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How to build sustainably


Certificates determine what counts as sustainable construction. The energy balance is based on the KfW standards already mentioned (for new buildings and major renovations are legally binding in the public sector KfW 55 and in the private sector KfW 70). The state of Hesse is playing a pioneering role here. Here all public buildings must be built in accordance with the passive house standard.

There are also three classes that relate to the total demand for renewable primary energy (Primary Energy Renewable, PER). In which Standard Passive House Classic the value is a maximum of 60 kWh / (m²a), for a Passive House Plus a maximum of 45 kWh / (m²a). The latter must also generate at least 60 kWh / (m²a) of renewable energy on the built-up area. With the Passive House Premium, only 30 kWh / (m²a) may be consumed and it must generate at least 120 kWh / (m²a) of energy.
In addition to energy efficiency, sustainability itself is also assessed. There are several certificates for this. The Green building label looks at criteria such as environmental protection, resource efficiency and health, that Blue building label on ecology, economy and socio-cultural aspects. This also includes the life cycle of a building including the reusability of building materials.

The British certification system Building Research Establishment Environmental Assessment Method (BREEAM) is around 30 years old and is the oldest and is used worldwide. In Germany, buildings that want to be certified according to this are checked by the German Institute for Sustainable Real Estate Management (DIFNI). The LEED from the USA is also an option. A local certificate is the system of the German Sustainable Building Council (DGNB). Certification according to guideline 160 of the German Facility Management Association (GEFMA) is also possible. There are also BNB for federal buildings and NaWoh for residential buildings. All of these certificates are used in Germany.

Building Information Modeling (BIM)

A digital planning method, Building Information Modeling (BIM), helps with sustainable construction through to successful certification. Roughly speaking, a digital twin is created of the structure to be built or renovated. All data is entered into this twin. All trades are involved and always have access to the data they need. This applies to times, costs, components and materials used.

This digital twin will later also be used for the energetic or sustainable operation of the building. Will it be torn down once - Buildings today have a life expectancy of between 50 and 100 years - it is possible to trace exactly which materials have been used and how they are to be disposed of, recycled or otherwise reused.
This method is already in use today - for example when dismantling power plants with huge amounts of reinforced concrete, which should be put back into a meaningful use.
BIM also has an advantage in terms of energy efficiency, which is essential for the sustainability of a building. Systems for converting and generating energy can be optimally planned, as can energy consumers. Both are so easy to coordinate with each other. Sensors and actuators can determine exactly when what energy is required in a certain room and where it comes from in the cheapest, because most efficient case - and all of this is digitally planned and later controlled with BIM.

BIM can also be used to determine which materials and components should be used for insulation. Because in times of global warming you shouldn't forget that Winter thermal protection in summer can also lead to overheating inside the building - For example, if the sunlight is too intense in glass surfaces that are too large. Or, to put it another way: the energy efficiency advantage through insulation in winter could be more than eroded in summer by significantly higher cooling costs.

Tip: The Federal Ministry of the Interior, Building and Home Affairs (BMI) has published a guide to sustainable building in which the topic is dealt with very exhaustively and in-depth. It can be downloaded here.