Book excerpt: The cost of operating a building far exceeds the cost of constructing it, and yet until recently little attention was paid to the impact of solar radiation on the costs of heating, cooling and ventilation. And now that there has been a surge in interest in energy efficiency and solar design, architects and designers need a practical guide to the modelling and application of solar energy data. There are many different models and techniques available for calculating the distribution of solar radiation on and in buildings, and these algorithms vary considerably in scope, accuracy and complexity. This book demonstrates which of these predictive tools gives the best results in different circumstances, including explaining which models can be best used in different parts of the world. The author has had over twenty-five years of experience of dealing with solar energy data from four continents and has used that experience in this book to show the development not just of knowledge but also the growing sophistication of the models available to apply it.