For a well-performing home, the embodied carbon in your material choices will have more impact than the energy your home uses over decades of operation.

That means the materials, fixtures and finishes you specify can now be one of the most powerful sustainability levers you have.

In this episode, I share how to think about low carbon materials, the low carbon alternatives available, and how to verify what you’re being told about a product’s carbon claims.

Listen to the episode now.

Hello! This is Episode 427. This is Way #27 of the 44 Ways to Create Your Sustainable Home series, and we’re continuing through Section Six: Choosing Materials, Fixtures and Finishes.

In this section, I’m covering specific criteria for choosing the products, materials, fixtures and finishes for your future home. Last episode, in Episode 426, Way #26, I talked about choosing for longevity and durability, and the five financial costs of any material decision.

Way #27 is: Choose for Low Carbon Footprint.

Selecting your interior and exterior products and materials with this in mind can be one key way to improve the sustainability of your home, especially in the impact that lower embodied carbon can have over the lifetime of your home overall.

Back in Way #18, Episode 418, I talked about embodied carbon: the emissions produced in extracting, manufacturing, transporting, installing, and eventually disposing of building materials. Every material selection in your home carries an embodied carbon cost, and in the average home, 1m2 of floor area equals 1 tonne of carbon emissions.

In that episode, I also talked about how, over time, our homes have become more energy-efficient in operation. And how, through good insulation, passive solar design, efficient appliances and renewable energy, the operational carbon that exists over a home’s lifetime has greatly reduced.

Consequently, the embodied carbon in the materials has become the dominant portion of the home’s total lifetime carbon footprint, and the necessary component to consider if we’re going to reach net zero targets.

So for a well-performing home, the material choices you’re making now will have more carbon impact than the energy the home uses over decades of operation. 

And so, choosing materials that are low in embodied carbon can be another way to create your sustainable home.

Timber is promoted as one of the lowest carbon materials available. Trees sequester carbon as they grow, storing it in the wood. When that timber is used in a building, that carbon remains stored for the life of the structure. Timber also requires relatively little energy to process compared to most other structural materials.

However, the key qualifier here is responsible sourcing. Timber from a well-managed forest certified under a recognised scheme, such as the Forest Stewardship Council (FSC) certification, means the forest is being replanted and managed sustainably. Examining the chain of custody can be helpful in determining if it’s come from a sustainable source. Timber from unmanaged or illegally logged sources has a very different impact. So always consider this when specifying timber products.

Now, a caveat here, because whenever you start exploring zero carbon homes, you’ll see timber is promoted as THE product to use, especially over higher carbon materials such as steel. I’ve personally spent time at timber plantations and their saw mills, watching how timber is felled and then processed in these locations. I’ve also spent time speaking with people in the industry who have very different opinions about the sustainability of timber and the transparency of certification systems.

Because, the case is this: timber plantations are mono-cultures. Less than half of every tree is used for structural timber, and a good portion of any plantation is culled for paper products. And there are several industries that really only exist to use the waste from the remaining part of the tree, such as shavings for pet bedding, and paper and toilet paper, which we don’t need timber pulp to make. 

And it still takes 25 to 35 years for a tree to be mature enough for structural timber. Timber is usually treated to be used in a home, and as a result, all waste and demolished treated timber has to be wrapped before it’s put in landfill. So, there’s definitely some holes in the sustainability claims.

There are some amazing alternatives that are also available: straw generally and products like Durra Panel that make building panels from waste straw; hemp, which sequesters carbon and has a negative carbon footprint; bamboo, which grows rapidly with a 3 to 5 year growth rate; and Cross Laminated Timber (CLT), which speeds up construction as a panelised, prefabricated product.

At the other end of the spectrum, there are products that are naturally high in embodied carbon due to their ingredients or their energy intensive manufacturing requirements. Materials we commonly use in our homes, such as steel and concrete, can be high carbon products, BUT there are ways of choosing lower carbon alternatives within these.

If structural steel is part of your project, ask your team whether recycled content steel is available, as it can now be accessed in many locations. 

Aluminium is another energy intensive material that has high embodied carbon, however some products do utilise recycled ingredients, so it’s worth checking with your manufacturer.

Low-carbon concrete mixes are increasingly available, using supplementary cementitious materials such as fly ash (a byproduct of coal combustion), slag (a byproduct of steel production), or geopolymer binders to replace a portion of the conventional cement. 

These alternatives can reduce the carbon intensity of concrete substantially while maintaining structural performance.

Sustainability claims are easy to make and difficult to verify without standardised data. Environmental Product Declarations, or EPDs, are one of the most reliable tools available for comparing the embodied carbon of specific products.

An EPD is a third-party verified document that quantifies the environmental impact of a product across its full lifecycle, including raw material extraction, manufacturing, transport, and end of life. It’s a standardised format, which means you can compare an EPD from one manufacturer with an EPD from another. 

Not every product has an EPD but it’s always worth checking, and if not available, speak directly to the manufacturer to see what more info you can find.

In this Episode, I cover:

• Why embodied carbon is now the dominant portion of a well-performing home’s lifetime carbon footprint
• Why timber is promoted as a low carbon hero, and the caveats about it
• Agroforestry as an alternative for sourcing timber
• Companies like Crafted Hardwood creating new products from hardwood waste
• Alternative low carbon materials worth exploring: Durra Panel straw board, hempcrete, bamboo, and Cross Laminated Timber (CLT)
• How to lower the carbon in steel, aluminium and concrete through recycled content and supplementary cementitious materials
• Why sourcing locally, and how a manufacturer runs their production line, both change a product’s carbon footprint
• What Environmental Product Declarations (EPDs) are, and how to use them to compare products
• The questions to ask your design team and suppliers so embodied carbon is tracked and considered in your material selections
• Why choosing sustainable materials is often a balance of priorities

Plus a whole lot more.

LISTEN TO THE EPISODE NOW.

RESOURCES:

Episode 418, on measuring your home’s carbon footprint >>> 44 Ways #18

Episode 256, on choosing building materials >>> Choosing Building Materials

Episode 232 with Jeremy Spencer, Positive Footprints >>> Carbon Zero Homes

Episode 233 with Jeremy Spencer, Positive Footprints >>> Sustainable Builder

Episode 250 with Derek Layfield, Durra Panel >>> Wall and Ceiling Panels

Episode 251 with Derek Layfield, Durra Panel >>> Compressed Straw Panels

Episode 280 with Dylan Viviers from Holcim >>> Low Carbon Concrete

Episode 281 with Dylan Viviers from Holcim, on how to specify it >>> Specifying Concrete

Product sustainability certification >>> Global GreenTag

A free guide to simplifying sustainability across research, planning, design, materials, and building, from Amelia Lee’s 30+ years in residential design and construction >>> 44 Ways to Create a Sustainable Home

Access the support and guidance you need to be confident and empowered when renovating and building your family home inside my signature online program >>> HOME Method