What is the driving force behind the project? Is it a failed piece of equipment? Are you taking advantage of a recently advertised incentive program? What are the desired performance attributes you hope to obtain from the technology?
To know what technology is going to be the best fit for your project, you must first identify what your project is and why you are doing it. For example, maybe you have not replaced any windows in the building because it was built 50 years ago. You just found out that another window has cracked, leaving you with more broken windows in the building than working ones. You ultimately decide that now, because of failing equipment, it is finally time to replace all the old windows.
Now you need to decide what kind of windows you want. Have you been losing a lot of heating and cooling through your windows? Maybe you have a new HVAC system but have not been able to see the energy savings because most of the energy was being lost through the old broken windows. In that case, you might want to go with windows with ENERGY STAR-rated windows that will better accompany your efficient HVAC system. Whatever the case may be, you need to start identifying the different needs and desired attributes you want from a technology. You can start to categorize these attributes into two groups: (1) those you NEED and (2) those that would be NICE TO HAVE.