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Thermal Comfort Sustainable Design

By Anthony Lieberman

After the NSW Government’s announcement on 27th October 2010 that they are going to slash solar feed in tariffs from 60c to 20c per kilowatt, the spotlight should now turn towards homes being thermal efficient in their design. 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 become action.

The problem with the current housing regulation is that the focus is not on designing homes to be naturally thermally efficient through design and specification, therefore we are creating stock that is ‘stuck in time’ for the duration of its life, potentially 50 to 100 years, or requiring a major renovation too early in its life. Governments need to play a role in educating and encouraging in going beyond their own regulation.

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

A home which is rated eight stars for thermal comfort is estimated to require around 70% 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 merely pass under the current BASIX regulations will require around 52 Mj/m2 p.a. (megajoules per square metre per annum) to heat the home and around 45 Mj/m2 p.a. 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 p.a. to heat and close to 10 Mj/m2 p.a. 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% 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% of the time compared to a BASIX committed home is estimated to sit between 13 and 27 degrees. So instead of needing artificial heating or cooling 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 thermal efficient home.

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

It is important to understand that 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 p.a.) then you have missed the only boat in the life of the building. Retrofitting doesn’t achieve the same results. It is important to discuss thermal comfort with your architect. 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.

Can you see the compelling reason unveiling itself to start designing and building homes that have thermal comfort at the core and truly reduce the need for high energy usage? So when you embark on your next major renovation or new home build talk with your architect or builder about thermal comfort. Go beyond regulation as the outcome will be rewarding.

This article was originally published in Climate Spectator in December 2010 and was written by Anthony Lieberman, Marketing Manager, Australian Living