Glossary of Insulation Terms

Below is an alphabetical listing of terms commonly used when referring to insulation.



A weighting filter often applied to decibel ratings to emphasise the characteristics of human hearing at low frequencies, written dBA or dB(A).

Accredited Construction Details

Accredited construction details are details of junctions at openings and at junctions between elements (such as wall/floor junction) that are designed to minimise thermal bridging and air leakage.

Air Infiltration

Air ingress into a building through cracks or gaps.

AS 3999

AS 3999 is the Australian standard set for thermal insulation of dwellings to ensure correct installation of insulation.

Australian Alliance to Save Energy (A2SE)

The A2SE is a coalition of business, government and environmental leaders that aim to inform, influence and advance the efficient use of energy in Australia across all sectors. A2SE is developing an Energy Productivity Roadmap that will show the steps Australia can take to double energy productivity by 2030.

BIM (Building Information Modelling)

BIM is an acroynm for Building Information Modelling. BIM is defined as 'The shared use of structured data' within the design, construction (or retrofit), operations / maintenance and deconstruction of a building. BIM enables those who interact with the building to optimise their actions, resulting in a greater whole life value for the asset.


Loose mineral wool insulation applied by blowing, usually into cavity walls or lofts.


BRANZ is a registered testing authority providing research, testing, consulting and information for the building industry in both Australia and New Zealand. BRANZ provide expert advice on building materials behaviour, energy and environmental planning, fire safety research, engineering and peer review, products appraisals and user-friendly commercial and domestic building technical publications.

Breather Membrane

A 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.

Building Code of Australia (BCA)

The Australian Building Code Board is a Council set up by the Australian State and Territories governments to produce and maintain The Building Code of Australia (BCA). The BCA is found in volumes 1 and 2 of the National Construction Code (NCC) and is produced to set minimal building standards for health and safety, building sustainability and efficiency.

Cavity Tray

A damp-proof membrane or pre-formed tray crossing the cavity of a wall at interruptions in the cavity. Rises from the outside of the cavity upwards at least 150mm.

Cavity Wall

A wall, normally external, comprising an inner and outer leaf with a space between the two.


CodeMark certifies building products, providing regulatory authorities and the market confidence and certainty through the issue of a Certificate of Conformity. The scheme provides a nationally and internationally accepted process for products to be assessed for compliance with the Building Code of Australia and New Zealand’s requirements.


When water vapour from the air comes into contact with cold surfaces, the vapour condenses on the cooler surface.


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


The transfer of heat by movement of air.


A calculated temperature at which water vapour will condense.


An isocyanate that has two isocyanate groups is known as a di-isocyanate. Di-isocyanates are manufactured for reactions with polyols in the production of polyurethanes.


The high strength polypropylene packaging applied to most Knauf Insulation roll products.

ECOSE® Technology

ECOSE® Technology is a revolutionary, no-added formaldehyde binder technology used in mineral wool products manufactured by Knauf Insulation. It is based on rapidly renewable materials instead of petro-based chemicals, reduces embodied energy and delivers superior environmental sustainability.

Embodies Energy

Embodied energy is the energy consumed by all of the processes associated with the production of a building, from the sourcing of raw materials and processing of those materials, to manufacturing, transport and product delivery.


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 Freedom Alliance

The Energy Freedom Alliance provides Australian homeowners with easy to follow information that enables them to take steps to make their homes high-performing, comfortable, and more energy efficient.

The Alliance is coordinated by climate solutions think-tank Beyond Zero Emissions, who produced the Zero Carbon Australia Buildings plan.

Environmental Product Declaration

An EPD is an Environmental Product Declaration and is the environmental equivalent of a technical data sheet.

It contains information about the embodied environmental impacts associated with a product, which are established by carrying out a life-cycle assessment (LCA).

The relevant standard for Environmental Product Declarations is ISO 14025, where they are referred to as "type III environmental declarations". A type III environmental declaration is created and registered in the framework of a programme, such as the International EPD® System.


EUCEB is a European Certification authority whose primary purpose is to guarantee products meeting the exoneration criteria of any carcinogenicity classification.


Eurofins is the global leader in providing manufacturers, distributors and realtors testing, certification and consulting on the quality and safety of their products. They also provide advice on how the results are interpreted and obtained.


FBS-1 is a registered trademark of ICANZ identifying products that comply with the test of short-term biopersistence. FBS-1 provides the consumer reassurance that the product is biosoluble and therefore any particles breathed in will be cleared quickly through the bodies normal process similar to clearing dust inhaled.


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


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.

Fire-resistance: heat transmission

Contains flames and inflammable gas for a short period of time, but does not prevent the transmission of heat to the other side of the construction (example: wired glass).

Flanking transmission

The transmission of sound into an area via an indirect route (e.g. between an upper and lower floor via common walls).

Frequency of sound

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.

Future proof

Aiming for the highest/best performing products for your home to ensure it is ready to meet future building requirements and demands for thermal and acoustic performance.


The Green Building Council of Australia (GBCA), established in 2002, aims to drive Australia’s property industry to the adoption of green building practices through market-based solutions. The GBCA supports the adoption of green building initiatives and technologies into mainstream design, construction and operation of buildings.


Glasswool is made from sand and recycled glass, limestone and soda ash. These are the same ingredients that are used to make familiar glass objects such as window panes or glass bottles. The glass is spun to form millions of fine strands of wool. These are then either formed into rolls and slabs or collected as a loose product. The formed product is sprayed with a resin which is used to bind the wool together to form a mat of material and then cured in an oven and cut to size and packaged as rolls or slabs to create the finished product. The loose glasswool is packed in bales and formed in situ within the building element during installation. 

Global Warming Potential

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

Green Roofs

A green roof is a roof which is partially or completely covered by vegetation and a growing medium. Green roofs can be either extensive or intensive. Extensive green roofs have shallow (typically 7–10cm) soil layers. They support sedums, moss, herbs and grasses and other vegetation where low or no maintenance is required. They are the lightest type of green roof. Intensive green roofs have a deeper soil layer (15cm upwards) and a wider variety of plant types can be grown, from lawns to ornamental bushes and semi mature trees.

Green/Garden Roof

A flat roof, often combining grass, plants and paving,  that is used to provide an outside area for social activities.


Global GreenTag is a unique certification program making choosing eco-friendly products easy. The program is the only ACCC approved National Certification Mark in the green building materials sector and is GBCA and GBCNZ recognised. It is an Australian developed system with a global focus providing ratings and certification for green building and other sustainable products based on life cycle assessment.

Heat Loss

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


The Insulation Council of Australia and New Zealand (ICANZ) is the largest trade association of insulation suppliers in Australia and New Zealand. ICANZ members provide approximately 70 percent of the insulation sold in Australia and New Zealand.

Impact Sound

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

Internal Floor

Any internal floor that is not a 'Separating Floor'.

Internal Wall

An internal wall is defined by the Building Regulations as a wall between a bedroom or room containing a W.C. and other rooms.

Interstitial condensation

Interstitial condensation is condensation that occurs within a building element. It can be very harmful if interstitial condensation occurs on surfaces within the structure, as this can lead to the rot of timber or oxidation of metal surfaces, and other problems. There are many instances when condensation can form on the surface or interface of two materials without causing problems i.e. the cavity side of an external brick or block leaf.


Horizontal structural element often used to support floorboards and celings.


An absolute temperature scale in which the temperature intervals correspond to those of the Celsius scale and the freezing point of water is 273 Kelvin (written 273K). When referring to temperatures on the Kelvin scale, refer to "Kelvin" and not "degrees Kelvin". Zero Kelvin (0K) is known as "absolute zero".


Life-cycle assessment or life-cycle analysis (LCA), is a technique to assess environmental impacts associated with the stages of a products life from cradle through to grave.


m2K/W (or R-Value) is the metric used to measure the thermal resistance of a material or construction element.

Noise Reduction Coefficient (NRC)

A single value for sound absorption, derived as the mean value of 4 frequencies in the range 250-2000 Hz.

Ozone Depletion Potential (ODP)

A relative index indicating the extent to which a chemical product may cause ozone depletion.

Party Wall

See 'Separating Wall'.

Passive House

The Passive House is designed and built for energy efficiency, comfort and affordability taking advantage of the climate to maintain a comfortable inside temperature year round. When considering the design for a Passive House the key concepts to consider are high levels of insulation, exceptionally high -performing windows, an airtight building envelope, mechanical heat recovery ventilation and minimised thermal bridging.

Product Data Template

A product data template is a structured ‘questionnaire’ for each construction product type that sets out groups of ‘properties’ that manufacturers have to fill in as ‘values’ in order to provide their data to the supply chain in a way consistent with BIM Level 2. 

Psi values

Psi values (W/mK) are used to calculate the Y value (W/m²K) for use in the SAP 2009 calculator for the effect of none repeating thermal bridges. Accredited construction details and associated Psi values for a new build design are available from the Planning Portal web site.


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


Inclined structural element used to support pitched roofs.

Rock Mineral Wool

Rock mineral wool (or stonewool), is an insulation material manufactured predominantly from volcanic rock, specifically basalt. The ‘recipe’ (charge) varies between manufacturers but other ‘ingredients’ typically include blast furnace and steel slags as well as dolomite.

These are heated to over 1,000°C, melted together and then spun (fiberised) into fine strands. These strands are sprayed with a ‘glue’ (binder) to form a mat of insulation before being ‘baked’ (cured) in an oven to create the finished product. Rock mineral wool has a high melting point, insulates through a wide temperature range, is an excellent acoustic insulant, and can be manufactured in a broad range of densities to suit many applications.

Separating floors

A separating floor is defined by the Building Regulations as a floor separating one dwelling from another.

Separating wall

A separating wall is defined by the Building Regulations as a wall separating one dwelling from another.


The underside of any construction element, but commonly used to decribe the area below a roof overhang or exposed floor (e.g. an outside, multi-storey carpark).

Sound Absorption

Sound energy converted into mechanical vibration energy and/or heat energy. Sound absorption is usually expressed as a sound absorption coefficient.

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 (dB)

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


A vertical framing element, usually timber or metal, used as part of the frame in a wall or partition.


The palletised, weatherproofed, compressed unit of delivery for most Knauf Insulation roll products.

Surface resistance

Surface resistance (Rs) is the reciprocal of surface coefficient. Its units are m2/K/W.


Temperature levels are commonly measured in degrees Celsius (°C) whereas temperature differences are measured in Kelvin (K). Each unit Celsius is the same size as each unit Kelvin, so that, if the outside temperature was 3°C and the internal temperature was 18°C the difference in temperature would be 15K. Note that the degree symbol ° is used with degrees Celsius but not with Kelvin.

Thermal Bridging

A thermal bridge (or cold bridge), is an area of a building which has a significantly higher heat transfer than the surrounding materials resulting in an overall reduction in thermal insulation of the object or building.

A thermal bridge describes a situation in a building where there is a direct connection between the inside and outside through one or more elements that are more thermally conductive than the rest of the building envelope.

Thermal conductivity

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.

Thermal Mass

The mass in a structure which is used to absorb solar heat during the day and then release the heat in the evening.

Thermal Modelling

Building Regulations require that thermal bridging be taken into account in SAP and SBEM calculations. The junctions that need to be accounted for include wall-floor junctions, wall-roof junctions, lintels, jambs, cills, intermediate floors, balconies, corners, party walls and other significant junctions. Their effects are expressed in terms of Ψ-values, or linear thermal transmittance values, and, unless they are recognised accredited details, they should be evaluated using thermal simulation software through 'thermal modelling', following agreed conventions and standards.

Thermal Resistance

A measure of the thermal resistance of a particular thickness of material. 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.

Thermal Resistivity

Resistivity is 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.

Thermal Transmittence

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

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.

Vapour control layer

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 underlayer

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.


Thermal conductivity (also known as Lambda) is the rate at which heat passes through a material, measured in watts per square metre of surface area for a temperature gradient of one kelvin for every metre thickness. This is then expressed as W/mK.


Is the metric used to express a U-value which is the metric used to express thermal transmittance.