Many construction-related products would not exist without adhesives and sealants as they cannot be produced with alternative fastening or sealing technology. For example, sealants are key for energy-saving multipaned glass windows and glazing elements as they retain the inert gas filling in between panes that improves the insulation value; they also improve the product longevity by keeping humidity out from the intra-pane area. As another example, engineered wood elements, which can replace steel beams and concrete elements and provide notable savings in the carbon footprint[1], can be produced only by relying on adhesives. Many other products crucial to the green energy transition in the building sector, such as photovoltaic panels, energy storage batteries and solar thermal units, would not be possible without adhesives and sealants either.

Sealants and adhesive tapes are also unique in providing air tightness to the building envelope, a key factor in energy efficiency. Mechanical fastening of insulation panels or membranes typically creates air leaks (holes), and windows and doors cannot be fit into the building frame in a way that would provide an airtight seal on their own.

Even when there is a choice between mechanical fastening and adhesive use, adhesives can provide clear sustainability benefits to the overall construction project. For example, by accommodating thermal deformation stresses, adhesive-based installation of foam insulation panels reduces the risk of insulation value degradation over time (cracking) compared to mechanical anchor-based installation.

_{[1]  ‘A sustainable bioeconomy for Europe: strengthening the connection between economy, society and the environment Updated Bioeconomy Strategy’. European Commission, 2018.}

While adhesives and sealants carry their own footprint from raw materials, production, logistics and use, the amount of adhesive or sealant in a final construction product is very low and often less than one percent of a building’s mass, overall. The embodied carbon added by adhesives and sealants is therefore minimal, compared to the overall building.

At the same time, considering only the footprint of the adhesive or sealant would miss the environmental performance benefits of construction products that are possible only with adhesives and sealants. To understand the true sustainability performance of adhesives and sealants, the focus should therefore be on the finished construction product[2].

Adhesives and sealants can reduce a construction product’s footprint before installation, for example, through weight savings or the enabling of wood-based construction materials[1].

While the exact savings depend on the specific application, adhesives and sealants commonly also enable use-phase energy savings (for example, through improved thermal insulation or air tightness of the building). The added footprint of adhesives and sealants is in some cases offset within days of installation[3].

_{[1]  ‘A sustainable bioeconomy for Europe: strengthening the connection between economy, society and the environment Updated Bioeconomy Strategy’. European Commission, 2018. [2] ‘Kreislaufwirtschaft und Klebtechnik’, Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM, 2020. [3] B. Brandt, E. Kletzer, H. Pilz, D. Hadzhiyska, and P. Seizov, ‘Silicon-Chemistry Carbon Balance: an Assessment of Greenhouse Gas}

Most adhesives and sealants are based on polymers and organic chemicals, which contain carbon as the main part of their chemical structure. The concept of renewable carbon is therefore relevant for adhesives and sealants. This approach focuses on ensuring the circularity of the needed carbon, to prevent a net addition of carbon to the atmosphere. Renewable carbon can be taken from the biomass (biosphere), from the atmosphere (carbon capture) or from recycling[4].

Biomass-based raw materials are already established in the production of adhesives and sealants. Due to their small weight percentage in any given item, adhesives and sealants are generally not the target of mechanical recycling processes[2]. At the same time, raw materials from chemical recycling, including from recycling of construction materials, are becoming available for use in adhesives and sealants. For example, active developments are underway to obtain adhesive raw materials from waste insulation foams. Additionally, the chemical recycling of unused adhesives and sealants residues themselves is being established.

For adhesives and sealants that are not (primarily) based on carbon, such as cementitious products and silicones, recycling of inorganic materials (‘urban mining’) offers new opportunities for renewable raw materials[5].

_{[2] ‘Kreislaufwirtschaft und Klebtechnik’, Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM, 2020. [4] M. Carus, L. Dammer, A. Raschka, and P. Skoczinski, ‘Renewable Carbon: Key to a Sustainable and Future‐Oriented Chemical and Plastic Industry: Definition, Strategy, Measures and Potential’. nova-Institut, 2020. [5] L. Tercero Espinoza, L. Rostek, A. Loibl, and D. Stijepic, ‘The Promise and Limits of Urban Mining’, Fraunhofer ISI, 2020.}

When adhesive- or sealant bonded construction products need to be repaired or have components replaced, several options exist for the separation of the bond. Large component dimensions favour mechanical release of the bonded joint; where necessary, this can be supported by suitable machinery[2].

Repair can be further facilitated by adhesive applications that provide selective release, as found, for example, in multilayer wallpapers, which leave behind a clean layer on the wall, or peelable mounting tapes that allow, e.g., for the reversible installation of bathroom fixtures without drilling into tiles.

Where mechanical separation alone is not feasible, debonding may, for example, be achieved by soaking the bonded area in a suitable medium to weaken or dissolve the adhesive. A long-established example is wallpaper removal.

In addition, adhesives and sealants support a wide range of repair scenarios and can prevent the need for replacement of entire building elements. For example, façade sealants can extend building lifetime and prevent damages; windows can be repaired by replacing only broken glass while retaining the frame. Adhesives and sealants can also help the prevention of follow-on damages by mending damages quickly, for example, sealing damaged rain gutters.

Aside from buildings themselves, adhesives and sealants are also key to the maintenance and repair of machinery. Important applications include thread locking, retaining, gasketing, sealing, vehicle window repair and more. In the EU, about 20% of machinery is intended for use in construction[6].

_{[2] ‘Kreislaufwirtschaft und Klebtechnik’, Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM, 2020. [6] ‘Scenarios for a transition pathway for a resilient, greener and more digital construction ecosystem’. European Commission, 2021.}

Separation of different materials in the sense of selective deconstruction is possible with adhesives and sealants. The large component dimensions that are common for construction products favour mechanical release of adhesive- or sealant bonded joints, where necessary supported by suitable machinery[2]. Examples include the mechanical removal of carpets, (structural) construction elements and insulation panels. The approach is in many cases no different from alternative fastening methods, such as mechanical nails, mechanical anchors or screws (which are unlikely to be selectively unscrewed during demolition). Compared to welding (of both metals and plastics), adhesives and sealants do not modify or fuse the substrates; separation of components can follow the bond line.

If adhesives or sealants remain on construction materials that are to be recycled after deconstruction, they may enter recycling processes. Due to their small weight percentage in any given item, adhesives and sealants are generally not the target of recycling[2]. Therefore, rather than being ‘recyclable’ themselves, adhesives and sealants primarily need to allow for the recycling of the main construction materials, and adhesive and sealants can indeed be compatible with the relevant recycling processes. Examples include adhesives used in wood joinery or pipe sealants. Alternatively, adhesive and sealants may be removable during recycling processes. Industrial processes for removal that can be applied to adhesives and sealants include soaking, washing, milling and grinding of the construction waste. Subsequent separation from the main construction materials may be achieved by flotation, wind sifting, air elutriation or sieving, amongst other options[7], [8].

_{[2] ‘Kreislaufwirtschaft und Klebtechnik’, Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM, 2020. [7] D. Eckert, R. Kocina, and D. H. Achenbach, ‘Förderung einer hochwertigen Verwertung von Kunststoffen aus Abbruchabfällen sowie der Stärkung des Rezyklateinsatzes in Bauprodukten im Sinne der europäischen Kunststoffstrategie’, Umweltbundesamt, 2021. [8] ‘Potenziale eines hochwertigen Recyclings im Baubereich’, VDI, 2016.}

Good recycling options already exist for most adhesive and sealants packaging formats (primary and secondary). Recycling of steel containers is well established with a very high steel recycling rate worldwide (70-90 %)[9], and recycled content of steel in Europe is also high, typically >50 wt%[10]. Recycling of paper and cardboard packaging is well established, with typical recycling rates for paper above 70% in Europe[11], [12]. Recycled content is high in most fibre-based packaging types, typically above 50 wt%[12]. Recycling of emptied or washed PE and PP plastics packaging is possible where related recycling infrastructure exists, and packaging is collected in the relevant streams.

Certain restrictions for adhesive and sealant packaging recycling have to be observed. Separate collection and recycling infrastructure may be required if the product left in the packaging after use is classified as hazardous. Such dedicated collection and recycling schemes are already implemented in practice for PU foam cans and are being established for silicone cartridges.

_{[9] ‘Metal Stocks & Recycling Rates’, United Nations Environment Programme, 2011. [10] ‘The Recycled Content of Steel for Packaging’, APEAL, 2017. [11] ‘Key Statistics 2020 European Pulp & Paper Industry’, cepi, 2021. [12] ‘Corrugated Packaging – A Recycling Success Story’, Corrugated Packaging Alliance, 2016.}

How to use Model EPDs to address market and regulatory needs for adhesives and sealants in the construction sector

Following the revision of the Model Environmental Product Declarations (Model EPDs), FEICA, Industrieverband Klebstoffe e.V. (IVK) and Deutsche Bauchemie e.V. (DBC) invited their members to a webinar to discuss the legal framework and upcoming challenges due to legislative initiatives (e.g., the revision of the Construction Products Regulation) in relation to EPDs in the adhesives and sealants construction sector.

One webinar was held in English, on 25 October 2022 and another in German, on 8 November 2022. FEICA members can click on the respective language to view the presentations. 

A video of the English webinar is also available on the FEICA Extranet here.

These are the proceedings of the FEICA webinar, which took place on 24 May 2022.

The key takeaways were:

• The energy efficiency of buildings is a key element of a climate neutral European Union. Adhesives and sealants are integral to thermal insulation and decarbonised heating solutions.
• Material efficiency addresses the (carbon) footprint embodied in construction materials themselves and the quantities of future demolition waste. Adhesives and sealants support weight reduction and the use of lower footprint construction materials. During the use phase of a building, adhesives and sealants facilitate maintenance, repair and renovation functions.
• When construction elements or entire buildings reach their end-of-life, multiple approaches exist for reuse and recycling. With the right design, adhesives and sealants applications can enable circularity at the end-of-life. 

You can download a summary of FEICA’s report 'Adhesives and sealants’ key sustainability role in the transition pathway for the construction ecosystem'.

The full report is available for FEICA Members only.

You can watch the recording of the webinar here.

These are the proceedings of the FEICA webinar, which took place on 25 February 2021.

The Construction Products Regulation (EU) No. 305/2011 (CPR) lays down conditions for the placing or making available of construction products on the market by establishing harmonised rules for the marketing of these products in the European Union. It aims to ensure that reliable information is available to professional users, planners and architects and public authorities and consumers in a common European language.

FEICA raises awareness about this legislative package within the adhesives and sealants industry.