Zero carbon housing  Zero-carbon housing and zero-energy housing are terms used interchangeably to define single family dwellings with a very high energy efficiency rating. Zero-energy housing requires a very low amount of energy to provide the daily needs and functions for the family occupying the home. The term carbon footprint, at present, does not have a concrete and universal definition. Thomas Wiedmann proposed a well received and generally accepted definition that defines carbon footprint as a measure of the total amount of carbon dioxide emissions directly and indirectly caused by an activity or accumulated over the life stages of a product. A carbon footprint can be divided into 4 levels: personal, product, organizational, and country. A personal carbon footprint is a measure of greenhouse gas emissions that are a result of daily life. Examples of contributors to personal carbon footprint are clothing, food, housing, and traffic. The emissions from the entire life of a product, extraction of raw materials and manufacturing, and recycling or disposal contribute to product carbon footprint. Greenhouse gas emissions from energy used in buildings, industrial processes, and company vehicles account for organizational carbon footprints. An entire country collectively generates a carbon footprint from carbon dioxide emissions generated by the consumption of materials and energy, vegetations and other carbon sequestrations, as well as the indirect and direct emissions caused by import and export activities. Zero carbon housing is a result of the building sector being one of the largest contributors to greenhouse gas emissions in urban areas. The calculation of the carbon footprint becomes detailed when considering secondary factors. Secondary factors involve the home’s occupant lifestyle such as diet, foods are consumed (example organic vs. non organic), frequency of yearly air travel, commuting mileage to and from work, school, etc., use of public transportation, and number, type, and use of private vehicles. Secondary factors also include fashion or type of clothes purchased and worn, frequency of recycling, recreational activities and use of financial and other services throughout a given year. The frequency of airline flights in a year is considered due to the amount of fuel consumption and other energy usage and emissions generated by one flight. A person that travels frequently may have a significantly bigger carbon footprint than someone who flies once a year for a vacation. The emissions for an individual flight are calculated by using the greater circle method. First, the distance between airports is determined. Then calculations are completed to account for indirect distances and by an emissions factor in relation to the type of flight (international or a short flight, and what class seating the person is in). Another contributing factor to a person’s carbon footprint is their personal vehicle which includes the type of car driven, the efficiency or miles per gallon (MPG) rating, and the number of miles driven each year.