The PV top-up-roof

The extreme sustainability in building can be considered as three different aspects: 1. The construction of the building. 2. The operation of the building during its lifetime 3. The building being torn down after service life. Under the assumption that not building is the best solution for sustainability, Point 1 can be easily dealt with by renovating existing buildings. This also brings the solution for point 3: not tearing down buildings will eliminate pollution and waste disposal. These two solutions emphasize the need to focus on the most sustainable way of operating a building during its lifetime, reducing energy and water consumption and yet be a healthy place to live. A study of existing housing projects in the Netherlands that are now at the end of their service life reveals some significant issues. In general there is very limited thermal isolation or none at all, often only single pane windows and all spaces are generally small. The proposed solution is applying external thermal insulation, new windows and a specially designed new PV top-up-roof giving both extra space and photo voltaic energy. The new roof will consist of both thermal and photovoltaic cells generating energy and the roof will also be cantilevered giving protection against humidity and thus protecting windows and applied outside thermal insulation. Unfortunately PV elements are still too expensive to be installed on a large scale. An appropriate financing scheme will facilitate this integral model of housing upgrading. Fortunately recent examples in Germany prove that with a small change of financing system this problem too can be solved.