How to Reduce Embodied Carbon in Construction

concrete stairs by tree - how to reduce embodied carbon in construction

No matter what you’re building, construction will almost always require a massive amount of energy. The use of power generates emissions, and materials and construction equipment also account for a significant portion of a building’s carbon footprint.

Fortunately, you can decrease embodied carbon levels in a new construction project with the right knowledge. Knowing what embodied carbon is and how you can minimize it can make your work much more sustainable.

What Is Embodied Carbon and Why Is Embodied Carbon Important?

A simple embodied carbon definition is that embodied carbon is the carbon dioxide emissions that come from the construction of a building and from the manufacture of the materials it’s made of. Embodied carbon is distinct from a building’s operational carbon emissions, i.e. the emissions produced by the building’s operations—operations like lighting, heating and cooling.

Similar to embodied energy, embodied carbon sums up all the power needed to create a given object, whether it’s a particular material, a component or the building itself. The difference between embodied energy and embodied carbon is that embodied energy doesn’t account for differences between sources of energy, which could contribute more or less to climate change (i.e., diesel fuel vs. solar energy).

What Is Embodied Carbon in Buildings?

In most cases, embodied carbon will measure the CO2 produced by extracting, refining and manufacturing building materials, transporting them to the site and using them in construction.

For example, the embodied carbon of a new home will include carbon emissions from the manufacture of the wooden framing used in the building, as well as from the operation of heavy machinery used in the construction process.

These embodied emissions are effectively built into the new structure. They won’t continue to cause environmental impacts as the building ages. However, measuring these emissions will help us understand how much impact certain materials or construction techniques can have on the environment.

There’s some debate regarding embodied carbon vs operational carbon in terms of what makes more sense for builders to focus on. While the green building industry has historically been concerned with operational carbon, there’s been a recent rise in interest in cutting embodied carbon as a way to lower a building’s footprint both immediately and over time.

In the past, embodied carbon accounted for a smaller portion of overall building emissions. More recently, however, operational emissions have started to fall due to greener construction and building management practices. As a result, embodied carbon is beginning to make up more of the total carbon emissions from buildings worldwide.

New homes and buildings are being constructed all the time. Construction is also speeding up as demand for additional structures increases. As a result, the global floor area is on track to double by 2060.

The growing demand is good news for the construction industry but bad news for climate change. The environmental impact of construction will worsen over the next few decades without major changes to the materials we use.

Experts, construction companies and homebuyers are looking for ways to reduce embodied carbon and the impact of new builds on the environment. Adopting the right materials and techniques makes it possible to slash embodied carbon emissions on various projects.

What Are the Units for Embodied Carbon?

In most cases, you’ll see embodied carbon measured in kilograms of CO2e per kilogram of material. CO2e is short for carbon dioxide equivalent. Eurostat explains that this measurement is “used to compare the emissions from various greenhouse gases on the basis of their global-warming potential (GWP) by converting amounts of other gases to the equivalent amount of carbon dioxide with the same global warming potential.”

They give the example of nitrous oxide, which has a CO2e of 298, meaning that its GWP is 298 times greater than carbon dioxide.

Measuring a material’s embodied carbon on the basis of its global warming potential gives builders a concrete metric they can use to determine how that material will impact the project’s overall footprint and to allow them to compare materials and products to make more sustainable choices.

How to Calculate Embodied Carbon

There are several types of embodied carbon calculator available online. One of the most popular is the Embodied Carbon in Construction Calculator (EC3), developed by the Carbon Leadership Forum. You can use this calculator and information about your construction project to estimate how much embodied carbon your project will generate.

Suppose, however, that you don’t need specific figures and just want to find ways to minimize the embodied carbon of a project. In that case, you can begin by identifying and reducing your use of high embodied carbon materials.

Common Sources of Embodied Carbon in Home Construction

cement flowing through pipe - how to reduce embodied carbon in construction

Levels of embodied carbon can vary significantly from material to material. These are some common construction materials that have a high carbon cost:

  • Aluminum: Aluminum production is an energy-intensive process, requiring 10 times as much electricity as steel. As a result, new aluminum will almost always drive up the carbon cost of a building project.
  • Plastics: Plastics are unavoidable, but they’re one of the worst building materials when it comes to embodied carbon. Some types of plastic generate much more embodied carbon than others. For example, polypropylene, which is used for sidings, pipes and carpets, is worse than most others when it comes to embodied carbon.
  • Foam: Foam is often important for making sure a home or building is well-insulated and energy-efficient, but certain types generate large amounts of carbon when manufactured.
  • Concrete: Concrete is the most abundant human-made material in the world and takes a lot of carbon to create. New types of concrete are more eco-friendly than those that contain conventional Portland cement, but they can be difficult to source or be more expensive.

Other common construction materials have a very low embodied carbon and could help you cut back on it in your next project:

  • Wood: Depending on its origin and the type of wood, lumber can be one of the most sustainable choices for a new building because it absorbs carbon dioxide from the atmosphere as it grows.
  • Bio-based materials: These are materials made from plant or animal products, like wood, straw, cotton, flax, leather and paper. Most bio-based products are sustainable. Many agricultural varieties, like wood or straw, even help capture atmospheric carbon.
  • Salvaged and recycled materials: For the most part, salvaging and recycling any material can slash its embodied carbon cost. Reclaimed brick would only cost the energy spent to reclaim and prepare it for new construction. This will often be much less energy-intensive than manufacturing new bricks.

Recycled materials often have a very low embodied carbon cost compared to new materials, so this is a good way to use typically high-carbon materials without driving up a project’s overall environmental impact.

For example, aluminum is highly recyclable and it’s possible to source large amounts of it for a project — especially as recycling becomes more popular. Finding a recycled version of a high-carbon material could help you reduce your carbon cost.

It’s also important to think about how the material may impact a building’s efficiency when considering embodied carbon. Energy-efficient construction principles allow a company or contractor to easily offset carbon cost with other green benefits. In some cases, a high-carbon material may provide efficiency improvements that outweigh its carbon cost. For example, a home solar system requires many high-carbon materials but will provide clean energy for more than a decade after installation.

Specialized equipment and appliances, like smart home HVAC thermostats and vents, may require you to purchase more devices and materials than you would typically need. However, they can often provide performance improvements that make them worth it.

Tips for Reducing Embodied Carbon in Construction

straw bale house - how to reduce embodied carbon in construction

No matter how big or small, any project can probably have less embodied carbon. These strategies can help you spot high-carbon sources in construction and find possible alternatives that may make the project more sustainable.

1. Use Low-Carbon Concrete

Concrete is the most widely used construction material worldwide, which makes it challenging to avoid. In some cases, it is possible to swap out concrete for low-carbon alternatives, like rammed earth. In others, it makes more sense to find and use low-carbon concrete.

It is possible to use more eco-friendly, low-carbon varieties of concrete, but you’ll have to go out of your way to source and use these materials.

For example, using less cement can help reduce the carbon cost of manufacturing concrete. Varieties with less cement, like “ashcrete” or fly ash-based, may be harder to find than standard concrete but will help you reduce your project’s embodied carbon.

Access to these materials can vary depending on where you are. However, these low embodied carbon concrete mixes will probably become easier to find as they become more popular.

2. Find Alternatives to High-Carbon Materials

Some materials, like concrete, are hard to cut out of a construction project. Others, like aluminum, plastic and foam insulation, may be more easily replaced. With insulation, embodied carbon levels will vary considerably, making alternatives easier to source. For example, spray foam insulation alternatives like soybean-based options, straw batting, cotton batting or wool could allow you to replace that material entirely.

It may also be possible to rely on recycled or reclaimed materials. Recycling aluminum uses 5% of the energy needed to manufacture the same amount of new aluminum. This is a great way to use the material without driving up your project’s carbon cost.

3. Source Materials That Capture Carbon

Several bio-based materials and agricultural products pull carbon out of the air as they grow. These items can significantly reduce your project’s embodied carbon.

The most common bio-based material is wood. Consider wood rather than vinyl for a low embodied carbon flooring option. You can also use materials like straw or cotton insulation to reduce the overall emissions associated with your construction project.

4. Employ High-Efficiency Design Techniques

How you design a new building, renovation or extension can significantly impact the embodied carbon necessary to make that design a reality.

The framing techniques involved in advanced house framing or optimum value engineering (OVE) can significantly reduce the amount of lumber used and waste generated in a new home construction project.

Many of these design techniques can also make a home or new building more efficient, meaning you can cut down your project’s embodied carbon and eventually save money on heating and cooling the building.

5. Reduce the Project’s Scope

The easiest way to shrink embodied carbon is to build less. A smaller home, fewer renovations and less new material will instantly eliminate some of the carbon necessary for your project. Less construction also means less worry about the project’s energy cost.

Repurposing or redesigning an existing space rather than building a new one will make your project more sustainable and easier to accomplish. A repurposed room or shed may provide all the benefits you need from an extension or new structure.

However, shrinking a project’s scope isn’t always an option. You may have already revised your plan to keep it as small and low-cost as possible.

If this is the case, you’ll have to find other ways to reduce the project’s embodied carbon total. However, if you haven’t reviewed your project or plan yet, you may find design elements to cut out, consolidate or replace.

How Homeowners Can Manage Embodied Carbon in Construction

Avoiding high-carbon materials, recycling, using high-efficiency design strategies and scaling down your project where possible will make it easier to avoid embodied carbon.

Modern design techniques can help minimize the amount of embodied carbon necessary for a new construction project. Knowledge of embodied carbon is the key to keeping your project as eco-friendly as possible, whether renovating or building an entirely new structure.

Learn all you can about the topic. The Rocky Mountain Institute (RMI) Embodied Carbon Initiative is a great next stop for information.

Feature image: Asia Culture Center; Image 1: Life of Pix; Image 2: Øyvind Holmstad

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