The Carbon Lite software tool will work alongside and inform the design process in the generation of low carbon buildings with optimum occupancy environments. The tool is innovative and will fill a market gap by responding to all stages of the design process including the inception and site analysis stage ensuring that low carbon principles are embraced right at the start of the project. It will be easy to use and will provide answers and guidance quickly and intuitively. Carbon Lite centres around three inter-dependant software packages: firstly a 'Strategy Wizard' is used to consider site analysis, followed by a sketch design package for assessing different design options. The third package comprises a 'Carbon Mixing Desk' that aids analysis of the technical and cost benefits of incorporating renewables into the design. It is vital to the success of Carbon Lite that effective dataflow is established between the user and the three packages; Cardiff University will define, develop and test this 'Data Structure'. In addition, Cardiff University, utilising its background and experience in sustainable design, will aid in the population of the system with design exemplars, and in the testing of the product.