on the subject of climate change, we set about making the house more thermally efficient.
What We Had Done Right
Before making any changes, it is worth pointing out what we had already done that was good from a thermal efficiency point of view.
Firstly, we had built a house that was double brick. We used anticon insulation to line the underside of the colorbond and in addition to this installed synthetic wool insulation between the rafters of the ceiling.
Secondly the house faced towards the north which enabled us to take advantage of the low winter sun to help heat the house in winter.
Thirdly, we installed ceiling fans in all rooms of the house (plus the deck), which allowed us to reduce the use of air conditioning, particularly at night, and also enabled us to increase the temperature setting on the air conditioner when that was required. We installed fans with stainless steel blades which we felt added to the architecture of the house rather than detracting from it (see photo below).
Things We Changed To Improve The Thermal Efficiency
The first thing we did was install 3M window film on all of the living area windows (including the bifold doors). This film reduces 99% of incoming ultraviolet radiation and about 80% of the incoming solar heat that would otherwise penetrate the windows. We used DMS Energy to supply and install the film.
Secondly, we installed whirlygigs in the roof of our house, allowing hot air from the ceiling cavity to be vented. We installed a ceiling vent at the top of the stairs to the second floor, allowing hot air from the ground floor to be vented outside. Whirlygigs are relatively inexpensive and can be installed by a home handyman, or you can get someone to install it for you.
Thirdly, we installed shade sails over the pool and deck. The shade sails protected the house from sunlight during the summer and we took them down during winter to allow the low-angle sun to penetrate and heat the wooden floor. The photo below shows the sails above the pool down, however the sail above the deck in the foreground is still up.
The End Result?
Our electricity bill for the 65 days from 12 December 2005 to 15 February 2006 was just $338, representing a reduction of $1,190, or 78%!!
What Else We Could Have Done
In the past year or so there has been a huge increase in the availability of compact flourescent lights (CFLs) that can be used to replace halogen lights.
Most of the lights in our house were halogen. In most rooms there were at least four halogen downlights. These downlights have two major disadvantages from a thermal efficiency point of view.
Firstly, contrary to poplular belief, they guzzle electricity. Four 45W downlights equate to 180W. Before the popularity of downlights, most rooms would have had a single 75W incandescent light. So you can see that using downlights uses up to 150% more electricity than the old fashioned light bulbs.
Secondly, halogens get very hot. A room with four halogen lights will become noticeably hotter with the lights on. I was physically unable to sit underneath the downlights in the loungeroom as I would become uncomfortably hot.
It is now possible to buy CFLs to replace the halogens. A typical CFL uses just 9W of electricity, representing an 80% reduction compare to the halogens. Better still, CFLs don't get hot, so they won't add to the heat load in your house. Even better, the price is coming down, with a 9W CFL available for about $13.50. If you replace four halogens in a room with four CFLs, and you use the lights in that room for an average of 3 hours per night, then your saving in electricity will pay off the cost of the CFLs in just over 7 months. In a house like ours, if we had changed out all of our halogens, I estimate that we would have saved about $100 per year, after paying off the initial expenditure in the first 7 months.
Without wishing to promote a particular store, Beacon lighting have an excellent range of energy efficient lighting.
