Biomass: Living or recently-dead organic material that can be converted into use as an energy source e.g. wood, agricultural crops and waste or ethanol and methane.

BREEAM: It stands for Building Research Establishment Environmental Assessment Method. An environmental assessment method for non-domestic buildings widely used across the UK.

Carbon Emissions: Also known as carbon dioxide (CO2), it is the primary greenhouse gas emitted through human activities. Carbon dioxide is naturally present in the atmosphere as part of the Earth's carbon cycle. Human activities are altering the carbon cycle, both by adding more CO2 to the atmosphere and by influencing the ability of natural sinks to remove CO2 from the atmosphere.

Carbon Footprint: The total amount of greenhouse gases emitted through an activity or from a product, company or person either directly or indirectly. It is generally expressed in equivalent tons of either carbon or carbon dioxide.

Carbon Neutral: Achieving carbon neutrality means measuring the carbon emissions, then balancing those emissions with carbon reductions or carbon offsets to reach net zero carbon emissions. CHP: It stands for Combined Heat and Power. The simultaneous generation of usable heat and power a single process.

Climate Change: A 'statistically significant' change in the "average weather" that a given region experiences. Climate change on a global scale refers to changes in the climate of the Earth as a whole, including temperature increases (global warming) or decreases, and shifts in wind.

Cogeneration or Combine Heat and Power (CHP): The use of a heat engine or power station to simultaneously generate electricity and useful heat.

Commissioning: Commissioning is the process whereby a building’s systems are tested and adjusted to ensure they are all functioning as they were designed to.

CO2e: Equivalent carbon dioxide (CO2e) is a distinct measure for describing how much global warming a given type and amount of greenhouse gas may cause, using the functionally equivalent concentration amount of carbon dioxide (CO2) as the reference.

Corporate Social Responsibility (CSR): A form of corporate self-regulation, whereby a business monitors and ensures its active compliance with the spirit of the law, ethical standards and international norms. In some models, CSR engages in "actions that appear to further some social good, beyond the interests of the firm and that which is required by law”.

Cost Benefit Analysis: a systematic estimation of strengths and weaknesses to determine options that provide the best approach for the adoption and practice in terms of benefits in labour, time and cost savings.

Deep Renovation: A building renovation term that captures the full economic energy efficiency potential of improvements. This typically includes a focus on the building shell of existing buildings in order to achieve very high-energy performance.

District Cooling: Working on broadly similar principles to district heating, district cooling delivers chilled water to buildings. In winter, the source for the cooling can often be sea water, so it is a cheaper resource than using electricity to run compressors for cooling.

District Heating: A system for distributing heat generated in a centralized location for residential and commercial heating requirements such as space heating and water heating.

Display Energy Certificates: Display Energy Certificates (DECs) provide an A-G rating for non-domestic buildings based on actual energy use, incorporating all energy uses in the building. UK-GBC has long called for their extension from public only to all non-domestic buildings.

Embedded Carbon: A generic term used to describe the range of greenhouse gas (GHG) emissions associated with the production of a product.

Energy: All forms of commercially available energy: electricity, natural gas, liquefied natural gas, liquefied petroleum gas, any fuel used for heating and cooling, coal, lignite, transport fuels, renewable energy sources (RES).

Energy Audit (Assessment): An inspection, survey and analysis of energy flows in a building or group of buildings, industrial process or installation with the objective of understanding the energy dynamics of the system under study.

Energy Consumer: A natural person or legal entity purchasing energy for his own end use.

Energy Efficiency: The use of less energy to fulfil the same function or purpose; usually attributed to a technological fix rather than a change in behavior.

Energy Management System (EMS): A system of computer-aided tools used by operators of electric utility grids to monitor, control, and optimize the performance of the generation and/or transmission system.

Energy Performance Contract: A contractual agreement between the beneficiary and the provider for the implementation of an energy efficiency measure, according to which payments for the investments are made in relation to the contractually agreed level of energy efficiency attained.

Energy Performance Measures: All actions that normally lead to a verifiable or measurable energy efficiency improvement.

Energy Savings: An amount of saved energy, which is determined by measuring and/or estimating consumption before and after the implementation of one or more energy efficiency measures.

EPBD: Its stands for Energy Performance of Buildings Directive. The Directive is the Directive 2010/31/EU (EPBD, 2003) of the European Parliament and Council on energy efficiency of buildings.

EPC: It stands for Energy Performance Certification. All commercial properties require an EPC which rates the energy efficiency of the building on a scale of A-G, where A signifies the highest level of efficiency. The EPC provides an asset rating of the building fabric and fixed services, based on a survey of the building.

ESCO: An energy service company or energy savings company is a commercial or non-profit business providing a broad range of energy solutions including designs and implementation of energy savings projects, retrofitting, energy infrastructure outsourcing, power generation and energy supply.

Facility Management: An interdisciplinary field devoted to the coordination of space, infrastructure, people and organization, often associated with the administration of office blocks, arenas, schools, convention centers, shopping complexes, hospitals, hotels etc

Feed in Tariff (FiT): A policy mechanism that is designed to encourage the adoption of renewable energy technologies and to help accelerate the move toward security of supply and grid parity.

Fossil Fuel: Any fuel source such as natural gas, fuel oil, coal that has a finite supply.

Fundraising: The process of soliciting and gathering voluntary contributions of money or other resources, by requesting donations from individuals, businesses, charitable foundations, or governmental agencies.

Global Warming: An increased warming of the Earth's atmosphere which can be caused by an increase of man-made gases that trap the sun's heat. This can effect changes such as sea level rises, changes in rainfall patterns and frequency, habitat loss and droughts.

Green Building: A comprehensive process of design and construction that employs techniques to minimise adverse environmental impacts and reduce the energy consumption of a building, while contributing to the health and productivity of its occupants.

Greenhouse Gas (GHG): These gases are so named because they contribute to the greenhouse effect due to high concentrations of these gases remaining in the atmosphere. The GHGs of most concern include carbon dioxide (CO2), methane (CH4), nitrous oxides (N2O).

Heat Pump: A system of groundsource pipes that extracts naturally occurring heat from the ground and increases its temperature using a heat pump. The heat is then used to provide building heating or hot water.

Investment Holding Period: The real or expected period of time during which an investment is attributable to a particular investor.

Investment Payback: A period in capital budgeting refers to the period of time required to recoup the funds expended in an investment, or to reach the break-even point.

LEED: It stands for Leadership in Energy and Environmental Design. A US developed green building rating system that encourages and accelerates the global adoption of sustainable green building and development practices.

Life Cycle Costing: A procurement evaluation technique which determines the total cost of acquisition, operation, maintenance, and disposal of items potentially being acquired.

Negawatt: A theoretical unit of power representing an amount of energy (measured in watts) saved. The energy saved is a direct result of energy conservation or increased energy efficiency. The term was coined by the chief scientist of the Rocky Mountain Institute Amory Lovins in 1989.

Private Finance Initiative (PFI): A way of funding public infrastructure projects with private capital. Developed initially by Australia and the United Kingdom, its variants have now been adopted in many countries driven by an increased need for accountability and efficiency for public spending.

Private Public Partnerships (PPP): A government service, which is funded and operated through a partnership of government and one or more private sector companies. PPP involves a contract between a public sector authority and a private party, in which the private party provides a public service or project and assumes substantial financial, technical and operational risk in the project.

PV (Photovoltaic): Solar photovoltaic's (PV) collectors are arrays of cells containing a material that converts solar radiation into electricity.

Recycling: The series of activities, including collection, separation, and processing, by which materials are recovered from the waste stream for use as raw materials in the manufacture of new products.

Renewables:  Generally defined as energy that comes from resources which are naturally replenished on a human timescale such as sunlight, wind, rain, tides, waves and geothermal heat. Renewable energy replaces conventional fuels in four distinct areas: electricity generation, hot water/space heating, motor fuels and rural off-grid energy services.

Retrofit: The process of modifying something after it has been manufactured. For buildings, this means making changes to the systems inside the building or even the structure itself at some point after its initial construction and occupation.

Refurbishment: During a refurbishment a building is improved above and beyond its initial condition. Refurbishments are often focussed on aesthetics and tenant amenities, but they can also include upgrades to the building’s mechanical systems and can potentially have an effect on energy and water efficiency.

Renovation: Renovations are very similar to refurbishments and the terms are sometimes used interchangeably. The major difference is the term renovation applies specifically to buildings, while refurbishment does not.

Return on Investment (ROI): A performance measure used to evaluate the efficiency of an investment or to compare the efficiency of a number of different investments. In purely economic terms, it is one way of considering profits in relation to capital invested.

Solar Heat Water (Panels): Panels that collect the solar radiation from the sun and use it to heat a liquid inside. This liquid then transfers its heat to the hot water in a cylinder for use in hot water requirements, e.g. domestic hot water.

Sustainability: The most widely accepted definition comes from "Our Common Future," Report of WCED, commonly known as the Brundtland Report (1983). It says "Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs."

Third-Party Financing: A contractual agreement under which a third party – in addition to the service provider, the energy supplier and the beneficiary of the energy efficiency measure – provides the capital needed for that measure and charges the beneficiary with a fee equivalent to part of the energy savings achieved through the energy efficiency improvement measure. The third party in question may or may not be an ESCO.

Waste-to-Energy: The burning of waste in a controlled-environment incinerator to generate steam, heat, or electricity.