Carbon Footprint of Buildings: Embodied Emissions and Decarbonization Options

Measuring the carbon footprint of buildings is a very complicated process.⁹

You not only need to know the total embodied energy of the building, that is how much energy was used to create all the materials used, but also the operational and end-of-life footprint to obtain the true amount.

In fact, the measurement involves more than the common building materials such as steel, brick, and concrete. You will also have to look at the amount of copper, glass, wood, aluminum, asphalt shingles, and other building materials that go into the building’s construction.

Even the most insignificant materials such as plastic, vinyl flooring, and house wrap used for insulation contribute to the carbon footprint of buildings.

The carbon footprint of steel and concrete are probably the two biggest categories and can be measured easily, but everything, from the energy used to power the structure after it’s built, to the demolition process, has an impact.

In addition, the location of the structure also plays a role in the carbon footprint of buildings.

This guide explains ow these metrics are added up, and how you can actually erase the emissions used to build any structure.

Carbon Footprint of Buildings: What Is Embodied Carbon?

Embodied carbon refers to the carbon emissions released in their millions of tons,⁸ during the building material’s life cycle.

Embodied carbon covers the whole process including disposal, construction, transport, manufacturing, and extraction of materials.

The carbon footprints of buildings start even before construction. Examples of construction materials that add to embodied carbon include steel, concrete, and insulation.

Embodied carbon produces more than 11% of greenhouse gas emissions worldwide.¹ Therefore, policymakers, manufacturers, and builders should prioritize this issue in order to meet climate goals.

Additionally, the reduction of embodied carbon emissions is an immediate and effective way of taking climate action.

Most emissions in the construction industry occur even before the construction phase of the building. Therefore, decreasing embodied carbon is a vital juncture in building decarburization.

Embodied Carbon Calculation

Researchers calculate embodied carbon as Global Warming Potential (GWP), and express the sum in carbon dioxide equivalent units (CO₂e). If you want to quantify the embodied carbon of a product, you conduct an analysis known as a Life Cycle Assessment (LCA).

The LCA can assess the lifecycle of a product and how each stage affects the environment.

The results of LCA are disclosed through Environmental Product Declarations (EPDs) which release valuable information to consumers about how a given building product impacts the environment.

Essentially, EPDs are the ‘nutrition labels’ of construction materials. They often include:

• Smog Formation
• Ozone Depletion
• Eutrophication
• Acidification
• Global Warming Potential

Carbon Emissions From Buildings and Construction

The carbon emissions from buildings and constructions are huge problems in the world today. The construction industry alone creates more than half of the greenhouse gas emissions.

These greenhouse gasses have led to the spread of infectious diseases, droughts, floods, rising sea levels, and rising temperatures.

Buildings alone use more than 36% of all energy that is generated, and not-so-surprising 70% of all generated electricity.

The carbon footprint of buildings should include all the carbon the building releases into the atmosphere at all stages which are the project’s design, construction, and operation.² The United Nations has put several protocols in place, such as the Kyoto Protocol, to emphasize decreasing greenhouse gas emissions.

However, there are no rules or regulations set for the construction industry to abide by.

Therefore, architects all over the world should be more sensitive and thoughtful at every design stage to keep building construction more sustainable.

These architects should understand the tree sustainability rings to include buildings and construction in the fight against greenhouse gas emissions and climate change.

Carbon Footprint of Buildings: Operations

Most of the carbon footprint of buildings is caused by the buildings’ materials.

However, there is an operational cost as well.

Among all the materials used in the construction industry, concrete and steel are the most problematic emitters.

Creating these two construction tools requires heating raw materials to very high temperatures. The energy used in the heating process typically originates from fossil fuels.

Consequently, the cement and concrete carbon footprint creation contributes 7% of the entire carbon emissions in the world, while steel makes 2.3 tons of carbon for every metal ton produced. In the remaining construction materials, aluminum is also a problematic emitter because it causes 3% of direct industrial carbon dioxide emissions in the world.

To put it into perspective, the materials that are used to construct a three-story home in the United States of America have an embodied energy of about 42,000 kilowatt-hours (KWh). In the US, 1KWh results in around 0.85 pounds of carbon dioxide emissions.

At this rate, the three-story building will create about 16 tons of carbon dioxide. Other estimates conclude that the three-story home would produce about 26 tons of embodied carbon dioxide, while even other estimates have numbers higher than these.

The fact that these estimates vary so much is not surprising.

Calculating the carbon footprint of a house has plenty of wiggle room because you’d have to consider a single material from mining, to production, to construction, to maintenance.

Then you’d have to do the same for every single material in a person’s house.

Therefore, a house’s carbon footprint can vary wildly depending on the construction materials used, quantities used, and where they came from.

Architecture and Climate Change: How To Manage Building Carbon Emission (Offsets, Location)

There’s no doubt that many homes contribute significantly to carbon emissions. The next step is learning how to manage building carbon emissions.

First, you should know that researchers all over the world are working on ways to reduce carbon during the manufacturing of important construction materials. Tree planting has been playing an important role in reducing the carbon emission in the environment.

In the meantime, architects should design structures that reuse materials, for example, recycled timber, and avoid high-carbon generating materials such as aluminum. The best route now is choosing to build with timber.

This is because timber originates from trees that have already sequestered carbon and using it in construction will prevent the carbon from being released again. Since architecture affects the amount of construction material used in building houses, it’s safe to infer that there’s a relationship between architecture and climate change.

Once you have made a decision to build a new house, you have two choices that determine how carbon-intensive it will be. The first choice is the size of the house you want because a mansion will require more building materials than say, a cozy cottage.

In the US alone, new homes have grown 45% in size since the 1960s, therefore needing more construction equipment per home.

The second choice is location. If you build your house next to your work or family, you will reduce your carbon footprint from transportation.

If you decide to build a second home across the country or overseas, you will add to your carbon footprint due to more air travel, or road transport. This could ultimately wipe out any carbon savings that you gained through smart building practices.

Of course, it’s important to note that construction is only the beginning. Once the building is done, it starts its own decades-long lifespan.

In these years the carbon footprint is no longer embodied energy rather, it’s operational energy. You now begin to measure the electrical, cooling, heating, and other needs that produce CO₂ in the process.

Building Decarbonization

First, what is building decarbonization?⁶

This refers to the process of eliminating or reducing carbon dioxide emissions that contribute to climate change from the energy sources of a building.

Building decarbonization has four main components, they include:

Components	Definition
1. Energy Efficiency	Making buildings energy efficient is the first step to building decarbonization. This means reducing the amount of energy the building needs to operate. For example, you can add wall insulation in your home so that heat does not escape in the cold months. Then the heating system will use less energy. You can also find other energy efficiency solutions such as LED light bulbs, a programmable thermostat, and other energy-saving equipment. Besides saving energy, these improvements help the house become more comfortable and you can save money on energy bills.
2. Electrification	Electrification involves replacing building equipment that uses fossil fuels with equipment that uses electricity. For example, you can replace your furnace, which uses natural gas to burn with a heat pump which uses electricity to cool and heat your house. Another example of electrification is exchanging your gas stove with an induction or electric stove.
3. Renewable Energy	Once you’ve replaced all the gas equipment and most of your appliances are electric, the next step is to decide where the energy for your buildings comes from. You can still get electricity from coal and fossil fuels. Whenever possible you should get electricity from renewable energy sources such as solar farms, wind energy farms, and hydrothermal power plants. Installing a solar array in the home also increases its value.
4. Managed Electricity Loads	Since more and more people are utilizing electricity to power their homes instead of gas and fossil fuels, the demand for electricity also increases. To manage this increased demand, you can shift your energy use to different times of the day to reduce the effect on the local energy grid. This helps decrease carbon emissions even more.

Carbon Footprint of Buildings: Why Is Building Decarbonization Beneficial?

Since fossil fuel resources are non-renewable, it’s inevitable that the world will need to stop using them, especially for buildings.³

There are many benefits of building decarbonization, they include:

Benefits	Explanation
Climate Action	The use of fossil fuel resources creates a lot of pollution and greenhouse gas emissions. Decarbonization efforts can eliminate pollution and meet emission reduction goals to combat climate change.
Managing Utility Costs	The price of electricity and natural gas is expected to rise substantially in the next decade. Using renewable energy sources and switching to an all-electric home will be a more affordable and stable option.
Preserving Affordable Housing	The four building decarbonization pillars -renewable energy, electrification, energy efficiency, and programs that are smart grid enabled- will make your home high performing. Additionally, your home will also be resilient against climate change and rising energy costs. If you make these upgrades you will ultimately reduce operation costs in the years to follow.

Net-Zero Buildings

Net-zero buildings refer to buildings that are either ‘net zero carbon’ or ‘net zero energy’. Buildings that are ‘net zero energy’ use energy efficiently and do not consume energy from utility-scale sources.

Rather, all the power needs of the building come from on-site renewable energy. But, that doesn’t mean that there was no emissions generated to construct it.

On the other hand, net-zero carbon buildings create net-zero carbon emissions annually. Zero carbon definition varies across governments and sometimes may include a carbon offsetting element.

A clear meaning of Net Zero Energy Building (NZEB),⁷ is a building that creates as much energy as it uses in the course of a year. At the moment, though research is still ongoing, there are only a few highly efficient buildings that meet the net zero energy criteria.

Additionally, countries have not yet agreed on common zero-energy metrics.

In the US, the National Renewable Energy Laboratory (NREL) and the Department of Energy (DOE) have been in charge of advancing the net zero energy concept in the country to date. NREL provides many definitions of net zero energy and they also encourage building operators, owners, and designers to decide which metric fits their project best.

Net zero energy may be defined as:

• Net Zero Energy Emissions
• Net Zero Energy Costs
• Net Zero Source Energy
• Net Zero Site Energy

Net Zero Energy Concepts	Definition
Net Zero Site Energy	This refers to the total amount of energy generated and consumed at a site such as a building construction site. Site energy does not regard how or where the energy originated. A net zero site energy house generates a unit of electricity for every unit the building consumes annually.
Net Zero Source Energy	This is the primary energy required to extract and convey energy to a site. Source energy also includes the energy that is wasted or lost during the generation process.
Net Zero Energy Costs	This metric is the simplest to use. In a practical sense, it means that the energy utility bill of the building is $0 in the course of a year. In this case, the building produces and uses its own energy. Sometimes building operators and owners can take advantage and sell renewable energy credits derived from the renewable energy generation on-site.
Net Zero Energy Emissions	Since conventional energy sources produce greenhouse gas emissions, a net zero energy emission building either does not use energy that results in greenhouse gas emissions or offsets emissions by exporting energy that is emissions-free.

Net Zero and Grid Connection

Most buildings that are net zero energy remain connected to the electric grid.

This allows the building to use the electricity generated from traditional energy sources when the generation of renewable energy does not meet the energy load of the building.

Conversely, in situations where the energy generation on-site exceeds the energy requirements of the building, the surplus is fed back to the utility grid as mandated by the law. The production of excess energy offsets any later period of excess demand and this is what results in a zero net energy consumption.

Grid connection is usually necessary because of the technology and cost limitations involving energy storage.⁴ To achieve a net zero energy balance most homeowners will need to be connected to the grid.

However, you should carefully evaluate the difference in how jurisdictions and utilities address payment for power exported from the building to the grid.

Net Zero and Energy Efficiency

The metric or definition used for a net zero building should not matter. At the end of the day, what’s important is reducing energy use through building designs that are efficient and can meet at least one criterion of the net zero energy building concept.

The most cost-effective strategy that also has the biggest return on investment is energy efficiency. If you maximize efficiency opportunities before turning to renewable energy plans you will reduce the renewable energy project costs needed.

Measures of energy efficiency include design features and strategies that minimize the demand side loads. Some of the features and strategies include:

• Water conservation
• Natural ventilation
• Passive solar heating
• Selecting windows and glazing carefully
• Sun control and shading devices
• Daylighting
• Air barrier systems
• High-performance envelope

Once you’ve reduced building loads, you can meet the loads with efficient systems and equipment. Examples include:

• Geothermal energy heat pumps
• High-performance HVAC
• Electric lighting controls
• Energy-efficient lighting

Mass Timber and Wooden Buildings

You may have heard of mass timber and wooden buildings.⁵ What is mass timber?

Mass timber refers to the utilization of state-of-the-art technology to dowel, nail, and glue wood products together in lots of layers, such as plywood.

Yet, unlike plywood, these mass timber materials an be used as beams, joists, posts and other weight bearing components.

These products are versatile and exceptionally strong and fall under the name mass timber.

Wooden buildings are now being constructed with mass timber. In the past, wood construction technology used light-frame wood.

In contrast, mass timber construction that is used nowadays involves creating houses with large solid wood panels, beams, or columns. These construction materials are usually manufactured off-site for load-bearing roof, floor, and wall construction.

Experts have engineered mass timber to be as strong as steel and concrete, but have a significantly lighter weight.

The products of mass timber are typically produced through adhesives, fasteners, and lamination. Most importantly, mass timber complements hybrid and light-frame construction options as an environmentally friendly substitute for building systems and carbon-intensive materials.

Additionally wood is a renewable resource making it a great construction material.

Reducing the carbon footprint of buildings through efficient architectural designs, building decarbonization, and net zero energy building programs will go a long way in combating climate change.

However, you can help diminish the amount of embodied carbon emissions in building materials and lower the carbon footprint of buildings by planting trees that will sequester emissions right now.

Frequently Asked Questions on Carbon Footprints of Buildings