AECB the sustainable building association

Air changes per hour (ac/h) (volumetric), the number of times per hour that the air inside a building is changed. Units m³ hr/ m³ @ 50 Pascals.

Air permeability defined in BS EN 13829. Units m³/m²hr at 50 Pascals or m/h @ 50 Pa.

Air leakage index per unit thermal envelope area (the CLP preferred definition). Units m³/m²hr at 50 Pascals or m/h @ 50 Pa.

BREEAM (Building Research Establishment Environmental Assessment Methodology) is the world’s longest established and most widely used method of assessing, rating, and certifying the sustainability of buildings

CLP The AECB’s Carbon Literate Design and Construction Programme

Cavity walls consist of two ‘skins’ separated by a hollow space (cavity)

Carbon Trust an independent partner of organisations around the world, helping them contribute to a more sustainable future through carbon reduction

Code for Sustainable Homes national standard launched in 2006 for the sustainable design and construction of new homes

Delivered energy the amount of energy which is supplied to final users, eg households, office buildings, schools, factories and cars

Energy Saving Trust a British organisation devoted to promoting the sustainable use of energy to reduce carbon dioxide emissions and helping prevent climate change

Embodied energy is the energy used to produce the materials with which a house is built. A house made using earth excavated from site has a lower embodied energy than one built using earth that has been imported because of the energy used in transportation.

Global Warming Potential (GWP) a measure of how much a given mass of greenhouse gas is estimated to contribute to global warming. It is a relative scale which compares the gas in question to that of the same mass of carbon dioxide (whose GWP is by definition 1). For example, methane, nitrous oxide and sulfur hexafluoride have GWPs many times that of CO2, although CO2 is being emitted into the atmosphere in much larger quantities.

Heat Loss Parameter (HLP) a building’s specific heat loss (in units of W/K) divided by the building’s floor area (measured internally i.e. within the thermal envelope). Units W/K.m²

Kyoto Protocol, also known as the Kyoto Accord, is an international treaty among industrialized nations that sets mandatory limits on greenhouse gas emissions. It was agreed in 1997.

Low-e glazing, or low-emissivity glass, is a type of energy-efficient glass designed to prevent heat escaping through an invisible coating which reflects heat back into the room

Manser Medal is awarded every year to the best new house designed by an architect in the UK. It was created in 2001 to celebrate excellence in housing design and was named to honour Michael Manser CBE, a designer of exceptional homes and former RIBA President.

Mechanical Ventilation with Heat Recovery (MVHR) a system of ventilating buildings, in which heat is recovered from the exhaust air stream to preheat the fresh air intake. Normally there are two sets of ductwork, both connected to an air-to-air heat exchanger, with the air flows in the supply and exhaust branches carefully balanced.

Passivhaus a low energy building standard. Passivhaus Institut (PHI) originator of the Passivhaus movement and of the Passivhaus Standard.

Passivhaus Planning Package (PHPP) a modelling and accreditation software tool developed and updated by the Passivhaus Institut.

Pressure test A fan blows into a doorway and measures the amount of air delivered to maintain a certain pressure

Primary energy the amount of energy mined or extracted at source; e.g., from coal, oil, natural gas, uranium or wood. Includes losses within processes such as electricity generation and transmission.

Retrofit to refit an old building with new insulation and building services that were not available at the time it was originally built

Royal Institute of British Architects (RIBA) champions better buildings, communities and the environment through architecture. It provides the standards, training, support and recognition that put its members – in the UK and overseas – at the peak of their profession.

Stack effect natural ventilation – the warm air inside a building is less dense than the cooler external air. Consequently, summer air tends to be drawn in through openings at the base of the building, with cool air moving up and out through openings in and near the top of the building.

Thermal bridge a continuous element of building fabric that goes from the outside to the inside, such as a window sill or a steel reinforcing tie in cavity wall brickwork, through which heat can flow and thus be a source of heat loss

Thermal capacity the ability of the constituent materials in a building to store heat, for a given rise in temperature, measured in units of kWh/K for a whole building or in Wh/K.m² to indicate the building’s thermal capacity per unit floor area.

Thermal envelope the insulated external fabric of the building. Useful space heating energy the amount of heat actually put into the heated space.

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