Energy Efficient Home with $42 Electric bIll for 90 days Gowrie Park, Tasmania

Our house was always going to be an energy efficient design. I had researched it since I was a teenager, 25 years ago. Circumstances over time has seen it progress through several design/construction stages rather than a straight build from a completed plan.   In hind sight, I would recommend that anyone building a home, place considerable importance to making sure that construction has the least chance to be affected by the weather or more specifically, the Tasmanian winter. Don't ask how I know this.    The house site works included removal of a large Tasmanian Eucalypt from the North Eastern corner. This was cut up and trucked 1.5 kilometres to a local saw mill and sawn, racked, kiln treated and dressed to make the tongue and groove lining for the lounge room ceiling and toilet walls.    The house is orientated North. A floating concrete slab was chosen for it's passive thermal mass qualities. No "fly ash" or "Hemp-Crete" concrete options were available locally back in March 2003. With hydronic hotwater heating pipes imbedded into the living rooms sections of the slab, 30mm styrofoam insulation was used under all of the slab, slab strength beams and slab sides. If I has my time over, I would have used waffle-pods with extra styrofoam between the waffle-pod sections and on the outer slab sides. This would mean only a flat earth pad would be needed with circumference boxing. Much faster construction time and much easier to do. Hydronic heating means gentle warmth in the home without noisy forced air circulation with its dust an allergy problems. The slab concrete had black pigment added to darken the colour to assist in solar heat uptake in winter. The surface was ground to a terrazzo like finish with a clear satin epoxy finish. The winter sun does reach deep in to north living rooms, but alas, the solar temperature gain in the concrete is only just a few degrees due to the oblique winter sun angle.   Back in 2004  when the frame was being chosen, no custom steel frame company options were available in Tasmania. Our 0.5mm thick high tensile steel frame was pre-fabricated in Geelong Victoria and delivered on one semi-trailer truck. 90% of the steel frame sections could be easily lifted my two not so strong people. The other 10% steel frame sections could be easily lifted by 4 so strong people. This made unloading the semi-trailer and arranging the framing easy. The steel frame is termite proof and more consistently accurate than wooden frames. My 85 year old father and myself 50 years old, erected the frame easily with just the two of use. Frame erection took the two of use about a week. The frame is "nailed" to the concrete pad with a Ramset gun that used 22 bullet blank gun cartridges to fire them in. Hex and Phillips head drive screws were used to secure the joints of the frame and roof trusses. I added extra steel strap bracing than specified by the framing engineer, for my own piece of mind. All external walls have R2 glass batts. Some internal walls have R2 Sound batts -eg between lounge and main bedroom etc.   R3.8 glass batts were used in between the rood trusses and loose Rock wool placed inside the rood trusses - with a mind the minimising thermal bridging. A plywood spacer was used between the steel roof trusses and the steel top-hat battens, again for a thermal break. Light Colorbond custom orb roofing was secured with extra screws. Climate change will see more intense weather events in the future. Perforated sisalation rap was used both under the glass batts and under the Colorbond sheeting.   All external walls have 30mm wood battens screwed to them for both a thermal break and the bring the fibre cement cladding to drop past the 30mm styrofoam layer around the outside of the slab. It was originally planed to finish the outside with render. Recently a friend has become the Tasmanian agent for EcoBuild products which have different stone surface options and will add another R2.5 to the walls - budget permitting. This option will also add another thermal break for the walls. A thermal camera and can at present easily see the wall frame with the camera's ability to differentiate as small as 0.1 degrees temperature difference. No roof temperature "leakage" is visible with the thermal camera.   Back in 2004, our local suppliers for thermally window options were limited. I wanted low maintenance which means aluminium, or UPVC. UPVC was three times the price from only one locally represented company. So Aluminium double glazed was chosen from a manufacturer in Wynyard, Dargavels. No thermal break option available then. Their are now more UPVC and thermally improved aluminium options available at more competitive prices. We maximised the North facing windows and minimised the East, West and South windows. For natural light, we have Clerestory windows into the kitchen and the bathroom/toilet. Half the Northern wall is an open veranda and the other half is a double glazed inclosed sunroom/conservatory.   Mid-winter sun angle is only 27 degrees. The vertical walls in the conservatory have been measured at 55 degrees on a sunny day in mid winter. When sunny, this space is opened to the house by a sliding door and bedroom window with appreciable heat exchange with the house. We will be adding thermal mass dark tiles or slate to the conservatory north walls to maximise the sun's gift of free winter warm.   For the winter months, the Quantum 315 Litre heatpump hotwater service is the primary heat source for the hydronic floor heating and the household washing and shower needs with the 30 evacuated tubes adding what they can. In summer, the 30 evacuated tubes provide 100% of all hotwater needs with enough hotwater to spare for a the luxury of an occasional spa bath. The shower dome does a great job of reducing the moisture into the house and gives a more comfortable shower.   2011 being our first winter in the house, we have heated the hydronic floor to about 22 degrees, just once in the mornings on most days. This allows the heatpump and evacuated tubes to make the most for temperature recovery of any midday warmth and sun. On cool nights, this has been sufficient heating for us. On cold nights, we supplement the floor heat sink with a Fujitsu wall mounted reverse-cycle heatpump air-conditioned. It is a Norcia model that is about the most efficient in the 6kw range. Using the heatpump for a couple of hours at 20 degrees is enough to keep us comfortable for the evening. Morning temperatures in the house are typically 17 degrees and this is without any overnight supplementary heat input. The 17 degrees of a morning is not uncomfortable when the floor is at that temperature and there are no air movents from drafts. Energy efficiency will improve when the eve soffits and EcoBuild cladding is finished.   A grid connect 2.1Kw solar PV system looks on track to provide an average 8 Kwh that is expected from this system. In the summer months, we were only consuming about 8Kwh per day for the whole house. In winter this has gone up to 20Kwh. The 2.1 Kw PV system is producing about 4 Kwh average per day in winter and will probably produce 12 Kwh average per day in Summer. The PV system should supply more than two thirds of our electricity needs. I hope to install the already purchased 1.5 meter diameter overshot water wheel into the three streams that converge together about 60 meters from the house. It should produce usable power over the winter months.   Energy efficient appliances help to minimise electricity usage. These include Meile Upright freezer 310 Kwh per year, LG front loading clothes washer 300 Kwh per year, Electrolux Fridge 230 KwH per year, Whirlpool dishwasher, Electrolux Ceramic & Induction cooktop, St George two burner Gas Hob.   Water is gravity feed from a spring feed stream to a 45,000 litre tank and then gravity feed to our house, arriving in a  40mm pipe at 50 PSI / 0.4 BAR pressure. This is ample supply for the house. This supply also permits four 18 meter diameter fire fighting water sprinklers on all four corners of the house to operate by the turning of just two ball valves and no added energy needed.   A large food garden is in the early stages of construction. It's produce will make good use of the 2m x 2.5 pantry / natural cool room which is completely insulated on the south eastern corner of the house.  It currently is maintaining about 4 degrees lower than adjacent rooms. A low mounted wall air vent and small wind powered Whirlybird Turbine Vent to draw the cool close to ground air through the pantry will aid the current 3 to 4 degree lower than ambient temperature the sealed room maintains.   Overall, we are very pleased with the comfort and energy efficiency we have acheived so far, which will only improve with completion of the building.