Glossary β Fire resistance of sandwich panels
Plain-language explanations of the terms used in the five articles on the new rules for assessing the fire resistance of sandwich panels. This glossary explains abbreviations, materials, calculations and documents. It covers the scope discussed in the series: non-loadbearing walls made from factory-made panels with two metal facings.
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Common abbreviations:
EI Β· DIAP Β· EXAP Β· PIR Β· DoP Β· CE Β· AVCP Β· OWU
1. Fire resistance and class designations
Fire resistance
The ability of a building element to maintain its required functions during a fire for a specified period. In this series, we assess complete walls, including panel joints, fixings and supports. The result applies to the conditions described in the documentation.
E β integrity
The ability of a wall to prevent the passage of flames and hot gases that could ignite materials on the other side. In the designation EI, the letter E describes this function. It must not be confused with reaction-to-fire class E.
I β insulation
The ability of a wall to limit the temperature rise on the side opposite the fire. The assessment checks whether the temperature remains within the permitted limits. This concerns behaviour during a fire, rather than the normal thermal insulation of a building.
EI and classification period β EI 15, EI 20, EI 30, EI 45, EI 60, EI 120
An EI class means that both integrity E and insulation I are maintained. The number indicates the required time in minutes: for example, EI 30 means at least 30 minutes, and EI 120 means at least 120 minutes. The classes correspond to fixed periods, so a result of 41 minutes may justify EI 30, but not EI 45.
Reaction to fire
Describes how a material or product contributes to the initiation and development of a fire. The assessment considers, among other things, its behaviour when exposed to fire. The reaction-to-fire class of the core does not determine the fire resistance class of the complete wall.
Reaction-to-fire classes: A1, A2, B, C, D, E and F
These designations classify products according to their reaction to fire. A1 is the class with the most stringent requirements; class F means that the requirements of class E are not met and is not the same as NPD. Where applicable to a given class, additional designations may indicate smoke production and flaming droplets or particles.
Exposed and unexposed faces
The exposed face is subjected directly to fire during the test. The unexposed face is on the opposite side of the wall, and it is there that the temperature rise is assessed for criterion I. It is not necessarily the external face of the building.
Direction of fire exposure
Specifies the side of the wall from which the fire acts. Assessment in one direction does not automatically mean that the same scope has been confirmed for the opposite direction. This matters, for example, when the coatings differ between the two sides of a panel.
2. Panel construction, coatings and core
Sandwich panel
An element consisting of two facings with an insulating core between them. This series concerns factory-made panels with metal facings. The wall being assessed is formed from panels that have been joined and fixed in place.
Non-loadbearing wall
A wall that is not intended to carry loads from other parts of the building, such as floors or the roof. It must nevertheless carry the loads associated with its own function, including its self-weight. This series concerns such walls made from sandwich panels.
Self-supporting panel
A panel capable of transferring the loads acting over the span between its supports to those supports. This term does not mean that a wall made from the panel is a loadbearing wall of the building. Supports and fixings are still required.
Insulating core
The internal layer of a panel between the metal facings. It may be made, for example, from PIR foam or mineral wool. Its type and structure affect the properties of the complete panel.
PIR
An abbreviation for rigid polyisocyanurate foam. It is an insulating material used as the core of sandwich panels. The designation PIR alone does not specify the fire resistance class of a wall.
Mineral wool
An insulating material made from mineral fibres, used, among other applications, as a panel core. Its composition, density, fibre orientation and organic content are also relevant to the assessment. The material name alone does not mean that any type of mineral wool can be substituted for another.
Metal facing
The external sheet-metal layer on one side of a panel. It is bonded to the core and may have a protective or decorative coating. The facing and the coating are different parts of the product.
Organic coating
A thin finishing layer on the surface of the sheet metal, based on organic constituents such as resins. It protects the surface and gives it its appearance. Its type, colour and fire properties may be relevant to an EXAP assessment.
Organic substances and binder in mineral wool
Mineral wool may contain organic constituents, including the binder that holds the fibres together. Their content is one of the characteristics considered in the assessment. The binder within the wool must be distinguished from the adhesive bonding the core to the sheet metal.
Adhesive bonding the core to the facing
A material used to bond the core to the metal facing of a panel. It must be distinguished from the binder within mineral wool. Changes to the adhesive are subject to separate assessment rules.
Core density
The mass of material per unit volume, usually expressed in kilograms per cubic metre, or kg/mΒ³. It is one of the characteristics used to identify the core. A change in density must be assessed within the limits permitted for the particular construction.
Fibre orientation
The arrangement of the wool fibres within the core, for example in relation to the surfaces of the facings. It is not the same as the horizontal or vertical installation of complete panels. A change in fibre orientation may require the scope of the assessment to be checked.
RG β degree of reflection
A measure of the light reflected by a surface, determined relative to magnesium oxide taken as 100%. In the grouping discussed here, lower values indicate darker surfaces and higher values indicate lighter surfaces. RG groups help establish the permitted direction of a colour change.
RAL
A system for designating colours using established codes, such as numbers from the RAL CLASSIC collection. The code makes it easier to specify a colour, but does not describe all the properties of a coating. A RAL number alone does not replace the data required for an EXAP assessment.
PCS β gross heat of combustion
The quantity of heat released when a material undergoes complete combustion under specified test conditions. In coating assessments, this parameter helps describe the coatingβs potential thermal contribution to a fire. A higher PCS value does not indicate a more favourable fire property.
Emissivity
A surface property describing its ability to emit thermal radiation. It is relevant to heat transfer. It must not be equated with the degree of light reflection RG or assessed solely from the name of the colour.
Flame retardants
Additives used to reduce the flammability of a material. Their use may be a production stage that affects the reaction-to-fire classification. In Article 4, this is one of the examples relevant to determining the appropriate AVCP system.
3. Testing, spans and application of results
Fire test and test specimen
A test examines the behaviour of a specific construction under conditions defined by a standard. In this series, the specimen is a wall with a defined construction, dimensions and installation method. The result does not automatically cover every product bearing the same trade name.
DIAP β direct application of test results
Rules allowing a test result to be used for specified changes to the tested construction. For the walls discussed here, these rules derive primarily from the test standard EN 1364-1. Every change must meet all the conditions assigned to it.
EXAP β extended application of test results and EXAP report
An assessment that allows test results to be used for specified changes beyond their direct application. For the walls discussed here, the rules are set out in EN 15254-5. An EXAP report documents which changes can be justified and under what conditions.
Extrapolation
Determining a permitted scope beyond the value directly tested, for example for a greater span. In this series, this is done in accordance with specified EXAP rules. It does not mean extending a formula arbitrarily beyond the limits stated in the standard.
Field of application and scope of classification
Describes the constructions for which the confirmed class may be used. It covers, among other things, wall construction, span, core type and installation conditions. The designation EI 30 or EI 60 alone does not replace checking this scope.
Span β distance between supports
In the examples discussed here, this is the distance between the centre lines of the supports between which the panel spans. It is not the overall length of the panel. Nor can it automatically be equated with the dimensions of the test furnace opening.
Tested span length
The distance between supports used in the test actually carried out. It is the starting point for extension calculations. In the separate additional-test rule described in Article 5, this distance is denoted by the symbol X.
Target span β span length in the extrapolation tables
The span for which we want to confirm a particular fire resistance class. In the ranges discussed from the extrapolation tables of the 2026 edition, the term span length refers to target spans. However, the meaning of each dimension must be checked in the particular rule, especially when the symbol X is used.
Panel orientation β horizontal and vertical installation
Specifies the direction in which panels span between the wall supports. In horizontal installation, the panels span horizontally; in vertical installation, they span vertically. The rules for extending results may differ between the two arrangements.
Deflection and deformation
Deformation means a change in the shape or dimensions of an element. Deflection describes its bending away from its initial position. The examples give the maximum deflections measured during the test under consideration.
Expansion allowances
Gaps left during installation that allow the wall to expand as it heats up. Their size and arrangement form part of the tested construction. When a dimension is increased, they may need to be increased accordingly.
Joints, fixings and fasteners
Joints connect panels to one another, while fixings secure them to the supports or structure. Fasteners are the components used to make those fixings, such as suitable screws. Their type, number and arrangement form part of the construction being assessed.
Loadbearing capacity of fasteners
The ability of fasteners to carry the loads assigned to them. In this series, this also concerns maintaining that ability under fire conditions. Calculating the permitted span alone does not confirm that the fixings have sufficient loadbearing capacity.
Panel self-weight
The load resulting from the mass of the panel itself and the force of gravity. It must be carried by appropriate supports and fixings. When the span is increased, it must be taken into account in the structural assessment.
Time margin
The difference between the time for which the required criteria are maintained in the test and the time required for the selected class. For a test result of 41 minutes and class EI 30, the margin is 11 minutes. The EXAP rules specify how this margin may be used.
Time reduction β factor k and the unit min/m
The number of minutes deducted from the result for each additional metre of span under a particular rule. The notation 6 min/m means a reduction of 6 minutes per metre. The appropriate factor depends on the conditions of the rule, so one value cannot be applied to all panels and classes.
The symbols Lβ, tβ, T and X, and the notation max
Lβ is the span at the start of the calculation segment under consideration, tβ is the corresponding time, and T is the time required for the target class. X denotes the span of the specimen in the additional test under the rule described in Article 5. The notation max means selecting the larger number, for example max(6; 10) = 10.
4. Documentation, obligations and the supply of products on the market
Test report
A document describing the specimen tested, the test procedure and the results obtained. It establishes what was actually tested. It serves a different purpose from an EXAP report or a classification report.
Classification and classification report
Classification assigns the appropriate class to a construction on the basis of the results and the applicable assessment rules. The classification report states that class and its field of application. For the fire resistance of the walls discussed here, the applicable standard is EN 13501-2.
DoP β declaration of performance (Polish: DWU)
A document drawn up by the manufacturer that states the performance of a specific product-type and its intended use. The manufacturer is responsible for ensuring that the products supplied conform to the declared performance. A laboratory report provides a basis for assessment but does not replace the DoP.
CE β CE marking
Marking affixed by the manufacturer in accordance with the applicable legislation. By affixing it, the manufacturer assumes responsibility for the product's conformity with its declared performance and the applicable requirements. CE marking does not mean that the product is suitable for every use.
Assessment of performance (Polish abbreviation: OWU)
Activities undertaken to establish a product's performance on an appropriate technical basis. Their results may be documented in the relevant reports. The Polish abbreviation OWU does not mean that an additional document bearing precisely that title is always required.
AVCP β assessment and verification of constancy of performance
A system of rules defining how tasks are divided between the manufacturer and the notified body. It concerns the assessment of performance and its maintenance during production. The applicable system is determined by legislation and the technical specification, rather than by the manufacturer's free choice.
AVCP system 1
A system involving a notified certification body. It includes, among other tasks, assessment of performance, inspection of the manufacturing plant and factory production control, and ongoing surveillance of that control. The manufacturer remains responsible for its own obligations and for production conformity.
AVCP system 3
A system in which a notified laboratory assesses the product's performance, while the manufacturer carries out factory production control and takes samples. It does not include a certificate of constancy of performance or surveillance of that control by a notified body. In this series, it applies to the fire resistance of the walls discussed.
AVCP system 4
A system in which the manufacturer carries out both the assessment of performance and factory production control. It does not provide for tasks requiring the involvement of a notified body. It may be used only where permitted by the applicable rules for the product and characteristic concerned.
FPC β factory production control (Polish: ZKP)
Continuous, documented checks of materials, the production process and products. Its purpose is to ensure that successive products manufactured retain their declared performance. It is carried out by the manufacturer, including where testing is performed by an external laboratory.
Certificate of constancy of performance
A document issued by a certification body under a system that provides for such certification, for example system 1. It concerns the specified product and scope of assessment. A certificate covering reaction to fire does not automatically confirm fire resistance.
Notification and notified body
Notification concerns a body's authorisation to perform specified tasks within the European system for the assessment of products. Its scope may cover specified standards, products, characteristics and tasks. Before commissioning an assessment, check whether the laboratory's scope covers the required service.
Accreditation
Formal confirmation of a body's competence to perform activities covered by its scope of accreditation. For a laboratory, it may cover specified test methods. Accreditation is not the same as notification and does not remove the need to check the scope of notification.
NPD β no performance determined
A designation indicating that no determined performance has been declared for a particular characteristic. It is neither a reaction-to-fire class nor a fire-resistance class. It should not be equated with class F.
Product-type and intended use
A product-type describes a specified set of performance characteristics associated with a particular combination of materials and production method. The intended use states what the product is intended for. The declaration and technical documentation must relate to the same product-type and intended use.
Essential characteristic and performance
An essential characteristic is a product characteristic related to the requirements for construction works, such as fire resistance. Performance describes the outcome of the assessment of that characteristic, expressed, for example, as a level or class. One example is class EI 60 under specified conditions of use.
CPR β EU legislation on construction products
The abbreviation stands for Construction Products Regulation. In this series, it refers to Regulation (EU) No 305/2011 and the new Regulation (EU) 2024/3110. They lay down rules governing, among other matters, assessment, the declaration of performance and the placing of products on the market.
Placing on the market
The first making available of an individual construction product on the European Union market. It is not the same as first describing a model in a catalogue or signing a contract for products that have yet to be manufactured. To determine when it takes place, the circumstances relating to products that have already been manufactured must be examined.
Making available on the market
The supply of a product for distribution or use on the European Union market in the course of a commercial activity. It may be supplied in return for payment or free of charge. The first such supply constitutes placing the product on the market.
Transitional provisions
Rules governing the transition from old legislation to new legislation. They may retain the application of certain earlier requirements for specified products or documents. The CPR transitional provisions and the rules for applying the new edition of the EXAP standard need to be checked separately.
5. Standards and reference documents
EN, PN-EN and BS EN
EN denotes a European Standard. PN-EN is its adoption as a Polish Standard, while BS EN is its adoption as a British Standard. The number and year identify the document and edition to which a reference relates.
CEN
The European Committee for Standardization, the organisation that develops European Standards. Its members are national standards bodies. CEN is neither a laboratory that assesses panels nor a body that issues a classification to a manufacturer.
Product standard β EN 14509
A standard specifying requirements for a particular group of products and the rules for assessing their performance. EN 14509 covers factory-made, self-supporting insulating panels with two metal facings. In this series, it provides the reference framework for the sandwich panels discussed.
Test standard β EN 1364-1 and EN 13820
A standard describing how a particular test is to be performed. EN 1364-1 covers fire-resistance testing of non-loadbearing walls. EN 13820 describes the determination of organic content in thermal insulating products; in this series, it relates to the core material.
Classification standard β EN 13501-1 and EN 13501-2
A standard specifying the rules for assigning classes on the basis of data from the appropriate assessment. EN 13501-1 covers reaction to fire, while EN 13501-2 covers, among other matters, fire resistance. In this series, the EI classes of walls are determined in accordance with Part 2.
Harmonised standard
A European Standard developed for the purposes of specified European Union legislation. Under the CPR route discussed here, publication of its reference in the Official Journal of the EU is relevant. EN 14509 is the product standard used here for declaring performance; the EXAP standard itself serves a different purpose.
Annex ZA
The part of a standard that sets out its relationship with the relevant European requirements. In EN 14509, it identifies, among other matters, the characteristics subject to assessment and the applicable AVCP systems. It is relevant when determining the obligations of the manufacturer and the notified body.
Dated and undated references
A dated reference identifies a specific edition of a standard, for example EN 14509:2013. An undated reference gives the number without the year and refers to the latest edition, including amendments. An assessment must therefore consider both the main standard and the documents to which it refers.
Withdrawal of a standard and conflicting standards
Withdrawal changes a document's status within the collection of standards. When implementing a new European Standard, national standards bodies withdraw conflicting standards by the specified deadlines. This does not automatically mean that every earlier test loses its value; the documentation and the rules governing the use of the results must be assessed separately.
GNB-CPR and position paper NB-CPR/23-936r3
GNB-CPR is the Group of Notified Bodies for construction products. Document NB-CPR/23-936r3 concerns the presentation of assessment-of-performance results under system 3. It is an informative position paper, rather than legislation or a stand-alone EXAP method.
Basis of this glossary
This glossary explains the terms used in CERTBUD's five articles on EN 15254-5:2026. It preserves the distinctions and conditions described in those articles. Detailed assessment rules and the sources for individual statements are provided in the relevant articles in the series.
The reference documents include EN 14509, EN 1364-1, EN 13501-1, EN 13501-2, EN 15254-5, EN 13820, Regulations (EU) No 305/2011 and (EU) 2024/3110, and position paper NB-CPR/23-936r3. These definitions help explain the content of the series; they do not replace the full provisions of those documents.
All articles in the series
New rules for assessing the fire resistance of sandwich panels
Further parts of the series will be published in stages. Links to the articles will be added as they are published.
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2 of 5 β The new rules in five examples β coming soon
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3 of 5 β Facing colour and the scope of classification β coming soon
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4 of 5 β Where the new requirements come from β coming soon
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5 of 5 β Manufacturersβ frequently asked questions β coming soon
