Carbon Leadership Forum

Carbon Emission Targets

In 2015, countries around the world came together to negotiate the Paris Agreement, a historic framework underpinned by the long-term goal to stop global temperatures from rising above 2°C. In an effort to further ensure the prevention of irreversible climate change, governments also included an ambitious target to limit temperature rise to 1.5°C, which would require emissions to peak by 2020 and fossil fuels to be phased out by 2055.

Each year, the built environment contributes almost 40% of CO2 emissions worldwide. Overall, most of this is due to energy required to operate existing buildings, including lighting, equipment, heating and cooling. However, between now and 2060 the world’s population will be doubling the amount of building floorspace, equivalent to building an entirely new New York City every month for 40 years. Ever heard of “embodied carbon”?

Most of the carbon footprint of these new buildings will take the form of embodied carbon — the emissions associated with building construction, including extracting, transporting, and manufacturing materials. Over the past two decades, we’ve made significant progress in reducing carbon emissions associated with operating buildings. However, according to Architecture 2030, “new research from the IPCC, the UN, and the scientific community stresses the critical importance of a 2030 milestone: if we do not achieve a 45-55% reduction in total global emissions by 2030 we will have lost the opportunity to meet the 1.5/2 ℃ warming threshold and climate change will become irreversible. The immediate focus for embodied carbon reductions must therefore be on the next decade. Annually, the embodied carbon of building structure, substructure, and enclosures are responsible for 11% of global GHG emissions and 28% of global building sector emissions. Eliminating these emissions is key to addressing climate change and meeting Paris Climate Agreement targets.”

The Built Environment

These requirements warrant two critical considerations for evaluating carbon reduction strategies: How much energy can a strategy potentially save? And, what is the timeframe for realizing these savings? Since some reduction strategies result in an initial increase of carbon emissions, we need to pursue initiatives that can produce a net reduction within a critical 10- to 20-year timeframe. In short, we need strategies that produce large savings fast.

The built environment is a critical source of savings. As an end user of fossil fuels, the built environment accounts for more emissions than any other sector, producing nearly half of total global greenhouse gas (GHG) emissions.  The current gold standard for reducing emissions from buildings is to build new, zero net energy (ZNE) buildings – super-efficient buildings powered by renewable energy sources. This is an important step to realize a carbon neutral built environment, but there is a problem with this strategy: building new, ZNE buildings will generate substantial emissions.

Two other sources of emissions may be even more important to address in the short term: embodied emissions from building materials, products and construction processes, and operating emissions from existing buildings.

Embodied Emissions

Making building materials and products cause greenhouse gas emissions. Activities such as mining, driving trucks, running factories, and combining chemicals result in emissions to the air, earth, and water. Embodied carbon is the sum impact of all the greenhouse gas emissions attributed to the materials throughout their life cycle (extracting from the ground, manufacturing, construction, maintenance and end of life/disposal).

Significant progress has been made to understand how to reduce operational emissions. However, there is a gap in our knowledge and effort toward reducing embodied emissions. The Carbon Leadership Forum is working to bridge that gap to enable a comprehensive understanding of all emissions from buildings throughout their life cycle.

Life Cycle Approach

Environmental Life Cycle Assessment (LCA) is a standardized method used to quantify environmental impacts of buildings from material extraction and product manufacturing through use and end of life and disposal.