As for sustainability, the focus should not only be on new building realization but foremost on existing houses. Renovating houses is more environmentally friendly (e.g. concerning materials and energy usage) and cheaper in the end. In the Netherlands up to about 50% of the existing houses have some kind of sustainable quality like insulation, double glazing or energy reducing installations. The first step in any renovation building project should be to measure and document the quality of the houses in detail. Air quality, ventilation, moisture and condensation in the construction, thermal bridges, heat leakage, energy usage etc. should be measured by e.g. blower door tests, smoke detection tests, infrared imaging, monitoring occupants' behavior and modeling (calculations) in order to investigate each problem in relation to the others. Based upon these measurements causes and solutions of the detected problems should be considered. Solving one isolated aspect, however, will frequently result in increasing other problems. Moreover, from the beginning of the project all building partners should operate as a team in order to be able to realize integrated renovation design. Building Information Management tools are recommended to share information and knowledge during realization by the contractors. All partners should be responsible for the quality of the end result, also after delivery of the project. In renovation projects, detecting and solving current problems should precede the application of new advanced sustainable technology, although it can be done simultaneously.