The climate change that is affecting our planet has been an ongoing topic during a long period of time. During this time many goals has been set in order to decrease the greenhouse effect. On January 1, 2022, the government introduced a requirement that all new buildings shall be climate declared. Calculation of a building´s environmental impact can be carried out using lifecycle analysis (LCA), for environmental impact in the construction phase only modules A1-5 are considered.The purpose of this thesis is to perform and examine the process of climate declarations, both with and without a model-based tool. Furthermore, the study aims to investigate obstacles, difficulties and improvements that arise when performing climate calculations with model-based tools.The following method choices for this study are a case study and interviews. The case study is based on producing climate declarations with and without model-based tools. The interviews were held with four respondents with knowledge and experience regarding climate calculations and model-based tools. Two climate declarations have been produced, where one was carried out manually and the other with the help of the BIM tools.The result of the climate declaration is presented below:-Without model-based tools: 41 188,67 kg CO₂e per m² Atemp-With model-based tools: 40 020,53 kg CO₂e per m² AtempThe difference between the climate impact is approximately 2,8 percent, which is insignificant.The interview study showed that model-based tools contribute to improvements, such as early indications, automatic information flow and visualization. Challenges that may occur include a lack of communication, knowledge, and a limited budget.