BIM in Retrofit
In recent years, an increasing number of studies indicate the importance of retrofitting the existing housing stock in order to improve sustainability. Retrofit has received greater attention within the current research agenda given that it has a crucial role to meet sustainable targets( Kemmer; Koskela 2012). Given that a large share of the buildings that influence climate currently and in the future have already been built, efficient actions regarding retrofitting and renovation are demanded. Gholami et al.( 2013) state that one of the challenging issues during the retrofit process is to find an approach that improves collaboration and integration during works.
Building Information Modelling( BIM) is an approach for managing construction project information, which includes functions needed to model the lifecycle of a building. BIM provides the basis for new designs and construction capabilities, and changes roles and relationships in the project team( Eastman et al. 2011). BIM tools enable stakeholders to manage project information across its several stages in a virtual environment and can be used for many purposes in new construction or in retrofits( Sheth et al. 2010). Thus, there is a potential to use BIM tools to assist the process of retrofitting, such as 4D BIM.
According to Kymmell( 2008), 4D BIM simulates the construction process in a virtual environment. The main benefit of having the project in its virtual form is the possibility of experimenting construction activities and making appropriate adjustments before execution. Graphical simulations can reveal potential problems in their origins, and opportunities for their improvement in terms of construction works, equipment involved, spatial conflicts( logistics), security issues, among others( Eastman et al. 2011). Thus, simulation supports decision-making from the very early construction stages and facilitates the development of solutions( Capeluto; Ochoa 2014).
The simulation of construction’ s sequence is based on a preliminary programme, schedule of works and a BIM model. What-if scenarios can be visualized in 4D sequences to help communicate the advantages and disadvantages of various scheduling options( Kymmell 2008). Early 4D BIM simulation can provide to stakeholders a better understanding of the related processes and constraints that can affect construction operations.
Ultimately, 4D BIM simulation enables the understanding of potential disruption to occupants, which supports a better decision-process and mitigates the impact of construction activities on home environment. The 4D BIM simulations can be used as a visual management tool, given that images representing the different stages of the construction process can be displayed on site to workers. Dave et al.( 2013) argue that collaborative planning can be enhanced with the support of 4D BIM, where the team visually gains deeper understanding of the project when compared to traditional approaches( i. e. meetings discussing the schedule of works).
In the context of project delivery in the retrofit of existing housing, an optimal solution is the one with the capacity to cope with compressed lead-times and to cause minimum disruption to occupiers. Site layout, temporary accommodations, site facilities and storage, logistics and the construction programme and time-scales might affect not only the residing family but also the neighbourhood. The effects on occupiers depend on the family profile and on the need for temporary relocation of the family for the duration of the works. In order to determine appropriate scenarios that are effective for saving cost and time, early stage simulation methods are likely to be helpful to overcome uncertainty, to evaluate the performance of different design strategies,
Using 4D bim in the retrofit process of social housing 281