In order to address concerns related to global warming and increased atmospheric carbon content, the life cycle assessment (LCA) tool has demonstrated usefulness in the building and construction sector. The LCA is used to evaluate environmental impacts concerning all stages of the building process from “cradle” to “grave”. The LCA helps promote sustainable development by considering environmental indicators such as stratospheric ozone depletion, eutrophication, global warming potential, and many more. It is of an interest to know the degree of impact on a given environmental indicator if an input is changed in terms of the type or amount of the materials used. The LCA software Athena IE4B was employed to analyze data of a selected timber building. This study was aimed at evaluating the sensitivity of LCA analysis on a hybrid timber building, which was done via two case studies. Case 1 focused on changes in the volume of wood materials, meanwhile Case 2 focused on simultaneous changes in the volume of materials for wood, steel, and concrete. In Case 1, it was observed increasing wood materials increased environmental indicators, with stratospheric ozone depletion being the most sensitive and global warming potential as the least sensitive. Case 2 discovered that proportionally increasing wood materials in relation to steel and concrete materials decreased environmental indicators, with eutrophication being the most sensitive and stratospheric ozone depletion as the least sensitive. This study helped support the feasibility of using Athena IE4B for LCA analysis in the initial assessment of a building.