Sustainable Design Principles 101 – Multi-Residential Australia

This post is designed to guide design teams during early design stages prior to any form of drawing mark-up. It describes a pathway of continuous building improvement through easy low hanging fruit strategies to incorporation of renewable technologies and advanced design principles. As sustainability becomes engrained in the construction industry it is important that stakeholders maintain an understanding of what the market expects both presently and going forwards into a low carbon future.


Achieving Targets – The Basics

Generally a multi-residential apartment building built to BCA standards (electric hot water, 6 star Nathers and standard air conditioner) will have approximately the same impacts as the benchmark average dwelling (4.2 tonnes/person/year). They tend to be smaller (less space to heat and cool), have longer design lives and high occupancy (reducing the impacts on a per person per year basis). The chart below represents the life cycle Impacts of a typical multi-residential apartment building.

Capture 2

Typically there are a number of “low hanging fruit” design improvements that are low cost and low risk to implement. The measures focus on operational energy which generally makes up 70%-80% of the total life cycle impacts. The measures are detailed below for a standard apartment building with a mix of one and 2 bed apartments, please note these are indicative figures and will vary depending on final design, density, services and materials used.

Sustainability Measure

Typical percentage improvement
Gas hot water system 25%-30%
Lighting motion sensors/timers in common areas 6%-8%
Apartment Energy Monitoring 2%-4%
Behavioural Change Programs 2%-4%
Low flow shower heads (5l/minute) 1%-2%
Limit refrigeration space to less than 750mm 0.6%-0.7%
Ventilated refrigeration cabinetry 0.4%-5%
Total approximate 37%-45%


With implementation of the above measures the building will achieve approximately a 37% to 45% improvement sitting at a Silver medal rating. To achieve greater improvements renewable technologies are needed.


Renewable Technology Typical percentage improvement
Solar Hot Water (1m2 per dwelling) 3%-4%
Solar PV (1kW/ 10m2 per apartment) 5%-7%


The majority of medium rise flat roofs can easily accommodate the above with room left over for other elements such as flues and skylights. The low hanging fruit combined with some renewable generation will typically achieve around a 45-55% improvement.


 Achieving Targets – Best Practise

For higher ratings to be achieved, there will need to be upwards of 1 kW and per apartment and over 10m2 of roof space available alongside the measures detailed above. This can require careful consideration of roof designs from the outside and in some instances, consideration of options off-site such as community owned solar PV farms may be required.

Renewable Technology Typical percentage improvement
Solar PV (2kW/ 20m2 per apartment) 10%-14%
Solar PV (3kW/ 30m2 per apartment) 15%-20%
Solar PV (4kW/ 40m2 per apartment) 20%-28%


Roof Orientation for PV:

Capture3Once a residential building gets above 4 storeys, or a commercial building gets above 3 storeys, it will likely end up in a position where the solar technologies that are required are constrained by the roof space that is available. In this situation the design team should take roof design into consideration from an early stage and optimise it for solar panel installations. The following guidelines should be considered:

  • By installing panels “flat” on a roof, many moor panels can fit because they do not need separating for shading.
  • Shading from surrounding objects and buildings is an important consideration however it is rarely a problem in multi-residential buildings taller than their surroundings. PV can be very worthwhile even if partially shaded and can may still deliver significant carbon savings compared to other measures.
  • For designing roofs in this situation, the following considerations should be made.  Note that the below loss figure for varying orientation and pitch are applicable to Perth (latitude of 32 degrees):
  • The orientation of the roof can significantly aid the amount of PV or Solar Hot Water that can be installed in the diagram above

– North facing panels at 32 degree pitch gives optimum energy gain over the whole year (100%)

– Dropping pitch to 5 degrees only results in a loss of approximately 9% (91% of optimal generation)

  • If panels are to be pitched at lower than 10 degrees, consideration should be given to at least annual cleaning until it is proven that soiling is not effecting generation.
  • If possible, avoid hips in roofs as these significantly reduce the amount of PV that can be installed.  It is far better to pitch the roof in two directions only.  Even pitching north and south in two directions is likely to result in a better overall result than in four directions.  The south facing panels may generate less power per panel than the east or west, but more panels will be able to be installed because hips won’t have to be avoided and this will more than make up for the slight loss of efficiency in south facing panels.
  • Very wide gutters can significantly affect the available roof space for solar collectors.  Consider overhanging the roof structure over a required large gutter.
  • Protruding services that break up the roof space should be designed if possible on the south side of the building.  This reduces the losses due to shade for solar collectors across the whole roof.
  • Roofs with multiple heights are complex due to overshadowing.  If possible avoid this.

For solar hot water systems the same rules apply however slighting more consideration may be required to match demand with pitch, so a higher pitch to meet the higher winter water heating demand.  This is not such an issue with PV as it can be fed into the grid when generation is higher than demand.


Advanced Design

Some of the recommendations listed below represent paradigm shifts not only in actual construction but also in the marketing and sales strategies that may be required to ensure a developments viability. There may be times when it makes more sense to invest the money that would go into some of these expensive onsite solutions to other local projects that can deliver more value and higher CO2e savings. Examples of this may include Investments in street light upgrades, existing housing retrofits, solar panels on local schools and buildings, behaviour programs, community farms, bicycle infrastructure etc.


The more people a building can house the less impact per person that building will have. Furthermore for every person that is housed in a sustainable building that takes one more person out of the average, unsustainable building – moving society towards a low carbon economy faster.

Typical multi-residential buildings have approximately 50% of the total floor area dedicated to actual living space, the rest tends to get tied up in common areas, car parks, plant rooms etc. By minimising the common areas you reduce impacts on two fronts: living area available for the same volume of materials, and reducing the operational energy required to light and ventilate the common spaces (this can typically take up to 15% of the total CO2e emissions).


ratio net dwellable area/gross Floor Area Life Cycle Reduction in Emissions
50% -3.1%
55% -5.6%
60% -7.7%
70% -11.0%
80% -13.5%


There are numerous ways that common areas can be reduced:

Capture 8

Space efficiencies can also be gained by increasing the number of stairwells whilst reducing the common walkway areas.


Although stairs are likely to be the more expensive option, this could be recouped by adding the spare hallway space into each apartment, in the example above this provides an extra 8.75m2 per apartment.

Typology (Beds and bathrooms)

Environmental impacts can be reduced through increasing the occupancy of the apartments themselves. Whilst 2 bedroom 2 bathroom apartments are fashionable, with good design that (rarely used) spare bathroom could be a third bedroom instead. This provides an increase in the overall sustainable living space of the building without impacting on the floor area being constructed


In many ways embodied carbon is equally (and perhaps more) important a consideration than operational energy. eTool LCAs will typically assume current grid intensities throughout the 100+ year predicted design life of a building. This means operational energy makes up around 80% of the total impacts. In reality over the next 100 years the grid will decarbonise and operational energy will contribute much less over time. The embodied carbon in materials on the other hand is locked in from the year the material is manufactured and transported to the site. There are many low impact alternatives to common materials in construction. Timber and CLT can be used in place of concrete and steel. Where concrete is necessary fly-ash or blast furnaces slag blends should be incorporated, these are waste products that can directly replace a proportion of the concrete thereby reducing its impacts.

graph 1

Timber veneers and plywood should be avoided due to the high impact of the glues and resins used in these products. Plasterboard also has very high impacts. Alternatives such as plain hardwood, bamboo or MDF represent significant savings. IF plasterboard is to be used 6mm sheets should be preferred to 12 mm sheets with acoustic requirements met through insulation which is typically low in CO2e emissions.

graph 2

Carpets (especially wool) should be avoided with cork or polished concrete finish preferable. If absolutely necessary carpets should be dark coloured (to avoid replacement through soiling) and plant based materials such as jute and sisal should be specified that have natural/non-synthetic rubber backing.

graph 3


There tends to be little difference in terms of environmental benefit between CFL lights and L.E.D lighting Increasing natural light levels using solar-tubes, skylights or similar means less use of artificial lighting energy. Specifying lighter matte colours to surfaces such as the balcony, ceiling and walls will bounce light deeper into the dwelling thus increasing natural lighting. Light shelves in windows is another passive way to divert and bounce light deeper into the dwelling. Similar systems using adjustable louvres can also be used. Providing translucent shading material in addition to heavier curtains allow the option of diffused daylight to penetrate whilst maintaining privacy. The top of the windows is where light penetrates deepest into the dwelling, so it is important to ensure that this part of the window is not obstructed by drapery or blinds. Translucent partitions between rooms also allow light to be drawn into deeper rooms. Clerestory windows also provide a method of introducing more natural light into central rooms.  Ideally these should be utilised with higher ceilings and high reflectance surfaces in order to encourage light to penetrate.  In order to prove the value of these initiatives a daylighting simulation should be undertaken to ensure expense is not incurred for no benefit.  This will likely make this recommendation hard to justify economically (there will be many far easier wins elsewhere in the building.

Gas cookers over electric

In regions with fossil fuel dominated electricity grids such as WA, gas represents a large advantage over electricity for providing energy to cook with.  This is due to the heat and electricity losses associated with distributed power.  Burning the fuel (gas) at the source eliminates these losses and is a more efficient way of using the fuel. The majority of gas cookers sold today include safety features that automatically turn off the gas when no flame is present. Rinnai has also developed the ‘inner flame’ technology that produces a flame that is directed inwards which is about 27% more efficient than standard gas stoves. The drawback to moving to gas cooking is that a gas pipeline may need to be installed. If the implementation of this strategy is outside of the project budget the developer may offer the strategy as an upgrade package for purchasers. This eliminates the need for upfront capital while promoting best practices and educating the public.

Or Induction cooktops

An all induction cook-top is an alternative that could deliver carbon savings over a standard electric cook-top.  Induction cook-tops work by transferring electrical energy through induction from a coil directly to the magnetic pan. Only the area in contact with the coil heats up and therefore the cooker can be up to 12% more efficient than a standard electric conduction cooker.  The controls on an induction cooker are also far more precise giving a greater range of cooking techniques.

Car Park Ventilation

By applying a detailed engineering design to the car park ventilation systems, it is expected that the fan run times could be considerably cut down especially when natural ventilation is utilised.  Computational fluid dynamics would be utilised in this technique to determine how to best move air through the car park to maintain acceptable CO2 levels with minimum energy demand.  Gains may also be achieved in reduced ducting.  At least a 20% saving in ventilation may be achieved.


Biodigesters turn food and or human waste into gas that can be used in cooking. Although not well established in western countries this technology has been used for hundreds of years in China and India. Communal or individual systems exist that may be incorporated into an innovative building design.


The appliances that go into the building can make a significant proportion of the recurring impacts.  Modern appliances tend to have fairly small warranty periods in relation to the lifespan of a building.  TVs in particular can often not last more than 10 years.  Ensuring that appliances are purchased second hand and those that are purchased new have a long warranty and are kept for as long as possible can provide significant carbon savings.  In this recommendation we have assumed each appliances lasts twice as long as the standard warranty. Where appliances are installed they should also be of the higher MEPS rating bands for energy efficiency.

Thermal Performance

Modern 6 star dwellings in Western Australia need very little in the form of heating/cooling. The developer with sustainability in mind will provide only ceiling fans for cooling and renewable biomass pellet heaters for heating. Bio Where air conditioners are provided they should be single split units which can obtain higher efficiencies generally than multi splits. A COP/EER of 5 is exemplary.

Tri-generation, deep geothermal and shallow ground source heat pumps can also be appropriate in very large developments with high demands such as precincts with swimming pools. However they entail very high outgoing capital costs and the environmental benefit should be considered carefully against other technologies.

Swimming Pools

Most importantly swimming pools should be appropriate for the size of the development. Proportionally 50m2 pool shared amongst 100 dwellings will have 100x fewer impacts per dwelling than the same size pool provided for a single dwelling. Where pools are installed they should ideally be naturally heated through ambient air and install pool covers that contain the heat when the pool is not in use. Typically including a pool cover which can operate automatically or manually for 8hrs per day during the pools closed hours has a 28% saving in the pools heating energy demand. Pool pumps efficiency should also be considered carefully, high-efficiency pool pumps of up to 9 stars MEPs rating are currently available on the market.

 Hot Water

Alongside solar thermal technology and low flow shower heads, an opportunity exists to warm the inlet temperature of the water by using a heat exchanger. Water exiting apartments in the sewerage drains will have a higher temperature than the normal inlet temperature of water coming into the building from the mains, particularly in winter.  By passing the inlet water over the warmer outgoing water, the temperature can be increased. A 5% reduction in energy demand of the hot water system can be achieved.

For communal systems there will be significant heat losses in the pipe carrying the hot water around the building as well as from the individual water storage tanks. Based on the conservative assumptions of a 25mm pipe with 25mm of insulation (125mm total diameter) the heat losses are estimated to increase the hot water demand by 10%. Correctly installed 50mm pipework insulation could therefore reduce the losses through hot water pipe by approximately 5%.



The door is always open at eTool for questions surrounding design decisions. If a project is in concept phase we are happy to sit down for an hour and discuss potential strategies and targets. Full targeting sessions are also available at low cost to determine more accurately the costs involved in achieving design aspirations. Following this our full LCA will provide the most detailed environmental assessment available.


Benchmarking Philosophy

eTool recently changed from offering numerous fairly localised benchmark options to a single international average benchmark for each building type.  The decision making process was interesting so I thought I’d quickly document it.

The purpose of the eToolLCD benchmark is:

  • To establish a common measuring stick against which all projects are assessed so that any project can be comparable to another (for the same building type);
  • To create a starting point, or “average, business as usual case” from which to measure improvements.

From the outset we’ve always understood that a benchmark needs to be function specific.  That is, there needs to be a residential benchmark for measuring residential buildings against etc.  The first point essentially addresses this.

The second point introduces some complexity.  What is, or should be, “average, business as usual”?  More specifically, are people interested in understanding how their building performs when compared compared locally, regionally, nationally, or internationally?

When we started trying to answer this question, some scenarios were very helpful.  If a designer wants to compare locally, the benchmark needs to reflect the things that are most important to the overall LCA results.  The two most critical things are probably electricity grid and climate zone.  Localising just these two inputs gets pretty tricky and the number of possible benchmark permutations starts to add up pretty quickly.  In Australia there are four main independent electricity grids (NEM, SWIS, NWIS and Darwin).  In the Building Code of Australia there’s 10 climate zones.  Accounting for which climate zones occur within each grid, there’s about 20 different benchmarks required.  To add to the complexity though, the NEM is split into different states (New South Wales, Victoria, Australian Capital Territory, Queensland, Tasmania and South Australia).  Generally, because the National Greenhouse and Energy Reporting guidance splits the NEM into different states, the NEM is usually considered as six different grids. So there’s upwards of 50 different benchmarks we’d need to create and maintain for Australia alone just to localise electricity grids and climate zone.

One disadvantage of this method is it’s still not all-accommodating.  It doesn’t account for remote grids of which there are many in Australia.  An example is Kunnanurra which is 100% hydro power.  So even in this scenario where we had 50 or so benchmarks for Australia, there’s still big potential for a designer patting themselves on the back for a great comparison to the benchmark when really it’s just a local condition, and vice versa.  The same can be said about an off grid scenario (effectively just a micro grid of it’s own).

The other disadvantage is maintenance of all these benchmarks.  Expanding the above scenario internationally there could easily be 1000’s of possible benchmarks.  There’s so many that it would be hard for eTool to initially create them, and even harder to subsequently maintain them.  Clearly the localised benchmark option had some big challenges.

At the other end of the benchmarking philosophy we considered just having generic benchmarks, or even one global benchmark.  This is perhaps a more user-centric, or building occupant sensitive system.  That is, the building occupants are probably more interested in this measure as it’s more about how they live compared to the global community.  So a building may be “average” compared to the local context, but actually be very low impact compared to the broader average (due to favourable local conditions).  Conceivably, the local conditions contributing to the ease with which a building can perform may be part of people’s motivation for living in a particular area.

The disadvantage of the generic benchmarking approach is that it isn’t as useful for a designer to compare their building’s performance against this as the local conditions (which may create a significant advantage of disadvantage) aren’t considered.  This was a big consideration for us, eToolLCD is a design tool, it has to be relevant to designers.  Interestingly though, the way eToolLCD is generally used is the base design is modelled, and then improvements are identified against this base design.  The benchmark is usually only used towards the end of the process as a communication and marketing tool.

Also, there’s no reason why the designer can’t model their own local benchmark, for example, a code compliant version of their own design.

This topic spurred some serious debate at eTool.  In the end, the deciding factors were:

  • A local approach couldn’t really be adopted without localising at least the grid and climate zone for each benchmark option.  That is, it would have been too difficult to go half way with localisation (for example, only localising climate zone and not grid), as this really just revoked the whole advantage of localising the benchmarks.
  • Taking the very localised approach was going to put a huge benchmark creation and maintenance burden on eTool which wasn’t necessarily productive
  • The choice of a generic benchmark didn’t detract from the function of eToolLCD as a design tool.
  • Greenhouse Gas pollution is a global problem not a local problem, we feel people probably need to measure and improve their performance against a global benchmark rather than a local one.

So the single global benchmark was the direction we choose.  Once this decision was made, we needed to determine how to statistically represent global averages.  We decided to choose an aspirational mix of countries to make up the global benchmark, that is, select the standard of living that we felt most people in the world aspire to and determine the average environmental impacts of buildings in these demographic locations.   This does mean the global benchmarks are generally higher than the actual global average building stock for a given function.  That doesn’t stop us from estimating what the sustainable level of GHG savings is against this aspirational benchmark (90%+).  It also enables us to strive for this level of savings without adversely effecting our standard of living aspirations (globally).  The global benchmark created using this approach is the residential benchmark.  More information about how this was conducted can be found here.

For those people or organisations that would like a customised benchmark, eTool can provide this service.  Please get in touch.

Brown Paper Background

eTool International Residential Benchmark (Methodology Summary)

Below is a summary of our approach to the International residential benchmark.  A full EN15978 report on the benchmark model can be found here.  International Residential Benchmark Weighted x10 dwellings v28

In light of eTool’s recent exploration into global markets, we thought it prudent to create a “global” benchmark for housing developments.  eTool will be using this benchmark for all future housing projects. The reasons an international statistically mixed use benchmark is the most robust model to compare designs against are as follows:

  • The planet does not care what kind of house you build only how close it is to zero carbon. A mixed use benchmark provides a fair comparison of performance across different house types be it apartments, detached, maisonettes etc.
  • The planet does not care where you build your building, only how close it gets to zero carbon. Climate change is a global problem, whilst regional benchmarks can be useful for comparing similar buildings in the same area they can produce unfair results.  For example, a house built in a low carbon grid area (e.g. Brazil) may have emissions of 2 ton/person/year.  This may only be a small improvement against the average Brazil house as they both have the benefit of a low carbon grid.  Conversely a building in WA may have higher emissions (say 3 ton/person/year)  but despite having higher emissions than the Brazil case could show a larger improvement against the average WA house.  A single benchmark is the only way to give correct credit for the true sustainability performance of a building.

Before getting into the nitty gritty, it’s important to understand the purpose of the eTool benchmark, which is:

  • To establish a common measuring stick against which all projects are assessed so that any project can be comparable to another.
  • To create a starting point, or “average, business as usual case” from which to measure improvements.

Benchmark Form and Structure

The benchmark has been created to represent an average dwelling built in a developed country, the statistics for a range of developed countries have been population weighted and combined into a single theoretical average dwelling.


The statistics used in the benchmark are based on data obtained for each country. The construction type and dwelling size statistics take new build data wherever available, as this data is generally reliable and represents a picture of the way buildings are currently being built across the developed world. For residential buildings there is a mix of houses and apartments. This is the latest breakdown of the new dwellings density mix across the countries considered in 2010:


The occupancy is calculated by dividing teh countries population by the number of dwellings to give an average. This is weighted by population to give a global average of 2.52.
For the single dwelling element (59% of our average dwelling) a building structure has been modelled taking a cross section of commonly used construction techniques. In this instance, the data was obtained for U.S.A.  The U.S.A makes up the largest proportion of new housing in the developed world and is considered to represent a fair “average house.”  Construction techniques are unlikely to differ significantly enough to impact on the overall modelling, whilst brick houses may be more common in the U.K. and Germany, timber framing is far more prevalent in Japan and Sweden.


A similar approach was taken with windows, internal walls, floors and roofs. The vast majority of those installed in new builds across America and Europe are double glazed and allowances have also been made for the smaller proportions of other window framing options currently in common use.


For the multi-family dwellings, a standard concrete frame structure has been taken with one level of car parking and typical auxiliary and common layouts, such that the apartment living area represents approximately 50% of the total floor area of the building.  The total impacts of this building have been weighted on a per m2 basis and 56 m2 has been added to the model to represent the apartment element.

Benchmark Operational

Existing data has been used for operational energy, and arguably new build data would be preferable, but total existing data is generally a lot more robust (and readily available). Whilst new build energy figures were available for some countries, the figures tend to be from modelling completed for regulatory purposes and are therefore theoretical. In many countries there is a perceived “performance gap” between modelling results and actual consumption mainly due to differences in occupant behaviour, but also because of limitations in software and methodologies used for the modelling. The hope is that there will be continued industry effort towards monitoring of new build housing performances. Until further data in this area is available, we have a robust snapshot of how average buildings are currently performing by taking existing housing data.

The data for total residential fuel consumption was divided by the total number of dwellings in each country analysed. This was then weighted according to population to give a final figure for the average energy consumption of a developed country dwelling.


End-use percentage estimates were then used to determine where this energy is being used in the dwellings.  Again, U.S. data[ix] has been used to represent the average.


Other impacts such as appliances and cabinetry and finishes have also been included by the estimated proportion of dwellings estimated to include these.

The global average water consumption is considered fairly consistent across most developed countries with America and Australia having higher water consumption due to larger garden sizes.  A conservative nominal 169l/person/day has been assumed for water supply and treatment.


[i] Populations by country 2010

[ii] Characteristics of New Housing U.S.A

[iii] Statistics Bureau Japan

[iv] EU Odysee Data 2008 downloaded on 11.7.2014

[v] Australian Bureau of Statistics Average floor area of new residential dwellings 2012

[vi] U.S. Energy Information Administration – Annual Energy Outlook 2014 – Energy Consumption by Sector and Source,ref2014-d102413a

[vii] Odysee energy database for EU and Norway (2008) downloaded from in July 2014

[viii] Statistics Bureau Japan Chapter 10 Energy and Water

[ix] U.S. Energy Information Administration Residential Sector Key Indicators and Consumption,ref2014-d102413a




Research Shows Sustainable Apartments are a Priority for Perth Community

Research conducted by Psaros in partnership with the Conservation Council of Western Australia (CCWA) and the Property Council has indicated that the Perth community rates sustainability, public transport and walkability as some of the top priorities concerning the future of the Perth inner suburbs.

CCWA Director Piers Verstegen said

“This ground-breaking research dispels some deeply-held myths that have been holding Perth back from becoming more sustainable, more affordable and more liveable.”

“Our capital city is shaking off its ‘dullsville’ image, but there is a lot more that needs to be done. In particular, the research shows that high quality eco-friendly developments around transport links are strongly supported by the majority of Perth residents.”

“While there can at times be vocal opposition to individual developments, there is much broader and stronger support for increased density than planners and Local Councils might think. This is great news for our environment. For every sustainable apartment that is built, less energy is used, less waste is created, less natural bushland is destroyed and more trips are taken by public transport.”

Below is a quick summary by Psaros of some of the findings of the report. You can read the full report here.




Undertaken by leading social research provider Ipsos between 4 – 17 June 2014. Respondents who live within 10km range of the Perth CBD were recruited in an online survey and focus group analysis. An even distribution of voters between 18 and 65+ with majority being single or two parent families with kids and older couples without kids. Final sample size n+524.

Main findings

There is very strong support for more medium & higher density apartment-style developments around transport hubs (71% support) and in inner areas (68% support).


The top three priorities for Perth’s future are;

•    an increase in public transport (train, light rail, buses) (95% support)
•    more eco-friendly buildings that generate their own power, collect rainwater and use less energy (89% support)
•    well-designed, safer bike paths to get to work and other places (86% support)

The most appropriate housing types for Perth city are:

•    a mix of mid-sized apartments, townhouses & retail / cafés (like Leederville and Northbridge) (79% support)

•    a mix of high-rise, town houses and parks (Like South Perth) (71% support)

Over half of residents (55%) would support increased building height limits to allow for higher density around transport links and 50% would support relaxing building height limits if developments are eco-friendly; .

The majority of respondents (73%) do not believe that the benefits of a separate house and garden outweigh the benefits of inner city living.

The majority of respondents (69%) do not consider low density living in detached single housing to be a more affordable option .

Perceived benefits of apartment living include:

•    easier to maintain (71% agree, 8% disagree)
•    reduce the need for land clearing (70% agree, 8% disagree)
•    lower environmental impact than detached housing (54% agree, 17% disagree)
•    save on energy costs (44% agree, 15% disagree)
•    save on car running costs (42% agree, 23% disagree)

3 in 5 inner city residents are likely to move house in the next 5 years; 73% would consider living in medium density housing and 50% in higher density housing.


Future Grid Sensitivity


The standard assumption eTool makes when conducting an LCA is applying the current emission factor of the electricity grid for the specific region over the life of the building. While renewable energy source do not currently make up a large percentage of the energy grid, the cost of renewable technologies has fallen dramatically over recent years. The Australian government also has a legally binding obligation to reduce its emissions by 5% on 1990 levels, under the Kyoto protocol. The Australian government has also committed to an 80% reduction by 2050.

If the decreasing cost of renewable energy trend continues and becomes competitive with coal and gas, the market will naturally shift away from fossil fuels, particularly if fossil fuel subsidies recede. There is also a small but growing consumer demand for more ethical electricity tariffs. This shift of energy sources into the electricity grid opens a potential for a change in the way grid emissions are calculated with life cycle assessment.

Modelling Decarbonisation

Presently in eTool we assume that the grid fuel mix remains at today’s levels for the life of the building. Whilst this is a good conservative position, and drives the right behaviour in terms of energy efficiency, it may divert some focus from other areas of the building, which may be more important if a more realistic future scenario of grid electricity impacts are used.

In response, we have created two other grid emission factors: a 2050 grid and a 2030 grid. The 2050 grid assumes an 80% reduction in the current grid intensity. The 2030 grid takes the average grid intensity over the next 40 years, assuming a linear move towards 80% renewable generation by 2050. The modelled reduction in CO2e intensity is achieved by:

  • Eliminating the most carbon intensive fuels from the current Australian electricity mix and replacing these with a combination of renewable sources, and
  • Increasing the thermal efficiency gas powered generators from 34% up to 50% (implementation of combined cycle turbines)

The fuel mixes and assumed thermal efficiencies for the different grids modelled is shown in Table 1. There are a few flaws in this method that we need to declare: Firstly, the scenarios assume reductions in CO2e intensity of tailpipe emissions only. It does not account life cycle emissions for electricity, which includes impacts associated with fuel extraction and transport upstream from the power plant as well as downstream impacts associated with transmission and distribution. Secondly, if we accepted that this would be enough to meet the 80% reduction in emissions required, the demand for electricity (or energy in general) could not increase. If there is an increase in demand, we would need to further reduce the intensity of Australian emissions and the target is on absolute GHG pollution, not pollution per dollar of GDP, per capita or per kWh. Nevertheless, we think the approach is suitable for the purposes of illustration and discussion, which is the goal of this technical article.


Table 1: Modelled Grid Fuel Mixes

Life Cycle Impacts of Residential Buildings

The graph below illustrates how the lower grid scenarios impact on a single residential dwellings life cycle emissions.  Proportionally, embodied emissions have a much larger impact than operational as the grid de-carbonises.

annualised GHG


Reconsidering Design Decisions

Generally speaking, there will be a move toward electric based solutions as the grid de-carbonises and the impacts of electricity become competitive with gas. A few recommendations that we typically apply to residential dwellings are shown for the different grid scenarios below.

Design decisions

In this instance, the annual CO2e savings associated with PV have more than halved in the 2050 scenario. Savings from embodied impacts in materials become much more important as the grid decarbonises and materials make up a larger proportion of a buildings CO2e. Moving to fly-ash concrete or replacing carpets gives greater savings than installing a gas hot water unit, which under todays grid scenario would ordinarily provide significantly more.

It’s important to note is that while the transition to a low carbon grid will likely occur incrementally over the coming years, the embodied impacts of the materials are locked in from the day of manufacture. Providing that the grid does decarbonise, material choice can be considered to be equally as important as operational energy, especially when dealing with buildings with a long design life.

What about the gas grid?

We have yet to add a CO2e intensity for future gas grids but watch this space.  There is potential for a reduction in the gas grid emission factor with more input into the gas grid from landfill collection and anaerobic digestion. Then again, potential impacts of shale gas fracking will also need to be considered.

The technologies that make up a dwellings services (cookers, boilers, heat pumps etc.) typically have a lifespan of no more than 20 years. Our approach at eTool remains to recommend the lowest carbon solution based on today’s grids with the assumption/hope that they will be replaced with whatever the lowest carbon solution happens to be in 20 years time.

The future may also bring an appropriate price on carbon and studies show that $150+/tonne reflects the true cost of climate change (social and economic cost), which will drive behavior. For example, a gas hot water system is significantly lower in carbon emissions today but in 20 years time when it is replaced, the electricity grid may have decarbonised such that a heat pump is now the low carbon option. Perhaps the occupant will be further incentivised by the price of a renewable electricity grid versus finite gas with a high carbon price.

What about Materials Future Impacts?

The manufacturing of some materials will decarbonise over the coming years, such as the use of biomass in the heating processes in cement production. However, for a building constructed today, the key structural elements of a building such as the impacts associated with the concrete or steel are locked in on the day of construction. The recurring impacts of replacing high carbon materials like plasterboard and carpet may also decrease as the economy de-carbonises. For some elements, this may be due simply to using renewable electricity in the manufacturing plant. For others it may require something more innovative such as developing sheep food that does not make them burp and fart.

There is a high level of uncertainty associated with future impact intensities for the system processes and materials making up a buildings use phase. For example, as Australia’s economy de-carbonises, the impacts associated with energy inputs, maintenance, replacement, repair, water use, and transport will likely decrease (particularly with regard to global warming potential). This has not been accounted for in the analysis. One could potentially model the effects of this parameter on GWP alone as we do know Australia’s current commitments to reduced greenhouse gas emissions, however, even this is very speculative as we do not know how the economy will decarbonise (through efficiency, reduced growth, alternative fuels, renewable energy sources or other mechanisms). The building energy inputs, and the fuel mix for manufacturing products used through the building life span has therefore been assumed constant, and set at today’s values throughout the modelled life cycle of the building.

What else might change?

Australia has been seeing first-hand the effects of climate change for a number of years. The meteorology department has confirmed that 2013 was the hottest year on record experiencing a greater number and intensity of heat waves than ever before. Even if global CO2e emissions are kept within the threshold for a 2 degree global rise in temperature, we will still need to adapt to the climatic changes that have resulted from our current emissions. The Garnet Institute makes the following predictions regarding changes to climate in Perth assuming no mitigation:


–          4 degree rise in average temperature in Perth,

–          56% increase in number of days over 35 degrees by 2070

–          15% – 45% reduction in rainfall in Perth by 2070

–          15 – 65% increase in number of days with “Extreme fire risk”


In the best case scenario with emissions stabilising at 450 ppm, there is still a 2 degree rise in average temperature across most of Australia. The reality is that we have already passed 400ppm and 550ppm (3 degree rise) is realistic. To adapt to these changes we will see a greatly increased use of air conditioning across all building types to maintain thermal comfort.


-Researched and written by Pat Hermon 


Research Sources




EN 15978 and eTool LCA Normal System Boundary

EN 15978

In 2011 the European Committee for Standardisation (CEN) released a new standard for measuring the environmental sustainability of buildings.  We grabbed a copy of this standard, EN 15978 soon after it was published to understand how eTool stacked up against the requirements.  We breathed a sigh of relief, although we had a few things to tidy up, what we were happy with was that we actually needed to reduce the scope and system boundary of a normal eToolLCA to report to EN15978.

Background to EN15978

This standard was one of the first to be released by CEN Technical Committee 350.  It was part of a much broader project to fully define how to measure the sustainability of buildings.  Within TC 350 there were working groups determining how to measure a building’s:

  • Environmental Performance,
  • Social Performance, and
  • Economic Performance.

Impressive.  The full suite of sustainability covered under one set group of standards.  And it doesn’t stop there, there are also working groups covering civil works and construction products.  Incredibly, they are making very good headway through this arduous scope with 8 standards already published and another four under development.  EN15978 is the key to measuring the environmental pillar of sustainability.

How Does it Work?

Well, it’s kind of complex you have to read the detail of the standard, and a good number of the standards referenced.  That said, we will summarise as best we can.  The basic philosophy is to rely 100% on LCA as the method of measuring environmental performance.  So there is hence a heavy reliance on ISO 14040, 14044 and 14025 which eTool LCA software also heavily draws on.  The standard gives guidance on how to apply LCA to buildings.  It effectively defines the goal, scope and method for LCA practitioners working on buildings.

The System Boundary

The diagram below shows the system boundary of EN 15978 is shown below.  For existing users of eTool LCA, or those who rely on eTool ratings, our standard system boundary is also shown.  We think the EN 15978 have essentially done a fantastic job putting this together (with a few exceptions we discuss below).

EN 15978 and eTool LCA Normal System Boundary

EN 15978 and eTool LCA Normal System Boundary

The largest omission from the system boundary is what EN15978 calls “non building related energy use”.  They essentially include HVAC, domestic hot water and lighting but exclude all other energy used within the building.  This makes sense at first glance, after all, these areas are certainly the most heavily influenced by the building designers, and other energy use is very heavily occupant driven.  There are however some strong arguments for including all energy used within the building, a few of which are listed below:

  • A building designer can influence occupant behaviour, and as such these aspects should be considered by architects and engineers, for example:
    • Energy monitoring has been proven to influence occupant behaviour in both commercial and residential buildings and should be considered by the design team
    • In residential buildings, energy use per occupant generally drops off with higher occupants per dwellings due to the base loads (refrigeration, living area entertainment, standby loads, lighting and heat losses from hot water systems) being spread between more occupants.  Buildings that allow and encourage more occupants per dwelling will (all else being equal) use less energy per occupant, and hence should be differentiated.
    • In commercial buildings, an integrated fit out of work stations can have huge positive impacts on energy use through the use of central servers for data storage and processing and mini computers at work stations drawing very little power.  A seamless implementation of such systems may require architectural and engineering consideration during the design of the building so should be factored.
  • Building integrated renewable energy systems should if possible be sized to meet the entire load of the building, not just the base building loads, so designers should be aware of the entire loads.
  • Developers can have a large influence on the building performance (at least initially) through the final fit out of appliances (residential) and work stations (commercial) so this should be within scope so we don’t drop the ball on this opportunity.
  • Vertical transport (elevators, escalators etc) for medium rise buildings can be heavily influenced by design:
    • The building envelope needs to cater for the most efficient plant geometrically
    • The use of stairs or ramps should be encouraged through design to reduce reliance on plant
    • The building electrical systems should be designed to cater for regenerative drives etc
  • Communicating the total impact of buildings without accounting for occupant energy use is very misleading.  Imagine moving into a building marketed as ‘energy neutral’ building only to find your power bill only drops 25%

Environmental Indicators

The suggested list of reported indicators is quite comprehensive for EN15978 and is shown in the below summary table:

 EN15978 Indicators

EN15978 does state that not all indicators need to be reported, but the documentation must specify the reasons for omission.  Interestingly toxicity, land use, biodiversity are missing from the above list.  The standard states that this is due to there being no scientifically agreed calculation method within the context of LCA for these indicators.  We’ll watch this space as we know some of these missing indicators are of great interest to many users of eTool.

EN 15978 and eTool LCA

After we read EN15978, we documented the required changes, pushed them into our product roadmap we got back to other work.  It wasn’t for another year though before it hit us how important this standard was.  All of a sudden, we weren’t “those guys from Western Australia who think they’ve nutted out how to truly improve the environmental performance of buildings”, EN15978 established that LCA was indeed the most appropriate tool for profiling green buildings.  Standards such as this one lend huge credibility to solutions like eTool that were released prior to the standard.  We were definitely barking up the right tree when we naively stood in front of the cameras on the ABC’s New Inventors and demonstrated the humble beginnings of eTool!

The recent uptake of LCA by the Green Building Council of Australia in their Greenstar tool heavily references  EN15978.  This has prompted us to build a suite of reports that are compliant with the standard, and those it references.  Importantly, we’re not going to remove any functionality form eTool, or contract the scope or system boundary.  Users will simply have the opportunity to report to either the EN15978 scope or the more expansive eTool LCA scope.  Similarly we’ll continue to upload more indicators into eTool LCA, our focus for the next 12 months will be plugging the gaps for EN15978 reporting.  There’s likely to be a lot of low hanging fruit here, and some trickier ones that may take some additional programming so we’re not entirely sure when we’ll be reporting on all 22 indicators just yet.  Our reports will be compliant with EN15978 though by still listing these additional indicators with “INA” (Indicator Not Assessed) in place of the calculated values which is accepted in the standard.  We’ll also allow users to report indicators currently available in eTool that aren’t required by EN15978.  Our general position on indicators is that global warming is our biggest environmental problem and hence our main efforts will continue to focus on solving this.

Brown Paper Background

eTool Residential Benchmark For Australia

Before getting into the nitty gritty, it’s important to understand the purpose of the eTool benchmarks, which is:

  • Establish a common measuring stick against which all projects are assessed so that any report is comparable to another (for the same type of project).
  • Create a starting point, or “average, business as usual case” from which to measure improvements.

The benchmarks are not an average of existing stock but rather an average of new stock. Hence any efficiency requirements etc in the Building Codes etc are taken into account. When comparing to the benchmark, the target is pretty simple. Effectively Australia has to drop it’s GHG emissions by about 90-95% on a per capita basis for us to become sustainable global citizens. With this in mind, what we should be trying to do is drop our building’s emissions by 95% against the benchmark to ensure the building is stabilising the climate.

Creating the business as usual benchmark is pretty complex. For residential buildings in Australia there is a broad density mix from detached through to apartments. This is the latest breakdown of the new dwellings density mix in Australia (from ABS) over the last two years:

DetachedSemi DetachedLow Rise ApartmentsHigh Rise Apartments
Proportion of New Dwellings61%13%7%19%

For each of these density types, eTool have formulated a BCA code compliant building. We have then created a nominal statistical mix of  floor areas to match the average new dwelling size in Australia (214m2). In this way we come up with a “dwelling” that is a mix of densities and matches the size of the average Australian dwelling.

A similar approach is taken for operational energy. In this case we first research the most up to date residential energy estimates for Australia.  This data comes from ABARE Energy in Australia 2012. It gives us guidance on the total energy used per household (existing housing stock) in Australia and also the fuel mix split (electricity, gas, wood etc). We then use other end use percentage estimates to determine where this energy is being used in the dwellings.  The most commonly quoted breakdown of household energy use in Australia is from the “Your Home Technical Manual” which is actually a reference to the “Energy Use in the Australian Residential Sector, 2008”.  This report is commonly referred to as the “Base line report”.  This report itself actually states:

The study identified a paucity of end-use data for residential energy use in Australia, particularly in regional areas. Some of the appliance energy consumption estimates used in this study rely on research that is 15 years old or, alternatively, on work undertaken in New Zealand. 

The study recommends an comprehensive end use energy monitoring program which we believe is being undertaken. Until the results are out we’re a feeling our way in the dark a little.  Not withstanding this, the study is useful to guide the decisions about where we’re using our energy. To verify the Base Line Report figures we also took some state government studies (eg Sustainable Energy Development Office in WA) and statistics from other countries (notably the BRANZ HEET study and also stats from the US). The largest unexplained discrepancy seems to be in the estimates for heating demand.

The Base Line Report suggests that 38% of total end use energy in Australia homes is dedicated to heating and cooling purposes.  This seems very high given the following facts:

  • The comprehensive HEET study from BRANZ in New Zealand (a much colder climate, and one dominated by heating requirements) only calculated 34% of end use energy dedicated to thermal performance.
  • The WA SEDO estimate for thermal comfort energy demand is also much less, hence it’s hard to believe the additional demand is due to cooling.
  • A large percentage of Australia’s population (Perth, Sydney and Brisbane) all live in quite mild or warm climates where heating would not make up more than 50% of the thermal control energy demand (and less still of the actual end use energy demand)
  • Heating is the most end use energy intensive thermal comfort mode as cooling typically utilises either apparent cooling methods (evaporative or fans) or heat pumps, both of which have effective Coefficient’s of Performance of 2.5 or more. This means for every one unit of energy input, 2.5 units (or more) of heat is dissipated of pumped from the dwelling when cooling. Heating on the other hand requires more energy than the actual heat load demand theoretically required to heat a space (or at least the same amount). This is mainly due to flue losses.

The high estimate in the Base Line Report may be linked back to the ABARE Energy stats which are also questionable. The Energy in Australia 2012 document from ABARE gives a biomass figure for residential energy use that equates to 6280MJ / household /annum.  When this is calculated in terms of mass of wood, it works out at 400kg of timber per household in Australia.  Even if one in every 5 houses (studies suggest it’s more like one in every 10) is using a wood heater that was their primary source of heat, that’s 2t of wood per annum they would need to be burning in order for the ABARE data to reconcile. To give you an idea, an average small box trailer full of wood is about 250kg. We’re not convinced there’s 2 million households in Australia receiving 8 trailers of wood per annum to heat their homes. The BRANZ HEET study further supports the proposition that ABARE have overestimated biomass consumption in the Australian residential sector.  BRANZ calculated that each wood heater uses 4,500kWh (one tonne) of wood per annum.

Without making any adjustments to either the end use demand figures, or the top down supply figures the numbers don’t reconcile very well. For example, trying to “fit” the biomass, gas and LPG energy into the end use break down “squeezes” electricity out of the hot water and space heating categories. There simply isn’t enough low grade heat requirements in dwellings to account for all the biomass. However, when we aligned the biomass use predictions with BRANZ, and adjusted the demand figures to better match some of the competing studies we got good reconciliation.

This also supports the total residential demand estimate in the Base Line Report which is quite a bit lower than the ABARE stats.

Once we knew the amount of energy the existing housing stock were using, we then determine how this would differ in new dwellings.  Some energy use would remain pretty static (eg appliance use and refrigeration). Lighting, hot water and heating and cooling have relatively new BCA code requirements focussed on energy efficiency. For these end categories appropriate adjustments were made to account for the newer technologies and associated demand.

Heating and Cooling (Thermal Control)

The heating and cooling energy requirements are the most complex, as there are very few stats on what equipment is being deployed in new houses. The NatHERS system does help this situation and we make an estimate of the deployment of heating and cooling technologies in the current housing stock as follows:

  1. Estimate the heating verse cooling loads for buildings in the top 20 populous NatHERs climate zones (85% of Australia’s population). This works out to be 60% heating and 40% cooling.  
  2. Estimate the efficiency of each type of heating and cooling technology
  3. Estimate the deployment of each type of heating and cooling technology
  4. Adjust estimates such that total energy consumption matches our adjusted ABARE figures and the split in thermal demand matches the NatHERs weighted average for Australia

This then informs our decisions about what people are likely to choose for new houses.  The summary is found in the following tables:

Electric Heat PumpElectric Fans or Evaporative Coolers
Existing Stock Cooling Demand50%50%
New Housing Stock Cooling Demand60%40%

Electric Heat PumpElectric RadiatorsGas FluedGas Internal HeaterWood Heaters
Existing Stock Heating Demand20%10%17%51%2%
New Housing Stock Heating Demand35%0%20%40%5%

For each major BCA climate zone or population centre then simply divide the NatHERs energy demand estimates for a 6 star dwelling for the building between these categories and apply appropriate efficiency or COP figures to determine what the end use energy demand will be.

Hot Water

The building codes have now banned the use of electric resistance storage hot water systems in all residential buildings apart from class 2 building (strata buildings). Some state governments also discourage the use of electric heaters in class 2 buildings. This has led to a huge shift from electric storage hot water heaters to gas, solar, and heat pump units. This is a great thing for reducing the carbon intensity of the delivered hot water to dwellings (see more explanation on hot water fuel types here).

Using the same reconciling procedure between the end use energy estimates and the adjusted ABARE data we get the following mix of fuel uses for meeting demand in Australian existing housing stock:

Fuel Contribution to Water Heating Demand of Existing StockFuel Contribution to Assumed Water Heating Demand of New Stock
Natural Gas and LPG77%79%

Note, this doesn’t imply that 77% of water heaters are gas fired, it implies that 77% of energy used by water heaters is gas. The difference is that gas water heaters have lower efficiencies than electric resistance heaters (99%) or heat pumps (approximately 270%). With a gas water heater, depending on the age of the heater, it may be as low as 50%, and won’t get much better than 85%. So the mix of heaters installed in existing buildings is actually more slanted towards electric.

New buildings will tend more towards gas due to the current BCA requirements. With this in mind, we’ve used the figures in the right hand column for the split in fuel use for new dwellings.

gas v electricity

Are You Using Gas or Electricity In Your New Home?

We are passionate about reducing the carbon intensity of buildings first and foremost. It’s what we live and breathe, so we try to look at every consideration when putting our recommendations forward…we don’t take it lightly! Here we give some key considerations to help you make a sound decision when choosing between gas or electricity.

Industry and government have portrayed electricity as a clean and efficient source of energy, and it is, at the point of use. Perceptions of gas (sorry, “Natural Gas”) are similarly affected by public opinion and government policy that focus on the point of use. This ‘point of use’ perception is reinforced by the way most people interact with electricity and natural gas in their everyday lives, flipping a switch or turning on a burner and paying a monthly bill. They rarely see or understand the generation side of electricity, the power plant, or the extraction and transportation of natural gas or the ultimate carbon emissions associated with combustion.

The Life Cycle Story of Electricity

Apart from solar photovoltaic (still a tiny contributor to most electricity grids), all our electricity starts life on the output side of a turbine. These turbines are usually driven by steam, but there are some power plants that use wind or water (Hydro). So where does the steam come from? To make it we need heat, and lots of it.  At present we’re getting the overwhelming majority of this heat from coal or gas (the only real exceptions here are reactors that use nuclear power, geothermal plants that use the heat deep under the Earth’s crust, or solar thermal energy).

Coal is the cheapest form of heat for power plants, unfortunately though it’s also the dirtiest. The furnace exhaust of a coal-fired boiler is full of green house gases and also abrasive fly ash which renders it very unsuitable for heat recovery (it basically wears components out way too quickly to make it viable). In fact, most coal-fired power plants are lucky to capture one third of the heat energy as electricity.

When power plants use gas, there are two advantages. Firstly, burning gas releases less greenhouse gas than coal for equal amounts of heat (it’s still very bad for the planet, but not as bad as coal). Secondly, the waste gases produced from gas-fired turbines can be sent through a heat exchanger which drives a secondary turbine. The combined cycle gas fired turbines capture up to 60% of the heat and turn it into electricity (nearly twice as efficient as normal coal-fired plants).

Once the electricity is produced, we lose more of this energy during transmission and distribution. In Australia, about 7.5% of the electricity generated at the power plants is lost before it gets to the consumer. So when you look at the life cycle of fossil fuel generated electricity, you can see that we’re not getting much bang for buck.

There are also some other minor hidden impacts of electricity generation, although these impacts are very small compared to the CO2 released during combustion. They include:

  • Parasitic loads, which basically means they use some of the electricity generated to run the plant itself.
  • The carbon emissions associated with extracting the fuel source. This can be due to fugitive emissions (for example, methane that escapes from a coal seam as it is mined, crushed and transported, or gas that needs to be flared during processing)
  • The carbon emissions associated with transporting the fuel to the power plant
  • The embodied emissions of the power plant infrastructure

Using electricity in a building for heating water, cooking or space heating is the final step in the chain. The use of electricity at the home doesn’t add any environmental impacts (you don’t release any CO2 in the building, that all happened up stream).

The Life Cycle Story of Gas

Likewise, the natural gas used by a building must be extracted from the ground, processed or refined to remove impurities, and finally transported to the residence. All of these extraction, processing, and transportation steps require energy. And of course there’s the fugitive emissions of gas that escapes at the well, refinery or during transport. In total however, direct use of natural gas in the home is usually far more efficient than sending it to the power station to turn to electricity before returning that electricity to your home. The valid concerns regarding the latest significant source of gas production from “fracking” should not be discounted and may alone be enough to counter any climate change argument for the use of gas.

Of course when you burn gas you emit a lot of carbon dioxide at the building. In most cases however, you can capture a lot more of the heat than is usually captured by your electricity generator when they burn fossil fuels (particularly if they are relying largely on coal which is certainly the case in Australia). For example, good quality gas storage hot water units and instantaneous water heaters now run at 85% efficiency as opposed to coal-fired power plants (30%) and combined cycle gas-fired power plants (55%). So generally you get more “use” out of the gas by burning it on site.

Some Comparisons

Let’s now look at some examples of how electricity compares to gas in terms of local grid networks in different regions. Below we estimate the energy demand of an average house (2.4 people) and look at how that can be delivered with a range of technologies using both electricity and gas. We have chosen a number of regions to demonstrate the importance of local characteristics (largely relating to electricity energy sources).

  • Victoria:  Present heavy reliance on black and brown coal for electricity, standard gas supply impacts
  • Tasmania:  High renewable hydro content for electricity, standard gas supply impacts
  • Western Australia: The home of eTool, electricity generated largely by gas and coal fired plants with quite low thermal efficiencies, standard gas supply impacts
  • United Kingdom:  A fairly typical greenhouse gas profile for Europe (mix of gas, coal and nuclear with small but growing renewables content). Far lower greenhouse gas intensity than the average Australian electricity supply. Standard distributed gas supply impacts
  • Sweden: A very low carbon electricity grid. Gas supply not common, assumed standard distributed gas impacts


Cooking – Cook Tops



Assumed Technology

Efficiency (%)

End Use Energy Demand (MJ)

Greenhouse Gas Emissions (kgCO2e / Annum)





Western Australia

United Kingdom


Electric Induction








Electric Element








Gas Ring Burner









Cooking – Ovens


Assumed Technology

Efficiency (%)

End Use Energy Demand (MJ)

Greenhouse Gas Emissions (kgCO2e / Annum)





Western Australia

United Kingdom




















Water Heating

Please note that water heating load would vary depending on climate. For simplicity in comparison we have assumed a mild climate in the below energy demand calculations. We’ve applied the same demand across all regions so the carbon emissions are comparable between the electricity grids for the same demand profile (despite the fact there’s no mild climates in Sweden!). Similarly we’ve assumed the same solar radiation (an average of Australian capital cities approximately weighted by population). Note that the conclusions drawn below assume standard sized hot water systems with typical efficiencies, tank heat losses and solar collector size (where applicable).




Assumed Technology

Efficiency (%)

End Use Energy Demand (MJ)

Greenhouse Gas Emissions (kgCO2e / Annum)





Western Australia

United Kingdom


Electric Storage








Gas Storage








Gas Instantaneous








Heat Pump (COP3)








Heat Pump (COP5)








Solar, Electric Boost







Solar, Gas Inst. Boost








Note that in many mild climatic regions families can successfully turn off their boosters for solar hot water systems and run on 100% solar.  The above calculations however assume “average” use of the system, so the booster is left running and switches on whenever the water temperature drops below the set point.  There is also a requirement for hot water systems to periodically heat themselves up to a high temperature to ensure that legionnaires diseases doesn’t get established, so this also influences energy use regardless of hot water demand.

Space Heating

The following figures assume a conditioned space of 180m2 and a heating energy requirement of 50MJ/m2/year which about average for a new compliant house in Perth. For simplicity in comparison we have assumed the same ambient temperature in different regions to calculate the below technology efficiency.



Assumed Technology

Efficiency (%)

End Use Energy Demand(MJ)

Greenhouse Gas Emissions (kgCO2e / Annum)





Western Australia

United Kingdom


Elec. Air Source Heat Pump (COP4)








Elec. Air Source Heat Pump (COP5)








Gas Heater, Flue, High Efficiency








Wood Pellet Heater








Is This Enough Information to Make a Decision?

What about if our grids use more renewables, and the carbon intensity reduces?
This is a really valid point that needs to be considered carefully. If the advantage of using gas is marginal, definitely think twice about implementing it over the electrical option. We know that as governments respond to climate change the carbon intensity of electricity grids will drop, quickly eroding any advantage that the gas solution may have had. Australia is lagging a little in this regard; we’re a very large emitter per capita and have secured some of the easiest targets to obtain in our Kyoto negotiations. That said, the government has committed to reducing total greenhouse gas emissions by 80% on year 2000 levels by 2050. That’s only 37 years away and most buildings we knock up today will still be around at that point. With this in mind, there needs to be a very clear advantage in using gas over electricity to justify its use.

There is a slim possibility that existing gas networks may be utilised for distributing renewable gases. This is already happening in some innovative communities where sewer gas is being collected, refined and sent back to apartments for cooking. This may somewhat alleviate any concern building designers may have been encouraging the use of what is essentially a fossil fuel network (natural gas) over electricity grids that can be more easily transformed to renewable sources.

What About Solar Electricity?

Now begins the philosophical debate. If you have a roof top solar PV system large enough to meet all your home energy demands with 100% clean renewable energy, would you use gas or solar electricity for your heating sources?
Electricity seems the obvious choice. Interestingly though, it may not be when you look at the net benefits of choosing each option. Let’s say with your solar PV system, you are energy neutral, that is you use as much as you generate. Of course you need to export into the grid in times of high generation, and import when your usage outpaces your production, but over a whole year you’re energy neutral.

If you’re doing this whilst cooking with electricity and then you swap to gas, you’ll be using a little more energy in the building as your gas cooking appliances aren’t as efficient as electricity. That said though, you’ll be exporting more electricity as you’ve displaced some demand with gas. These electricity exports will be reducing the demand for the normal fuel sources used by your generators. If this is coal, then the net result will be better for the environment as your greenhouse gas “credit” for exporting electricity will be bigger than the impact of using gas at the home. There are numerous variables that you may want to consider here, the most important of which is probably when you’re exporting and importing and how that relates to the generation of fuels being employed during those periods.

Researched and written by Henrique Mendonca and Richard Haynes


Research Sources









Recognising eTool LCA for International Urban Development

Over the last year, PhD students and lecturers at Curtin and Murdoch Universities have been been conducting worldwide research into tools that can measure and model carbon emissions and carbon consequences of variations of design in urban developments. Along with one other tool, eTool LCA was highlighted as the best in the world for quantifying and lowering the environmental impact of the built form through design. The paper was recently published by the International Journal of Climate Change: Impacts and Responses and covers the following…

Abstract: This paper examines a framework for calculating carbon dioxide equivalent (CO₂-e) emissions in urban developments, including emissions inherent in: materials, construction, operation, transport, water, and waste processes over the life cycle of a development. The paper takes a holistic approach to urban design, to include not only the CO₂-e emissions inherent in the individual buildings but also in the infrastructure and service provision of the community as a whole metabolic system.

A range of carbon assessment tools is examined to assess their capacity for measuring CO₂-e emissions in terms of this framework. The tools are reviewed for their applicability to four case studies in Western Australia: Peri-urban development (greenfield), Urban redevelopment (brownfield), Mining camps, and Indigenous communities, which demonstrate the type of settlement patterns that carbon assessment tools must respond to. The case studies are also indicative of the challenges facing other urban developments around the world in cutting CO₂-e emissions and enhancing sustainability.

The results of the study show that two tools are currently available that can measure and model carbon emissions and carbon consequences of variations of design in urban developments. The tools CCAPPrecint and eTool are highlighted in this paper as outstanding examples.

Read the full paper here