Project RoofKIT!

First some general information about the RoofKIT project

conceptual graphic showing circular principles
deputy mayor of wuppertal announcing RoofKIT GIF
©SDE21 | RoofKIT announcement

RoofKIT Project Overview


With a share of around 40%, the building sector is one of the largest energy consumers in Europe and is responsible for around 36% of CO2 emissions. The aging building stock of the EU (approx. 35% of the buildings are 50 years or older) contributes to the fact that approx. 75% of all buildings are classified as energy inefficient [European Commission, 2019]. In Germany, approx. 90% of building energy requirements are for buildings built in 2000 and older. In addition, the EU provides that in the near future, green areas or agricultural areas for urban and municipal expansion areas will no longer be converted into building land.

New mines

The vast majority of our construction materials are still taken from the earth’s crust, used and then disposed of. They are consumed and consumed in the truest sense of the word and are not borrowed from natural or technical cycles in order to subsequently merge again. This still dominant linear approach has profound consequences for our planet. We are intervening heavily in existing ecosystems. Climate change, extinct fauna and flora systems and natural material reserves that are running low testify to this. Sand, copper, zinc or helium will soon no longer be technically, ecologically and economically reasonable taken from natural sources.

Future economic and ecological development is therefore closely linked to the question of where our resources come from. Since our mines are running dry and CO2 values ​​are reaching alarming levels, we have to radically rethink all economic sectors. It is no coincidence that we are experiencing a beginning change in the mentality of our society, which sees its livelihood threatened by climate change, scarcity of resources and the pollution of our environment.

Our already built environment plays a key role here. It must be viewed as a depot and future resource supplier, a new mine: the urban mine. Viewing this anthropogenic (man-made) depot as a temporary state aimed at an endless cycle of resources represents a radical paradigm shift for the construction sector. The quantitative potential of the existing urban mine as a material supplier is gigantic. The challenge is to develop new technologies in order to convert these materials into a new generation of qualitatively sustainable, i.e. ecologically non-harmful, technically pure and economically attractive – because endlessly recyclable – building materials. The project RoofKIT will proof, that this is 100% doable already today.

New grounds

We believe, that our current cities have a huge overlooked potential of building ground and energy harvesting areas: rooftops. According to investigations of the Volkswohnung GmbH in Karlsruhe, rooftops are the biggest asset in the portfolio of the company, and we believe that this is not only the case in Karlsruhe but in many cities worldwide. It is a reserve that we should start to address. Moreover, we believe, that with the current boom of prefabricated houses, those two questions could and should be combined: how to design module-based prefabricated light-weight housing structures for roof top settlements? Here we see with our project partners a huge potential for the future. And an impact not only in a technical sense, but also in a social sense: providing housing in inner cities for all levels of society. On top, we see also the befit for the existing structures, as they achieve an upgrade in programmatic and functional services, as it is the goal to incorporate new community space types within the roof-top structures and understanding the additions as energy producers.


Given the points discussed, the KIT team chooses the roof top-up as its site of intervention. The idea is to design a prototypology, that can find its application anywhere. We understand the term prototypology in contrast to a prototype as a physical manifestation of a prototypical ideology or thinking. Therefor the science and theory can be applied in various location, even if the physical form might and need to change adapting to the given context. It is therefore the idea to leave the RoofKIT prototypolgy (living lab) on site in Wuppertal.

New construction principles

At the same time, RoofKIT will develop new design principles in order to make the reuse technologically possible. Once this state of a real cycle-based construction industry has been reached, it is necessary to create so-called material passports and connect them with a digital cadastral system so that future generations know where, in what quantities and when and where available materials will be available. RoofKIT will also develop those passports and data ports and make them available for everyone.


However, we will not be able to meet the demand for resources from the urban mine alone due to the non-existent technologies for 100% transformation of the materials. We increasingly have to close this gap with a shift towards regenerative cultivation, breeding and cultivation of future building materials, instead of continuing to rely on finite fossil, mineral and metallic deposits.


New growth

RoofKIT will therefor work with traditional biological building materials such as wood (which is especially important in the black forest area we are settled in) and new innovative new materials coming directly from our laboratories. The concept of industrialized construction within and with respect for undisturbed natural cycles does not promote a step back into the pre-industrial age; it tries to describe ways to make progress within the given economic environment, to modify it and ultimately to reinvent it. Our concept comprises the application of state of the art prefabricated lightweight timber construction modules, which guarantees maximum flexibility for different rooftop situations and functional requirements and reduces the problem of additional loads on the existing structure. The prefabricated timber modules achieve a constructive precision, that makes it possible to plan connections, which allow a sorted disassembly.

New energy harvesting systems

The energy concept of the unit will be a self-evident part of the architectural design process from the very beginning: a synthesis of passive measures (e.g. use of solar energy and daylight, natural ventilation, passive cooling) for high indoor environmental quality and

innovative solutions for energy supply yielding carbon neutrality over the year. This also includes improvement of the urban microclimate around the building by known approaches (e.g. green surfaces, unsealing area on the plot, etc.), and applying other innovative coatings in order to minimize absorption of solar radiation and dissipation of heat from the building.

The use of recycled materials and components will also include – as far as possible – the solar panels. Reassembled PV modules with existing PV cells will be integrated into the roof(s) and facades. If thermal absorber walls are applied as a heat source for the heat pump they will be fabricated with recycled materials as well.


Comfort and well-being are of utmost importance for living spaces. Besides the selection of healthy materials, which provide a high indoor air quality, strong emphasis will be put on the availability of daylight and on thermal comfort. Parametric studies for the summer period will be performed to achieve a façade design with optimal sizing of glazings, optical properties and adequate shading, which minimizes overheating by solar input and still guarantees daylight and a view to the outside. The combination of shading and solar harvesting will also be considered. As RoofKIT is a lightweight construction, the dynamics of indoor temperature have to be studied in detail and the potential use of phase change material (PCM) is considered to artificially increase thermal mass. Insulation of the envelope combined with selective exterior surfaces will minimize cooling and heating loads.

Passive cooling (discharge of internal thermal mass) will be achieved by natural ventilation during nights. An additional cooling technology for peak loads – e.g. during heat waves or exceptional use patterns – will be designed as well – either based on active ventilation with pre-cooled air or radiative cooling as a synergetic usage of the heating system.

Heating energy will most likely be supplied by a heat pump system. Performance assessment will show whether a larger thermal storage (preferably based on phase change materials to reduce the volume, or activating the ground under the building site) will be included additionally to a battery storage. For heat transfer, a radiative system will be applied to maximize thermal comfort. Radiant temperature asymmetry will be avoided with a highly insulated building envelope. The radiant heating system itself will either be hydronic or IR heating panels will applied, if the additional electricity demand will not harm the carbon-neutral energy concept.