This paper presents the results of the study of the influence of the design method on construction productivity in the area of installing the manufacturing tools in cleanroom facilities. Two new concepts were specially introduced to allow the comparison of productivity between the installations of various manufacturing tools. The two concepts are: Index of Complexity (IC) and Work Load Indicator (WLI). The IC is a measurement of the congestion around the tool and conditions for routing the connections. The WLI is the product of the IC and the number of connections of a certain type, such as piping, ductwork or electrical. The man- hours effectively spent by each trade to install various tools have been plotted against the corresponding WLI of each of the tools, and a regression analysis was performed on the resulting curves. The curves represent the expected productivity for tool installation and they are dependent upon the design method used. By comparing the productivity curves of tool installation when 2D design was used with the curves of 3D design we have determined what the level of complexity that warrants the use of 3D versus 2D is. The paper presents the logic behind IC and WLI, as well as the results of the comparison between 2D and 3D design.