The aim of this applied research project is a cleaning robot which automatically cleans the outside of windows on a facade with vertical jambs and horizontal bars. The facade has to possess certain constructive properties. This “interface” enables the cleaning robot -- which is detachable from the building and portable -- to operate on any respectively designed facade on several buildings. A special cleaning-head keeps the water used for cleaning in a constant cycle. It is wielded through a filter and reused. The cleaning robot in operation is quicker, safer and cheaper than manual cleaning. Its use is environment-friendly and considerate with regard to resources.