High-performance thermal insulation is crucial for preventing heat loss and reducing energy bills in buildings and industrial sectors such as manufacturing, petroleum, and cryogenics. Conventional insulation materials, including glass wool, polystyrene foams, and many recycled cellulose products, degrade in thermal performance under humid conditions. In contrast, specifically designed porous insulators made from cellulose can behave differently, sometimes insulating even better with moisture. Unlike conventional materials, these advanced cellulose-based insulators can show complex thermal conductivity behavior, sometimes becoming better insulators with increasing humidity. This unique behavior happens because moisture can cause the structure of these advanced cellulose-based insulators to swell, which reduces heat conduction through the solid fiber network. While this offers the potential for enhanced insulation performance in humid environments, the underlying mechanisms governing these unconventional responses remain poorly understood, which limits practical applications. This project will close this important knowledge gap by studying how cellulose fiber dimensions, pore structures, and moisture collectively govern thermal transport in cellulose-based porous materials. This research will also create valuable learning opportunities by involving students at all levels in research, training, and curriculum development. The goal of this project is to understand how moisture