# Mycelium-Based Thermal Insulation for Domestic Cooling Footprint Reduction: A Review
## 5 Conventional Insulation Materials
### Phenol Formaldehyde
#### 5.2.2 Renewable Insulation Materials
Flax fiber wool insulation is commonly manufactured into solid or partially solid rolls or as loose insulation materials. It requires treatment with a fire retardant, often accomplished using substances like ammonium salts or sodium borax. Flax wool insulation is part of a vapor-permeable system regulating relative humidity and providing a healthy indoor environment. Flax wool has a thermal conductivity of about 0.038 W/m\(\cdot\)K, comparable to other natural fiber insulations such as hemp and sheep's wool. Flax wool is more expensive than mineral wool but has a lower energy demand in production and the potential for recycling [71]. Hemp insulation, derived from natural hemp fibers, is an environmentally sustainable and biobased thermal insulation material that offers several advantages for enhancing buildings' energy efficiency and indoor air quality. One key benefit is its non-toxic, hypoallergenic nature and its resistance to mold and pests. Additionally, hemp insulation exhibits a high thermal resistance of 3.7 per inch and a low conductivity of 0.039 W/m\(\cdot\)K, enabling effective thermal insulation. It also possesses excellent acoustic isolation properties, reducing noise in buildings. Furthermore, hemp insulation is user-friendly, easy to install, non-abrasive, and can be cut with various tools. However, it is essential to consider some limitations associated with hemp insulation, including its relatively higher cost than conventional materials like fiberglass or mineral wool. Moreover, some regions may need more availability and compatibility of hemp insulation with specific building codes or standards [72]. Recycled insulation materials are made from reused or reclaimed materials, such as plastic bottles, newspapers, glass, or denim. These materials are processed and transformed into insulation products used on roofs, walls, and floors to improve energy efficiency and comfort. They offer environmental and health benefits, such as lower energy use, lower carbon emissions, better indoor air quality, and good thermal and sound performance. However, they also have disadvantages, such as higher cost, lower availability, need for additives or treatments, and lower R-values or higher density than conventional insulation materials [73; 74]. Wood wool insulation is a natural and environmentally friendly product that combines fire resistance with outstanding acoustic and thermal performance. Produced from wood slivers obtained through log cutting, these slivers are mixed with a natural binding agent and additional additives, then compressed into boards that undergo dehydration in an oven. First, it is sourced from sustainably managed forests and adheres to the principles of complete recyclability following the 'cradle to cradle' approach. Moreover, its exceptional heat storage capacity enables it to maintain a comfortable indoor temperature during summer and winter. Additionally, it exhibits high vapor permeability and possesses excellent moisture-regulating capabilities, effectively preventing condensation and inhibiting mold growth. Its commendable sound-insulating properties reduce noise transmission between rooms or from external sources. Furthermore, it boasts easy installation, facilitating application between rafters or other beam structures. The availability of wood wool insulation in various surface textures, collars, and sizes allows for customization to meet diverse design requirements. However, it is essential to acknowledge the drawbacks of wood wool insulation. It tends to be more expensive than alternative insulation materials like mineral wool or cellulose. Additional fire protection or mold resistance treatments may be required depending on the additives utilized in the production process. Additionally, it may not be suitable for highly humid or wet environments, as it has the potential to absorb water and compromise its insulating properties. Therefore, when considering wood wool insulation for a specific application, it is crucial to evaluate its advantages and limitations [71].