Introduction

Daylight can be perceived very differently depending on the context. What was once the principal source of light is today, sometimes, considered an energy efficiency measure. Some others, a requirement or an element that cannot be missing in any space. To sensitive minds or in a certain kind of project, it may be seen as an architectural asset, which should be used to shape a space and create a certain ambiance. And, just to mention one more recently developed perception, daylight is also considered a crucial element in human health, performance and well-being.

Despite of the different perceptions, daylight it is mostly known as a good thing. Accordingly, every building design process is full of decisions made in pro of it. However, many of these decisions are based solely on the designer’s experience and educated common sense. The issue is that, even if experience and common sense are crucial for designing, the problem of predicting in detail how much daylight will be available on a space is hardly addressable by using only educated guesses. Errors in the designer’s decisions will not be fatal, but they can lead to overheating, glare, darkness and excessive solar heat gains and cooling energy consumption, among others. Some of the problems mentioned above may be avoided by means of tools that help verify what the designer is thinking. One of the most common examples of such tools area simulation tools. Consequently, Groundhog is a lighting simulation tool that intends to expand the use of lighting simulation, with the purpose of enhancing the interior quality of buildings.

Groundhog sees three kinds of potential users: students, professionals and academics. Each of these groups demand different things from the tools they use. Students, for instance, want stable, cheap and accessible tools with a great learning communities. Researchers, on their part, tend to prefer transparent tools that do not act as black boxes and that can implement state-of-the art methods. Finally, practitioners demand transparent, modern, stable tools that have outstanding technical support.

Every one of Groundhog’s characteristics was chosen with the purpose of satisfying the previously mentioned requirements. First; it is Free (as in freedom) and Open Source, which ensures transparency and allow transferring state-of-the-art methods to industry. Second; it is a SketchUp® extension, which is a widely used, stable, friendly and relatively cheap 3D modelling tool that offers free licenses for non-commercial purposes. Third; it uses Radiance as its calculation engine, which is a widely known, validated, free and reputed lighting simulation suite. Fourth and final; it encourages collaboration and has an open documentation, which allows decentralizing many tasks such as technical support and tutorial writing.

In summary, Groundhog is a tool that aims to expand the use of lighting analysis with the purpose of enhancing the energy efficiency and the interior quality of buildings. In order to do that, it was designed and developed for maximum market penetration. That is, its vision is to be a so good that practitioners realize that the benefits of performing lighting analysis are greater than its costs.

Natural and Electric lighting

Groundhog is a tool that intends to integrate Day and Electric lighting. I warn you, however, that I am a Mechanical Engineer, with studies in Daylighting. I try to keep myself up to date, but I do not pretend to know everything. In fact, one of the reasons why Groundhog is fully Open Source because I need others to add their knowledge.

Accordingly, Groundhog is, up to today, mainly a daylighting tool; but I am making efforts to integrate electric lighting properly. Any suggestion, feedback or comments are welcome!

Direct communication with research and development

Groundhog is Open Source, which allow you to see what it does and how it does it. In this case, it is important to notice that, unlike other Radiance-based tools, Groundhog uses an unmodified Radiance version. This has a few advantages:

• Every time a new Simulation Method is presented (they are often developed using Radiance), it is easy to integrate it to Groundhog

• If you know how to use Radiance, learning Groundhog will be very easy... there are very few details to consider.

This is not a book

This is not a book, it is a Gitbook, which means it is meant to be written collaboratively. Although I may write most of it, Groundhog and its documentation are Open Source. Please, feel free to modify, enhance or fix things you see are mistaken, and even write whole chapters you think are missing.