A technical claim is useful only when its boundaries can be checked. A certificate identifies what was assessed, a test report describes the method and sample, and a project calculation connects that evidence to a particular building.
For a material, request batch documentation, a certificate or declaration, key test reports, and technical specifications. For an assembly, ask for scope of use, layer composition, substrate requirements, and installation method.
For the finished building, review the energy model, construction records, concealed-work inspections, and commissioning results. If a website figure cannot be connected to this evidence, treat it as an unverified promise.