When determining the R value for a wall in the Wall Component Settings dialog, there should be an option to enter the total wall value directly, rather than having to enter the Lambda values for each of the wall components.
Many walls may have insulation values within a given component, such as with framed walls that have a 1" layer of sprayed foam insulation and another layer of pumped-in fiberglas. Currently there doesn't appear to be any way to get the appropriate information entered into the system.
Also, considering the present limited composition of the "look up" listing of materials and Lambda values, the ability to make direct entry of total wall R values makes much more sense.
I realize that some people may not understand how to calculate the R value of a wall, so providing a system for doing so is reasonable, but the system as currently implemented doesn't get the job done.