# Enhanced Resistance to Fire of the Bark-Based Panels Bonded with Clay
## 4 Conclusions  
These ecologically friendly, 100% natural and recyclable composites can be mostly used with respect to their thermal insulation, acoustics and fire resistance properties [66]. In this research, the thermal conductivity of the bark clay composites was investigated. The board with the lower thickness (19 mm) had a similar value as reported from [PERSON] et al. [60,62] and [PERSON] et al. [67]. The panel with density of 600 kg/m\({}^{3}\) has excellent thermal conductivity values despite a high density, and it can also serve as thermal insulating material. Another advantage of the bark clay boards as an insulation material is mostly in the accumulative capacity, similar to wood cement boards. Clay surfaces can regulate temperature because they are able to absorb and diffuse water  
Figure 7: Thermal conductivity of the composite boards with larch bark and clay. vapor very well. Clay boards can significantly improve the climatic stability of indoor spaces that have low ventilation rates. Thus, moisture mass must have equal consideration to thermal mass in passive buildings. A few centimeters of clay absorbent material is sufficient to buffer a daily relative humidity (RH) cycle, and about 40 cm of an absorbent wall might buffer an annual cycle in a standard room [68]. Besides these properties, clay boards are excellent in absorbing odors. The same occurs for bark insulation boards [69]. In the case of sound absorption, bark-based panels can absorb sound better than OSB, particleboard, MDF and poplar plywood. Therefore, the values of the sound absorption coefficient confine their application as structural elements for reducing noise effects in residential buildings, and open new ways for deeper research in this field [6]. In addition, clay is very good at reducing noise levels. Clay boards have excellent fire resistance properties, and they can be used, for example, as the fire protection of wooden or metal structure surfaces. The mixture between larch bark and clay generated a composite with enhanced resistance to fire. The results are consistent with the findings of [PERSON] et al. [40], regarding the role of bark composites as coating materials with acceptable fire resistance. Bark boards with clay, similar to wood cement composites, have non-essential mechanical properties. Therefore, there is a limited use for non-structural paneling applications [70]. The disadvantage of the bark clay composite panels is also the tool wear (circular saw and band saw, milling head), that can be optimized by the reduction of the board's thickness of 1-2 mm, to obtain a thin fire-resistant coating. These layers can protect a flammable substrate from fire by the thermal insulation effect. A trend in recent years is that coatings represent the addition of clay to improve resistance against fire, especially formulations with nanoclay [71; 72]. A new type of fire-resisting coating with bark and clay could be considered as a follow-up of this analysis. The following research perspectives in this area should focus even more deeply on the synchronization of ecological, economic, and social aspects of sustainability of ecologically friendly, 100% natural and recyclable composites with respect to their thermal insulation, acoustics and fire resistance properties [73; 74; 75; 76]. Conceptualization, E.M.T., and M.C.B. ; methodology, C.S. and T.S. validation, R.R. ; formal analysis, R.R. ; investigation, C.S. and T.S. ; resources, L.K. ; writing--original draft preparation, E.M.T., and L.K. ; writing--review and editing, L.K. ; visualization, E.M.T., and M.C.B. ; supervision, R.R. and M.C.B. All authors have read and agreed to the published version of the manuscript. This research was supported by the Slovak Research and Development Agency under contracts no. APVV-17-0583, APVV-18-0378, APVV-19-0269 and VEGA 1/0717/19 and ITMS project code: 313011T720 \"LignoPro\". The authors declare no conflict of interest. * _[PERSON] et al.