Households have a big impact on energy efficiency in Poland. About 80% of final energy in the construction
sector is used for heating buildings. Due to the significant role which is assigned to the thermal
modernization in European documents, the paper attempts to assess the environmental benefits of the
investment consisting of thermal insulation of the building external vertical walls, with the use of LCA
analysis and divided into three categories of damage. A methodology for assessing the benefits has been
proposed and the analyses for different variants have been performed, including the condition of the
building before thermal insulation, the used heat source, the type of thermal insulation and the climatic
zone in which the building is located. It has been shown that the investment, for all examined variants, is
beneficial for environmental reasons. In the worst case, the reduction of the burden on the environment
as a result of the investment occurs after 5 years, while in most cases only after one year. The obtained
environmental benefits depend primarily on the condition of the building before thermal insulation and
the used heat source. The greater are the advantages, the bigger is the demand for thermal energy of the
building that also depends on the climate zone. Because of the thermal insulation material the greatest
environmental benefits are found in the case of ecofibre. Taking into account three categories of damage,
the greatest benefits were achieved in the Resources category.