The outlet can offer savings if its dimensions and condition suit the project. However, not every cheaper batch is suitable for every wall. The most important factors are the reason for the reduction and whether the material can be inspected. First-grade and off-spec batches should be compared at the level of the finished cladding, taking waste into account. First-grade refers to a product that meets the manufacturer's specified requirements. The outlet may include surplus stock, end-of-series runs or off-spec material. The name alone does not define the type of defect or its significance. Not all such offers should be treated as a single technical category.

An insulated sandwich panel is a prefabricated element in which the facings work together with the core. It can simultaneously enclose the building and reduce heat loss. However, its properties depend on the entire construction, not only on the type of foam or mineral wool. To use it well, the panel cross-section must be combined with the supports, connections and function of the facility. Rigid facings and the core bonded to them form a single element. For this reason, a failure of adhesion between the layers is not merely a visual defect. The panel should not be assessed as a loose set of two steel sheets and insulation. The parameters refer to the complete product.