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What is an energy efficient home?
How can I design my home to be energy efficient?
Orientation & Siting
Layout & Zoning
Insulation
Windows
Glazing
Shading
Solar Rebates
Landscaping
Ventilation & Draught Proofing
Thermal mass
Energy Ratings
5 Star Energy Requirement
NatHERS
Firstrate
Checklists
FAQ's
Please download a pdf version of our energy efficient housing brochure
An energy efficient home is one incorporates common sense design principles that makes the building efficient in terms of
without compromising on comfort.
In fact, an energy efficient home is generally more comfortable, easier to maintain and costs no more to build than a conventional home.
General Guidelines
For a house to be really energy efficient you need to have all the right elements of design. These include a consideration of:
By carefully considering the position of your house on your chosen block, you can maximise the passive solar design advantages that can make your home more comfortable all year round.
The following points should be considered when selecting a block of land:
The orientation and siting of your home can make a huge difference to your energy bills and your comfort. The 'ideal' home is sited with the daytime living areas facing north with the long axis of the house running east-west (Opportunities for this are fairly rare, and the good news is that variations on the orientation can be up to 30 degrees to the east and 20 degrees to the west of true north, with no major effects on the solar advantage. Bear in mind that some extra sunshading may need to be considered however). Large windows on the north side of the house let the sunshine in during winter, but can be easily shaded from the summer sun. This will make the house warmer in winter and cooler in summer.
To prevent overshading from neighbours, allow a set back of at least 6 metres from a single storey house to the north, and at least 11 metres from a double storey house. If this is not possible, you might be able to use a clearstorey window to allow adequate sunlight into the home. Note that this window will require sufficient shading for summer comfort.
Locate the daytime living areas facing north and have north facing windows capture the winter sun. All bedrooms and utility areas should be located on the south side (this assumes that the northern facade maximises the use of daytime living spaces to benefit from winter sun entry- bedrooms and other rooms can also face north, if the design allows it). Following an open plan style of home will also help. Not only does it make the best use of all available space, it should allow light to penetrate easily and air to circulate freely around the home. Design open areas so they can be reduced in size by closing doors, to minimise the areas needing heating and cooling at any one time.
The single most important measure to make your house energy efficient is the addition of insulation to the walls and ceilings (minimum levels of insulation are now mandatory through the 4 star legislation). Insulation is the material that slows down heat transfer through the external surfaces of your home. It can make your home up to 10oC cooler in summer and 5oC warmer in winter.
In an uninsulated house approx. 40% of heat loss takes place through the roof and ceiling, whilst around 35% of heat is lost through walls and floors.
The performance of bulk insulation materials is specified with an `R-value'. The greater the `R-value', the more effective is the insulation at resisting conducted heat flow into your house in summer, and out of it in winter. For the Adelaide plains, the recommendation is R3.0 for the roof and R1.5 for the walls. For other locations within SA, please refer to our insulation fact sheet. Note that reflective foil type products do not have an 'R-value', but are very effective in minimising heat transfer. They do need to have an associated air gap next to them for them to work effectively.
Insulation materials
The sun's rays pass easily through normal windows. This can provide welcome heat in winter, but can lead to overheating in summer, as the heating power of sunlight shining directly on east and west facing windows is around 1,000 watts per square metre (the amount of heat from a one bar radiator). About 88% of this heat will pass through a window made of 3mm float glass.
Double-glazed windows however, while they are good at reducing conducted heat transfer, do not significantly reduce radiant heat transfer, and they need to be used with effective external shading in summer. (Double glazed windows can have some treatments applied that allowed them to perform well in reducing heat transfer, but the extra cost tends to be only financially viable in larger commercial buildings that have high airconditioning costs. They are very effective at slowing heat losses to the outside, and so they are very popular in very cold climates.
Ideally all north facing windows should be full length, so when the winter sun is low in the sky, the heat will penetrate well into your home. Use minimum or zero glass on the east and west sides, and small glass areas on the south side of the house.
The total window area should be less than 25% of the total floor area of the house (these proportions are a guide only, as new energy rating software for houses considers this and a range of design features when assessing the overall rating of the house). If windows are made too large they can make the house uncomfortably hot in summer and hard to keep warm on cloudy winter days and nights.
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How Much Window Area? (guide only) |
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Facing Direction |
Recommended % of Wall Area |
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North |
60 % |
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South |
30 % |
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East |
15 % |
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West |
0-7 % |
R value or U value
Normal glass in windows has a low 'R' value and can allow relatively large amounts of thermal energy in and out of your house. Advances on glazing technologies now mean that there are options for designer to choose from to improve the thermal performance of windows.
The 'R' value of the window (or its inverse 1/R, is called the 'U' value, which measures heat flow, or thermal conductivity), is one part of measuring the performance of the glass / window. The other way heat gets into a building is from direct solar gain, ie the suns direct rays.
Shading Coefficient or Solar Heat Gain Coefficient (SHGC)
The Shading Coefficient is a measure of how much solar energy is admitted through the glass. The higher the number, the better for passive heat gain. Another way of describing the amount of solar heat gain through a window is the Solar Heat Gain Coefficient (SHGC). The SHGC represents the percentage of the available solar energy that enters the interior of the home. The higher the number the better for passive solar heat gain.
The shading of sun is vital in keeping your house cool in summer.
Well designed shading greatly reduces heat entry, adding significantly to summer comfort in the home. It can also significantly reduce the need for, and running costs of, airconditioning equipment. The most effective way to keep summer heat out of the house is to use adequate external shading. North facing windows can be easily shaded with fixed shading devices, such as an eaves overhang, horizontal shade or awning, and pergolas.
These shading devices must be designed so that they allow sun entry in winter and totally shade the windows in summer. In Adelaide, to achieve this, the width of the fixed shading on the north side should be 0.5 times the vertical height of the window (at the top of the window). Attention should be paid to adequately shading east and west facing windows; whilst south facing windows generally do not need shading.
Whilst important, internal shading such as curtains and blinds will never be as effective as external shading because the radiant heat from the sun has already passed through the glass. To get the best performance from curtains and blinds you need to ensure that they should be opaque and of light colour, to maximise the reflection of sunlight. Pelmets are a good way to reduce heat loss. Tinted or reflective glass should be used where it is not desirable to obstruct the view, and internal shades with a reflective backing should be used where it is not possible to install external shading devices.
A truly energy efficient home harnesses energy from the sun. Current government rebates for photovoltaic systems (the generation of electricity from the sun) and solar hot water can make these renewable energy technologies cost effective - enabling significantly lower running costs and reduced greenhouse emissions. More information on these rebates can be found here.
Landscaping can enhance your property and provide benefits to you in maintaining more comfortable conditions in your home. By carefully planning the landscaping around your home, you can control the entry of heat, as well as the quality and direction of the breezes you allow to blow through it.
Breezes entering your house will be cooler if they have passed through gardens or courtyards that have shade, pools or shrubs and lawns. The layout of your garden can also be used to screen or direct breezes.
In summer, a cool breeze flowing through the house helps cool down the house and it's occupants at night. The house need not face directly into the prevailing summer breeze, but can be offset at an angle of up to 45 either way.
While adequate controllable ventilation is essential to provide fresh air, prevent condensation, and help cool a house on summer nights, draughts can create discomfort and lead to energy losses in both summer and winter.
In winter, draughts can account for up to 25% of heat losses. Reducing these draughts can be a cheap and cost effective way of reducing heating and cooling costs. New houses should be built to minimise draughts, by avoiding gaps at construction joints between different wall materials, and where walls join or meet the ceiling and the floor, and by ensuring that doors and windows fit snugly in their frames. Draughts can be further reduced by:
The term Thermal Mass refers to the ability of building materials to store heat. Building materials that have a high thermal mass, such as internal bricks and masonry and a concrete slab with hard floor coverings, can store large amounts of heat without a large temperature change.
In places where the difference between day and night temperatures is 8oC or more, there are benefits in using high levels of thermal mass inside north living zones to stabilise internal temperatures in both summer and winter. The correct use of thermal mass inside a house can significantly improve both thermal comfort and energy efficiency.
A balance, however, needs to be achieved between the thermal mass, window areas, and insulation levels, to suit the climatic conditions. This can be done now efficiently with the new generation rating tools, about to be introduced across Australia.
Floors
Energy efficient homes make good use of concrete, tiled or slate floors, because apart from being easy to clean, they play a big role in absorbing heat in winter. The floor must be able to absorb as much heat as possible during the day and then release the stored heat into the room at night. Carpets and rugs act as insulators, so the slab floor can't absorb as much heat.
Tiles, slate or any other heat absorbing hard surfaces are ideal and work well when situated in rooms that have north facing windows.
In 1996, the Australian Government attended the Kyoto conference on global warming. Australia was set a target for the year 2010 of 108% of its 1990 Greenhouse gas emissions. (Australia has not endorsed this Protocol yet, but attempts to achieve these targets through the National Greenhouse Strategy). Approximately 12% of these emissions result from activities in the residential sector. In order to minimise these Greenhouse Gas emissions from this sector, house energy rating systems (HERS) have been developed to rate the energy efficiency of new and existing housing to allow the comparison of the heating and cooling needs of different houses.
The energy required to heat and cool a house can therefore now be measured by computer simulation.
There are several rating systems available. These are the NATHERS (Nationwide House Energy Rating System), Firstrate and checklists. The new version of NatHERS, called Accurate, was introduced in May 2006, ready for the introduction of the 5 star energy efficiency performance requirement for all new houses in SA. FirstRate will be upgraded, and the name will remain unchanged. Other checklists that may be used by housing development companies will reflect the minimum legislative requirements.
Since 1 January 2003, all new homes built in South Australia are required to achieve a minimum level of energy efficiency. This level is defined under the Building Code of Australia (BCA) and in the South Australian Housing Code.
The State Government is committed to improving the energy efficiency of homes in order to reduce greenhouse gas emissions and minimise peak electricity loads. The energy efficiency requirements mean that all new homes must be designed and constructed to achieve efficient use of energy for heating and cooling.
There are several ways to comply with the new legislation. The most common is to comply with the requirements of the 'Deemed to Satisfy' legislation that is documented in both the Building Code of Australia and also in the South Australian Housing Code. Alternatively, your house design needs to achieve a minimum five star rating using the approved computer rating software.
The 'Deemed to Satisfy' option specifies levels of added insulation required in the ceiling and roof of new houses. In climate zone 5, for example, (which covers metropolitan Adelaide), the minimum required levels of added insulation are effectively R2.5 and R1.0 respectively. (This is to achieve overall levels of insulation in ceilings and walls of R2.7 and R1.4 respectively as required by the legislation).
If you or the builder choose to use the NatHers or FirstRate computer program to achieve the minimum four star requirement, there is no mandatory requirement to include insulation. The computer rating system was chosen as an alternative way to satisfy the legislation to allow people flexibility in the selection of a range of alternative design options in the design of their houses.
In practise, achieving a five star rating is relatively easy and generally the only extra costs are for the insulation in walls and ceilings, a price that is paid for in the first few years in the home in extra comfort levels and reduced energy costs.
For more information contact Planning SA.
The main computer based house energy rating system in Australia is called NatHERS (the Nationwide House Energy Rating scheme) that is a tool that can be used to give houses an energy efficiency rating from 0 to 5 stars.
The characteristics of the house envelope are assessed, including the levels of wall and ceiling insulation, the orientation of the house, window size and shading, and the thermal mass of the structure.
A 0-Star rating indicates that the house is inefficient and will be uncomfortable without a lot of heating in winter and a lot of cooling in summer. A 5-Star rating indicates that the house has achieved a high level of energy efficiency, and will require minimum levels of heating and cooling to be comfortable in winter and summer. Houses which achieve a 5 star rating will be more comfortable to live in, have lower energy bills, and costs to install heating and cooling equipment should also be lower.
Details of the house design and construction, and its orientation are entered into the program, along with a postcode, which links the program to a database of climatic information for your location.
A thermal simulation for the house is run using half hourly weather data, and the program calculates the energy required for heating and cooling the house (in MJ/m2 per year) to achieve target levels of thermal comfort. The heating and cooling energy requirements are then used to calculate a Star Rating for the house.
Once the data has been entered into the program, it is easy to try out design modifications to see what effect these have on the star rating. An experienced user will be able to show you how to optimise the energy efficiency of the house. Another form of rating is the Firstrate program, and due to its characteristics, is the main program that is used in South Australia. Both are acceptable under the legislation, and both give similar results.
To obtain a NatHERS or Firstrate rating, you will need to contact an assessor in your state.
Firstrate is an alternate rating scheme. While it works in a different way to rate your house, it is based on NatHERS and will give similar results. It also responds instantly to changes you make to the design of your house, so it is particularly useful as a design aid because of its relative ease in obtaining a rating, it is the main rating system in use within South Australia.
House energy checklists are an alternative to computer programs, and are used to guide you in the design decisions you make in the selection of materials etc in your house. There are several land developments such as 'Mawson Lakes' and 'Northgate' that require a minimum point score (using a checklist) before development approval can be obtained. They are based on NatHERS and the point score is normally adjusted to represent the percentage savings in overall energy use of the house. They are slightly different to NatHERS and Firstrate, in that they often also take into account the selection of the appliances and hot water services in your house design, both of which are the other major energy users within your home.
| Q | If my chosen block does not face the right way, does this mean that I can't build an energy efficient house? |
| A | Correct orientation gives you the best chance to capture winter sun. If this can't be done, more effort is required on the other aspects of the house design to achieve comparable efficiencies.Note that a fair deviation from true North can occur with only small changes to the overall benefit in energy efficiency. |
| Q | My new house plan has all the daytime areas facing south. How can I improve the layout? |
| A | Often it can be as easy as asking the designer or builder to mirror image the plan for you. If this cannot occur, consider improving the characteristics of the glass, consider possibly upgrading to double glazing, or incorporating a northern facing sklight to get some winter sun into the body of the house. |
| Q | Do open plan houses and two storey houses with large stairways need to be zoned? |
| A | Large open plan homes and two storey houses allow heat to travel through them easily. This means more energy is required to heat them than if they were able to be divided into smaller areas. Zoning can often be done by incorporating doors to allow this in the early planning. They can be `in wall' sliders if you only want them for winter periods, and don't want them to show at other times. It is easier and possibly cheaper if they are incorporated into the design, rather than retro fitting them later. |
| Q | What is an insulation R-value? |
| A | The level or performance of bulk insulation products is measured by its Thermal Resistance or 'R-value'. The greater the 'R-value', the more effective is the insulation at resisting conducted heat flow into the building in summer, and out of it in winter. Reflective foils work in a different way than bulk insulation, and they do not have an 'R-value' on their own. They are still very effective at minimising heat flow, however, particularly the inflow of summer heat. |
| Q | Are batts or loose fill insulation better? |
| A | The important consideration is the R-value of the insulation material. For the same R-value, there should be no difference in performance between loose fill insulation and batts (providing both have been installed correctly). Note (1) that covering ceiling joists with insulation may create a hazard for anyone who needs to work in the roof space and (2) batt colour does not make a difference to the performance of insulation. |
| Q | Should I consider energy efficient lighting? |
| A | Yes! Whilst fluorescent lighting (globes and/or tubes) can be relatively expensive to buy, they will last much longer than ordinary incandescent globes, with significantly reduced energy consumption. They're great for areas where the light is on for long periods - like kitchens, family rooms and hallways or for outside night security lighting. |
| Q | Can reflective foil laminate (RFL) be used as an insulator? |
| A | Yes - but its positioning in the walls and ceilings is important in terms of its effectiveness. |
| Q | Do louvres and venetian blinds reduce heat loss? |
| A | Louvres, venetian blinds and vertical blinds are not good insulators, as they have air gaps that allow warm air in the room to contact the cool glass. Performance can be improved by lining with a closely woven, tight fitting curtain. For RFL to work effectively, it needs to have an associated air gap next to it. The detailing of the wall or ceiling is therefore very important. |
| Q | Will NatHERS or Firstrate tell me how much my house will cost to run? |
| A | The NatHERS (Nationwide House Energy Rating System) and Firstrate rating systems currently only assess the thermal performance of the housing envelope, ie the need for heating and cooling, and not the costs associated with running appliances within the house. (This is always tricky, as it is difficult to predict your actual usage of appliances within your home. Appliance running costs are therefore often referred to as averages or as quarterly running costs for specified periods of time). Therefore these rating tools are not designed to predict actual running costs. A higher star rating will however, allow you to minimise the running costs of those appliances used to keep you comfortable. The cost of running each appliance in your house, including heaters and airconditioners can quite easily be worked out by knowing their respective energy consumptions and the time they are used. |
| Q | How much does a rating cost and where do I get one? |
| A |
The average cost of a rating is about $170. There are a number of people who can perform the rating for you. Most building designers and architects can arrange one for you or contact:
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