Frequently asked questions (FAQs)

purenit consists of shredded rigid polyurethane foam and a PU binder. When laminated PU insulation boards are shredded, small quantities of particles from mineral-coated fleece and aluminium foil fall off in addition to the rigid PU foam; these are taken into account when determining the material properties and have no direct impact on further processing. purenit contains no wood or wood-based materials.

purenit is made from so-called production by-products, i.e. material remnants , arising for example, during edge processing or from faulty batches. This means the base material is free from undefined impurities, ensuring that purenit has a consistent and controlled property profile. Recycling in the sense of reusing waste therefore does not take place. However, by reusing the material remnants from production, waste is prevented in the first place.

purenit is moisture-resistant but not waterproof in the sense of a sealing or structural waterproofing. For example, it absorbs moisture when exposed to driving rain or splashing water, but it dries out completely again under suitable conditions (e.g. exposure to sunlight). This does not cause any material damage, and overall swelling and shrinkage behaviour is very low.

purenit is a functional, pressure-resistant insulation and construction material. Although many of the mechanical properties of purenit are comparable to those of wood-based panels (P5 / P7 boards), it may only be used in applications for which no structural verification is required.

Due to its resistance to moisture and rot, purenit is suitable for applications where exposure to moisture cannot be ruled out and would otherwise lead to material damage, for example in bathrooms and sanitary areas (bathroom furniture, partitions, etc.). At the same time, its low thermal conductivity combined with high compressive strength makes it suitable for use in components and/or component connections where a low thermal bridge effect and mechanical load-bearing capacity are required, such as in the window area. purenit meets the emission requirements of AgBB and can therefore be used indoors without restriction.
Use in outdoor areas requires suitable protection against weathering and UV radiation (e.g. coating,structural waterproofing or cladding).

purenit can be machined with standard workshop and construction-site woodworking tools and machines, i.e. it can be sawn, sanded, drilled and milled.

• Sawing: high rotational speeds with feed control, carbide-tipped saw blades for wood-based materials (e.g. 60–80 teeth for 250 mm Ø)
• Milling: approx. 15,000-20,000 rpm

Various mechanical fasteners can be used for purenit:

• Wood or chipboard screws, preferably panhead or washer head
• Nails/staples

It is recommended to pre-drill screw holes to the core diameter of the screw, especially in areas near corners and edges. Edge distances of at least five times the screw diameter must be maintained.

purenit can be bonded using almost all types of adhesives. The choice of the appropriate adhesive depends primarily on the material to which purenit will be bonded to. 

The following adhesive systems are frequently used for bonding:

• 1-component or 2-component PU adhesives are moisture-resistant and ideal for demanding joints. They are highly suitable for bonding purenit to itself or to other materials. 

Additional suitable adhesives:

• PUR hot-melt adhesives are used primarily in industrial production and allow fast bonding.
• Contact adhesives are a good choice, particularly for bonding veneers or laminate sheets (HPL) to purenit.

Important notes on bonding:

• Test bonding: When combining purenit with unfamiliar materials, always carry out a test bond to ensure optimal adhesion.
• Absorbent vs. non-absorbent materials: Since purenit itself provides good adhesion, the choice of adhesive depends mainly on the material surface that will be bonded to purenit (e.g. PVC, metal, wood or mineral substrates).
• Surface preparation: In some cases, the pre-treatment of the bonding surfaces with a primer may be required, particularly when bonding purenit edges. 

For specific applications, the adhesive manufacturers’ recommendations provide detailed information on suitable adhesives and processing parameters such as open time, pressing time and pressing method. 

purenit can be painted or surface-treated using common paints and coating systems, including solvent-based products. It is important to prepare the surface if necessary (light sanding and priming) and to ensure that any multi-layer coating is suitable for the intended application area, particularly with regard to weather exposure. Recommended paints / coating systems:

• PU acrylic paints
• water-based systems

For outdoor use:

• UV-resistant paints
• opaque wood protection paints
• Glazes generally do not produce a satisfactory visual result.

purenit is very adhesive-friendly and therefore easy to laminate; to prevent deformation, both sides should be coated as symmetrically as possible. Possible coating materials include, for example:

• HPL
• CPL
• aluminium and other metals
• wood veneer

Ensure a uniform bonding surface and select a suitable contact adhesive or PUR adhesive according to the chosen bonding method.  Coating temperature: approx. 15–25 °C. Preliminary bonding tests are recommended.

Standard plaster systems achieve good adhesion on purenit (possibly with a bonding agent). Due to the thermal expansion behaviour of purenit, the application area is limited to small sections with proper mesh reinforcement. For larger areas, such as roller shutter box covers, plaster carrier boards (ETICS insulation boards) should be bonded on.

It is generally possible to install tiles on purenit.

• If necessary sand the surface lightly and/or prime with deep-penetrating primer
• In wet areas, waterproofing is always required
• Use thin-bed tile adhesives with high initial adhesion (e.g. flexible adhesive)
• Optional: prior levelling compound or mesh fabric for higher loads
• Deflection must be prevented by an appropriate load-bearing or substructure

• Regulated under building law as a thermal insulation material according to ETA-18/0604 (the former national building approval Z-23.11-1819 was replaced by the European Technical Assessment ETA-18/0604).
• The ETA forms the basis for the CE marking and the Declaration of Performance according to the Construction Products Regulation (CPR).
• The ETA also defines the fire performance in accordance with DIN EN 13501-1.
• Construction applications in Germany are additionally covered under the general construction type approval Z-23.15-2169. Among other things, the design values for thermal conductivity are defined in the general construction type approval

Applications using purenit that require structural verification are not covered by building authority approval.

• Non-load-bearing components or building elements such as:
• packers and frame extensions
• Façade elements (non-load-bearing)
• claddings
• insulation elements
• fastening and mounting systems for windows that do not require fall protection

do not require building authority approval.

The fastening of windows that are not required to provide fall protection does not require building authority approval.
purenit is therefore frequently used as a support shim or support plate under window frames, as a frame extension, or for front-of-wall installation systems.

The “Blue Angel” certification system currently does not provide an assessment option for PU insulation materials. As purenit consists largely of PU, certification is therefore not possible.

Certifications according to DGNB, BNB, QNG, LEED or BREEAM are awarded to entire buildings, not for individual construction materials.
purenit does not violate any devaluation or exclusion criteria in building certifications according to DGNB, BNB or QNG. In particular, purenit is free from the following substances or substance groups:

• halogenated or partially halogenated blowing agents
• HBCD 
• TCEP (< 0.1%)

Compliance with the requirements of LEED and BREEAM has been evaluated and confirmed by an auditor.

The airborne sound insulation of monolithic (single-layer) components made of purenit can be estimated based on component mass. A technical expert opinion from a renowned building physics institute is available.
Sound insulation of multi-layer components is difficult to estimate and can only be reliably verified through appropriate testing.

The fire behaviour of purenit is classified in accordance with DIN EN 13501-1 and is confirmed through regular repeat testing.

• Class E purenit – normally flammable (similar to wood and most construction products)
• Class C-s2,d0 purenit C – flame-retardant

purenit is suitable for circular use and recyclable. The manufacturer puren has developed a closed-loop system in which material and cutting residues are reused:

• Reuse of production residues: puren produces the material purenit from the residual material from its own polyurethane (PU) insulation production, as well as from material residues from other PU manufacturers. No waste materials are used; only single-grade materials. Clean, single-grade PU rigid foam residues can be returned to the company free of charge in accordance with a contractual agreement. A pilot project for the return of construction-site cutting residues has been successfully launched in the Berlin area.
• Closed material cycle: purenit is the result of an internal material cycle within the company. This concept makes it possible to produce a new, high-quality functional material from previously generated residues. The company refers to this cycle as “Next Step PU.”
• Thermal recovery: Residues generated during processing on the construction site that cannot be returned to the internal material cycle can be thermally recovered.

A comprehensive life-cycle assessment in the form of an Environmental Product Declaration (EPD) is in preparation and is expected to be available in 2026. 
A similar assessment document (FDES) has already been published for France.

The manufacturing process of purenit is highly efficient:

• production is based on production residues and therefore requiring very few primary resources
• no addition of solvents or harmful substances
• no water consumption in the product
• low energy demand (also compared to wood-based panels)

As a result, purenit has a very low CO2 footprint.