Buildings and Climate Change

Building are the places where we spend most of our time, either at home, at work, shopping for food and goods, entertainment, and many, many others. Buildings use about 70% of the energy that is generated and about 60% of the materials and products produced.

The energy to operate a building over its life cycle is used for lighting, heating and air conditioning, hot water supply, powering building equipment, maintenance, refurbishing, and demolition. All of this energy is supplied by some mix of fossil fuels and renewable energy, provided by utilities or at the building site. The use of fossil fuels, including coal, gas, diesel, gasoline, and fuel oil, emits carbon dioxide and other greenhouse gases including methane, nitrous oxide, and sulfur dioxide. Other greenhouse gases are also emitted during the operation of buildings including the refrigerant gases used in air-conditioning, and the release of blowing gases used in insulation. The various greenhouse gases associated with building operations is commonly known as operational carbon emissions.

The greenhouse gases emitted by buildings in 2020 represented about 39% of all global GHG emissions. The makeup of this 39% is comprised of the operational carbon emissions described above, and the greenhouse gases associated with providing the materials used to create the buildings and the equipment and furnishings used in the buildings, known as embodied carbon emissions. The makeup of the 39% of total global GHG emissions is 28% operating carbon emissions , and 11% embodied carbon emissions.

Operating Carbon Emissions

Architects and engineers recognized the impact of operating emissions on climate change and created certification systems like BREAM and LEED in the 1990’s, and the 2030 Challenge by Architecture 2030 in 2006. The reductions in building operating emissions in the U.S. from 2005 to 2023 are shown in the chart below.

Source: Architecture 2030

This decline in U.S. operating emissions occurred with a building area growth of +22.5% over the same time span.

Embodied Carbon Emissions

Engineers and material scientists began evaluating the greenhouse gas emissions relating to materials and products using early versions of Life Cycle Assessments (LCA) in the 1990’s, developing methods and standards over the next decade, and becoming a common approach to evaluate embodied emissions around 2010.

Architecture 2030 issued the 2030 Challenge for Products in 2011, and at the same time the Carbon Leadership Forum (CLF) established a home at the University of Washington. The CLF worked on foundational elements of embodied carbon since their formation in 2009, and started major outreach to the design community in 2018 with the Carbon Smart Building Day during the Global Climate Action Summit. [The History of the Carbon Leadership Forum, CLF]

If one compares the 17 years it took to reduce operating emissions in the U.S. by 28.4%, and assuming the design community mobilized around 2016, embodied emissions would reduce by about 28% by 2035. Architecture 2030 in their renamed 2030 Challenge for Embodied Carbon, stated that embodied carbon emissions from all new buildings, infrastructure, and associated materials must be reduced by 65% by 2030, and by 100% by 2040. This represents a major acceleration in how we approach embodied carbon reductions vs our actual performance in reducing operating emissions.

2020 CO2 Budget

Source: Architecture 2030

Reductions in embodied carbon emissions has been led largely by western European countries, with North America trailing behind by 5-10 years. Global reductions have gotten off to a slow start, with the rate of reductions starting to pick up around 2020 - 2022. If the building construction sector wants to stay on track for a 50% chance to reach a 1.5C target, this delayed progress in embodied carbon reductions will require us to reduce building embodied carbon by about 20% per year starting in 2024. [Global Carbon Budget 2023, Earth System Science Data, Friedlingstein et al].

2024 CO2 Budget

Four years have gone by since 2020 and we are still emitting 40 GtCO2e/year. AND, the probability has reduced to 50%.