THIS TUTORIAL HAS NO BEEN REVISED IN A WHILE, SO IT MIGHT NOT WORK WELL
When performing annual daylighting simulations, it might be very useful and efficient to group windows and treat them as if they were only one. This is a feature that was planned from the beginning of Groundhog development and is now a reality.
This can be easily done by right-clicking two or more selected windows. Groundhog will ask for a name for the group (i.e. 'Kitchen south-facing windows' or 'First floor east windows'), which will be lately used for naming the files when exporting in "Groundhog distribution". Windows without groups will be exported in files using their names (assigned by right-click --> assign name). It a window does not have a group or a name, it will be exported by assigning a generic name. This is not recommended, since it is difficult to recognize different windows by the content of the .rad file.
There is a button in the Groundhog Toolbar that allows seeing the groups. This button assigns random colors to each group, and is deactivated like any other tool (i.e. by pressing the space-bar). When deactivated, everything goes back to normal and the previous materials are assigned.