Understanding the optimal conditions for internal building environments is a matter of balancing a variety of complex issues. Windows, for example, that do not insulate from heat loss or gain will expand energy consumption in keeping the working environment pleasant. If they allow for too much light, employees can suffer from eye strain and fatigue. Reflective glass produces glare which can prove troublesome for motorists passing on nearby roads and tinted glass reduces both light and absorption but increases electric lighting consumption. Windowpane technology has come a long way in recent years to provide buildings with the optimal glassing. However, even with the multitude of options available, from windows prepared with low-conductance gas fills to heat absorbing glazing, or windows with spectral-selective coatings or low E-coatings of metal oxides, choosing the correct pane is not a simple matter at all. Clearly, no one type of window is suitable for all applications, and most probably, the optimum solution lies in a mixed variety of pane types. Under the EC-funded IMAGE project however, two investigations where concurrently run in order to better understand the complexities involved. The first of these developed a standard testing procedure aimed at assessing the performances of advanced glazing systems in laboratory and outdoor conditions. The second investigation involved marketplace exploitation potential, looking at such factors as determining the environment life cycle as well as the cost-benefit analysis in using advanced glazing systems. Additionally, design integration studies were initiated with the purpose of gaining feedback which is essential for manufacturers wanting to understand both the market forces and constraints involved. Currently, the project has resulted in the development of simulation software capable of representing the performance of glazing systems, and a new software support tool called the GDST (Glazing Design Support Tool) that allows manufacturers to evaluate their products through a multi-variant performance appraisal. The innovation behind the standard testing procedures is its ability to prove performance under a variety or real climatic conditions as well as the inauguration of a set of standards, or "IPV" ratings, that summarises overall performance in representative matrices such as room comfort level, energy consumption, environmental impact and comparative analysis of different designs. Glass may be clear-cut, but integrating advanced glazing systems for optimal environmental and energy conditions, is far from being as clear as glass.