The chemical composition considerations for customized outdoor sauna rooms permeate multiple aspects, including the main structure, enclosure system, functional components, and surface treatment.The core lies in ensuring structural stability, durable performance, and safe use of the facility under long-term exposure to harsh outdoor environments such as high temperature, high humidity, ultraviolet radiation, and temperature fluctuations through precise matching of material chemical properties. Chemical composition not only determines the weather resistance, corrosion resistance, and thermal performance of materials but also directly affects the environmental attributes and biocompatibility of the product. Therefore, it needs to be systematically analyzed as a key technical indicator in customized design.
The chemical composition of the main structural materials is the foundation of weather resistance and mechanical properties. The solid wood commonly used in customized sauna rooms (such as red cedar, Finnish pine, and Alaskan yellow cedar) is a natural polymer material, mainly composed of cellulose (approximately 40%–50%), hemicellulose (approximately 20%–30%), and lignin (approximately 20%–35%), and contains small amounts of extractives (such as terpenes). These natural components endow wood with excellent moisture regulation and certain antibacterial properties. However, the polysaccharides and lignin in wood are susceptible to hydrolysis and oxidation by moisture and microorganisms. Therefore, pressure preservation treatment is necessary, introducing chemical preservatives to block degradation pathways. Commonly used systems include water-soluble copper-based compounds (such as ACQ: alkylammonium copper), oil-soluble copper azoles (such as CA-B), or boride systems. Their active ingredients penetrate the cell wall and form stable complexes with cellulose and lignin, inhibiting the growth of fungi and decay fungi. For metal frames, aluminum alloys are mainly composed of aluminum and small amounts of alloying elements such as magnesium, manganese, and silicon. Anodizing treatment on the surface forms a dense alumina (Al₂O₃) film, significantly improving corrosion resistance. Stainless steel relies on chromium (≥10.5%) and nickel to form a passivation film (mainly Cr₂O₃) on the surface, blocking oxygen contact with the substrate and preventing electrochemical corrosion.
The chemical composition of the enclosure system determines its thermal insulation, waterproofing, and heat resistance performance. The walls and roof often employ a double-layer structure. The inner sauna panel is typically made of carefully selected coniferous wood, with its chemical composition as described above. It undergoes high-temperature drying and surface anti-cracking coating treatment. The coating agent may contain heat-resistant resins (such as phenolic resins or modified polyurethane) and flame retardants (such as phosphate esters or magnesium hydroxide). If the outer waterproof panel is a resin-based composite material, it is commonly made of glass fiber reinforced polyester (FRP) or polyvinyl chloride (PVC) skin board. The former uses unsaturated polyester resin (containing styrene crosslinking monomers) and glass fiber as the base material, while the latter uses PVC resin (containing plasticizers such as phthalates or environmentally friendly citrate esters) as the main component, combined with stabilizers (calcium zinc or organotin compounds) and UV inhibitors (such as benzotriazole). The chemical composition of the insulation layer varies depending on the material: mineral wool is made from basalt or blast furnace slag melt and drawn into fibers, with its main components being a silicate network (SiO₂, Al₂O₃, CaO, MgO), possessing high temperature resistance and low thermal conductivity; polyurethane foam (PUF) is produced by the reaction of polyols and isocyanates (such as MDI or TDI), and its closed-cell structure gives it excellent thermal insulation properties, but attention must be paid to the residual free isocyanates and the environmental friendliness of flame retardant modifiers (such as the addition of phosphorus and nitrogen-based flame retardants).
The chemical composition of functional components and surface treatments is related to safety and durability. If the heater is electrically heated, the heating element is often a nickel-chromium alloy (Ni-Cr, containing approximately 80% Ni and 20% Cr) within a stainless steel sheath. Its high-temperature oxidation resistance comes from the dense oxide film formed by Cr. The inner wall of the wood-burning furnace is often lined with refractory bricks, whose chemical composition is mainly alumina (Al₂O₃) and silicon dioxide (SiO₂), supplemented with small amounts of magnesium oxide (MgO) and iron oxide (Fe₂O₃), possessing high melting points and low thermal shock resistance. The insulation material for electrical circuits must be a moisture- and heat-resistant polymer, such as cross-linked polyethylene (XLPE) or silicone rubber. The former relies on molecular chain cross-linking to improve heat resistance and moisture resistance, while the latter, with Si-O-Si bonds as the main chain, has excellent temperature resistance and anti-aging properties. Surface protective coatings (such as wood wax oil or water-based paint) often contain natural oils (linseed oil, tung oil), resins (rosin derivatives), and antioxidants (vitamin E or hindered phenols), maintaining the wood's breathability while blocking direct moisture and ultraviolet radiation.
Environmental and safety considerations are paramount in custom-designed outdoor saunas. For indoor areas in close contact with the human body, the migration and release of harmful chemicals must be limited. This includes selecting low-formaldehyde-release adhesives, halogen-free flame-retardant systems, and phthalate-free environmentally friendly plasticizers to ensure compliance with food contact or medical-grade safety standards. Preservative-treated wood should use low-toxicity or non-toxic agents, and direct contact with drinking water or food should be avoided in the design.
Overall, the chemical composition system for a custom-designed outdoor sauna is a complex engineering project balancing performance, durability, and environmental friendliness. By scientifically selecting and controlling wood extracts, preservatives, metal alloy components, polymer-based composite materials, and surface treatment chemicals, the stable performance and long-term safety of the facility in complex outdoor environments can be guaranteed from the outset. This ensures that the customized result not only meets user needs in form and function but also provides reliable life-cycle protection in terms of the materials themselves.
