A Detailed Guide to the Carbon Emissions in Construction

Construction may not be the first industry that comes to mind when you think of contributors to greenhouse gas emissions. However, the building and construction sector is responsible for up to 37% of all energy-related carbon emissions.

We must be highly cautious moving forward since it is estimated that 60% of buildings that will exist in 2050 haven’t been built yet – the equivalent of building a city the size of New York every month until then.

By Rose Morrison, managing editor of Renovated

See our resource hub: Sustainable Construction: A Comprehensive Guide

Embodied vs. Operational Carbon

To date, most research and development have gone into solving the greenhouse gas problems once buildings are already occupied – known as operational carbon. Ways to improve operational carbon emissions in construction are awareness of water consumption, recycling initiatives, and using renewable energy sources.

Embodied carbon is created in the manufacturing, construction, and demolition phases. It is responsible for 50% of whole-life carbon emissions in buildings, with most of the problem occurring in the early stages.

Carbon Emissions in Construction: A building under construction in a city at night

How to Reduce Carbon Emissions in Construction

With the call for net-zero emissions in new construction, cities are using tactics such as using solar energy to reduce operational carbon and offset embodied carbon emissions in construction.

However, to truly reach net-zero status, manufacturers and builders will need to address the embodied carbon issue at the source. Luckily, many new approaches could help.

  1. Repurpose Existing Buildings

Repurposing unused buildings rather than constructing new ones can significantly impact embodied carbon since the emissions of the existing structure are already a sunk cost. Adding on to the building through renovations should be approached with caution using other carbon-reduction methods.

However, builders can reduce a project’s embodied carbon by 50% if they can save a pre-existing foundation and main structural elements. Those parts of a building consist of the highest carbon-emitting construction materials: concrete and steel.

  1. Use Low-Carbon Concrete

Concrete is the source of 8% of the world’s carbon emissions, which is more than the shipping industry and more than the contributions of each individual country except the U.S. and China.

The primary source of carbon emissions in concrete is cement production. Cement is created by heating limestone to extreme temperatures to separate carbon monoxide from carbon dioxide. The carbon dioxide is released into the atmosphere along with the carbon emissions from fossil fuels used as a standard heat supply.

Cement manufacturers are researching new materials to use in production that would significantly reduce the amount of embodied carbon. Leftover materials from steel and power production, such as slag and fly ash, are proving to be effective alternatives.

  1. Improve the Manufacturing Process

Steel is the next highest source of embodied carbon in construction next to concrete. Manufacturers believe they can considerably reduce emissions by improving the manufacturing process.

Improvements in technology are allowing for the capture and reuse of emitted carbon dioxide. Alternatively, manufacturers in Sweden, Germany, and Australia are developing a new method of production that doesn’t create carbon dioxide at all.

In the typical production process, iron ore is reduced through a reaction of iron oxide and carbon monoxide, resulting in pig iron and carbon dioxide. This new method uses hydrogen gas instead of carbon monoxide, producing pig iron and water vapor, thereby reducing carbon emissions in construction.

  1. Find Low-Carbon Alternatives

Being intentional in the design process can lead to minimizing embodied carbon in construction. Architects should efficiently reduce the need for carbon-heavy materials in their projects and use low-carbon-emission alternatives whenever possible.

Implementing low-carbon concrete and steel is a good start. However, there are many other alternatives with low embodied carbon. Bamboo is a renewable material that is 30-50% stronger than traditional wood choices, and MDF boards made out of rice straw in California are performing just as well as wood fiber.

  1. Reuse Construction Materials

Recycling and reusing building materials can reduce carbon emissions, and most materials such as plastics, metals, brick, wood, and concrete, to name a few, are all recyclable. Reusing these materials rather than creating them from scratch can significantly impact the environment.

For example, producing 1 ton of aluminum typically creates 17 tons of carbon dioxide. However, the carbon output from recycled aluminum is only .6 tons for every ton of aluminum. This aluminum has many uses, including metal roofing. Plastic can also be recycled and used for cladding instead of higher carbon-emitting siding options.

  1. Prefabricate When Possible

Studies have shown that using prefabrication on a build can reduce carbon emissions. Greenhouse gas emissions from transportation are reduced when most of the work is done in one location. Material waste is also lower at prefabrication sites since builders can use leftover materials on the next project.

Roadblocks to Embodied Carbon Reduction

Despite the apparent benefits of reducing embodied carbon, those in the construction industry are still struggling to make necessary improvements. Here are some reasons why.

  1. Lack of Government Policies

Despite global attention to global warming and the necessity of reducing greenhouse gas emissions, very little policymaking has addressed the issue of embodied carbon in construction. Until lawmakers provide concrete legislation that will enforce net-zero building practices, construction companies and building manufacturers will continue to make their own judgment calls.

  1. No Set Definition for Net-Zero Building

There currently is no one definitive standard for net-zero. This leaves a lot of wiggle room for cities to offset embodied carbon by implementing operational carbon-reduction strategies. While these methods of reducing a building’s carbon footprint are extremely important, they are just a bandaid solution to the initial problem. Architects need to address carbon emissions in the initial planning phases to make the most significant impact.

  1. The Expense of Low-Carbon Materials

Unfortunately, most low carbon-emitting materials cost more, which can deter most construction companies and clients who do not have room in their budget. Hopefully, as the technology needed to create these supplies becomes more commonplace, their cost will decrease, making them more accessible.

How Legislation Could Help

Future legislation could help the construction industry’s reduction efforts by creating and enforcing net-zero building regulations. Creating a set definition for net-zero and determining ways of enforcing these building regulations would necessitate the adoption of low carbon-emitting construction.

As an alternative, they could impose a carbon tax that would require manufacturers to pay for their carbon emissions. A carbon tax would encourage the implementation of methods and materials with low embodied carbon and might jumpstart the transition to net-zero building practices.

Hope for the Future

We are working towards a future with fewer carbon emissions. The World Green Building Council is hoping, by 2030, to reduce embodied carbon emissions by 40% and reach net-zero status in 2050 for all new construction, infrastructure, and renovation projects.

In the United States, California has taken steps towards embodied carbon reduction by implementing the Buy Clean California Act, which dictates appropriate levels of carbon emissions on certain building materials.

While not perfect, these measures are certainly a start in the right direction. Similar legislation has been presented in other states, but no others have passed it yet.

Rose Morrison

About the Author

Rose is the managing editor of Renovated and has been writing in the construction industry for over five years. She’s most passionate about sustainable building and incorporating similar resourceful methods into our world. For more from Rose, you can follow her on Twitter.