As it is states in the European Commission report for the THERMIE Programme, Tools and Techniques for the Design and Evaluation of Energy Efficient Buildings, design tools:

“…includes a diversity of tools, from those used to inform the design process by indicating trends in energy use associated with strategic design decisions, to tools to predict the energetic performance of detailed architectural and engineering proposals. In some cases, design tools have been developed to replace laborious calculation procedures used in the design process. […]…They can save considerable time if used correctly, cutting a week’s work on paper to possibly an hour or less in the case of a computer based design tool. Other tools have been developed to determine the behaviour of physical phenomena which would previously have been too complex to examine by hand. In some cases this extends to assessing interactions between design elements which were previously treated in isolation.[…]…Design tools are not always calculation methods. Many other forms of tools have been developed to assist the building designer in arriving at more energy-efficient solutions. Handbooks, tabulated data, etc. have been compiled to assist in energy efficient design. The computerisation of information sources allows designers to locate required information quickly…” (The European Commission Directorate-General for Energy (DGXVII), 1995, p.2 )