A carbon footprint is the total amount of greenhouse gases (GHGs) produced to directly and indirectly support human activities, expressed as a single figure. This is typically measured in tonnes of carbon dioxide equivalent (CO2e) per year. The term accounts for all six major greenhouse gases outlined in the Kyoto Protocol, including carbon dioxide, methane, nitrous oxide, and fluorinated gases.
Explanation: In the context of the UK residential sector, a home's carbon footprint is primarily a measure of the emissions generated from its construction, operation, and maintenance.
Operational Carbon: This refers to the emissions generated by the day-to-day use of a building. The largest contributor here is typically the energy used for heating, hot water, and electricity. For example, a house with an old, inefficient gas boiler will have a significantly higher operational carbon footprint than a modern, well-insulated home with an air source heat pump. The emissions associated with operational energy use are a key focus of Building Regulations, specifically Approved Document L (Conservation of fuel and power), which sets standards for a building's thermal performance and energy efficiency.
Embodied Carbon: This accounts for the emissions produced during the entire lifecycle of a building, from the extraction of raw materials and manufacturing of building products to their transport, installation, and eventual disposal or demolition. Retrofitting a house, for instance, might reduce operational carbon by improving insulation, but the production and installation of that insulation will have its own embodied carbon footprint. The goal is to choose materials and methods that minimise both embodied and operational carbon over the building's lifespan.
When we talk about reducing a home's carbon footprint, we're considering both its energy use and the materials used in its construction or renovation. The UK government's commitment to achieving net zero emissions by 2050 means there is a strong focus on decarbonising our housing stock, which includes improving energy efficiency and moving away from fossil fuel heating systems.