This book is a researched work on calabash fibre (Lagenaria siceraria). There were five (5) fibre content loading compositions. The reinforcement ( Calabash fibre ) and binder (PVC resin) were compounded using hand layup technique . Samples of the treated and the untreated composites were subjected to tensile and flexural strength, Scanning Electron microscopy (SEM), water absorption, thermal conductivity , Specific heat capacity , thermal diffusivity and density tests. 10% NaOH Alkali treatment for 24 hours was sufficient to remove impurities from the fibre, enhanced good interfacial fibre-matrix bonding. The Thermal Conductivity result of the treated sample (D) of 40wt% composition has better thermal conductivity of 0.14W/mk. The density and water absorption values were evaluated. The newly developed composite has lower thermal conductivity than polyvinyl chloride and can be used for such thermal insulation applications as low temperature thermal insulation limits of 15 oC to -75oC refrigeration and cold rooms' insulation and for hot water condensate as in thermo-flask applications.