When undertaking a significant energy retrofit project, architects employ various tools to help them successfully identify potential areas for improvement. Some of the most valuable assets in an architect’s toolbox are companies that provide building analysis. A building analysis service team that can completely test, measure, and document the gaps and opportunities for energy savings in a building will provide the architect with a wealth of information and resources needed to successfully complete the project. However, when it comes to windows, traditional building analysis services often fail to deliver a complete evaluation of the building, and miss several of the key components that can impact energy use. Besides the energy efficiency rating of the window - other considerations like occupant comfort and air tightness should be included when designing a window replacement strategy during a retrofit project. Architects who choose a building analysis service that provides a complete evaluation of the windows and fenestration in the building will have better information, more options, and a greater chance of creating a successful energy efficient design that provides a faster return-on-investment for property owners.