Tool calculates CO2 emissions from buildings

USA: A US team has developed what is claimed to be a first-of-its-kind tool that can calculate how much carbon dioxide buildings and homes produce.

The new CO2e Rating Index tool will allow researchers to calculate energy efficiency on a whole new level, the developers say. For example, it can calculate and compare the emissions from one house using renewable energy against one that is not energy-efficient. In that way it can produce estimates showing how much renewable electrification can reduce carbon emissions on a day-by-day basis.

Another benefit of the CO2 Rating Index is that researchers can now show that carbon emissions are directly dependent on when electricity is being used and is also affected by weather and other conditions.

This would allow for the implementation of energy efficiency measures, such as programming a heat pump water heater to raise water storage temperatures during “green time,” when carbon emissions are at the lowest, or reduce the heating during “red time,” when emissions are at the highest.

“While the auto industry has made great strides in reducing carbon emissions from vehicles, the most well-known emitter of CO2, many people don’t know that buildings themselves are responsible for about 35% of greenhouse gas emissions due to burning fossil fuels for power, heating and cooling,” said Philip Fairey, deputy director of the University of Central Florida (UCF) FSEC Energy Research Centre, and a board member of the Residential Energy Services Network (RESNET), which developed the tool.

RESNET is a not-for-profit organisation founded to develop a national market for home energy efficiency.

Fairey presented the CO2e Rating Index at the ASHRAE International Building Decarbonisation 2022 Conference this month in Greece. 

Previously, RESNET established what is known as the Home Energy Rating System, or HERS, Index, which is a measurement that allows for easy comparison of energy performance of homes.

The HERS Index provides the consumer information on how energy efficient their home is compared to other homes.

While the HERS Index is valuable in determining energy efficiency and showing how renewable energy is more beneficial than energy obtained from fossil fuels, there haven’t been any tools to show the effectiveness of building decarbonisation.

The tool will be used by trained specialised home raters to rate homes along with the current HERS tool rating index.

“While the HERS Index is based on total annual energy consumption, we realised we couldn’t use the same process to evaluate CO2 emissions because utilities produce carbon at different intensities and different times of the day and the year,” Fairey said.

“Weather conditions greatly affect CO2 emissions, and the CO2e index software allows us to evaluate these different conditions during different times of the day and different months of the year to gain an accurate estimate of carbon emissions. And since the emissions produced by electricity generation are expected to decrease over time as power generation becomes cleaner, the long-term generation emissions are more consequential than the short-term emissions.”