# The Evaluation of Historic Building Energy Retrofit Projects through the Life Cycle Assessment
## 3 Thermal Insulation for Historic Buildings
XPS products may be perforated, and cut and adjusted at the building site, without any loss of thermal resistance [10]. Extruded polystyrene (XPS) is produced from melted polystyrene (from crude oil) by adding an expansion gas, i.e., HFC, CO\({}_{2}\), or C\({}_{6}\)H\({}_{12}\), where the polystyrene mass is extruded through a nozzle with pressure release causing the mass to expand [22]. The thermal conductivity of XPS varies with temperature, moisture content, and mass density. As an example, the thermal conductivity of XPS may increase from 34 mW/(mK) to 44 mW/(mK) with increasing moisture content from 0 vol% to 10 vol%, respectively. XPS products may be perforated, and also cut and adjusted at the building site, without any loss of thermal resistance [23]. Regarding the use of bio-materials for the built environment, for acoustic and thermal insulation of historic buildings, we focused our attention on the analysis of a bemp material (bio-material) already present on the Italian market: ISOLKENAF 80 Kg/m\({}^{3}\). Kenaf is a plant that belongs to the hemp family. Its scientific name is Hibiscus Cannabinus, and it has no THC. The first uses of Kenaf date back as far as 2800 BC. The plant was highly valued for its easy workability in making artefacts, ropes, and textiles. Kenaf in Italy grows on the banks of the Po River in the Po Valley; it is sown in March and harvested with corn harvesters from November; it does not require special care or pesticides and has a significant positive impact on the soil, freeing it from weeds [27]. The insulation products in Kenaf meet all the requirements for use in the building industry and are widely certified. They are ecological and bio-natural (ANAB-ICEA-certified); excellent for thermal and acoustic insulation; eco-sustainable and recyclable; thermally bonded without the use of adhesives; inert to insects, rodents, and birds; unsusceptible to rot insensitive to moisture, and breathable. Additionally, they do not require a vapor barrier and do not release pollutants. ISOLKENAF is characterized by perfect stability over time because of its strong natural fibers. The panels maintain their high insulating performance over time. The arrangement of the kenaf and hemp fibers guarantee thermal and acoustic performance superior to traditional products. In addition, the use of strong, extensible natural fibers provides the panel greater resilience and compactness (Figure 2). It is a product that can be used for floors, roofs, in facade walls for internal or external coats, or for thermal insulation with dry systems. Produced without polluting chemical adhesives, it is fully recyclable during disassembly, and it is an eco-sustainable product with high performance throughout its life cycle. This material favors the transpiration cycle of the building envelope, and it regulates the degree of humidity, retaining excesses in the cold months and releasing them in the warm months; it has received the LEED certification. Its morphological and physical-mechanical characteristics are displayed in Table 1.  
Finally, by the analysis of the state of the art, we selected two insulating materials, i.e., polyurethane panels and hemp panels, to apply to the energy retrofit project of the case study.