# Mycelium-Based Thermal Insulation for Domestic Cooling Footprint Reduction: A Review
## 3 Mycelium as a Base for Thermal Insulation  
### Exploring the Hidden Dimension of Fungi  
Mycelium has recently garnered increasing attention from academic and industrial sectors due to its minimal energy requirements during growth, absence of by-product generation, and extensive potential applications [4]. Mycoloy, a subdivision of microbiology, delves into the domain of fungi--a multifaceted and expansive kingdom that incorporates molds, yeasts, and various types of mushrooms [5]. While mushrooms are the visible reproductive structures of fungi, most of their bodies grow below ground as  
Figure 1: Study selection flow chart.  
a woven-like network called mycelium. Mycelium is the root-like formation of a fungus, made up of a network of thin, white threads that range from 1 to 30 micrometers in width (Figure 2) [6]. Bio-derived materials present a remarkable opportunity for exploring architectural and product design innovations. Among these, mycelium-based materials stand out as particularly promising, offering a significant pathway for creating environmentally conscious materials that leave minimal impact throughout their entire lifecycle. Mycelium filaments have multiple layers that exhibit varying chemical compositions, comprising proteins, glucans, and chitin [7]. Mycelium has been recognized as the most expansive living organism on Earth. The substrate functions as a nutritive reservoir of organic matter that sustains the expansion of the mycelial infrastructure. In natural ecosystems, these organic substances commonly originate from the residues of organisms, including plants and animals, and their by-products found within the surroundings [8]. A single cubic inch of soil has the potential to harbor up to 8 miles of mycelial cell networks [9]. The life cycle of fungi typically remains inconspicuous until the development of reproductive structures known as fruits. Given that fungi propagate via spores, the efficacy of their life cycle hinges upon the successful formation of these spore-producing organs, commonly referred to as mushrooms [10]. Fungi exhibit a widespread presence across diverse ecosystems worldwide, showcasing remarkable resilience under extreme conditions such as deserts, polar regions, aquatic depths, and high salinity zones. Some fungal species demonstrate notable adaptability when temperatures surge during the warmer summer. Among the fungi varieties well-suited for elevated temperatures, those suitable for indoor cultivation encompass the Pink Oyster (21-29 \({}^{\circ}\)C), Reishi (21-27 \({}^{\circ}\)C), Antler Reishi (15.6-26.7 \({}^{\circ}\)C), Shiitake (10-26.7 \({}^{\circ}\)C), and King Stropharia (15.6-26.7 \({}^{\circ}\)C). For outdoor mushroom patches and plug spawn, favorable choices include the Phoenix Oyster (18-24 \({}^{\circ}\)C), Reishi (21-27 \({}^{\circ}\)C), Shiitake (10-26.7 \({}^{\circ}\)C), and Garden Giant (4.4-32.2 \({}^{\circ}\)C) [11].  
Materials derived from mycelium can enhance the air quality within indoor environments. Fungal mycelium has been shown to possess natural air-purifying capabilities, particularly in terms of particulate matter (PM) filtration. The porous structure of mycelium enables it to trap and filter airborne particles, including PM\({}_{2.5}\) and PM\({}_{10}\), thereby enhancing indoor air quality [12]. Additionally, mycelium has the potential to regulate indoor humidity. The hygroscopic nature of the mycelium allows it to absorb and release moisture, helping to maintain optimal moisture levels. This natural humidity regulation contributes to a comfortable indoor climate [13]. Furthermore, mycelium can sequester over 16 metric tons of carbon from the atmosphere within a month [14].  
Figure 2: Schematic representation of mycelium structure [10].