• Posted by: walidjuma

In this three part series, founder and director of PassivEnergy, Rob Iacono demystifies the questions surrounding energy ratings, sustainable home building and his tips of what to consider when chatting with your builder. Today, Rob gives insight into the term ‘sustainable’ and his top ten must haves in order to build a sustainable home.

Read part one – What the heck is an energy rating?


It is often thought that having a sustainable home will cost more to build and maintain, but this couldn’t be further from the truth. By making a few conscious decisions during the design stage, you can keep your build affordable and the home cheaper to run throughout the year. Here are my top ten secrets to achieving sustainable success:

  1. Orientation

The amount of sunlight capable of penetrating into your home is largely based on which way the block of land faces the sun. This is very important and having a site that orientates well in relation to the sun is the first step to succeeding in the sustainability department. Having north to either side of the house will provide a greater number of hours where the sun can penetrate through to the living areas and therefore reaches more rooms. If north faces the rear, while not as beneficial as the side, it can still allow for sunlight to enter the living areas.

North facing the front of the dwelling provides the least benefit as the front is normally reserved for one room plus the garage, and the remaining rooms will not benefit from this. Having the sun penetrating to your living areas during the winter days will mean you will come home at night to a naturally warm home.

  1. Design Layout

Having a good home design layout goes hand in hand with the orientation of your block. Having the living areas facing north will assist in having the warmth of the sun reach the rooms that are used the most. Bedrooms can also be orientated north or east so that they can capture the morning sun. The south side of a dwelling will not receive much sunlight, if any, so it is ideal to place rooms such as the bathroom, laundry, toilet’s and the garage to the south areas as they do not require sunlight and have little effect on the 6 star energy rating.

  1. Size and ceiling height

When thinking about the size of the home, keeping rooms to a moderate size will help keep it comfortable all year round. It is really important to understand that the more volume of air inside the house, the harder it is to have it stay warm in winter and cooler in summer. Some things to consider in relation to sizing:

  • A master bedroom that is big enough for a queen bed, bedside table and chest of drawers.
  • A lounge to accommodate only couches and a TV unit.
  • Hallways / entry foyers that don’t span half the house and are two meters in width.

All these tricks work to keep the volume of air comfortable.

  1. Window location and size

Windows play a very important part in allowing the sun to come in during the colder months which works to heat the home for free, as opposed to having to turn on your heater or electric blanket, and consume power that you will inevitably get a bill for. Having said this, excessive windows in the wrong area will have a negative impact on your 6 star energy rating and will make it harder for your home to stay warmer during colder nights. Having too much glazing will mean that heat will escape at night and the cold air will enter. Keep south facing windows smaller and avoid wall to wall glazing in large open areas.

  1. Ventilation

Correctly placing windows can also assist with cross ventilation which will help keep your house cooler in the warmer months. Sliding windows allow more air to enter the house then awnings but casement windows help capture the air travelling around the dwelling and bring it into the home. It is ideal to look at a window rose diagram of the area to work out where the wind comes from and place the windows accordingly.

  1. Shading

The summer sun sits a lot higher at noon than the winter sun. Therefore, correctly using shading will help keep the sun out in summer but allow it to come into the house in the winter time. The use of shading will depend on your climate, as warmer climates will require more shading to compensate for the extra months where the sun is out. Cooler climates, where there are fewer months with sun will require less shading to allow for.

  1. Thermal Mass

Thermal mass can include any dense material like concrete and bricks. The materials have the ability to store energy, heat or cooling, and release it when necessary. When the room is warmer than the surface area, thermal mass will absorb the heat. When the room is cooler than the surface area, it will release the heat back into the room. For example, at night when the temperature drops, it will release the heat back into the room resulting in a warmer room for longer. This helps to balance out the temperatures throughout the day. Thermal mass needs to be designed and allocated correctly to achieve maximum benefit.

  1. Insulation

Insulation acts as a barrier from the external elements and can greatly improve the overall comfort of a home. Insulation comes in many forms including bulk, reflective and boards. It can be used in the floors, walls and the roof / ceiling, creating a thermal envelope. Insulation is measured in R-Value and the higher the R-Value, the more resistance it can achieve to external elements. However, the general rule of thumb is that after a certain R-Value, the cost of insulation increases significantly while its performance increase becomes smaller.

Typically rule of thumb is:

  • R2.5 in the external walls.
  • R4.0-R6.0 in the ceiling.
  • R1.5-R2.5 in timber sub floors
    1. Building materials

    Certain building materials have a higher R-Value than others, and can be used alongside insulation to keep your home comfortable. The standard way of construction in Australia is brick veneer, where the stud work acts as the structural component and the brick sits externally. While this method helps protect from external elements like wind and rain, it does little in regulating a comfortable year round temperature. Reverse brick veneer construction has the bricks sitting on the inside of the frame work, allowing it to use its thermal mass properties to keep the internal temperatures more constant, with insulated stud work on the exterior, cladded in a light weigh material.

    Expanded Polystyrene (EPS) is a lightweight material and comes in a range of thicknesses. At 100mm, it has an R-Value of 2.7 so when used on upper floors, it can be used in conjunction with insulation to achieve a higher R-Value and provide better thermal comfort.

    1. Sealing

    Providing adequate sealing around your home can reduce the amount of air leaking out, and can help keep the warm air inside and the cold air outside during a cold winter night. Doors, windows, exhaust fans and penetrations can all cause drafty dwellings if not installed and sealed correctly. However, the more air tight the dwelling, the more risk of condensation forming. Adequate vapour barriers, wall wrap and sarking can help combat condensation if used correctly.

    And as a side note…

    1. Human behaviour

    All the points above are redundant if the home occupants are not conscientious about their actions. Making adjustments to your habits such as wearing more layers at home when it is cold, opening curtains as soon as that warm winter sun comes up, opening windows on hot summer nights to allow heat build to escape and being aware of how the home is operating – only using your air conditioning or heater when it is necessary, all aid in achieving a sustainable home and lifestyle.

Have more questions? If you’d like to work with me then get in touch today, let’s get you started on the right path!

READ PART THREE HERE – Having the “chat” with your builder.