*Review* **Applications and Properties of Hemp Stalk-Based Insulating Biomaterials for Buildings: Review**

**Borja Martínez, Ernest Bernat-Maso and Lluis Gil \***

Department of Strength of Materials and Structures in Engineering, Polytechnic University of Catalonia, 08222 Terrassa, Spain; borja.martinez@upc.edu (B.M.); ernest.bernat@upc.edu (E.B.-M.) **\*** Correspondence: lluis.gil@upc.edu

**Abstract:** There has been increasing interest in green and recyclable materials to promote the circular economy. Moreover, the climate change of the last decades has led to an increase in the range of temperatures and energy consumption, which entails more energy expenditure for heating and cooling buildings. In this review, the properties of hemp stalk as an insulating material are analyzed to obtain recyclable materials with green solutions to reduce energy consumption and reduce noise to increase the comfort of buildings. Hemp stalks are a low-value by-product of hemp crops; however, they are a lightweight material with a high insulating property. This study aims to summarize the research progress in materials based on hemp stalks and to study the properties and characteristics of the different vegetable binders that could be used to produce a bio-insulating material. The material itself and its microstructural and physical aspects that affect the insulating properties are discussed, as is their influence on durability, moisture resistance, and fungi growth. Research suggests using lignin-based or recyclable cardboard fiber to develop a bio-composite material from hemp stalk, but long-term stability requires further investigation.

**Keywords:** hemp stalk; bio-insulating material; sustainability; sound absorbing properties; thermal absorption properties; green composite material
