The building industry is an energy-intensive sector with a hefty carbon footprint.
This footprint comes from the production and transportation of materials, the construction methods the sector uses, and the operation of the finished buildings throughout their lives.
Using the lowest carbon footprint building materials is sometimes possible, but we must avoid the most carbon-intensive materials wherever possible.
According to some estimates, the building sector is responsible for half of all climate change and half of the waste that goes to landfills yearly.
But we all need buildings to live and work in, so what can we do to reduce the impact of the construction sector on our planet?
Well, for a start, we can do a lot in the building industry to reduce our carbon emissions. For example, we can use raw materials containing low embodied carbon and install green technologies in the buildings we produce, resulting in low carbon emissions and greater energy efficiency.
This article will explain what makes up the carbon footprint of the building sector, why that’s important, and what you can do about it, including some examples of the lowest carbon building materials available on the market.
Read on if you want to learn more.
What is a Carbon Footprint?
The carbon footprint of a person, organization, product, or building is the total amount of greenhouse gas emissions they release into the atmosphere.
We often define carbon footprint on a per-year basis, but a complete lifecycle analysis will measure the carbon emissions generated over the entire lifetime of a product or activity.
Greenhouse gas emissions include carbon dioxide and other gases commonly used by people, such as methane (aka natural gas) and nitrous oxide, produced from agricultural activities, natural vegetation, and the oceans.
Studies have quantified the amount of greenhouse gas emitted by different countries, and how much of their total emissions come from different sources. The categories covering construction, shelter, food, and transportation contributed the most.
The more greenhouse gases emitted, the greater the global warming effect and the more pronounced the climate change impacts worldwide.
What Is the Carbon Footprint Of a Building?
The carbon footprint of a building can take into account all sources of greenhouse gas emissions, which could include the following elements.
- Sourcing of the raw materials
- Manufacture, processing, and transportation of building products
- The construction process.
- Energy usage of the building once it is in use. This includes heating, cooling, and maintenance.
- End-of-life considerations. This would include whether any building parts can be reclaimed, reused, recycled, or whether they end up in a landfill.
The discipline of Life Cycle Assessment can put numbers on the overall global warming potential of the building materials you use and your project overall. This can be a helpful guide to making the most sustainable decisions.
This article will look at the embodied carbon of building materials themselves, but bear in mind some important considerations are specific to each project and can cause your project’s carbon emissions to balloon rapidly.
For example, you could use products made from renewable bamboo culms that are great at sequestering carbon, removing it from the atmosphere, and helping to mitigate global warming.
However, if you have to transport those bamboo products halfway around the world, the carbon dioxide emitted from the fossil fuels used to power the container ship will quickly outmatch the carbon bound up in the bamboo.
Similarly, you need to watch out for adverse environmental impacts that can be caused by chasing low carbon emissions for your project.
For example, using local materials might seem like a good idea, but if you get your timber from an area that is an essential habitat for protected species, the benefit of low carbon dioxide emissions from transportation could be outweighed by the impact on this valuable habitat.
All I’m saying is, don’t switch off the critical thinking part of your brain and blindly follow the numbers. They are estimates to be used as a guide alongside your expert judgment that can help you make the right choices. Nothing more.
Now that we’ve got a good grasp of a carbon footprint and how to use it to inform materials choices, let’s look at some examples of low-carbon materials you could use today.
5 Examples Of The Lowest Carbon Footprint Building Materials
This one could be controversial in some circles.
Oak takes a very long time to grow to maturity (40-60 years for red Oak and well over a hundred years for slower-growing species), and the dearth of native, deciduous woodlands in many countries has resulted in a strong preference for softwood timber in construction.
However, according to the Centre for Industrialised Architecture (CINARK) at the Royal Danish Academy, the global warming potential of an Oak tree is -1063 kg CO2 eq/m3. This is the best material on their list in terms of global warming potential.
Oak takes carbon out of the atmosphere and sequesters it, having a beneficial effect on global warming by reducing the concentration of carbon in the atmosphere.
As well as sequestering a lot of carbon, Oak benefits the environment by not requiring harsh chemical treatments to protect it from fungal attacks, thanks to its excellent resistance to moisture.
2. Softwood Timber (Spruce)
Spruce grows widely across the northern states of the US, Europe, and Asia. Anywhere it enjoys a northern temperate climate.
It is very soft, medium-weight, and has excellent mechanical properties for construction.
Spruce trees grow much faster than Oak and can be ready for harvest as lumber after 30 years.
Spruce has a global warming potential of -777.5 kg CO2 eq/m3. Like Oak, this wood is excellent at sequestering carbon because it locks in more carbon than is emitted by its cultivation, harvesting, and processing.
3. Cross-Laminated Timber
Cross Laminated Timber is made from multiple layers of lumber boards that are laid perpendicular to each other. The individual boards are glued together, forming sandwiches that usually contain three, five, or seven layers.
The finished composite boards typically range in thickness from 5/8 inches to 2 inches and are available in widths up to about 9 1/2 inches.
Thanks to the alternating grains in the finished boards and panels, they have very good dimensional stability and are very strong. This makes them ideal for flooring, roofing, and load-bearing applications, such as framing components.
Cross Laminated Timber has a global warming potential of -664 kg CO2 eq/m3, again sequestering carbon from the atmosphere.
4. Straw Bales
Straw bales are next on the list with a global warming potential of -128.2 kg CO2 eq/m3, not bad for an agricultural byproduct.
Straw is the leftover stalks of cereal crops like wheat, barley, or rice and is normally used as bedding for animals or simply burned.
A piece of farm equipment called a baler collects the straw and gathers it together to form bales held together by twine.
Before being used for construction, the bales are compressed, which gives them strength and reduces their susceptibility to fire.
Mainly used for residential buildings, straw bales provide excellent insulation, so as well as having very low embodied carbon, they can help to minimize the heating and cooling requirements of the building, reducing energy consumption and its associated carbon dioxide emissions.
We’ve got an article on straw bale construction that you can read here.
5. Reinforced Concrete (And Its Alternatives)
I want to include reinforced concrete on this list as an example of a highly carbon-intensive construction material (concrete has a global warming potential of 288 kg CO2 eq/m3, and steel is 8831.2 kg CO2 eq/m3).
Concrete is one of the most widely used materials on the planet, second only to water! Therefore, anything that can be done to reduce the embodied carbon it contains could significantly reduce global carbon emissions.
The production of Portland cement, used in concrete, requires very high energy input. Similarly, the steel used in the rebar for reinforcing the concrete contains high embodied energy.
The embodied energy in the steel can be reduced by using recycled steel, which requires less energy than initial steel production.
Better yet, if rebar can be reclaimed, rerolled, and properly quality assured, you can bypass the steel production step altogether.
The cement formulation for use in the concrete can also be improved by using less energy-intensive materials such as fly ash or blast furnace slag, which can replace up to 40% of the Portland cement.
This substitution not only reduces the amount of carbon emitted but has also been shown to improve the strength of the concrete.
Building construction uses a lot of carbon-intensive products, meaning the construction industry is responsible for half of global carbon dioxide emissions.
By using low-carbon building materials, we can play our part in reducing total carbon emissions and helping to mitigate global warming.
The industry is a long way from becoming carbon neutral, but we can minimize buildings’ embodied carbon by using low-carbon building materials like the ones listed above.
Other materials that could have made it onto the list include engineered bamboo, made from bamboo strips layered and glued together similarly to Cross Laminated Timber. Or mineral wool used for insulation.
The point is that many building materials have low carbon footprints, and their increased adoption will make us a greener construction industry that might one day achieve net zero.
Just make sure you do your research before choosing the best sustainable building materials for your project.
Doing this can significantly reduce the embodied carbon of any new building you’re involved in constructing.
If you’re interested in finding out more about how to select sustainable building materials, please read our article “23 Sustainable Building Materials You Can Use Today.”