After the NSW government’s announcement in October that it is slashing solar feed-in tariffs from 60 cents to 20 cents per kilowatt, the spotlight should now turn towards thermal efficiency. By incorporating the principals of thermal efficiency into the building of our homes, we need to lower energy use at the core and not rely on offsets. Offsetting doesn’t really change our energy usage habits, it just makes us aware. This awareness should now be translated into action.

The problem with current regulation is that the focus is not on designing homes to be naturally thermally efficient through design and specification. Therefore, we are creating housing stock that is ‘stuck in time’ for the duration of its life – potentially 50-100 years – or doomed to require a major renovation very early in their lives. Governments need to play a role in educating and encouraging home builders to go beyond regulatory requirements.

Heating and cooling account for around 40 per cent of energy use, making them the largest energy users in the average home. So it makes sense to design an energy efficient home that doesn’t require a heater or an air conditioner. There is also the bigger picture to consider, of cutting back on greenhouse gases.

A home that is rated eight stars for thermal comfort is estimated to require around 70 per cent less energy to heat and cool the home to that of a BASIX committed home (five stars). BASIX is the NSW government-regulated standard for homes. Thermal comfort is simply how hot or cold you feel.

Looking at the thermal calculations, a traditional home that has been designed to pass the current BASIX regulations will require around 52 Mj/m² pa (megajoules per square metre per annum) to heat the home and around 45 Mj/m² pa to cool the home. For example, to heat a 270 square metre traditional home, the energy requirement would be 14,040 megajoules per annum which, when converted, amounts to 3,900 kWh per annum.

At this stage we recommend that you have a look at your energy bills to put this into perspective, remembering that we are only talking about the heating and cooling portion of your energy bills. For the purposes of this article we haven’t taken into account the other energy savers, including LED lighting, energy efficient appliances etc.

By comparison, a home that is rated at eight stars for thermal comfort that goes beyond regulation is estimated to require around 15 Mj/m² pa to heat and close to 10 Mj/m² pa to cool the home. Therefore, to heat a 270 square metre eight star sustainable home, the energy requirement would be approximately 3,780 megajoules per annum which, when converted, is 1,050 kWh per annum. This represents a 73 per cent reduction of energy required to heat and cool the home to that of a BASIX committed home.

An eight star home in the eastern suburbs of NSW is estimated to have stable temperatures between 17 and 24 degrees 95 per cent of the time compared to a BASIX committed home is estimated to sit between 13 and 27 degrees. So instead of needing an artificial heater or air conditioner you may only need to put on a jumper during winter or turn on the ceiling fan on a hot day in summer in a thermally efficient home.

Thermal comfort modeling looks at the location temperature, orientation, sun and prevailing winds, so each area and each house will have a different outcome. Note that all of these calculations are based on one particular home in Rose Bay NSW.

If your home is not designed, modeled and tweaked by a thermal comfort assessor, and constructed to require close to zero heating and cooling loads (Mj/m² pa) then you have missed the only boat in the life of the building. Retrofitting doesn’t achieve the same results. For a thermal comfort assessment to be thorough, the home needs to be split into zones and can be modeled using the AccuRate system, as one example. This modeling will give you the heating and cooling load scores that you need to see where improvements can be made.

So when you embark on your next major renovation or new home build talk with your architect or builder about thermal comfort. And go beyond government regulation – the outcome will be rewarding.

Anthony Lieberman is communications manager at sustainable building management and consultancy, Australian Living