Limits of natural ventilation through windows in office buildings.

Many HVAC systems built in the time between 1960 and 1980 have now reached the end oftheir lifetime and require retrofitting. When HVAC retrofits are performed in connection withbuilding renovation, there is often a potential for reduction of thermal loads. The questionwhether a renovated building should have an airconditioning plant or free ventilation oftenrevolves around arguments of energy consumption and investment. However it is not takeninto account that there can be no thermal comfort in many cases of cooling loads and outdoortemperatures. For the buildings with HVAC-systems the room air flow is well known, but theflow when an open window is mostly unknown.In this research project at the Hermann-Rietschel-Institute investigations are made onventilation by opening the windows. The limits of free ventilation with windows are given byair temperature and air velocity. Now we have first results of the still ongoing investigations.