LCA Design Life and Functionality

Why This Post?

Well, it turns out it’s REALLY important. My eyes opened to this on the first life cycle assessment we conducted four years ago now. I probably didn’t realise how important it was until more recently though.  The crucial moment was when we did some back of the envelope, top-down carbon budgeting to understand how much greenhouse pollutions our buildings could push into the atmosphere and still enable a stable climate. And this is where it gets interesting. The workings to our rough carbon budget for buildings are here and they throw out a fairly large challenge. In fact, for residential buildings, we need to go net zero operational carbon, and then reduce the remaining embodied emissions by nearly 90%.

Often when you hear the term embodied energy, embodied carbon or embodied impacts, it’s associated with materials choices. Or at least that’s the normal approach to reducing embodied impacts. But there’s an elephant in the living room that’s not being addressed, and this post discusses that. If you don’t want to read about it, sit back and enjoy this video (apologies for the less than professional sound quality).


Some LCA Basics

Life Cycle Assessment isn’t just about measuring impacts. One of the key elements of ISO 14040 is to consider the “Functional Unit” of the object of your assessment. The functional unit enables comparisons between variations of the product or services. In the case of buildings, it would correct for things like design life and size. Inherently, it’s correcting for the function of the building. And the formula for the impacts of a building hence becomes:

Life Cycle Assessment Impact Equation for Residential Building

Life Cycle Assessment Impact Equation for Residential Building

As mentioned above, most people focus on reducing the impacts when trying to improve building environmental performance. In reality though, it’s the denominator that often has the most effect on the impact of a building. And this stands to reason. If your building houses more occupants, or lasts longer, it’s providing more benefit for the same initial and disposal impacts (construction and demolition).  As mentioned in a related post here, we actually need to reduce our embodied emissions by nearly 90% to hit a sustainable level of GHG emissions.  So we need every bit of help we can get, and some focus on functionality and design life presents us with some very low hanging fruit.

Design Life

Extending design life is a brilliant way of improving the impacts per functional unit for a buildings. This is because most maintenance, energy and water inputs are pretty constant over the building’s life, where as the initial materials, construction, demolition and disposal impacts are quite independent of design life. For residential buildings in Australia, for example, these initial and end of life impacts total approximately 25% of the total life cycle impacts. So, by doubling design life without any change to energy efficiency, you can reduce the overall impacts of your building by over 12%.

How to Influence Design Life

In order to answer this question we really need to think about what is driving demolitions. There are two good surveys that answer this question quite well. One is from the US and the other Australia. They compliment each other in their answers. Here are the results:

US Study Conducted By Athena:

Reason for RedevelopmentProportionCategorised ReasonProportion
Area Redevelopment35%Not Related to Durability61.3%
No Longer Suitable for Needs22%
Code Compliance Too Expensive2%
Socially Undesirable Use1%
Maintenance Too Expensive0%
Changing Land Values0%
Out Dated Appearance0.90%
Lack of Maintenance23.80%Lack of maintenance / neglect26.4%
Other Physical Condition2.60%
Structural or Material Problem3.50%Durability Issue3.5%
Fire Damage7%

Athena, Demolition Survey – Building Service Life Study – Phase Two

There seems to be a surprisingly large proportion of buildings that are being redeveloped for reasons other that structural integrity. So, building strength and durability seems to be only part of the design life story. It gets a lot more interesting when you read this study further, as it turns out the longest lasting buildings are actually timber. This was counter intuitive to me, I would have expected the steel and concrete buildings to be lasting longer than the timber ones. The other interesting thing was that there seems to be a hump that a building needs to get over at the 30-50 year mark, and once it’s over that, it’ll last a long time.

Service Life of Structure Type


The Australian survey supports the theme that durability is only part of the story.

Reason for RedevelopmentProportion
Demolished for Site Redevelopment58%
No Longer Suits Owners Needs28%
Building Becomes Unserviceable8%

Dynamics of Carbon Stocks in Timber in Australian Residential Housing

Redevelopment Probability

These studies suggest that the durability of a building only plays a small role in predicting service life. Other factors, predominantly redevelopment pressure, are actually more important. The strategies to counter this are relatively simple. I’ve listed a few below:

  • Increase density compared to surrounding suburb through:

– Building value : Land value ratio
– Maximise yield

  • Diversify lot ownership, which increases difficulty for redevelopment in the future
  • Design quality (create timeless character by ensuring house is designed for the site and surrounds)
  • Enable retrofitting (enable occupant density to be increased or building use to be transformed easily without demolition)

Other strategies that assist in extending the service life of the building (or materials) include:

  • Ensure appropriate materials are used to weather any likely natural disasters in a region (e.g. fire)
  • Where redevelopment potential is very low, focus construction methods
  • Design for deconstruction (extend materials service life beyond the building)

We should be thinking of buildings as permanent features, that may stand for many centuries. Whilst this would be a paradigm shift in Australia, there are countless examples of suburbs within the world’s major cities where average design life of existing structures would be well in excess of 100 years. These are cities like London, Paris and Rome where this resilience to redevelopment is in itself the appeal of these cities. There are still pockets of historical buildings in Australian cities also, and our aim should be to promote this approach to the extent that it become the norm.


Increasing functionality is perhaps slightly simpler. It does require buy-in from the owner. In the residential context it really comes down to increasing occupancy within the same space. This doesn’t necessarily mean sacrificing life-style. Very well considered design will yield efficiencies in ensuring that every square metre of floor space is well utilised. Integration of stairs, corridors, studies, entertainment areas etc into bedrooms or living rooms are examples of efficient design. It also pays to compare our current residential functional average to that of our past, and also other countries. The chart below shows that over the last 35 years, Australia has trended badly in terms of environmental sustainability in relation to functionality of residential buildings. During this period, the average size of new buildings has significantly increased, whist the occupancy per dwelling has dropped. It’s encouraging to see a recent reversal in this trend, and we hope it continues.

Australian Residential Building Functionality TrendsWhen we look at he space per person, it’s increased from 54 to 96 square metres.  Compare this to the average space per occupant in the UK of 32 square metres and it’s clear that we have some wiggle room in this area.

In commercial buildings, there’s very good financial incentive for improving floor plate efficiency as it means greater rent. Small changes can yield big uplift in rental revenue. Intelligent strategies to improve floor plate efficiency include:

  • Sharing services between floors
  • Optimising lift size, speed and number
  • Minimising services risers
  • Minimising circulation ways

The common areas associated with large apartments or office buildings are also very worthy of attention. In Australia particularly, car parks often amount to 25% of total floor space or more. This is a huge burden on the useful floor area of the building, not only in terms of embodied impacts, but also operationally, due to lighting and ventilation requirements. Currently, car park efficiency is an area that doesn’t receive a lot of attention. We have yet to see a design brief where a developer has stipulated a target floor area per car park. Good practice internationally is 20 square meters per car space, and this is with a normal 90 degree layout. If the car park is large enough to accommodate loop, by moving to 45 degree angle parking the space requirements can be reduced even further. This is enabled by reducing the required space to pull in and out of the park to a single lane for 45 degrees nose-in parking, whereas 90 degree parking requires two lanes. It’s not uncommon to see car parks in Perth buildings requiring 30 square meters of space per car park, so there’s huge potential in this area for efficiency improvements and cost gains. Could that three level basement car park be optimised and reduced to two? Ask the question and refer to some international benchmarks on car park design, you might be pleasantly surprised.


The most frustrating thing about all these great opportunities to improve a building’s design life or functionality is that we rarely get to help people do it. The reason is, it’s usually been designed by the time we’re engaged. There’s a nice chart, a version of which is below, that explains how as a project progresses from brief to concept to construction and onwards, the ability to influence it’s environmental performance drops off sharply. This post effectively explains a bit part of the reason why. There are other design opportunities that also need early consideration to become feasible as well. We recognised this pretty early on at eTool and developed way of running ‘scoping study’ LCAs to help design teams identify and reduce environmental impact ‘hot spots’ in their concept designs. We’ve taken this a step further now by offering a target setting service. We can help a design team develop performance targets for their building before a concept design has even been dreamt up. All we really need is a draft brief and we can profile the life cycle impacts of a normal approach to delivering the intended function of the building. We then use this model to simulate improvements that the owner and design team want to target, these can include design life or functionality improvements. Early feedback on this service has been great, get in touch if you want more information.

Building Life Cycle Environmental Influence





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.

The One Planet Living Journey

Cundall is the world’s first consultancy to be formally endorsed as a One Planet Company by sustainability charity BioRegional. In this presentation Simon Wild will talk about how Cundall have achieved this endorsement including some of the challenging targets we have set against the 10 One Planet Living principles, originally developed by WWF and BioRegional. Mark Pitman will then explain how the have approached this in Perth and discuss how the One Planet Living Principals can apply to Western Australia.

During this seminar, you will hear about the successes, failures, lessons learnt, obstacles so far, and the challenges ahead to run a business within the resources of a single planet.

Attendance of this event will earn 1 GBCA CPD Point

When: Thursday 14 March, 2013 at 4:15 PM (WST)

Where: Level 1, 40-44 Pier Street, Perth

Tickets: Register here


Update: Quantifying the benefits of the Sydney Harbour Bridge

The Sydney Harbour Bridge is the world’s largest steel arch bridge and acts as a passage for rail, vehicular, bicycle and pedestrian traffic between the Sydney central business district (CBD) and the North Shore. For the last 80 years, the bridge has been an international icon of Australia and all the social benefits associated with it are immeasurable. But what about all the steel, concrete, manpower and all the other impacts involved with the construction of the bridge. Has it paid itself off from an environmental perspective?

The material list includes 53,000 tonnes of steel, mostly imported by boat from the UK, 95,000 cubic metres of reinforced concrete and 18,000 cubic metres of granite that was transported 300km from the North of Sydney by specially built ships.

Using historic Australian records of the construction of the bridge, an eTool LCA was conducted to quantify and compare the results and benefits for both society and the planet.

Here are some interesting results:

Carbon impact of materials is dominated by imported steel for the arch followed by concrete for foundations.
Assembl­y impacts are very low when compared to total construction impact due to the use of cranes and manual work (6 million hand driven rivets!)
Transportation impacts are associated with materials transportation, especially the 79% imported steel from the UK.
Recurring painting maintenance and repair work represents only 6% of total embodied impact and will significantly increase bridge life.
Global Warming Potential (tonnes of CO2e)

Materials 270,693 83%

Assembly 6,499 2%

Transport 27,519 8%

Recurring 20,295 6%

Total 325,006

The predicted design life of the bridge used in the LCA was 300 years. This is another interesting topic because since the bridge is built with independent steel structures, the parts that present structural problems that can’t be repaired on site are replaced with new ones.

So, using eTool LCA results we were able to compare the embodied carbon impacts of the bridge with the operational carbon savings in reducing distances and fuel combustion.

The distance from Cammeray to Sydney passing through the bridge nowadays is 7 km and the route before the bridge via Gladesville was 17.6 km. Calculating CO2 emissions associated with fuel combustion savings over all these years and the average amount of vehicles crossing the bridge everyday, it represents a total savings of 11,850,720 tCO2e. The embodied impacts of construction achieved a carbon pay off due to transport fuel savings around 1955, and since then with the growth in transport across the bridge, have been repaid a further 35 times!

Whilst researching the LCA, we had a chat with Peter Mann, the asset manager of the bridge, who thinks the bridge will last another 300 years under the current maintenance regime. The bridge will potentially pay itself off a couple hundred times by then, which is an incredible environmental payback on an infrastructure project.

This is a great example of just how powerful LCA analysis is when evaluating infrastructure.
eTool LCA was designed to be totally scalable and used in any project from infrastructure to commercial and residential.

Contact us for more information about designing with eTool and getting the best outcome for your next project.

This assessment was conducted by Henrique Mendonca.

An update – Is the LCA on the Sydney Harbour Bridge too simplistic?

Absolutely!  Conducting an LCA on something as complex as the harbour bridge is much more complex than assessing a single product or building.  The reason being is that its influence is far reaching.  In a simple product LCA, practitioners will normally use an attributional method of assessing impacts.  In the case of a large piece of infrastructure that has far reaching influence, it’s more appropriate to use consequential analysis (see this article for more info ).

We definitely simplified the assumptions around the consequences of the bridge being built verse not being built.  We assumed the vehicle movements from north to south would not have significantly changed with or without the bridge.  This is incorrect for a number of reasons:

  • The bridge may have actually encouraged people to buy and use cars because it made their use even more attractive than before the bridge was built
  • Without the bridge, people may have chosen an alternative transport method (eg. ferry) or reduce their trips across the harbour because the car trip was too inconvenient via the long route.

However, after conducting this simple analysis, the advantages of the bridge were so clear that making further assumptions about how the bridge has influenced the above behaviour didn’t seem worthwhile as it is very unlikely it would have changed the overall result.  It may have doubled the payback period, but would not have changed the result from net positive to net negative.

The other part of the analysis that is quite important here is the forms of transport we didn’t mention. We just assessed the impact of reduced car use.  We didn’t assess the even greater efficiency advances associated with train, tram (up to 1958), bus, bicycle and pedestrian use.  In fact, nowadays, nearly 20% of people crossing the bridge daily are not travelling by car.  Furthermore, there have been significant policy changes that have impacted the bridge’s influence on sustainability. Originally the bridge had 6 vehicle lanes, 2 tram lanes and 2 train lanes;  the trams more than likely carried more passengers than the vehicle lanes during their tenure.  That’s not to say trams and trains (driven by largely coal fired electricity) are the silver bullet to sustainable transport either, however they are a vast improvement on typical car use.

Was there a more sustainable option?

Of course, for example, if in 1923, instead of initiating construction of the bridge we had been able to halt car sales and development of transport infrastructure we could have avoided an incredible increase in carbon emissions in the Sydney region due to transport. Perhaps a bit extreme? This debate is a big can of worms, and halting development isn’t actually a prerequisite of sustainability.

It turns out that due to education and health (very nice by-products of development) the human population on earth is set to stabilize at about 9 billion people.  (

At that level we could afford to emit about one tonne of carbon per person per year and the earth would be able to naturally draw this from the atmosphere. So our brief is to determine a lifestyle that accommodates 9 billion people on one planet.

For the harbour bridge, this probably would have meant two vehicle lanes (for buses and unavoidable commercial traffic run on biofuels and renewable electricity), an extra cycle lane or two, four heavy rail lines and four light rail lines (both run on renewable electricity).
So we have a few paradigm shifts to make before we reach this utopia (imagine it, it will be fantastic) but it’s not unrealistic over the next 80 years of the harbour bridge’s lifespan (think of where the world has come in the first 80 years since the bridge was opened, it would have been very hard to imagine in 1932).  On another positive note, it’s possible that “peak unsustainability” per person has probably been surpassed in Australia, we are finally trending the right direction.

The Insulation Sweet Spot

How much insulation is enough?  If I double the R value, does that mean I halve my heating and cooling loads?  Unfortunately it’s just not that simple, increased insulation has diminishing returns in reduced heat transfer.  To explain this, first, let’s start with carefully defining R Value.  It’s a measure of resistance to heat transfer and can be stated as follows:

Using the above formula gives the R value in SI units which we will work in for the rest of this article.  To convert to US Imperial units, you need to times the RSI by 5.678.  Now lets use the above formula and apply it to an example of a wall. We want to calculate the heat transfer value, which will then give us the heating/cooling energy requirement for our heating/air-conditioning system and from that we’ll be able to work out the cost. The formula now looks like this:

The assumptions we are using are below, some of these are inflated to accentuate the potential savings:

  • Area of external wall: 100m2
  • Temperature difference between internal thermostat set point and external temperature: 15 Degrees C (quite a difference, either hot climate trying to cool or cool to cold climate trying to heat)
  • Coefficient of Performance (COP) of Heating or Cooling Device: 2.5 (relatively poor)
  • Assume that we are paying $0.25c for every kWh of delivered energy to the building
  • 24 hour average occupancy, so continual maintenance of desired temperature.

We’ll start with a single brick wall (RSI Value of 0.106) and then slowly increase the insulation to determine how much money we can save. Here’s how much the heat transfer reduces as R value increases:

As you can see, the reduction in heat transfer is huge, at least initially. In fact nearly 80% of the heat transfer is stopped with just RSI0.5 insulation. As you increase the R Value further the savings in heat transfer drop off significantly:

  • RSI0.5 to RSI1.0: 11% extra heat saving
  • RSI1.0 to RSI2.0: 6% extra heat saving
  • RSI2.0 to RSI3.0: 2% extra heat saving
  • RSI3.0 to RSI4.0: 1% Extra heat saving

So what about the effect to costs? See the following graph for the details on the heating and cooling cost savings for our conceptual building:

Once again, we see a very big drop off in savings as R Value increases. And these savings are potentially inflated, if the average internal temperature to external temperature difference was halved to 7.5 degrees C, we’d see these values halve also.
There is obviously a sweet spot somewhere between RSI1 and RSI4, probably around the RSI2.5 mark. Of course, this depends on the insulation costs, the cost of the structure to house the insulation and the design life of the building. For example, going from RSI2 to RSI4.0 may only require a small increase in insulation costs, but if the wall framing need to be increased in width by an inch, this could be quite costly.

The other important consideration here is that this is all based on theory. What is actually going to happen in an average building is probably going to further lessen the impact that your wall insulation has on your heating and cooling costs. For example, if you poked five small 100 x 50mm holes in the insulation of our conceptual house, depending on drafts etc, you’d probably reduce RSI3.5 walls insulated walls to the equivalent of RSI3.0.
In windy climates or pressurised buildings, this could be a lot worse. Similarly there are likely a lot of other easy wins to increase the actual performance of your house that don’t relate to your wall insulation, for example:

  • Glazing type (R Value)
  • Glazing area (lots of windows usually means lots of heat transfer)
  • Floor insulation (appropriate in cooler climates)
  • Floor ground coupling (appropriate in warmer climates)
  • Efficiency of your air-conditioning and heating system
  • Cost and carbon intensity of your energy supply source (eg gas verse electricity)

I hope this helps explain the R Value sweet spot.
For the control freaks out there who want to know exactly where that is for their particular building/climate/energy mix etc, get in touch!

Australian Energy Use Explained

This is a really interesting topic. It turns out that Australia is extremely rich in energy sources.  I love the below diagram from the Publication “Energy in Australia 2010” by the Australian Bureau of Agriculture and Resource Economics and Sciences. Two things become very evident. The first is easy to see, we are exporting an ENORMOUS amount of energy. In fact, we export 10 times the amount import, and use only 25% of the energy we produce.  The other point of interest nearly needs a magnifying glass. There’s a tiny line at the bottom of the diagram signifying the flow of renewable energy production. It’s nearly insignificant next to the non-renewable energy production.  Although approximately a third of the non renewable energy we export is uranium (there is a difference between low carbon and renewable), it still highlights how dependent Australia is on fossil fuels.


Before going on, I’ll attempt to quantify the figures in the above diagram. What is a petajoule (PJ).  Well, one petajoule of electricity would power a standard 200W lightbulb for over 150 Million years.  Or in other words, would power 150,000,000 light bulbs burning non stop for one year. Of course you’d power a hell of lot more energy efficient compact flouros but let’s not go there. It’s A LOT of power. Where does it go? Well about 75% is exported and the rest of consumed internally.

Looking at the internal Australian demand for energy the figures get a little mixed up and hard to follow in the flow diagram. I’ll do my best to explain. We lose a lot of energy in the production of electricity (represented largely by the circle in the middle of the diagram). This is because your average coal or gas fired power station in Australia has a thermal efficiency of around 30%. So 70% of the energy created (heat) from burning the fossil fuels escapes directly into the atmosphere as waste heat. We also loose energy in tranportation (gas, oil, coal etc), transmission and distribution (electricity).

The remaining energy then finally makes it to the consumers in the form of electricity, distributed gas, LPG, diesel, petrol or other fuel. How we use this energy is listed on the right hand side of the diagram. The two that seem to get all the attention are “Residential” and “Transport”. The others actually account for more energy consumption (commerce and services, agriculture and mining, manufacturing). So we can very nearly breath a big sigh of relief in the knowledge that most of our energy consumption is related to industry and business – not our problem, right?  Wrong.

As consumers, we are the ones that demand that energy production. Sure, some of these goods and services are exported, however we also import (usually more) goods and services that in turn demand somebody else’s energy consumption.  So our personal energy use in Australia, when you average it per person is equivalent to leaving forty old energy guzzling light bulbs on all day all year.

So is 60% or more of our environmental damage caused by our consumption of goods and services? I ran a personal energy audit a few years ago to try to verify this. Quantifying the energy demand associated with residential electricity and gas was a piece of cake. As was the energy content of the fuels used in my vehicle.  Reliable coefficients for air travel were also easy to come by. Where it got tricky was trying to quantify the primary energy content of my groceries. Energy content of groceries? Yes, how much of the “Agriculture and Mining” energy use in the ABARE figures above were required to fill my fridge and pantry?

I found the data in a great report co-authored by CSIRO and The University of Sydney.  “Balancing Act, Triple Bottom Line Reporting of the Australian Economy” is a four volume, 400+ page treasure chest of economic and environmental information. It splits our economy into 135 sectors and includes figures for energy us and carbon emissions per dollar spent in each sector.  So by reading through this report, I not only understood how much primary energy my food was responsible for, but also realised that all my expenditure (from clothing, to healthcare, to recreation, to dining out) all had an associated energy requirement.

To complete my energy audit, I categorised all my expenditure from bank statements into the most appropriate economic sector, did some simple maths and had an energy consumption estimate relating to my goods and services. To my horror, it turned out that consumption accounted for over 60% of my energy demand (whilst transport AND residential made up only 30%). Consumption = energy. If we want to do the right thing by the environment, switching off the lights might not be where we should be looking. We should in fact be feeling about 10,000 times more proud of the refurbished 2nd hand couch (avoided consumption) than cleaning our teeth in the dark to avoid turning the light on.

So why is this information so important?
Read my next post “What’s Carbon Got to Do With Me” and I’ll attempt to explain this too.

Check out the sources of this article here:

This article was written by Rich

Design Civil Structures with eTool LCA

When we created eTool LCA, our aim was to reduce the global carbon footprint through the built form.
Initially we thought about buildings; residential, commercial and community based structures that would benefit from using a design life tool from conception to build to use. But this only gives us half the picture.

With eTool LCA we can look at all type of built forms including civil structures such as roads, bridges and dams. These types of vital infrastructure use energy through materials, transport, assembly and recurring maintenance just the same as traditional buildings, so it’s important that we account for them as well.

Watch our short video showing you how to build a road…

Using eTool LCA’s custom template feature, you can easily input the exact specifications of any structure, in the case of a road, we included the width, length and a combination of materials.
Once you’ve created an example template, you can add as many as you like and compare the environmental and cost implications across a number of variables to help with the decision process.

This LCA was based on an average 1km asphalt road with the following building specifications –

Floor Area: 1000m2
Floor Width: 500mm

Sign up to eTool LCA today and give it a go or contact us to order an assessment.