Almost 18% of carbon dioxide and 10% of carbon monoxide emissions are considered to be attributed to buildings because of increased needs for heating, cooling and lighting. It is thus important to turn the building sector into a more sustainable way of designing, building and renovating. Answering this need, the SMART_WIN_II project improved and realised suitable glazing technology with increased potentialities to offer three optical states, namely clear, reflective and scattering modes. The latter modes can offer an increased modulation magnitude of the light flux, a near perfect reflective state and a glazing with only one reflective face respectively. Glazing with different optical states in different areas, or simply patterning constitutes an novel way of exploiting the optical and thermal behaviour of windows. Unlike most conventionally technologies, liquid crystals have an increased potential in making patterning feasible, particularly with fenestration systems. In order to gain a better knowledge on the impact of patterning on fenestration systems, a model pattern system was developed. This was used for running simulations with a wide range of parameters including transmission range, pattern number, pattern size and outer situation. The derived results allowed researchers to specify decision criteria for the better performing patterned system. The optimal pattern and the patterning effects on the solar heat gain of the window were also defined. More specifically, if specific areas were darkened at high outer light luminance levels instead of the complete surface, visual comfort could be further enhanced. In this way, an increased use of daylight instead of artificial light could be achieved. Apart from daylight provision, this technology also provides visual contact with the outside world, solar protection, and glare reduction offering a convenient and pleasant working environment. This novel way of manipulating the optical properties of day lighting systems by using tunable layers of liquid crystals may lead to a new category of day lighting systems with increased marketing potential.