The operational energy in construction projects has already reached its lowest, so the production and use of building materials have a significant share in CO2-e emissions. Wooden buildings are commonly used to reach a reduction of embodied emissions. The impact analyses are generally conducted based on the LCI obtained from the BIM models. The absence of guidelines on BIM modelling for LCI is a possible cause for deviations in the LCA, particularly when assessing the environmental burden of timber building, as certain components are modelled without accurate representation of the real quantity or completely omitted. This study investigates the differences in the GWP of a modular timber building comparing the inventory originated from simplified (LOD200) and detailed (LOD400) BIM models. The impact evaluation is executed through the LCA method. The GWP increase of 14,7% is observed when the LOD400 model serves as the LCI source.
With cut-off criteria at the GWP contribution above 5% and more than 10% variation in the GWP of the material based on the two models, the adequate quantity estimation of the following materials is found to be critical: insulation, bitumen felt, and aluminium flashings. Elements typically omitted in modelling (fasteners, sealants, membranes, etc), and thus LCA is found to contribute by 15% to the total GWP, with the highest share of 6% belonging to fasteners. Currently overestimated GWP of the insulating material by over 50% tends to be wrongfully identified as the hotspot, calling for its reduction. The outcome of this study provides correction methods for the analysis based on LCI obtained from BIM models. Due to the industry’s reservation towards advanced BIM modelling for LCI purposes, this study suggests alterations which can be applied in the current enforcement of 2023 Danish LCA legislation or can direct the industry’s development in the long run.