This thesis presents a comparative Life Cycle Assessment (LCA) of T-shirts made from different fiber types—cotton, synthetic materials, recycled wool (MWool®), and linen—focusing specifically on the environmental impacts of the use phase and contrasting them with the production phase. Utilizing OpenLCA software and datasets provided by Manteco®, the study models cradle-to-gate production impacts alongside the impacts of domestic washing, drying, and ironing practices over a functional period of 10 years. The system boundary includes yarn production, weaving, finishing, and standardized laundering modeled according to ISO 6330:2000 procedures. To reflect realistic consumer use, the analysis incorporates user behavior data from multiple countries and adapts the functional unit to a service life of 10 years, accounting for the variable durability of different fibers.