Low Impact Material Specification

Last Updated:
March 18, 2024
STEP 2 - Low Impact Material Choices
Creating a low energy home designed for climate is a good first step, but if the house is made from materials that are themselves very high in carbon content, or degrade the environment elsewhere, a big opportunity has been missed. This section looks at low carbon material selection strategies and sustainable specification more broadly, and what to consider when targeting a low impact home.

Choosing Building Materials for Low Impact

Selecting materials is traditionally pretty straight forward, with 3 criteria dominating:

  • Does it look nice?
  • Does it fit function?
  • And can it fit in the budget?

In a perfect world where suppliers took responsibility and accounted for environmental impacts this might be enough to consider.

But we don't live in a perfect world. If we are not careful material choices can lead to:

  • Deforestation
  • Habitat loss
  • Pollution
  • Resource depletion
  • Health impacts
  • And of course, increased carbon dioxide release

As consumers of materials, builders and designers are responsible for literally millions of dollars of product specification.

So, our choices are important, and really do count in sending market signals.

By choosing more sustainable options over less sustainable, we can effect change and have a positive impact beyond just the energy performance of the home.
What we choose effects how the market grows!

In this section we will start by looking at how to minimize embodied carbon in materials we choose, and then address strategies to reduce the other broader sustainability impacts of materials in our homes.

What is Embodied Carbon?

As we discussed in the Carbon Footprint of our Homes section, there are 2 broad carbon impacts from our homes.

1.     Operational Carbon, and

2.     Embodied Carbon.

Operational Carbon (the carbon dioxide released through energy used in the home over the life of the house) is addressed in Steps 1, Step 4, and Step 5 of the Roadmap to Zero Carbon Homes.

Step 1 looks at minimising heating and cooling energy needs through Good Design.

Step 4 looks at minimising energy use though Efficient Appliance Selection.

And Step 5 looks at adding photovoltaics for Energy Generation.

These steps minimise energy needs and offset operational carbon impacts.

But what about the energy used and associated carbon released in the creation of the materials from which the house is made?

This is known as Upfront carbon, (A1 to A5 in the diagram below), and represents the sum of carbon released from the energy used in extraction of resources, through manufacturing, and then transport and construction onsite, to the point of handing over the keys.

When researching low emissions products you may come across the term Embodied Energy. What is the difference between Embodied Energy & Embodied Carbon?
A. Embodied energy is the energy used to extract, manufacture, use, maintain and then dispose of a product at end of life (A to D).  Embodied carbon is the carbon dioxide released at each of these stages, which depends on the carbon intensity of the fuel source used at each stage.

Beyond Upfront Carbon, we can also look at carbon dioxide released over the full lifecycle of a home.

Further carbon is released in the Use Stage, through maintenance and repair, (B1-B5) and in the End of Life Stage, through energy expended in demolition, processing and disposal (C1-C4).

All stages together are known a Lifecycle Embodied Carbon.

Of all the embodied carbon over a building's lifecycle, Upfront Carbon represents the biggest chunk, and is where we have the best data.
It is also the section of a homes life-cycle that builders and designers have the most impact on, as it is largely determined by materials specification. And this has led the World Green Building Council to set a challenge to the construction industry of 40% reduction in Upfront Carbon by 2030.

This is a realistically achievable number, and one we should all be aiming for in our own projects.

But it begs the questions,

How much Upfront Carbon is there in our homes and how do we minimise it?

I'm glad you asked.

Read on...

Average Embodied Carbon in the Australian Home

HERE’S AN EASY RULE OF THUMB TO REMEMBER:

1m2 House = 1T Co2 !

Actually, as we saw in the Carbon Footprint of our Homes section, it might be a little higher based on recent studies (see True Net Zero – including Embodied Carbon), but 1 to 1 is easy to remember!

 

When you think about it, this ratio is disgraceful.  That's more than 200 tonnes for the average new detached home.

This means there is more CO2 waste generated in creating the materials, than the weight of the home itself!

 

It seems a barmy number, and indeed, when I first started 20 years ago, embodied carbon figures were a lot lower.  But over the intervening years, there has been the realisation that as well as the actual energy to make a product, there are a lot of support activities that sit behind every unit of product that gets made.  There’s administration, and buildings full of computers, and marketing departments, and international conferences and sample products, and employees driving to work…  And it all adds up to a lot of CO2 for each unit of product sold.

 

At the moment embodied carbon is not considered in the National Construction Code, only operational energy use.  But with 200,000 residences being built every year, it needs to be, if we are to become a Net Zero industry.

It is the Elephant in the Room.

And it certainly needs to be on the industry's radar, to tackle once operational energy use is bedded down.

 

But, of course, YOU don’t have to wait to make significant impact in your own jobs!

Let's look at what it takes to create a low carbon structure...

How to build a low carbon structure

The pathway to a True Net Zero home is pretty straightforward.

1) Minimise Upfront carbon, aiming for 40%+ reduction.

2) Quantify the embodied carbon in the structure.

3) Offset the remainder, once you have minimised what you can. (See end of Step 5: Offsetting remaining embodied carbon)

Let's start then with the General Principles to consider, to minimise the upfront carbon on your next job.

Some are design focused, and some are materials focus. So even if you don't get involved in design, you can still have a big impact in the embodied carbon footprints of your jobs.

Avoid building bigger than you need

OK, OK, OBVIOUS RIGHT – BUT WHO’S GOING TO LISTEN?

This is the first general strategy for cutting embodied carbon, and before you pass it off as too idealistic hear me out.

I find most clients don’t want space for its own sake. Who wants extra cleaning?  

They want Spaces. They are after rooms and areas to perform a certain function in their homes. They are not after square meters.

 

More, they want those spaces to be beautiful and comfortable.  

That is, they want quality spaces, not space itself.

And with Australia having the world’s largest homes (>200m2 av.), and an average of 2.6 people per household, it is very often the case that there is plenty of space to be saved.

 

There are not many plans where a 200mm strip could not be taken off here or there on a room.  Or reconfigured to remove an otherwise wasteful hallway.

And every m2 you save, saves the owner ~$3000+ these days, to spend on the quality of the space. Or to put into PV.  Or to minimise the loan. Or to go on holiday...

 

And every m2 you save, saves another 1+ tonne of CO2 from warming the planet.

And every m2 you save is another m2 owners don’t have to heat, cool, or clean - saving even more.

Win-Win

 

So, if you are designing, or are asked your advice on a plan (as builders often are), make of your eye a scalpel, and see if there’s any slivers of fat to be taken off.  Both owners, and the environment will appreciate it!

GENERAL PRINCIPLES TO MINIMISE EMBODIED CARBON

Sub-Heading Navigation:

Avoid building bigger than you need (Current)

Renovate rather than build new

Maximise volume to wall area

Avoid unnecessary linings and finished

Re-use materials from demolition

Bring in recycled materials

Choose high recycled content materials

Choose low embodied carbon materials

Choose carbon sequestering materials

Choose local but consider transport

Design for deconstruction & recycling

Renovate rather than build new

THIS IS ONE FOR ALL YOU BUILDERS IN THE RENOVATION GAME – keep doing what you are doing!!  We should be doing more of it!

 

When should we renovate and when should we rebuild?

My thoughts have changed over time on this one.  Even a couple of years ago I would probably have sided with build new, unless the structure is in great condition.  

 

New homes tend to perform better, and with operational carbon until recently considered such a overwhelming dominant part of the environmental footprint, renovations could hamper the long term low carbon potential for the site…

 

But things have changed.

 

Grids are getting cleaner over time, and technology has moved on. This means carefully considered renovations can also achieve Net Zero outcomes.  

 

YOU DON’T NECESSARILY NEED TO BUILD A NEW HOME TO REACH NET ZERO!  

 

And for every m2 of house saved by keeping part of the old structure, ~1 Tonne of CO2 is saved from entering the atmosphere.  

For the average renovation where you keep ~100m2 of house, that will be 100+ tonnes CO2 saved.

That is significant!  And worth achieving where possible.

 

So, what does this mean?

When you get the inevitable question from friends, and potential clients, “Should I knockdown or Renovate”, just add these facts into your calculations when you consider structure and cost and potential performance.

 

We have a huge amount of existing building stock, and simply cannot afford to replace it all.

If we can keep most of it there and give it a new lease of life, the amount of energy, resources, dollars and CO2 saved will be enormous!

GENERAL PRINCIPLES TO MINIMISE EMBODIED CARBON

Sub-Heading Navigation:

Avoid building bigger than you need

Renovate rather than build new (Current)

Maximise volume to wall area

Avoid unnecessary linings and finished

Re-use materials from demolition

Bring in recycled materials

Choose high recycled content materials

Choose low embodied carbon materials

Choose carbon sequestering materials

Choose local but consider transport

Design for deconstruction & recycling

Maximise volume to wall Area

QUICK TIP WHICH REDUCES BOTH OPERATIONAL & EMBODIED CARBON.

CONSIDER SURFACE AREA!

I might have been a slow kid, but I can still remember having my mind blown that a shape with a small surface area could potentially hold more volume than a shape with a large surface area.

(It was right up there for me learning that salt is not the opposite of sugar, and that you can put them both in the same dish without them cancelling each other out, or creating some sort of explosion!)

…however, I digress.  

The point is that this principle can have a double environmental payoff for designers.

In the picture each floorplan has the same floor area, but Option A has less wall area than Option B, which in turn has less than Option C.

Less wall area per volume not only means less opportunity for heat transfer and so a better energy rating, but also less material and so less embodied carbon!

And LESS COST!

It’s like building smaller…
…without actually building smaller!

I’m not saying we all need to live in cubes (or better yet spheres!), I like a bit of in and out as much as the next person.

But it’s a worthwhile thing to ask in the design process.  

Could the plan be re-organised for less wall area?

What have you got to lose…

…except unnecessary expense?

GENERAL PRINCIPLES TO MINIMISE EMBODIED CARBON

Sub-Heading Navigation:

Avoid building bigger than you need

Renovate rather than build new

Maximise volume to wall area (Current)

Avoid unnecessary linings and finished

Re-use materials from demolition

Bring in recycled materials

Choose high recycled content materials

Choose low embodied carbon materials

Choose carbon sequestering materials

Choose local but consider transport

Design for deconstruction & recycling

Avoid unnecessary linings and finishes

THOUGH WE COULDN'T BUILD HOMES WITHOUT OUR TRADES, IT IS USUALLY THE CASE THAT IF YOU CAN AVOID A TRADE YOU SAVE SOME MONEY.

You also generally save material.

And therefore, save embodied carbon.

So, if you can avoid unnecessary linings and finishes, and still make it look great, do it.

Win-Win.

But this strategy does take detail in design.

If linings are removed and internals are on show, like this lovely unit by Breath Architecture, it is then important to detail exactly where services will run and where penetrations will be. In domestic constructions plumbers, electricians, and framers are not used to their roughin being on show...

This doesn't mean you can't use this strategy.

Just make sure the right level of communication is there about what you are trying to achieve, and make sure the plan detailing is top notch!

Otherwise, you may be calling those trades you missed, and reaching again for those linings, to cover up the mess...

GENERAL PRINCIPLES TO MINIMISE EMBODIED CARBON

Sub-Heading Navigation:

Avoid building bigger than you need

Renovate rather than build new

Maximise volume to wall area

Avoid unnecessary linings and finished (Current)

Re-use materials from demolition

Bring in recycled materials

Choose high recycled content materials

Choose low embodied carbon materials

Choose carbon sequestering materials

Choose local but consider transport

Design for deconstruction & recycling

Re-use materials from demolition

WHEN DEMOLISHING TO REBUILD IT IS WORTH CONSIDERING, WHERE POSSIBLE, IF MATERIALS CAN BE RE-USED.  

On this job we salvaged and cleaned 6300 bricks from the old house, which were then re-laid in the new house.

This not only saved a little for the owner, but saved in the order of 7 tonnes CO2 for the planet, compared to bringing in new bricks, (as measured by the new Epic embodied energy database. See below.)

Floor joists and floorboards were also put aside and sent to the cabinet makers to come back as lovingly crafted works of art.

And the best part of this approach, is that it was a way of paying homage to the existing home.  Which while it no longer suited this growing family, had stood for a number of years of active service, loyally sheltering its occupants behind solid walls.  

Now it's spirit lives on in a new house that has grown from the old,

like a phoenix from the ashes,

To carry on it's watch...

GENERAL PRINCIPLES TO MINIMISE EMBODIED CARBON

Sub-Heading Navigation:

Avoid building bigger than you need

Renovate rather than build new

Maximise volume to wall area

Avoid unnecessary linings and finished

Re-use materials from demolition (Current)

Bring in recycled materials

Choose high recycled content materials

Choose low embodied carbon materials

Choose carbon sequestering materials

Choose local but consider transport

Design for deconstruction & recycling

Bring in recycled materials

ANYTHING EXISTING IS ESSENTIALLY CARBON FREE, or at least very low carbon compared to new!

 

Just because you are building new doesn’t mean you can’t incorporate recycled materials, or materials with recycled content. Indeed, we need to be supporting such products to get the circular economy going!

And outcomes can look amazing, and the carbon benefits can really add up.

The slides show some favourites, and products to consider.

 

Bring in Recycled Bricks:  
Recycled bricks are easy to source, and each brick saves ~1.2kg CO2.  (Epic database)  

Use them for walls, paving, garden beds, fences, BBQ’s, etc.

Big CO2 savings are possible if doing a full brick veneer from recycled bricks.

Bricks can be cleaned and featured, or bagged or rendered, as in the back wall of the picture below.

And of course, they can add mass and performance to a home too!

Specify Recycled Timber:
Every m3 of recycled hardwood saves at least a tonne of CO2. (Epic Database)

And it can be used to make beautiful floors, stairs, kitchens, cabinetry, decks and whatever else virgin timber can make.  
You can even source re-milled if you want it to look new.

Recycled timber really adds character to a house, and if you know where it comes from also carries a story,

And the value for clients of a good story about the house should not be underestimated!

GENERAL PRINCIPLES TO MINIMISE EMBODIED CARBON

Sub-Heading Navigation:

Avoid building bigger than you need

Renovate rather than build new

Maximise volume to wall area

Avoid unnecessary linings and finished

Re-use materials from demolition

Bring in recycled materials (Current)

Choose high recycled content materials

Choose low embodied carbon materials

Choose carbon sequestering materials

Choose local but consider transport

Design for deconstruction & recycling

Choose new materials with high recycled content

Recycled materials are more often than not, not re-used directly, but mixed in with virgin material to make brand new products.

The more recycled content that goes into the new material, the less virgin material is needed and the lower the footprint.

So, take a minute when looking for products to check:

1) If there's any recycled content

2) What the percentage is?

Check between manufacturers.

Ask sales reps when they visit to show you the products with recycled content. They will take these sorts of comments back to head office.

And you will start to build up a specification list of materials containing recycled content.

This industry, like all industries, need dollars to grow.

So, what are some materials to look out for?

Insulation:

So many options.  Various suppliers.  Many suppliers are 70-100% recycled, either with recycled glass, or PET plastic, or newspaper! A quick google investigation is all it takes, and checking the spec sheet. Why would you specify insulation without recycled content?

 

Crushed Concrete aggregate:

Sub slab & pavement base (instead of virgin sand); pipe bedding (instead of virgin aggregate); spreading around site in muddy conditions – basically anything virgin can do, recycled aggregate can do!

Ask at your local landscape supplies what options they have in recycled.

There's many other products and the pics below are just the beginning to your research.

SO WHERE DO YOU FIND ALL THIS STUFF?

Vic:

https://directories.sustainability.vic.gov.au/buy-recycled/

NSW:

https://recyclingnearyou.com.au/education/recycledproducts

Australia:

Product finder | Global GreenTag - globally recognised certification  (search for “recycled”)

Find Secondhand and Upcycle Businesses | The Junk Map

And of course, just Google it!

HOT TIP: Add ONE more recycled/recycled content product to each new build! In no time you will be a leader in sustainable construction.

GENERAL PRINCIPLES TO MINIMISE EMBODIED CARBON

Sub-Heading Navigation:

Avoid building bigger than you need

Renovate rather than build new

Maximise volume to wall area

Avoid unnecessary linings and finished

Re-use materials from demolition

Bring in recycled materials

Choose high recycled content materials (Current)

Choose low embodied carbon materials

Choose carbon sequestering materials

Choose local but consider transport

Design for deconstruction & recycling

Choose low embodied carbon materials

CAN YOU HOLD 2 THINGS IN YOUR MIND AT THE SAME TIME? YOU NEED TO, TO CHOOSE EFFECTIVE LOW EMBODIED CARBON MATERIALS.

The first is the Embodied Carbon Intensity of a material, usually measured in kg CO2 per volume. The Construction Material Pyramid above shows this. Like the food pyramid the materials to use less (from a carbon point of view) are at the top.

The second is the amount of the material in the home.

You have to keep both of these things in your mind when specifying materials.

The graph below shows the breakdown of embodied carbon from the materials in a standard brick veneer home.

The top 3 CO2 emissions in this case are coming from the brickwork, followed by the concrete, and then the steel roofing.

But if you look at the Construction Material Pyramid, you will see that bricks are only mid-way up the pyramid, and that concrete is actually pretty low in embodied carbon per m3. And yet in the brick veneer home these two materials were the two most significant sources for carbon emissions.

What's going on?

The reason of course, is that there was a big volume of each in the house in the study.

The steel tray deck roofing that comes in 3rd is actually one of the most carbon intensive products on the pyramid.

So why only 3rd?

This is because steel sheet is only 0.42mm thick, so even though it covers the whole roof, the cubic meter volume isn't that high.

So, you can see that when thinking about where the carbon savings may be on a building, you do need to have an idea of carbon intensity as per the Construction Materials Pyramid...

...AND, as a rule of thumb, you should be checking your high-volume materials first, because better choices for those materials are likely to have a big impact on the overall Upfront Carbon in the house.

In this instance, low-%-cement-concrete, and recycled bricks are likely to have a big impact on overall embodied carbon, as they significantly reduce embodied carbon in those materials per m3, and there are a lot of m3 on the job.
Whereas changing to a roof tile will only have small savings, because while tiles are less carbon intensive that steel per m3, ceramic or concrete tiles are a lot thicker and so actually increase the material volume, compared to the steel roof.
Thus, per m2, while there is some saving, it is generally only small.

So, check out the Constructions Materials Pyramid.

Learn where materials sit on it.

And where possible, choose materials further down the list,

...especially for high volume components.

Let’s improve the carbon health of our buildings.

Low Embodied Carbon Concrete

Developed by the ancient Romans, concrete is often the material of choice for footing design in Passive Solar designed homes, spreading mass evenly & cost effectively throughout the house, and locking it to the mass of the earth below to stabilize internal temperatures. It also acts as an energy well; absorbing winter sunlight and re-radiating the heat once the sun goes down.  And in summer it is a coolness store, taking many days of hot weather to heat up.  In a house with good solar access, well designed windows and good insulation, a concrete slab will usually add around 1 star in thermal improvement, compared to a timber subfloor. 

Unfortunately, mainly due to the cement and steel inside, concrete can be very high in embodied carbon.  But there are things you can do to significantly reduce the embodied energy while retaining the operational benefit on concrete.

Recycled glass, low cement concrete. (Note: if using recycled glass bottles, all sugars must be washed off thoroughly first.)

The cement in concrete is very energy intensive to make, with 1 tonne of cement releasing around 1 tonne of CO2. 

To reduce the embodied energy, up to 60% of cement can be replaced with slag and fly ash, which are both waste products, (slag from iron smelting, and flyash from coal power plants).  These products have a similar bonding mechanism to cement, and most concrete companies will be willing to do some cement replacement.
(Most will have a 30%replacement mix ready to go.) 

When buying bagged cement, look out for ones advertising they are a triple blend. (Cement/Slag/Flyash)

Steel is also very high in embodied carbon, and there is a lot of steel to provide tension strength in our modern slabs and tilt up panels.  Look out for steel made from scrap recycled and produced in ARC furnaces.

Lastly the plastic underlay membrane and bar chairs can also be sourced with recycled content.

Through such specification you could quite easily save around 5 tonnes of CO2 in a standard pour.

And if you want to make it fancy, seeding slabs with recycled glass and polishing it, give that hard performing eco slab the 'bling' it deserves!

Choose Low Embodied Carbon Cement for Brickwork
Boral Blue Circle. 30-50% cement replacement.

Each recycled brick saves around 1.2kg CO2, so each m2 represents around 60kg savings.

So on a 200m2 home, with 60m of external wall, and 3m of brick wall height, that's 10.8 tonnes of CO2 saved if using recycled bricks.

But did you know you can minimise the embodied carbon further with your mortar choice?

Whether you specify recycled brick or not will depend on the project, and the desired look, or if the home is being rendered.

But whatever brickwork gets specified, look for cement blended with slag and/or flyash.

This is an easy thing to specify and it doesn’t cost a thing, or change the look at all. And it is a totally legitimate cement to use for mortar!

Check the contents on the back of the bags you use, or the specs sheets.  

If the cement you are using doesn’t have slag or flyash, you can do better.

While we have been discussing focussing on the big volume materials to lower a homes embodied carbon, this is also true...

Little wins add up!

It’s these little choices, like what mortar to specify, that when done in aggregate over a whole house, that will also make a big difference!

GENERAL PRINCIPLES TO MINIMISE EMBODIED CARBON

Sub-Heading Navigation:

Avoid building bigger than you need

Renovate rather than build new

Maximise volume to wall area

Avoid unnecessary linings and finished

Re-use materials from demolition

Bring in recycled materials

Choose high recycled content materials

Choose low embodied carbon materials (Current)

Choose carbon sequestering materials

Choose local but consider transport

Design for deconstruction & recycling

Choose carbon sequestering materials

WHAT IF WE SUCKED CARBON OUT OF THE AIR AND USED IT TO BUILD WITH?

We can! It’s called plants.

Or, in the carbon accounting world, it's called materials containing Biogenic Carbon.

 

Using agricultural products, that sequester carbon as they grow, can make a big impact on the embodied CO2 in your project. Wood may first come to mind, but you can also consider options like straw or hemp, which—unlike wood—are annually renewable.

Or bamboo & cork, where the plant isn’t killed, & grows back ready to re-harvest in 5-10 years.

And then there’s sisal & textiles...

But should we count them as carbon negative materials? Should the carbon absorbed in the growing be offset against the carbon released in the fabrication?

Generally, in LCA practice they are not counted because the biogenic carbon comes out at end of life as the material breaks down, so there’s usually a zero-sum gain.

And you can get perverse incentives to just whack on more timber than you need to meet zero carbon objectives.

 

But it is hard to see there’s not some benefit, especially for quick turnover crops & plantation timber.  If we can use biogenic materials to supply the growing housing stock, whilst still maintaining plantation size & soils, a lot of CO2 can be drawn down & removed for at least the best part of a century while the house it is in stands.

And arguably this is an important time for even temporary removal, as we work to flatten the carbon curve.

So, these products are worth supporting!

NOTE: A word of warning with forest timbers however.

While they are beautiful, and could be a great carbon sequestering material, they are only of benefit if the harvested forest is becoming more resilient & healthier over time.  Ie. Is log size increasing over time? Is forest size staying the same or getting larger? Is total forest carbon increasing?  

If not, the forest is likely losing carbon & biodiversity – something we can’t afford.

Due to past deforestation & the huge extinction rate & biodiversity loss, habitat protection must be the critical factor for decision making.  

So, make sure you do your research when going down this route...

 

The other agricultural crops mentioned above get a big tick.

So, with them - go for it!

And soak up that carbon!

GENERAL PRINCIPLES TO MINIMISE EMBODIED CARBON

Sub-Heading Navigation:

Avoid building bigger than you need

Renovate rather than build new

Maximise volume to wall area

Avoid unnecessary linings and finished

Re-use materials from demolition

Bring in recycled materials

Choose high recycled content materials

Choose low embodied carbon materials

Choose carbon sequestering materials (Current)

Choose local but consider transport

Design for deconstruction & recycling

Choose local but consider transport

Grams of CO2 emitted per km for various transport types

MOST TRANSPORT IS STILL FOSSIL FUEL BASED. SO THE LONGER THE TRIP, THE MORE CARBON IS RELEASED.

THE RULE OF THUMB THEN IS TO CHOOSE LOCAL WHEREVER POSSIBLE.

However, that is not all there is to it. Transport type makes a difference as can be seen above.

Goods transported in container ships, because they can carry so much, are pretty low in embodied carbon from per unit carried. Because of this, it can be the case that material coming from overseas (say New Zealand) by container vessel, are lower in embodied carbon, than the same materials trucked a long distance (say from Queensland to Vic).

Of course, the shipped material may have been trucked a long way to get on the ship in the first place. Without a fair bit of research this may sometimes be hard to know.

So, the general rule of local rather than international does still hold.

But if you do know that a 'local' material has been trucked hundreds of miles to get to you, or worse yet, came by plane, you might want to look around for something different...

GENERAL PRINCIPLES TO MINIMISE EMBODIED CARBON

Sub-Heading Navigation:

Avoid building bigger than you need

Renovate rather than build new

Maximise volume to wall area

Avoid unnecessary linings and finished

Re-use materials from demolition

Bring in recycled materials

Choose high recycled content materials

Choose low embodied carbon materials

Choose carbon sequestering materials

Choose local but consider transport (Current)

Design for deconstruction & recycling

Design for deconstruction & recycling

NOTHING DESTROYS THE SPIRIT MORE THAN A TRIP TO THE TIP!

We demolish. Put yet another house in a hole in the ground. And build a new one.

Does anyone else see something wrong with this?

With 8 billion people on the planet, does anyone think this is a viable strategy if we want to be prospering 1000 years from now? Or 10,000?

We need to see waste for what it is – a design failure. A failure to think beyond the sale, or consider our impact on the future.


Do we have all the answers?

No.

It is a mindset & systems change that is required.


But here are some questions all in the industry should start considering when designing, or choosing materials and building assemblies:


1. Can my structure be separated easily?

If its glued together, or takes a long time to separate, it won't be recycled – it’s headed for the tip.


2. Can the material be taken out & be re-used readily?

If not,

3. Can it be re-cycled into new product? (& ideally not down-cycled)

If not,

4. Can it be composted safely?

If the answer is 'No' to all those questions, it's time to start looking for better options...


Here's an eg. to get you thinking:

At end of life, the end beam on this suspended concrete slab, can be un-bolted and the polystyrene sheets slid out in pristine rectangles.

The top slab will be typically cut up and taken to crushing where magnets will take out the steel, and the concrete crushed to road base.

The structural rubber strips for the thermal break can be re-used.

The metal beams unbolted & recycled.

And the galvanised stumps unbolted from the pads and re-used or recycled too.

Not perfect, but a start on the way to circular economy thinking.

Less waste, means less resource use, less energy, and less carbon.
And a brighter future.

Start thinking End-of-Life on your next project.

GENERAL PRINCIPLES TO MINIMISE EMBODIED CARBON

Sub-Heading Navigation:

Avoid building bigger than you need

Renovate rather than build new

Maximise volume to wall area

Avoid unnecessary linings and finished

Re-use materials from demolition

Bring in recycled materials

Choose high recycled content materials

Choose low embodied carbon materials

Choose carbon sequestering materials

Choose local but consider transport

Design for deconstruction & recycling (Current)


Using Embodied Carbon Data to guide Product Selection

Wouldn't it be great if we had a ready resource that could quantify how much embodied carbon is in different building materials so that we could use that information to guide material selection in our buildings?

Here's the good news - WE DO!

There are various databases around the world that detail how much embodied carbon is generally contained in say, a brick, or a m2 of plasterboard, or a tonne of pine.

Internationally the ICE database is free to download and good for materials sourced from abroad, but it is not always that accurate for materials in the Australian context.

In Australia we have:

AusLCI

The ICM Database

The EPiC Database

All of these are useful, though the EPiC database tends to be the easiest and clearest (along with the associated manual) to use for the non-professional life cycle analyst.

Let's have a look at using the EPiC database and embodied carbon data...

USING EMBODIED CARBON DATA TO GUIDE PRODUCT SELECTION

Sub-Heading Navigation:

The EPiC Database

EPDs

Embodied Carbon of materials & assemblies

The EPiC Database

WHAT YOU BUILD OUT OF MAKES A BIG DIFFERENCE.

For those lucky enough to be part of the design process, or have input on material choice, you have the power to have a big impact on the amount of embodied carbon in a structure.

But do you know what material types tend to be low in embodied carbon, and which high?  How would you know?  

Well now there is a great free resource for comparing between material types which you should be taking advantage of.

The EPIC database by Melbourne University represents 4 years of work and data collection on the embodied energy of building materials in the Australian context, and can be downloaded as a pdf, and as a excel file, so that you can use it (with a bit of work) to examine your own wall floor and roof assemblies.

To make it easy I have graphed out some common materials, and some things may surprise...

Flooring:

While a timber subfloor has less embodied CO2 compared to a slab, the floor covering makes a big difference.  

For example, if you just polish the concrete, it only raises the embodied carbon to around 70kg CO2-e, and so as a system is actually reasonably low embodied carbon!

Walls:

In general, concrete block has considerably less CO2 than brick veneer, with FC sheet and Colorbond also pretty low CO2/m2 mainly due to the thinness of the material.

As a rule of thumb, recycled materials with minimal reprocessing have 95% less embodied carbon, so recycled brick veneer remains a great choice from an embodied carbon point of view.

Insulation:

You thought rockwool and glasswool pretty similar products?  Not in embodied carbon!

Timber:

More ticks for plantation pine.

Roof:

All pretty close, with concrete tile just coming in under colorbond (due to the fact it air-dries instead of getting fired).

Of course, there are many factors that feed into material choice, but now embodied carbon can also be factored in your calculations.

So, download the EPiC database and associated pdf, and see where your common construction elements rate!

https://msd.unimelb.edu.au/research/projects/current/environmental-performance-in-construction/epic-database

USING EMBODIED CARBON DATA TO GUIDE PRODUCT SELECTION

Sub-Heading Navigation:

The EPiC Database (Current)

EPDs

Embodied Carbon of materials & assemblies

EPDs

DO YOU WANT A WORLD WHERE BUILDING PRODUCTS COMPETE WITH EACH OTHER AS TO HOW LOW CARBON THEY ARE?

Yes? It's already starting.  

Let me introduce you to EPD’s.

EPD stands for Environmental Product Declaration, which is document made to quantify the environmental impact of a product, under a range of 8 sustainability indicators.

It is used for Life Cycle Analysis.  

 

But, since one of the indicators is Global Warming Potential (GWP), measured in kg CO2, they are very useful in comparing 2 similar products on their embodied carbon intensity.  Or, like I have done on the slides, comparing the EPD for Boral Envisia 20mpa concrete with standard concrete emissions as measured in the EPiC Database.

As you can see, Boral Invisia generates 165kg CO2 for every m3 of concrete, vs 328kg CO2 for industry standard practice in EPiC.  A whopping saving of 163kg /m3.  Or, on a standard 40m3 house pour, 6.5T CO2 saving! Well done Boral, (and other concrete companies offering similar products!)

Getting this sort of quality data takes effort for companies, and we need to be supporting those that do bother to undertake EPDs.

So how do you find them?

 

Australasia EPD keep a database at https://epd-australasia.com

Or you can find them on company websites.

But a word of warning: When comparing EPDs, make sure that they say they meet both ISO 14025 (Environmental Labels & Declarations), and EN15804 (Sustainability of Construction Works – core rules).  That way you know they are made for the construction industry and calculating on the same criteria, the idea then being that you can judge apples to apples!

And don’t be too intimidated.  Just look for the relevant table and the GWP figure.

And then factor the answer into your product choices!

 

EPDs are an initiative this industry needs to be able to achieve a low/zero carbon future.

Support it.

Use it.

USING EMBODIED CARBON DATA TO GUIDE PRODUCT SELECTION

Sub-Heading Navigation:

The EPiC Database

EPDs (Current)

Embodied Carbon of materials & assemblies

Embodied Carbon Material Assembly tables

LOOKING AT INDIVIDUAL MATERIALS WHILE USEFUL, DOESN'T REALLY HELP US TO COMPARE ASSEMBLIES.

These tables come from the True Zero Spreadsheet, used in the 2023 Design Matters National True Zero Carbon Challenge. Like the elemental graphs above, the figures are derived from the EPiC database. This time full wall, floor, and roof assemblies are shown for standard constructions.

These tables can be useful for showing the relative impact of assembly choices when considering what to build the house out of.

And multiplying by area of each assembly used on your jobs can give a very rough guide to the embodied carbon in the structure of your building.

When using these table, remember there is of course a lot of upfront embodied carbon outside of building structure, in electricals, plumbing, appliances, windows/doors, and landscaping.
But these table can be useful when making decisions to start the project down a low carbon pathway...

USING EMBODIED CARBON DATA TO GUIDE PRODUCT SELECTION

Sub-Heading Navigation:

The EPiC Database

EPDs

Embodied Carbon of materials & assemblies (Current)

Climate Active & Specifying Pre-Offset Products

IMAGINE IF PRODUCTS ARRIVED ONSITE ALREADY OFFSET?  CARBON FREE!

After all, why is it up to Designers and Builders to solve all the woes of the world?

Shouldn’t each building product account for it’s own carbon emissions?  Then we could just focus on producing Net Zero Operational Carbon buildings – which can be tricky enough!!

Well it is starting!  

Let me tell you about Climate Active...

 

Climate Active is a government enterprise that certifies businesses and organisations that have proven that they are measuring, reducing and offsetting the carbon emissions in their products.

It works like this:

1) Company first minimises embodied carbon in their product.

2) Company calculates remaining embodied carbon in their product in an EPD.

3) Company chooses a Climate Active certified offset scheme to offset the carbon left in the product.

4) This then allows them to then sell the product as Carbon Neutral!  

 

This is a fantastic innovation in the Australian market, and one the industry needs to get behind.

 

At the moment there are only a few building products in the Product section of the Climate Active site, but those that are there are pretty useful for construction! (On the site select the following preferences: Industry = "Building + Construction", and Certification = "Product")

I have already used the Holcim EcoPactZero product, and I can tell you from experience, nothing feels better than carbon neutral concrete pouring into the formwork!

And using Siniat Etex Carbon Offset Plasterboard is as easy as putting it in your plasterboard tender...

Just imagine the potential of this, if more manufacturers get on board!

So, vote with your wallets, and use the market to drive a better environment.

Note:

A quick message to Government: Offsetting only works if we have a robust, reputable, scientifically based and rigorously verified offset system that has public trust.  Such a system is crucial to get this country to Net Zero. This needs to be a priority.

Life Cycle Analysis, 3rd Party Certification, & Offsetting

What we have looked at so far is strategies to minimise embodied carbon in the structure, and how to use data to compare products and drive choices.

Well done if you are incorporating some of these strategies.

You should let people know, and market your sustainability initiatives!

If you want to go the next step however, and calculate your embodied carbon, and potentially offset it, that's where it is good to get professionals onboard. Carbon accounting and Life Cycle Analysis is a specialised field, and it's important when making claims we have 3rd party certification.

So where do you find someone who can calculate the embodied carbon left in your structure, and importantly calculate how much you have saved compared to standard construction?

One good source is ALCAS. The Australian Life Cycle Assessment Society.

www.alcas.asn.au

On their website you will find a Certified Practitioners lookup, who can carry out the service for you.

You can then use the results in credible marketing, or, if you want to offer a carbon neutral product to the market, to quantify and then offset the homes embodied carbon!

And you avoid Greenwash, with a robust claim of the project's sustainability credentials at the end of the process.

ALCAS also set up the Austalasian EPD database mentioned above, and run the AusLCI lifecycle database, and are one of the important contributors driving embodied carbon knowledge in the Australian economy.

Well done ALCAS!

Broader Sustainability Criteria & Material Choices

While this Roadmap is primarily about minimising carbon emissions and energy use, homes have many impacts on our environment beyond just carbon.

In this section we take a quick detour to look at some broader sustainability considerations when specifying materials in our builds.

They are,

Habitat Loss & Choosing Good Wood

Healthy Material Selection

Environmental Materials Specification

Habitat Loss & Choosing Good Wood

Timber should be the most sustainable material of all.  It takes carbon out of the atmosphere, gives us oxygen, and provides habitat for wildlife.  It is strong, flexible, insulative, and relatively low in energy to grow and fabricate.  And its compostable at end of life! The only downside of course, is that our forests have been so overharvested in the past, putting severe habitat pressure on other animals and ecosystems, that we now have to be very careful when we choose timber in our homes, that it comes from sustainable sources.

Supporting Natural Asset Management Decisions for Central Coast Council,  NSW Anu Vijayan Macquarie University, Sydney , Australia. - ppt download

Knowing what is sustainable timber is unfortunately sometimes a difficult thing, as it depends on sources and logging method, and supply, all of which can change over time.

Here's a rule of thumb when choosing timber, in order of preference from best to worst:

  1. Recycled and reclaimed timber.  (Can be beautiful and usually comes with a history which can be a great later talking point.  Sometimes expensive.  Stock not always constant. Not structurally graded. Check at the timber recycling centres that the timber is actually recycled, as most of the salvage yards do also sell virgin product.)
  2. Bamboo. (While not technically a timber, the bamboo shoot can be harvested and re-grows every 7 years or so.  There are now a lot of different board options for floors and laminates available for cabinetry & stairs.)
  3. FSC Certified timber.  (The Forest Stewardship Council is a 3rd party certifier assessing a triple environmental bottom line approach.  Though there have been issues, and there is much debate on the best forestry system, this one still has the tick from most green groups.)
  4. Plantation timber.  (While chopping down virgin forest for plantations is terrible.  We now have a lot of plantations, particularly in pine, so we may as well use them, as they keep pressure off the remaining forests. Check end grain. If the growth lines are very narrow, it's likely imported Baltic pine/spruce and to be avoided.)
  5. PEFC & AFS Certified timber. (PEFC is an international logging certification run by the logging industries.  AFS is the Australian version of this.  Again, there is much debate, and examples of good and bad practice under the scheme. Having this certification is much better than having uncertified timber, though we should support calls to close loopholes or inconsistency of practice where it exists.)
  6. Australian forest timbers (Will probably be covered by AFS certification, and also covered by government regulation, though make sure you check.)
  7. Overseas forest timbers. (Typically abstain from these unless you can find out reliably where the timber comes from and the certification scheme and forestry practice. Likely also to have more embodied carbon because of transport.)
It is worth taking some time to do research on your timber selection, especially on the bigger quantity purchases.  From an environmental point of view, while focussing on climate change and energy use is important, timber choices are directly leading to habitat destruction and ecosystem degradation today.  So, it is quite a critical decision!

Here are 2 resources to get you going:

For a pre-curated list of sustainable timber sources in Australia and suitable applications, download the Mullum Creek resource (& checkout what they are doing at that leading edge sustainable development too! Great work Paul & team.)

Mullum Creek | Timber

Further information and suggestions on timber to use, and timber to avoid.

Good Wood Alternative Timbers Welcome (rainforestinfo.org.au)

BROADER SUSTAINABILITY CRITERIA & MATERIAL CHOICES

Sub-Heading Navigation:

Habitat Loss & Choosing Good Wood (Current)

Healthy Material Selection

Environmental Materials Specification

Healthy Material Selection

Very few of the materials we use in construction these days are single material products. Most are amalgams, held together with glues and binders, or made from petro chemicals. Unfortunately, many of these chemicals leach out of the products over time, and can off-gas and build up in the indoor environment. In some cases, this can affect health, especially for those who are more chemically sensitive, and lead to what is known in the industry as 'Sick Building Syndrome'.

Unfortunately, the science in this area is in its infancy. Though regulators put limits on the amounts many chemicals are allowed to off-gas, these are usually based on short term exposure testing. Very few studies look at chemical effects with long term exposure. Added to that, these chemicals are not often inert, meaning they may be reacting and forming new chemistry with each other. Even less is known about that.

We certainly don't want to fear monger, but with the push for houses to become tighter, suggest taking a precautionary approach when specifying materials.

There are 2 things to look for:

CHOOSE LOW VOC

Firstly, for paints, glues, waterproof membranes and other liquids, choose products that are either 'low VOC' or 'zero VOC'.

VOC stands for Volatile Organic Compound, and is a measure of how much a product off-gasses.

Specify Zero/Low VOC for things that are wet that come in cans and tubes:
-Paint                         -Tile Adhesives                         -Glues
-Silicones                   -Polyurethane                           -Expanding foam
-Waterproof membranes, etc.

CHOOSE E0 OR SUPER E0

Secondly, for cabinetry, particleboard, medium density fibreboard (mdf), and other timber laminates, look for 'E0' rating, or 'Super E0'.

E0 is a measurement of how much formaldehyde off-gassing a product has. And the Australian legislated standard is E1, containing a higher level of VOC.

Most board products use a urea formaldehyde glue to bind together the small bits of wood fibre. Unfortunately, formaldehyde can off-gas, and formaldehyde is a known human carcinogen, as classified by the International Agency for Research on Cancer (IARC). So again, it is worth just taking a precautionary approach and swap to lower off-gassing materials where practical.

Urea Formaldehyde is used a a binder in many manufactured board products

Emissions levels can usually be found on specification sheets for board products, where the emissions class has not been featured in the product brochure.

So, as the picture above shows,

Specify E0 for manufactured timber products such as:
-MDF                       -Particleboard                   -Ply
-Cabinetry              -Achitraves & Skirtings     -Various trim profiles
-Etc.

As a general rule of thumb, focus on the big internal areas first, like the painting, the particleboard, the carpets, the floor finishes, and the archs, skirts and cabinetry.

External materials are not so important as there is plenty of ventilation on the outside of the home!

If you get your large internal surface area materials right, you are on your way to good indoor air quality even in a tight home.

A good place to start when looking for Low VOC and E0 products are:

https://geca.eco/

https://www.globalgreentag.com/

CONSIDER THE RED LIST

And for those who want to take indoor healthy materials specification to the next level, check out the REDLIST, put out by the Living Building Challenge.

The Living Building Challenge itself is a well-respected international sustainability certification and sets a very high bar.

But even if you don't do the challenge, it is worth checking out the list of materials they think are the worst to weed out, and try and avoid them too in your material specficiations.

https://living-future.org/declare/declare-about/red-list/#about-the-lbc-red-list

BROADER SUSTAINABILITY CRITERIA & MATERIAL CHOICES

Sub-Heading Navigation:

Habitat Loss & Choosing Good Wood

Healthy Material Selection (Current)

Environmental Materials Specification

Environmental Material Specification

As mentioned at the start of this Step, builders and designers are responsible for the specification of millions of dollars of product each year. If you are a builder or designer you sit in the middle of huge spiderweb of producers supplying product to the market. What you specify matters. What you specify send economic signals driving production. And you can have a huge impact on what we see in the future, through the decisions you make on every job.

This section will give you background on what to look for, and help guide when balancing pros and cons - which all materials have.

Unfortunately this section is still under construction.

But while we are busy in the background, here are some great sources of information to put you on the right track:

Guide to Sustainable Materials - by Breathe Architecture

Mullum Creek Materials Guides - by Paul Haar Architect and Mullum Creek

BROADER SUSTAINABILITY CRITERIA & MATERIAL CHOICES

Sub-Heading Navigation:

Habitat Loss & Choosing Good Wood

Healthy Material Selection

Environmental Materials Specification (Current)

SBA Tool: True Zero Spreadsheet Tool

Want to pinpoint high carbon areas, and calculate the embodied carbon in your own structures?
The 2023 Design Matters National True Zero Carbon Challenge will be using and test driving the The True Zero Spreadsheet, designed to work with the EPiC database, and developed by Positive Footprints. Once bedded down, a copy should also end up here.

CHECK BACK LATER FOR THE TOOL AND TRAINING VIDEOS.

COMING SOON...

WEBINAR:

Beyond Net Zero - Identifying & Reducing Embodied Carbon

The Net Zero Homes builders' course is a partnership between Design Matters National and the SA Gov, and was created by the author of this website (Jeremy Spencer - Positive Footprints), so covers much the same ground.

If you like listening rather than reading, this course will be for you. The good news is that all 5 modules are completely FREE until end of 2023, and are highly recommended.

Click the link below to go to the site.

Though we suggest watching the videos in order, Module 5, deals with the topics discussed in this step most closely.

Net Zero Energy Builder - Courses

Responsible Timber Selection

In this webinar for Builders Declare Australia (October 2020), Paul Haar untangles some of the confusion around responsible timber selection and environmental certifications. He interrogates the notion of wood as the ultimate renewable building material and introduces clear principles and methods for thoughtfully selecting timber for building projects. He then directs us to guides that make selection of responsible timbers easy, across all construction applications and budgets. Paul also touches on his self-help housing work with remote indigenous Australians, Candlebark School Library, Mullum Creek eco-housing project and CERES Fair Wood, to illustrate how his approach to timber sourcing has expressed itself in built outcomes.