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Jargon buster


  • Absorption

    The process of drawing fluid or gas into a porous material, such as a sponge soaking up water.

  • Acoustics

    The science of the generation, propagation, transmission, reproduction, reception, measurement and effects of sound and of the phenomenon of hearing.

  • Air infiltration

    The uncontrolled flow of air through cracks or gaps in the fabric of buildings. It is driven by wind pressure and temperature differences and as a result is variable, responding in particular to changes in the weather. Infiltration levels are strongly affected by both design decisions and construction quality.

  • Air Tightness

    Describes the ‘leakiness’ of the building fabric. An airtight building will resist most unwanted air infiltration while satisfying its fresh air requirements through a controlled ventilation strategy. Most existing buildings, even those built recently, are far from being airtight and because of unwanted air infiltration generate huge costs to owners and occupants, in environmental, financial and health terms.


  • Bioclimatic design / architecture

    Designing a building that is in harmony with the natural features and resources surrounding the site, taking advantage of free available renewable resources, e.g., using sunlight through passive solar, and reducing the impact on energy demand for heating and cooling by appropriate orientation, lay out and compact shape of the building.

  • Blow-in insulation

    Insulation that is blown into position (usually into cavity walls or lofts) through a hose connected to a blowing machine.

  • Breather membrane

    Repels water that penetrates an outer cladding material but is permeable to water vapour escaping from the structure. It is defined as a material with a vapour resistance between 0.1 and 2.0 MNs/g, although the norm is for breather membranes to have a maximum vapour resistance of 0.6 MNs/g.


    An environmental assessment scheme for buildings coming from the UK

  • Building envelope

    The structural elements (walls, roof, floor, foundation) of a building that encloses conditioned space; the building shell.


  • Acoustical absorption

    see Sound absorption

  • Cavity

    The empty space between studs or joists typically filled with insulation.

  • CE marking

    CE marking (also known as CE mark) is a mandatory European marking for certain product groups to indicate conformity with the essential health and safety requirements set out in European Directives.

  • CEN

    An acronym standing for European Committee for Standardization

  • Climate change

    Refers to changes in modern climate (see global warming).

  • Condensation

    Changing a substance from a vapor to a liquid state by removing the heat. The condensate shows up on surfaces as a film or drops of water.

  • Conduction

    The transmission of heat through, along or from one material to another material in contact with it.

  • Conductivity, Thermal (lambda value)

    The rate at which heat is transmitted through a material, measured in watts per square metre of surface area for a temperature gradient of one Kelvin per metre thickness, simplified to W/mK. The Lower the value, the better the thermal efficiency of the material.

  • Convection

    The transfer of heat by movement of air.

  • Cooling Degree Day (CDD)

    A unit, based on temperature difference and time, used in estimating energy consumption and specifying nominal cooling load of a building in summer.


  • Decibel (dB)

    A logarithmic unit of measurement that expresses the magnitude of a physical quantity (usually power or intensity) relative to a specified or implied reference level. The decibel is commonly used in acoustics to quantify sound levels relative to some 0 dB reference. The reference level is typically set at the threshold of perception of an average human and there are common comparisons used to illustrate different levels of sound pressure.

  • Density

    The mass of a substance per unit of volume of that substance.

  • Duct (ductwork)

    The channels through which hot and cold air is blown in a building’s heating and cooling system.


  • Efficient energy use (energy efficiency)

    Efficient energy use, sometimes simply called energy efficiency, is using less energy to provide the same level of energy service. An example would be insulating a home to use less heating and cooling energy to achieve the same temperature. Another example would be installing fluorescent lights and/or skylights instead of incandescent lights to attain the same level of illumination.

  • Embodied (or embedded) energy

    Embodied (or embedded) energy is a measure of the energy required to extract raw materials, manufacture the product and supply it to the point of use. A product that requires large amounts of energy to obtain and process the necessary raw materials, or a product that is transported long distances during processing or to market, will have a high-embodied energy level.

  • Emissivity

    Emissivity is a measure of the radiation emitted from a surface. ‘Black bodies’ (materials with matt black surfaces) have a high emissivity & emit large amounts of radiation. In contrast shiny surfaces, such as polished aluminium, have a low emissivity. This characteristic can be exploited in buildings by providing aluminium foil facings on insulation materials, facing out towards cavities to reduce the radiated heat loss. Matt black has a typical emissivity of 0.95, compared to 0.08 for polished aluminium. But most building surfaces, even white painted surfaces, have high emissivities, of around 0.90 to 0.95.

  • Energy need (for heating and/or cooling)

    Energy need (for heating and/or cooling): Energy required to heat or to cool a building. Unit: kWh/m²/year

  • EPBD - energy performance of buildings directive

    The EPBD, which came into effect in January 2006, is a European directive. It provides a common methodology for calculating the energy performance of buildings and for creating minimum standards of energy performance in individual member states. The directive applies to new buildings and to existing buildings subject to major renovations. It is currently under review.

  • EPS

    EPS - expanded polystyrene - is a lightweight, rigid, plastic foam insulation material produced from solid beads of polystyrene. Expansion is achieved by virtue of small amounts of pentane gas dissolved into the polystyrene base material during production.

  • EU Ecolabel

    EU Ecolabel is a voluntary scheme designed to encourage businesses to market products and services that are kinder to the environment and for European consumers - including public and private purchasers to easily identify them (


    Stands for the European Certification Board for Mineral Wool Products, a not-for-profit association, whose general purpose is to voluntarily certify the conformity of mineral wool fibres with Note Q of the Directive 97/69/EC (


    The European Insulation Manufacturers Association represents the interests of all major mineral wool producers throughout Europe (


    European Alliance of Companies for Energy Efficiency in Buildings (

  • Euroclasses

    Euroclasses provide common comparison platform for the reaction to fire behaviour for nearly all construction product. Building materials are divided into classes depending on how they influence ignition of fire, spread of fire and production of smoke (Commission Decision 2000/147/EC of 8 February 2000).


  • Faced Insulation

    Insulation with a facing already attached. Kraft paper or foil-backed paper are common facings.

  • Fiber Glass Insulation

    see Glass Wool insulation

  • Fiberisation

    The manufacturing process of turning molten raw material (e.g. for insulation; glass or stone) into fibres.

  • Final energy

    Final energy is a form of energy available to the user following the conversion from primary energy. Final forms of energy include gasoline or diesel oil, purified coal, purified natural gas, electricity, mechanical energy, etc… When going from primary energy to final energy, we must take into account the efficiency of the conversion device (typically a power plant in the case of electricity), and, as the case may be, of transportation. Generally speaking, a country always has higher primary energy consumption than final energy consumption, the difference between the two representing the losses in the energy system.

  • Fire reaction

    Fire reaction is the tendency of construction products to contribute to flashover. Flashover is the rapid transition to a state of total surface involvement in a fire. The time to flashover is used to determine the limits of the “reaction to fire” classification system.

  • Fire resistance

    Fire resistance is the ability of an element of structure to maintain its stability for a specific period of time as determined by the use and size of the building.

  • Frequency of sound (Hz)

    The frequency of sound is measured in Hz (hertz). The higher the value, the lighter the tone (bass - treble). The frequency of speech lies primarily between 125 and 8000 Hz, while audible sound lies between 20 and 20 000 Hz.


  • Glass Wool

    Glass Wool is an excellent insulation material made from extremely fine fibers of glass.

  • Global Compact

    The Global Compact is a framework for businesses that are committed to aligning their operations and strategies with ten universally accepted principles in the areas of human rights, labour, the environment and anti-corruption. As the world’s largest, global corporate citizenship initiative, the Global Compact is first and foremost concerned with exhibiting and building the social legitimacy of business and markets.

  • Global warming

    Global warming is the increase in the average temperature of the Earth’s near-surface air and oceans since and its projected continuation. The scientific consensus is that the increase in atmospheric greenhouse gases due to human activity caused most of the warming observed since the start of the industrial era, and the observed warming cannot be satisfactorily explained by natural causes alone. This attribution is clearest for the most recent 50 years, for which the most detailed data are available.

  • Global Warming Potential

    A measure of how the manufacturing process of a product contributes to global warming.

  • Greenhouse effect

    Greenhouse effect refers to the change in the thermal equilibrium temperature of a planet by the presence of an atmosphere containing gas that absorbs and emits infrared radiation. Greenhouse gases, which include water vapor, carbon dioxide and methane, warm the atmosphere by efficiently absorbing thermal infrared radiation emitted by the Earth’s surface, by the atmosphere itself, and by clouds.


  • Heat Flow

    The rate at which heat moves from an area of higher temperature to an area of lower temperature (W/hr). Heat flow is generally used to quantify the rate of total heat gain or heat loss of a system.

  • Heat loss

    Heat transfer from internal spaces to external areas through conduction, convection and radiation.

  • Heating Degree Days (HDD)

    Quantitative indices designed to reflect the demand for energy needed to heat a building. The number of heating degrees in a day is defined as the difference between a reference value of 65°F (18°C) and the average outside temperature for that day.

  • HQE

    HQE (High environmental quality) is an environmental assessment method for buildings coming from France.

  • HVAC

    HVAC is an acronym that stands for “heating, ventilating, and air conditioning”.


  • IEA

    Founded during the oil crisis of 1973-74, the International Energy Agency (IEA) acts as energy policy advisor to 28 member countries in their effort to ensure reliable, affordable and clean energy for their citizens.

  • Impact sound

    Sound transmitted between two areas by direct impact upon the dividing element (e.g. sound of footsteps on an internal floor).

  • Indoor air quality

    Nature of the air inside buildings or enclosed areas, as determined by odour, smoke, humidity, air conditioning (controlled air quality) or uncontrolled air quality

  • Insulation Density

    Denser insulation products have more fibers per m3.

  • IPCC

    IPCC - Intergovernmental Panel on Climate Change - is a scientific intergovernmental body tasked to evaluate the risk of climate change caused by human activity. The panel was established in 1988 by the World Meteorological Organization (WMO) and the United Nations Environment Program (UNEP), two organizations of the United Nations (

  • ISO

    ISO - International Standard Organization - is an international-standard-setting body composed of representatives from various national standards organizations. Founded on 23 February 1947, the organization promulgates worldwide industrial and commercial standards. It is headquartered in Geneva, Switzerland ( )


  • Joist

    Horizontal framing member set from wall to wall to support the floor or ceiling.


  • Kyoto Protocol

    A protocol to the United Nations Framework Convention on Climate Change (UNFCCC or FCCC), an international environmental treaty produced at the United Nations Conference on Environment and Development (UNCED), informally known as the Earth Summit, held in Rio de Janeiro, Brazil, from 3-14 June 1992. The treaty is intended to achieve “stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.” As of 2008, 183 parties have ratified the protocol, which was initially adopted for use on 11 December 1997 in Kyoto, Japan and which entered into force on 16 February 2005.


  • Lambda value

    Physical coefficient which measures the heat transmission behaviour of a material. Lower is the value, better is the thermal efficiency of the material. Unit: W/m.K

  • LEED

    LEED is an environmental assessment scheme for buildings coming from the USA

  • Life-Cycle Analysis

    Life-Cycle Analysis estimates the environmental impacts of a product throughout its lifespan. It consists in modelling the different steps of its life from raw material extraction to use to end of life, taking into account all resources consumption (material, energy, transports…) and all emissions (water, air,...)


  • Mineral wool

    Mineral wool refers to both glass and stone wool

  • Moisture

    Moisture refers to the presence of water, often in trace amounts. Excessive moisture is usually undesirable in buildings as it can cause rot in wood or other organic material, corrosion in metals, and electrical short circuits.


  • Noise
    Source dB
    Plane 125 dB
    Pneumatic Drill 105 dB
    Heavy Traffic 90 dB
    Business Office 65 dB
    Library 35 dB
    Quiet Forest 15 dB
    Threshold of Hearing 0 dB
  • Non combustible

    The material will not burn. Glass and stone wools have a natural fire resistance, and are considered non-combustible when tested in accordance to international standards.


  • Octave Band

    A range of frequency where the highest frequency of the band is double the lowest frequency of the band. The band is usually specified by the centre frequency.

  • OEM - Original Equipment Manufacturer

    Original Equipment Manufacturer is typically a company that uses a component made by a second company in its own product, or sells the product of the second company under its own brand.


  • Passive House

    Passive House or PassivHaus (German) refers to the voluntary standard for energy use in buildings. It results in very low energy buildings that require little energy for space heating or cooling. The PassivHaus standard requires that the building fulfills the following requirements:

    • The building must not need more heating energy than 15 kWh/m² per year
    • With the building de-pressurised to 50 Pa (N/m²) below atmospheric pressure by a blower door, the building must not leak more air than 0.6 times the house volume per hour (n50 x 0.6 / hour)
    • Total primary energy consumption (primary energy for heating, hot water and electricity) must not be more than 120 kWh/m² per year
  • Permeability

    The mass rate of water vapour flow through one m² of a material or construction of one grain per hour induced by a vapour pressure gradient between two surfaces

  • Polyurethane

    Polyurethane, commonly abbreviated PU, is any polymer consisting of a chain of organic units joined by urethane links. Polyurethane polymers are formed by reacting a monomer containing at least two isocyanate functional groups with another monomer containing at least two alcohol groups in the presence of a catalyst.

  • Primary energy

    Primary energy is energy that has not been subjected to any conversion or transformation process, e.g. coal, lignite, mineral oil, natural gas, uranium (nuclear energy), water, solar radiation, wind.


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  • R-Value

    see thermal resistance

  • Radiation

    The process by which heat is emitted from a body through open space, for example, sunlight.

  • Rafters

    A slope framing member that supports a pitched roof.

  • Relative Humidity

    A measure of the amount of moisture in the air with respect to the temperature. It is the ratio of the moisture present to the maximum amount of moisture the air can hold at that temperature.

  • Renewable energy

    Renewable energy is energy generated from natural resources - such as sunlight, wind, rain, tides and geothermal heat - which are renewable (naturally replenished).

  • Resistivity

    A measure of a material’s thermal resistance and is the reciprocal of its conductivity. It is a measure of the thermal characteristic of a material and is independent of its thickness.

  • Reverberation

    In an enclosed space, when a sound source stops emitting energy, it takes some time for the sound to become inaudible. This prolongation of the sound in the room caused by continued multiple reflections is called reverberation.


  • Sound

    Sound is the psychological effect caused by an acoustical signal (physical phenomenon). Sound is produced by vibrating objects and reaches the listener’s ears as waves in the air or other media. When an object vibrates, it causes slight changes in air pressure. These air pressure changes travel as waves through the air and produce sound. The hearing mechanism of the ear senses the sound waves and converts them into information which it relays to the brain. The brain interprets the information as sound.

  • Sound Absorption

    Sound energy converted into mechanical vibration energy and/or heat energy. The process of dissipating or removing sound energy; the property possessed by materials, objects and structures (such as rooms) of absorbing sound energy; the measure of the magnitude of the absorptive property of a material, object or structure. Sound absorption is usually expressed as a sound absorption coefficient.

  • Sound Absorption Coefficient

    The percentage of sound energy incident on the surface of a material that is absorbed by the material.

  • Sound insulation

    The ability of a building element or building structure to reduce the sound transmission through it. The sound insulation is measured at different frequencies, normally 100-4000 Hz. Airborne sound insulation is expressed by a single value, Dn,c,w , Rw or R’w. Impact sound insulation is expressed by a single value Ln,w or L’ n,w .

  • Sound strength

    Measured in dB (decibel). dB is measured at different frequencies.

  • Stone wool

    Stone wool is a mass of fine, intertwined fibers made of molten rock

  • Stud

    A vertical framing member used in both exterior and interior walls.

  • Sustainable Construction

    Sustainable Construction aims to reduce the environmental footprint of a construction over its entire lifetime, while optimizing the economic viability / affordability and the comfort of life for the occupants.

  • Sustainable Development

    ” [Development that] meets the needs of the present without compromising the ability of future generations to meet their own needs.” (Brundtland Report, 1987)


  • Thermal Bridge

    A thermal bridge is created when materials that are poor insulators come in contact, allowing heat to flow through the path created. Insulation around a bridge is of little help in preventing heat loss or gain due to thermal bridging; the bridging has to be eliminated, rebuilt with a reduced cross-section or with materials that have better insulating properties, or with an additional insulating component

  • Thermal Conductivity

    see conductivity (thermal)

  • Thermal Inertia

    Thermal Inertia is a measure of the thermal mass and the velocity of the thermal wave which controls the surface temperature of a material

  • Thermal Insulation

    Thermal Insulation refers to materials used to reduce the rate of heat transfer, or the methods and processes used to reduce heat transfer.

  • Thermal resistance (R value)

    It is measured in m2K/W and is equal to the thickness of the material (in metres) divided by the conductivity of that material. Surfaces and cavities also provide thermal resistance and there are standard figures for these resistances that must be taken into account when calculating U-values. The resistances of each material within an element are added together to determine the overall resistance of the element. The reciprocal of the overall resistance is the U-value. The higher the R-value, the more efficient the insulation.


  • U value (thermal transmittance)

    Commonly known as the U-value, it is a measure of the rate of heat loss of a building component. It is expressed as watts per square metre, per degree Kelvin, W/m2K. The U-value is calculated from the reciprocal of the combined thermal resistances of the materials in the element, air spaces and surfaces, also taken into account is the effect of thermal bridges, air gaps and fixings.

  • Unfaced Insulation

    Insulation with no attached facing.


  • Vapor barrier or vapour retarder

    A vapour control layer is defined as a material that substantially reduces the water vapour transfer through a building element into which it is incorporated i.e. polythene sheet materials or foil backed plasterboard. Vapour control layers are sometimes required on the warm side of the insulation, to reduce the possible risk of interstitial condensation within the construction element.

  • Vapor barrier or vapour retarder

    A vapour control layer is defined as a material that substantially reduces the water vapour transfer through a building element into which it is incorporated i.e. polythene sheet materials or foil backed plasterboard. Vapour control layers are sometimes required on the warm side of the insulation, to reduce the possible risk of interstitial condensation within the construction element.

  • Vapour permeable underlay

    A vapour permeable underlay repels water that penetrates a roofing finish but is permeable to water vapour escaping from the structure. It is usually defined as a material with a vapour resistance of not more than 0.25MNs/g.

  • Ventilation

    Ventilation is the intended and controlled ingress and egress of air through buildings, delivering fresh air, and exhausting stale air in combination with the designed heating system and humidity control, and the fabric of the building itself. Ventilation creates a positive flow of air that allows the house to “breathe” and helps prevent moisture build-up year-round.

  • Volatile Organic Compounds

    Volatile Organic Compounds (VOCs) are organic chemical compounds that have high enough vapor pressures under normal conditions to significantly vaporize and enter the atmosphere. A wide range of carbon-based molecules, such as aldehydes and other light hydrocarbons are VOCs.


  • Water vapor permeance

    Time rate of water vapour transmission through unit area of flat material or construction, induced by vapour pressure difference between two specific surfaces, under specified temperature and humidity conditions.

  • World green building council (WGBC)

    World green building council - WGBC - is a union of national councils whose mission is to accelerate the transformation of the global built environment towards sustainability. The current member nations of the WorldGBC represent over 50 percent of global construction activity, and touch more than 15,000 companies and organizations worldwide (


  • XPS (extruded polystyrene)

    XPS - extruded polystyrene - is a closed-cell, thermal plastic material manufactured by a variety of extrusion processes (single screw, twin screw). The main applications of extruded polystyrene insulation board are in building insulation and construction in general (


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  • Zero carbon houses

    Zero carbon houses produce no Carbon Dioxide and by combining all the available innovations can actually export carbon free energy back into the electricity grid