1. Start with the object behind the claim
A result is useful only when the reader can identify what was examined. A loose facer, a complete facing laminate, a finished board and an installed assembly are related, but they are not the same evidence object. Keep the specimen, its state, the method and the reported conditions attached to every result. [1–3]
This guide helps material engineers, quality teams and technical buyers compare documents without transferring a claim to a different object. It is an original reading aid, not a test procedure, a conformity document or a GRECHO product-performance report.
Material and facing evidence
This may concern an individual layer, a loose facer or a complete multilayer facing. Identify which of those was tested. A result for a metal ply, reinforcement or loose glass veil cannot silently become a result for every other part of the laminate. [2,3]
Finished-board evidence
This concerns a named board construction. The record may need to identify the core, facing, adhesive layer, rear face and other relevant build details. For acoustic evidence, retain the reported mounting and backing context as well as the number or frequency data. [1]
Installed-system evidence
This concerns the stated assembly and its interfaces. A material result does not automatically address joints, connections or the conditions of an installed insulation system. Name the actual system question instead of using “tested material” as a substitute for a system conclusion. [2]
These are scope distinctions, not a ranking in which one document is always better. Choose the evidence that answers the actual question; make the untested or unconfirmed part visible.
2. Match each document to the question it can answer
Read the object and limitation columns together. The table is an editorial comparison framework derived from the cited GRECHO technical guides, not a prescribed sequence of tests. [1–3]
| Evidence presented | What to identify | What it does not establish |
|---|---|---|
| A loose-facer air-permeability result | Material reference, specimen, method, original units and reported pressure conditions | The NRC or αw of a finished acoustic panel. |
| A material or laminate structure description | Each documented layer, reinforcement, coating, backing and contact side | A measured strength, barrier value or interchangeable replacement. |
| A crease or local surface mark | Observed place, specimen state, known handling and first documented observation | The identity of damage in every inner layer or a through-hole. |
| A hole finding in a named ply or complete laminate | Which layer or complete build, inspected area and detection scope | A numerical water-vapour or gas-transmission result without its own measurement. |
| An acoustic panel report | Rated descriptor, frequency data, panel build, test method and mounting | A sound-insulation result or the performance of every board using the same facer. |
| A statement about an installed assembly | Named application, actual construction and the interfaces covered | Automatic coverage of another installation or undocumented joints. |
A missing item does not prove that a material has failed. It identifies a question that remains open. Equally, a complete-looking table does not itself constitute technical acceptance. [1,2]
3. Ask seven questions before transferring a result
What exactly was examined?
Copy the material or product reference and revision. State whether the evidence concerns a single ply, a complete loose facer, a board or an installed assembly. A generic word such as “reinforced” is not an adequate layer description. [3]
What state was the specimen in?
Distinguish the original state from a conditioned, handled or otherwise changed state. Preserve the link to the appropriate comparison specimen. A later altered piece should not silently replace the original observation. [2]
Which side, direction and build were recorded?
Keep the layer sequence, relevant contact face and defined machine or cross direction where provided. Do not infer the intended contact side from the visible outside of a roll. [3]
What method and version does the document name?
Retain the original method designation and stated revision. Separate conditioning from the later measurement. A public standard summary or a reference in an article is not the complete test procedure. [1,2]
What conditions and result form were reported?
Keep the original units, qualifiers and conditions. Preserve “not detected”, “less than” or a stated reporting limit rather than rewriting it as absolute absence or zero transport. [2]
What changed between the two candidates?
Record differences in material, adhesive, core, backing or mounting. When several variables differ, do not attribute the outcome to the facer alone. [1,3]
Who needs to decide the next step?
State the unresolved comparison question for the responsible product, technical or testing party. An information gap does not automatically require a particular new test programme. [1]
4. Worked reading example: acoustic material and panel data
Illustrative document-reading scenario only. No product names, test values or GRECHO measurements are represented.
A team is comparing a proposed loose glass-veil facer with an existing acoustic panel. The material sheet gives an air-permeability result. The panel report gives NRC and frequency-dependent absorption information. The two documents are useful, but they do not answer the same question. [1]
The material record can support a discussion of the candidate under its stated measurement conditions. The panel report describes its named construction and mounting. Neither document alone establishes the acoustic result of a new panel that has not been identified in that report.
| Read this | Keep this distinction | Ask next |
|---|---|---|
| Air permeability of a loose facer | Material measurement, not a finished-panel absorption rating | Which specimen, method and pressure conditions belong to this value? |
| NRC or αw | Different single-number rating routes; not a universal conversion pair | Which frequency data and method support the reported descriptor? |
| The frequency curve or table | Data for the stated test construction | Are the core, facer, adhesive, rear face and mounting comparable? |
| A proposed facer change | A new comparison question, not an automatic result | What changed, what stays the same and which evidence needs review? |
A bounded handoff could read: “The existing absorption report belongs to the identified panel construction. The proposed facer has separate material data. Please review which evidence is applicable to the proposed change; panel performance after that change is not established by the loose-facer result.”
Similar NRC or αw values also do not reconstruct identical frequency curves. Keep the actual reported data and the tested build, rather than choosing on a headline number alone. Absorption is not sound insulation or a guaranteed room-noise reduction. [1]
5. Worked reading example: a crease and a barrier question
Illustrative observation scenario only. It is not a damage finding on a GRECHO product or a prescribed investigation plan.
A crease is visible after a documented handling step. That first record establishes an observed surface condition. It does not establish which inner layers changed, whether the whole facing has a through-opening, or what the remaining barrier performance is. [2]
Keep observation, investigation and measurement separate
A confirmed defect in a metal ply and a confirmed opening through every relevant ply are different findings. A continuous adjacent layer does not prove that the metal layer is unchanged. Conversely, a defect in one ply is not automatically an open channel through the entire laminate. Neither observation supplies a transmission rate.
“No holes detected” remains bounded by the investigated area and the method’s detection capability. It is not a universal statement that every layer is defect-free or that water-vapour transmission is unchanged. Preserve the source wording, including limits and qualifiers. [2]
Make the before/after comparison traceable
Link the baseline and conditioned records to the same defined material reference and revision, or explain the relationship between separate comparison specimens. Before and after do not necessarily mean the same physical piece can be measured twice; the responsible testing party determines an appropriate comparison.
Separate the handling or conditioning record from the subsequent functional measurement. If the method, temperature, humidity conditions or specimen state also change, do not assign the difference to the crease alone. Do not convert a conditioning label into a service-life promise. [2]
Use a bounded handoff statement
“A crease was observed on the identified sample in the recorded state. Inner-layer integrity and the relevant transmission function have not yet been established. Please link available findings to the baseline and conditioned specimens and identify the remaining functional question.”
A material result still does not resolve all joints and connections in an installed assembly. The installed-system question must remain explicit. [2]
6. Worked reading example: reinforcement is not full construction
“Fiberglass reinforced” does not uniquely identify a facing. Laid scrim, woven glass fabric and a nonwoven glass veil or mat have different structures. The original material naming and a confirmed layer list should control the comparison, not the appearance of two similar silver rolls. [3]
An open scrim can sit inside a multilayer facing that includes a separate continuous layer. Its visible openings do not establish the transport behaviour of the complete facing. Equally, a description such as “aluminium composite” does not prove that a particular reinforcement forms a continuous barrier.
Identify what actually changed
When two facings differ, ask whether only the reinforcement changed or whether foil, coating, adhesive and backing changed as well. Without that distinction, a different composite result cannot simply be attributed to the glass-fibre structure. Preserve the material revision, roll or batch reference, layer order and contact side. [3]
Write the result without overextending it
| Prefer this bounded record | Avoid this unsupported extension |
|---|---|
| “The document identifies a woven glass layer in the named laminate.” | “All reinforced facers are woven glass fabric.” |
| “The reported value belongs to the complete specimen and stated conditions.” | “Every product using this component has the same result.” |
| “The cited example belongs to the named manufacturer.” | “This proves GRECHO equivalence, certification or a supply relationship.” |
| “The intended board/system question remains subject to review.” | “The material result automatically approves the installed system.” |
GRECHO supports application-matched facer review, sample coordination and technical documentation coordination. An effective request identifies the board application, material reference, available evidence and unresolved question. Method selection, result interpretation and product or system decisions remain with the responsible parties. [1–3]
7. Common questions and source scope
Does this guide require a new full-board test whenever a facer changes?
No. It identifies the information that needs to be considered. The actual decision depends on the specific change, intended use, existing evidence and requirements of the responsible technical parties. [1]
Can an unfilled field be treated as a failed result?
No. “Not recorded” and “not verified” are information states, not failures. A bounded negative finding such as “not detected” must also retain the investigation scope and reporting limit. [2]
Can one layer name establish which side must face outwards?
Not by itself. Preserve the documented side and intended contact in the actual construction. A photograph of a roll or a generic label is not a product-specific application approval. [3]
Can third-party examples be presented as GRECHO test results?
No. Named manufacturer examples retain their original attribution. They do not establish GRECHO measurement results, a supply relationship or equivalence to a selected facer. [3]
Use with the companion record
The companion “Sample State & Technical Evidence Record” provides blank fields for object identity, layer/side information, state, method, evidence and unresolved questions. It is an optional documentation aid, not a product-release form.
Sources and limits
This original guide is based on the supplied readings of the following public GRECHO articles. Their technical boundaries are retained here. Linked pages are reading references. This guide reflects the referenced content as recorded on 18 October 2026, not a new audit of the websites or standards.
[1] NRC und αw: Frequenzkurven bei Akustikpaneelen lesen.
[2] Alukaschierung: Knickstellen, Pinholes und Barriere.
[3] Alukaschierung: Glasgitter, Glasgewebe oder Glasvlies.
No full standards text, third-party figures, private technical reports, customer records or product acceptance thresholds are reproduced. This guide does not certify any material, board or installed system.
