Low Impact Material Specification

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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 consider that 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!

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Avoid building bigger than you need (Current)

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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 if you want a low carbon home?

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Thoughts on this perennial questions have changed over time. Even a couple of years ago many would probably have sided with build new, unless the structure was in great condition.

New homes tend to perform better, and with operational carbon until recently considered such a overwhelmingly dominant part of the environmental footprint, renovations were often thought to 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.

TODAY, 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.

As a society, 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!

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Renovate rather than build new (Current)

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Maximise volume to wall Area

QUICK TIP WHICH REDUCES BOTH OPERATIONAL & EMBODIED CARBON.

CONSIDER SURFACE AREA!

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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.

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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!

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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?

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Maximise volume to wall area (Current)

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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.

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

Win-Win.

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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...

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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...

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Avoid unnecessary linings and finished (Current)

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Re-use materials from demolition

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

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On this job 6300 bricks were salvaged and cleaned 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...

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So what can be recycled?

Anything of value CAN be recycled and re-used or resold.

(If selling this is typically done by the demolition company, though when quoting, check that they will be separating valuable materials for recycling and not just dumping everything into a pit. If so, try others.)

However, when we look at materials that are commonly re-used in the new build from a demolition, bricks, floorboards, and large section feature timber are the materials most often salvaged and re-used. (Note: Roof tiles, pavers. and internal fittings should be considered too where they suit the new project.)

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Other materials tend to be more difficult to reuse:

For example:

Built-in cabinetry tends to be aesthetically dated, and where it is in good condition, usually needs a lot of work to reconfigure to fit other designs and spaces, so tends not to be economical to save in most instances.
Floor and wall tiles, while durable are glued so that salvaging is time consuming and results in a high percentage of breakage.
Windows tend to be single glazed and leaky and not up to today's performance standards (though this may change when today's homes start to be demolished), and
Appliances tend to be inefficient, where they are still working.

Also take care with re-using structural timber where there is no grading stamped on them. From a risk management point of view such timber is best converted to furniture, shelves, or flooring unless you are very confident of their strength class or have them re-graded.

Of course, the more things you can re-purpose, the more sustainable the outcome, so always be ready to think laterally too!

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And if you do find yourself with building materials onsite that you don't want, but have value, consider sharing on the Rival Cooperative app, or contacting The Junk Map and finding the contact details for your nearest salvage yard.

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Re-use materials from demolition (Current)

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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!

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Bring in recycled materials (Current)

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

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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.

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

1) If there's any recycled content

2) What the percentage is?

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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.

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So, what are some materials to look out for?

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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.

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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:

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NSW:

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

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Australia:

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

Find Secondhand and Upcycle Businesses | The Junk Map

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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.

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Choose high recycled content materials (Current)

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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.

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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.

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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.

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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?

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

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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?

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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.

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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.

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Let’s improve the carbon health of our buildings.

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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.)

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

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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.

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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!

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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!

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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.

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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!

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Choose low embodied carbon materials (Current)

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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!

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Choose carbon sequestering materials (Current)

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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.

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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...

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Choose local but consider transport (Current)

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Design for deconstruction & recycling

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

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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.

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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.

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