**1. Introduction**

Saving energy has been a major issue in recent years as part of the efforts to maintain the sustainable development of society. In 2022, the situation in Europe changed dynamically due to the military conflict in Ukraine, which resulted in the virtual collapse of energy markets and an uncontrollable rise in gas and electricity prices. Countries were forced to search for solutions in an unprecedented situation and the pressure for energy saving was intensified. The greatest potential of the construction industry lies in savings in heating buildings [1]. In new buildings, the desire to reduce heat loss is reflected both in the design of the building structure [2] and in the thermal parameters of the structures. However, the greatest potential, regarding the number of buildings, lies in existing structures, where the most common way of improving the energy balance has been additional insulation [3]. This can be implemented in two ways. The first is the use of suspended facade systems, which consist of a load-bearing (usually aluminium) structure, mineral wool thermal insulation, a windproof diffusion-open membrane, a ventilated air gap and a facing cladding board [4,5]. The second option is external thermal insulation using a composite system that is in full contact with the original surface of the facade and consists of thermal insulation (most often expanded polystyrene or mineral wool, or other materials that are used less frequently) and reinforcing layers of cement screed with fibreglass mesh, coloured primer and coloured thin-layer plaster [6,7]. Both options include a thick layer of thermal insulation that can be sized as required to provide the desired energy savings. Each of the two options has both advantages and disadvantages. In general, however, contact insulation is significantly more widespread. This is primarily due to its lower cost, which represents approximately one-third of a suspended ventilated facade system. The authors of this paper focused on the issue of sheet-metal facade components in contact-insulated facade systems, where secure

Faculty of Civil Engineering, Brno University of Technology, Veveˇrí 331/95, 602 00 Brno, Czech Republic **\*** Correspondence: ales.prucha@vut.cz; Tel.: +420-541-147-989

fastening to the substrate becomes increasingly difficult due to the increasing thickness of the thermal insulation.

Currently, 200 mm thick layers of thermal insulation are common, and 300 mm thick insulation is not an exception. These surfaces are largely unsuitable for plumbing work, mainly due to the impossibility of firm fastening, as the outer plaster layer is too thin, and the insulation itself is not a load-bearing substrate. While there are system solutions for connecting sheet-metal components to multi-layer plaster, e.g., parapet connection profiles with integrated adhesive surfaces for bonding metal parapets or connection profiles for inserting vertical facade flashings, these are always components intended to be fitted during the installation of the insulation system. Using these solutions requires precise coordination during the construction process. Moreover, they are not always applicable as they do not allow the fitting of sheet-metal structures during additional work onto older, previously insulated facades. This article deals with the issue of fastening sheet-metal components by bonding them to the surface of thin-layer plaster. It presents an initial series of tests to verify the perspectives of this technology for further research. The technology of bonding sheet-metal components to thin-layer plaster, if properly validated, would be widely applicable, even outside the field of contact thermal insulation systems.
