Measuring Carbon

When looking at a home’s carbon emissions, it’s important to measure embodied and operational carbon.

There are two types of carbon emissions associated with homes: embodied carbon and operational carbon. 

Embodied carbon incorporates emissions from the full life cycle of the home, including raw material extraction, shipping to the manufacturer, manufacturing, transport to the site, and construction and installation. Basically, it’s a measure of the home’s carbon emissions up until the day that home is sold.

Operational carbon represents emissions from the ongoing operation of the home, resulting largely from the energy used for heating, cooling, lighting, and appliances and other operating systems.

Measuring Embodied Carbon

The first step in measuring embodied carbon is to gather detailed data on the materials used in the construction of the home. High-impact materials like concrete, steel, and certain types of insulation drive up embodied carbon. Other products like wood, glass, and solar also contribute significantly.

Existing databases and Environmental Product Declarations (EPDs) offer emissions information—called emission factors—for each material. Emission factors indicate the amount of CO2 equivalent emissions per unit of material produced.

Then, a Life Cycle Assessment (LCA) can be conducted using software tools like Beam, EC3, or One Click LCA to calculate the embodied carbon of a home by integrating data on material quantities and emission factors.

For accuracy and credibility, embodied carbon assessments should be conducted and/or verified by a third-party auditor.

Finally, it’s important to document findings in a comprehensive report that details the methodology, data sources, assumptions, and results. This report can be used for certification purposes or stakeholder reports.

Measuring Operational Carbon

To measure operational carbon, first determine the energy consumption of the home. Energy modeling can be deployed for a new home. For existing homes, energy consumption data can be derived from utility bills, including electricity, natural gas, heating oil, and any other energy sources used. Smart meters and home energy monitoring systems can help collect precise, real-time data on energy use.

It's important to understand the energy mix used in the home. For example, if a home uses grid power sourced by fossil fuels, its operational carbon is going to be much higher than if it produces its own solar power. If the home is grid-tied, obtain information from the utility provider about the energy mix, including the percentage of energy coming from renewable sources versus fossil fuels.

Then, carbon emissions can be calculated using emission factors to convert energy consumption data into carbon emissions. Emission factors represent the amount of CO2 equivalent produced per unit of energy consumed and vary based on the energy source.

The Environmental Protection Agency provides emission factors for various fuels, and the International Energy Agency offers emission factors for different energy sources globally.

In order to create a formula, multiply the energy consumed (in kWh, therms, or other units) by the appropriate emission factor to get the total carbon emissions.

Be sure to incorporate all energy consuming elements, like HVAC, water heaters, appliances, lighting, and other miscellaneous electrical loads from electronic devices and TVs.

Sum up the monthly energy consumption data to get the annual energy use, and then use the corresponding emission factors to calculate the total operational carbon emissions for the year.

Achieving Net Zero Carbon

The first step in the journey to net zero carbon is utilizing sustainable design, building science, and green construction practices. Next, it’s essential to specify low carbon materials, for example those with Environmental Product Declarations. Once you’ve done everything you can to optimize performance, it’s paramount to purchase carbon offsets as the “last mile” solution to ensure that your projects are truly net zero carbon (and have a positive impact on the planet and people.)  

And, we can’t forget about the profit portion of the ‘PPP’ (people, planet, profit) equation. Building net zero carbon homes will not only elevate your brand, enhance your competitive advantage, and drive purchase intent with today’s discerning homeowners, they also sell faster, increase sale value, and can qualify for lower interest rates (for both construction loans and mortgages)!!  

Interested in learning more? Green Builder Media’s COGNITION Academy has robust courses on net zero carbon building, green building fundamentals, green product essentials and green building program like ENERGY STAR, Zero Energy Ready Homes, Indoor airPLUS, WaterSense, and HERS ratings. Visit the COGNITION Academy microsite for more information.

If you’re interested in purchasing carbon offsets to mitigate emissions from your products, projects or lifestyle, or if you want more information about Green Builder Media’s net zero carbon consulting services, contact me at sara.gutterman@greenbuildermedia.com.