What are the primary goals of creating a building model? Who are the key stakeholders?
The primary goals of creating a building model is to inform the stakeholders of the building design in a more visually accurate way to prevent miscommunication before the project starts. (As the project proceeds, any further miscommunication will be magnified) In addition, the building model is a great opportunities for construction planning as well as clash detection, which significantly reduces the chance of rework in the future. The stakeholders are generally the parties that are involved in the project such as the owner, the contractors, subcontractors, etc. who would directly or indirectly benefit from the use of BIM. They generally care about whether the design is in accordance to their expectation, whether the project is within budget and construction timeline.
Many door and window manufacturers provide Revit families for doors and windows that you can specify for your building design.
Manufacturers providing their own families enables for more specific details such as the dimensions, type of materials used, and any other regulations during the design process. For engineers, the more detail it gets, especially in the later phase of the project, can improve efficiency and reduce inaccuracies. The other aspect of providing their own revit families is to promote their product reputations in the market. Generally, the families provided on revit are very generic and they lack specific details such as R values, which are crucial in energy efficient building designs. Therefore, if a designer desires the final rendering of the project to be closer to reality. It is recommended to use revit families provided by those manufacturers.
What are the advantages of getting the Revit component families (for furniture, equipment, and fittings) directly from the manufacturer versus from an online sharing website like RevitCity.com?
Again, manufacturers can provide more details about the making of such furnitures that contributes to the engineering aspect of the design, whereas the components found on Revitcity are sometimes artistic pieces made by Revit enthusiasts that might add aesthetic values to the project but no engineering benefits to the design of the project.