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dot Survey of Energy Tools

dot Survey of Carbon Calculators

dash Comparing Carbon Calculation Tools

dash Comparing CO2 Emissions in Carbon Counting Tools due to Natural Gas and Electricity

dash Comparing CO2 Emissions in Carbon Counting Tools from Different Climates

dash Results: Carbon Emissions in Four Climates

dash Discussion, Conclusions

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The Carbon Neutral Design Project:
Carbon Calculation Tools:
Survey of Carbon Calculators


Pablo la Roche PhD
Associate Professor of Architecture

Charles Campanella
Research Assistant

California State Polytechnic University, Pomona
Department of Architecture
3801 West Temple Avenue
Pomona, CA 91768


NOTE: This research project is broken into a number of web pages. Please follow the links at the left, or the PREV and NEXT arrows at the bottom of the page to advance between sections.

PDF of full Research Report


Climate change is caused by an increase in the concentration of green house gas emissions due to human activities and is the most pressing environmental challenge facing our civilization. Buildings are responsible for a large portion of the world’s green house gas emissions and in the United States they are responsible for about half of all green house gas emissions of anthropogenic origin. To reduce human impact on climate it is necessary to reduce building related anthropogenic warming and the first step in this reduction process is to be able to adequately count carbon emissions. Accurate carbon counting, especially in the initial phases of the design process, will help to quantify the impact -in units of carbon emissions- of our design decisions in the project.

The objective of this project was to compare several carbon counting tools that can be used to quantify carbon emissions from residential buildings. Several carbon calculators and some energy modeling software were compared in the main areas in which buildings generate carbon emissions: a) operational energy, b) transportation to and from the building, c) providing water and disposing of water to and from the building, d) construction of the building and e) disposing of waste from the building.

The tools that are compared in this project had to be free and easy to use so that they could be used in the initial phases of the architectural design process, while providing sufficient precision to provide some useful input to the designer.  Fifty tools were analyzed. Ten of these tools provided no useful information for designers while forty of these provided useful results in at least one of the above mentioned areas. These forty tools are compared and organized in a table that indicates the types of results that they provide. A more detailed comparison is done in the area of operational energy. At the end a protocol for carbon counting with tool recommendations is provided.


1.1. Types of Carbon Counting Tools

There are several types of carbon calculating tools: carbon footprint calculators, which are available online to determine personal carbon emissions; carbon estimators, also available online for estimations of carbon emissions of buildings; and carbon calculators, which are available for purchase and that work with BIM systems for a more accurate analysis (1). This paper deals primarily with carbon footprint calculators and carbon estimators. Estimators usually produce results which are more usable for the designer than footprint calculators.

A building is directly responsible for the generation of CO2 by its operation, construction, water use, and waste generation (2). The building is also indirectly responsible for CO2 emissions generated by transportation to and from the building, which was also included. Most carbon counting tools offer the possibility to determine emissions from energy use in buildings and from transportation. Fewer of them can determine emissions due to water, waste or construction. A handful of these also offer the possibility to calculate the carbon impact from the food that we eat. Even though this could be a significant factor it was not considered because it could not be modified by the designer.

1.2. Carbon Emissions from Buildings

Energy used to operate the buildings is usually the single largest contributor to CO2 emissions. These emissions can be caused by energy used directly at the site (such as natural gas) or at the power plant (electricity). Emissions from operational energy include, heating, cooling, lighting and appliances. The tools that we have available to calculate operational energy offer acceptable precision, because they estimate the energy use in a proposed building, usually with energy modeling software. In an existing building the energy actually used in the building can be taken from the meter.

Carbon emissions due to construction processes are usually generated a) during the fabrication of the materials used in the building; b) during the transportation of materials to the building; and c) during construction of the building. These emissions are usually more difficult to calculate because it is not easy to determine with precision the origin and the amount of materials in the building.

Water provided to the building and coming out of the building also generates CO2 emissions. The water used in the building must be pumped from the source and treated while the waste water from the building must also be treated to remove physical, chemical and biological contaminants. These processes usually generate CO2 emissions.

Solid waste (not transported in water) coming from the building must also be moved from the building and treated. More waste requires more treatment and usually generates more greenhouse gases in the form of methane from the landfills.

People must move to and from the building, and the method by which they do this usually generates CO2 in varying amounts (bus, train, automobile) or non at all (walking, bicycle). Location of the building close to public transit lines or in urban areas with higher density usually helps to reduce CO2 emissions from transportation.


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