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The Power of Estimated Carbon Emissions to Drive Climate Action

We know that the building industry contributes a full 38% of all greenhouse gases worldwide. But, how did experts arrive at that percentage? 

Think about the approaches to measurement we use in everyday life. Calorie counter tools like Noom or MyFitnessPal don’t measure every single calorie in every bite. Instead, they provide calculations based on ingredients, portion sizes, and self-reported data which gives us a good estimate of the calories in, say, a bowl of ice cream vs. quinoa* to help us make an informed decision.

Think about calorie counters like MyFitnessPal, which make calculations based on ingredients, portion sizes, and self-reported data to give us informed, directional data.

The methods used to measure carbon emissions mirror this approach. Many of the techniques to calculate emissions are still early-stage, but they’re surprisingly effective at providing direction and moving the needle towards decarbonization.

The building industry has long relied on life cycle assessments (LCAs) to estimate the environmental impact of building projects. They’re already helping developers and city planners to prioritize low-emission building practices—what if we could make similar estimations easier and faster? Let’s take a closer look at how all this works.

* the answer may surprise you!

How are carbon emissions measured on a macro level?

Countries that signed on to the Paris Climate Agreement need to measure carbon emission cuts as they progress towards ​​limiting global warming to 1.5°C. Most countries use a “bottoms-up” approach that calculates national emissions according to specific activities, such as transportation, manufacturing, and agriculture. 

But, short of sticking a monitoring meter on every tailpipe, landfill, and cow, it’s impossible to get perfect data on each country’s greenhouse gas emissions. Instead, governments track inputs that contribute to emissions: the number of gallons of fossil fuels consumed, how many cattle are raised, and the total tons of waste produced. “From there, it’s just a matter of doing the right calculations,” reported Slate

Short of sticking a meter on every tailpipe, landfill, and cow, it’s impossible to get perfect data.

Some experts have criticized these calculations for being approximate. A 2016 report found that national carbon emissions are known “within 5-10% for most developed countries,” with the error on developing countries estimated to be “larger by unknown amounts.” 

However, approximations within 5-10% of actuals are surprisingly high, and are continuing to improve with more data and better technology. And measurement, even if imprecise, is crucial to motivate countries towards change as well as hold them accountable for reaching carbon reduction goals. Becoming comfortable with these fuzzy numbers, especially if everyone is being measured on the same scale, is important to help us move forward.

How are carbon emissions measured in the building industry?

The basic process is the same in the building industry: a bunch of small best guesses add up to create a bigger-picture measurement of total emissions for a particular structure or city. 

The building industry most commonly uses a methodology known as the Life Cycle Assessment (LCA). LCAs evaluate the environmental impact of buildings using data from their processes, materials, and use throughout the whole life cycle of the structure from cradle to grave. 

The comprehensive LCA format prompts builders to think through how to reduce emissions at every stage of the process.

An LCA estimates emissions across four stages, as defined by the Carbon Leadership Forum

  1. Production and construction stages: Including the energy used to extract raw materials, transport them to the construction site, power the equipment used to construct the building, and disposal of waste during the construction process. 
  2. Use stage: Including the energy used for lighting, heat, water, and repair or renovation of the building during its occupancy. 
  3. End-of-life stage: Including the energy used for demolition, disposal, and waste processing of the building if not repurposed for further use.
  4. “Externalized impacts beyond the system boundary”: This refers to the miscellaneous effects of reusing, recycling, or recovering materials or water from the project. 

LCAs are generally considered the best way to calculate the carbon emissions of a building, despite some studies questioning their accuracy. In our conversations with contractors and other experts in the industry, they acknowledge that even commissioning an LCA from two different providers often yields two different results. Besides the fluctuations in operational carbon during building usage, long-term estimations are complicated by the changing energy grid supplying the building. 

Although LCAs may be imperfect, the four-stage format prompts builders to think through how to reduce emissions at every stage of the process. LCAs are a step in the right direction toward meaningful decarbonization. 

Measuring emissions will keep improving

New technology and innovative approaches are rapidly improving the ways we measure emissions across industries. Europe, for instance, will put GHG sensors in as many as 600 commercial flights per year to measure greenhouse gases. Satellites can now pinpoint methane leaks and other emissions back to the source. The European Space Agency’s TROPOMI satellite provides accurate and timely observations of key atmospheric indicators, such as air quality, climate, and the ozone layer. 

In the building industry, the Carbon Leadership Forum has developed the CARE tool to quantify the carbon “savings” for retrofit or building reuse projects versus new construction. It empowers stakeholders to answer thorny questions with data – like “What if a retrofit achieves only a 50% reduction and you can replace it with a zero operating emissions building? What if a large addition is required to increase density or accommodate new uses? How does climate zone, grid intensity, and the condition of the existing building affect those considerations?”

CLF's new CARE tool helps compare estimated carbon savings for retrofits and reuse projects versus new construction.

Elsewhere, Princeton’s Zero Emissions Calculator for Communities (ZECC) will help city planners make greener choices based on emissions data. With this information, developers can make better decisions to invest in projects that move the needle toward decarbonization.

Ultimately, all efforts to measure emissions will bring us closer to a more accurate picture of what it will take to reach net zero. And, in the process, these efforts are supporting immediate changes that matter. 

You can’t manage what you don’t measure

LCAs are already influencing construction companies and property developers to make sustainable building practices part of business as usual. 

“More than five decades after it's been introduced, the demand for LCA is on the rise due to the accelerating environmental concerns—and keeps soaring,” wrote one architecture firm. “In the construction industry, it’s already been standardized by use of Environmental Product Declarations (EPDs). Several green building certification schemes, such as LEED and BREEAM, give building planners credits for providing EPDs for their selected construction products.” 

Construction projects that fail to make a meaningful effort to decarbonize will find themselves falling behind. The market demand for green building practices is strong; carbon-neutral buildings command higher rents, too. Tenants and consumers in general are demonstrating that reducing carbon emissions by any measure is more important than getting the number perfect. 

As more data is made available at scale to benchmark the built environment, policymakers and the building industry can gain insight into where we've improved and where we still need to focus. But, the problem is too urgent to wait until we have perfect systems for measurement—if that is even feasible. We have to act now, and informed estimates are a powerful way to start.


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