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Jargon Buster

A consistent message so everyone knows what everything really means


Airtight Construction
Airtight construction is draught-free construction. It is an essential part of the Passivhaus Standard (see meaning) to protect the building envelope from moisture, to ensure energy efficiency and to provide exceptional comfort.

Airtightness Test
Also known as an air pressure test, or a blower door test, this measures the total air leakage through the building envelope. It is presented as n50 or q50 tests and results – both testing air leakage.


The variety of plants (flora) and animals (fauna) life in a particular habitat but inclusive of all living things, from trees and flowers to animals and fungi, insects and microorganisms.

Biodiversity Net Gain
A development approach that measures the amount of biodiversity in a particular area which then has to be left in a better state (i.e. greater biodiversity) after the development works have been completed.

A Building Management System (BMS) or Building Energy Management System (BEMS) is a digital system to centrally manage a building’s mechanical and electrical equipment to control a building’s internal climate and environment e.g. monitor and adjust lighting etc.


Carbon is the common abbreviation for carbon dioxide equivalent (CO2e) within sustainability and greenhouse gas reporting but is not to be confused with carbon as a singular element or carbon dioxide (CO2) as a gas. Carbon dioxide is the most prevalent greenhouse gas and arises from numerous processes, such as burning fossil fuels. However, it is not the only greenhouse gas, so CO2e is used as a single metric to incorporate the impact of all the greenhouse gasses.

Carbon Footprint
The measurement used to quanitify the carbon impact associated with an activity, business, product etc.

Carbon Negative
This means you have a quantifiable positive carbon impact – your offsetting and other positive impacts are greater than the negative impacts.

Carbon Neutral / Carbon Neutrality (CN)
Balancing the carbon dioxide (equivalent – all GHGs) that is released into the atmosphere through everyday activities with the amount that is absorbed or removed from the atmosphere.

CDP (Carbon Disclosure Project)
This is a global non-profit that runs the world’s environmental disclosure system for investors, companies, cities and governments to assess their impact and take urgent action to build a truly sustainable economy. The CPD have created a system that has resulted in corporate engagement on environmental issues worldwide.

CSR (Corporate Social Responsibility)
This includes all environmental, economic, and social aspects of a company’s practices, policies, and decision-making. Its commitment serves as an important pillar for corporate culture and gives the stakeholders insights into company values. CSR is self-regulated and varies widely from one organisation to another. It denotes the company’s responsibility to society. It is an ideal practice that gives context to the sustainability agenda but is not limited to sustainability.


Demand Side Response
Demand side response is about intelligent energy use, to reduce energy demand in a building in response to building management needs, or even that of the local/national grid. Through a DSR enabled Building Management System (BMS), businesses and consumers can alter demand in real time. This could be enforcing power downs, reducing lux (illuminescence/lighting) levels in areas or altering temperature/environment controls, for a short period of time, for example.


Embodied Carbon
The carbon that is emitted in the construction of a building, through manufacturing, transport, storage and construction related activities up to Practical Completion (PC).  This should be inclusive of scope 1, 2 and 3 emissions (see meaning). Embodied carbon includes the following project lifecycle stages that cover cradle to practical completion:
A1-A3 – Product Stage – Raw material extraction and supply, transport to manufacturing plant, and manufacturing and fabrication
A4-A5 – Construction Process Stage – Transport to project site, and construction and installation activities

Enerphit (Passivhaus)
This is the Passivhaus Standard for retrofitting older buildings. The criteria for meeting the standard are relaxed slightly to acknowledge the challenges in insulating existing buildings.

EPD (Environmental Product Declaration)
An Environmental Product Declaration (EPD) is a standardized document informing about a product’s environmental impact and Life Cycle Assessment (see meaning). At minimum this should cover during manufacture (cradle to gate) but can extend to cradle to grave. The EPD provides a quantitative basis for comparison of products and services. It is normally provided by the product manufacturer and must be verified by an independent expert.

ESG (Environmental, Social and Governance)
ESG refers to a collection of Environmental, Social and Governance corporate performance evaluation criteria that assess the robustness of a company’s governance mechanisms and its ability to effectively manage its environmental and social impacts. Its purpose is to reduce risk and maximize opportunities for the company to maximise profitability ESG involves the disclosure of ESG data using a recognised framework, as such it makes it easier to compare companies. Its main audience is investors, customers, and suppliers.

ETS (Emissions Trading Standards)
ETS is an explicit carbon pricing instrument that limits or caps the allowed amount of GHG emissions and lets market forces disclose the carbon price through emitters trading emissions allowances.


Green Hydrogen
Green hydrogen is generated using renewable or low carbon energy and is lowest carbon form of hydrogen production. The process only emits water vapour.

Green Infrastructure
Green infrastructure is the development of a network of ‘green’ spaces and features, that deliver multi-benefits to their immediate environment, whether urban or rural. In the context of an urban regeneration scheme, Green Infrastructure may include tree planting, soft landscaping, green roofs, living walls etc. that may provide amenity, aesthetic biodiversity, air quality and natural cooling/shading benefits, amongst others.

Green-Blue Infrastructure
Similar to Green Infrastructure, Green-Blue Infrastructure has the additional benefit of being designed to improve, manage or control water movement in an area. In an urban environment, examples could include Sustainable Drainage Solutions (SuDS) such as swales, or green-blue roofs (green roofs designed to retain water from rainfall). These can provide benefits as with green infrastructure, but also support surface water and flood water management to reduce the risk of the flooding or extreme weather events causing disruption.

Greenhouse Gases
Greenhouse gases, such as carbon dioxide and methane, trap and hold heat in the atmosphere and contribute to climate change. Much of human activity emits greenhouse gases, such as burning fossil fuels for energy and transport, farming land for food production, and deforestation.

Greenwashing (aka Green Sheen)
Suggesting a business or product is performing at a higher level than it is. This could be an exageration or misleading, at one end of the scale, through to deliberately converying a false impression to deceive at the other end. Either way, it is the act of over-stating sustainability performance to convey a better image than the reality.

Grey Hydrogen
Grey hydrogen is produced using steam which is generated from fuels such as natural gas. Therefore this is not a renewable or low carbon hydrogen generation method.

A measure of how much solar heat gain is admitted through glass.


Heat Load
The maximum heat required for a room/area to reach an acceptable temperature on the coldest day of the year. It is measured in watts per square metre of floor area. (W/m²)

Heat Loss Form Factor
The ratio of a building’s thermal envelope surface (i.e. the insulated walls, floors etc.) area to the Treated Floor Area.  It is a useful measure of the compactness of a building. The more compact a building is, the easier it is to be energy efficient.


This is uncontrolled ventilation arising from the unintentional introduction of outside air into a building, through gaps in the building envelope.


LETI (London Energy Transformation Intiative)
This is a network of over 1000 built environment professionals that are working together to put the UK on the path to a zero carbon future. The voluntary group is made up of developers, engineers, housing associations, architects, planners, academics, sustainability professionals, contractors and facilities managers.

Life Cycle Assessment (LCA)
This is a standardised, science-based tool for quantifying the impact of multiple products & processes in order to assess lifetime environmental impact. It takes into consideration all the steps that lead from raw material through manufacture, distribution and usage to final disposal. An LCA can both measure a building’s lifetime impacts and, at the same time, quantify the impact of a single material in the building.


This is the measure of airtightness used in the Passivhaus Standard. It is the total number of air changes per hour at 50 Pascals. (ach@50Pa) – Pascals are a unit of pressure.

Nabers UK
This is the measure of airtightness used in the Passivhaus Standard. It is the total number of air changes per hour at 50 Pascals. (ach@50Pa) – Pascals are a unit of pressure.

Net Zero Carbon (NZC)
This requires consideration of Scope 1, 2 and 3 emissions (see meaning). These are supported with a proactive and positive set of actions to minimise emissions before then looking to offset the remaining emissions.


Offsetting / Carbon Offsetting
The process of investing in schemes that sequester (or absorb) CO2 (or CO2e) from the atmosphere. In theory, this allows for the balance or offset of the emissions calculated with the natural sequestration.

Operational Carbon
The carbon that is emitted during the in-use operation of a building or asset. This should be inclusive of scope 1, 2 and 3 emissions (see meaning). This should be subject to on-going monitoring and annual reporting as a minimum, to allow for offsetting. Operational carbon includes the following project lifecycle stages that cover building operation:
B1-B5 – Use Stage – Use, Maintenance, Repair, Replacement and Refurbishment
B6 – Use Stage – Operational energy use
B7 – Use Stage – Operational water use


Paris Agreement
A legally binding international treaty on climate change, adopted at COP21 in Paris in 2015. Its goal is to limit global warming to well below 2, preferably to 1.5 degrees Celsius, compared to pre-industrial levels.

Performance Gap
Is the difference between the thermal performance predicted from building modelling and the actual measured energy in-use once the building is built and occupied.

Primary Energy Demand
This is the energy demand for heating, domestic hot water, auxiliary power and household electricity, divided by the floor area. It includes the energy losses from distribution, conversion and delivery of the fuel to the end-user. It is presented per square metre of floor area per year. (kWh/m².yr)


This is the measure of airtightness used in the Building Regulations. It is the volume of air changing per hour through each m² of building fabric at 50 Pascals. (m³/h/m²@50Pa) – Pascals are a unit of pressure.


RIBA 2030 Challenge
A RIBA backed initiative to provide a stepped approach to reaching NZ across operational energy, embodied carbon and potable water.


Science Based Targets
Provide a clearly-defined pathway for companies and financial institutions to reduce greenhouse gas emissions in line with what the latest climate science deems necessary to meet the goals of the Paris Agreement.

Scope 1 emissions
Scope 1 greenhouse gas emissions are released as a direct result of an activity carried out by an organisation or process, also known as direct emissions e.g. from transportation or heating via an on-site boiler.

Scope 2 emissions
Scope 2 greenhouse gas emissions are indirect emissions created by the purchasing of energy that is used by the organisation or process.

Scope 3 emissions
Scope 3 greenhouse gas emissions are also indirect emissions, but are created through 15 categories (Purchased goods or services, capital goods, fuel- and energy-related activities, upstream transportation and distribution, waste generated, business travel, employee commuting, upstream leased assets, downstream transportation and distribution, processing of sold products, use of sold products, end-of-life treatment of products, downstream leased assets, franchises, and investments). Not all categories will relate to every organisation but are required for net zero carbon economies. Scope 3 emissions are typically more difficult to calculate as they are not directly within an organisation’s control and are reliant upon supply chain and upstream partners to share information about various processes.

SECR requires obligated companies to report on their energy consumption, efficiency measures and associated greenhouse gas emissions with reference to an intensity metric within their financial reporting for Companies House. Organisations must comply with the legislation if they meet two or more of the qualification criteria below: – 250 or more employees, – Turnover in excess of £36 million, – Balance sheet in excess of £18 million.

Space Heating Demand
The total energy required to heat the building for a year. It is presented per square metre of floor area per year. (kWh/m².yr)

Sustainability is focused on how a business affects the world. It is driven by the need to have a positive impact on financial, social, and environmental aspects of the company’s influence and is not necessarily related to maximising profits. This approach does not follow a recognised framework and can be challenging to understand impact. Although an Environmental or Carbon Management System and ISO14001 can establish robust policies and procedures that support wider sustainability management, sustainability management encompasses more principles than these systems.


Task Force on Climate-related Financial Disclosures (TCFD) is an investor-focused disclosure framework that asks companies to supply information on the environment’s impact on them. That is, the risks that climate change may pose to its operations. It encourages firms to align disclosures to what investors need to inform their decisions – both on the positive and negative side. Firms that are taking proactive measures to build climate resilience into their scenario planning may benefit by disclosing through TCFD to signal their efforts to investors.

Thermal Bridge
A localised weak area in the envelope of a building where heat flow is increased compared to adjacent areas.

Thermal Envelope
A thermal envelope aims to form an environment that prevents drafts and heat transfer from a building’s interior to the exterior. It is the structure that separates the external environment with the internal environment – more than air separation, this is about thermal (heat) transfer.

Treated Floor Area (TFA)
The useful floor area within the thermal envelope (i.e. insulated wall, floor ceiling etc.) of the building.


A measure of heat loss through a building element. It is measured in watts per square meter of surface per degree of temperature difference between inside and outside. (W/m².K)


Whole Life Carbon
Whole Life Carbon assessment (sometimes referred to as Life Cycle Assessment or LCA) describes the combined impacts of both operational and embodied emissions over a building’s entire lifecycle and its ultimate disposal. Similar to Whole Life Cost, Whole Life Carbon should be managed and assessed to minimise overall carbon emissions over a building’s entire life cycle and therefore support decision making to maximise carbon saving measures during design and construction phases.
Lifecycle stages B1-B7, C and D are also considered when reviewing whole life carbon


Zero Carbon
Zero carbon describes something (process, product, business) with no carbon impact and does not require reduction/offsetting. This is a rare status.

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