Sustainability at DMG: our new energy-efficient building

Our new Building 6 was officially opened just before the end of last year. Find out why it is an “Energy Efficient Building” and what that means in this interview with the architect responsible, Ingo Krümmel.  

DMG: What does it mean when a building is classified as energy efficient in Germany? 

Ingo Krümmel: An “Efficiency House” is an energy-efficient building standard. It consists of two criteria: How high is the building’s total energy requirement? And, how good is the thermal insulation of the building shell? You can fine-tune these two criteria to make the building more energy efficient. 

DMG: And to what extent have we been able to fine-tune our new building? 

Ingo Krümmel: The new DMG building is an Efficiency House 55 EE. “EE” refers to the renewable energy class; it indicates the proportion of renewable energy used. Efficiency House 55 means that the building only requires 55 % of primary energy compared to a reference building defined in the German Buildings Energy Act. Plus, the transmission heat loss is only 70 %. The structural thermal insulation is hence 30 % better. 

DMG: Was it simply a case of building thicker walls or were additional steps taken to meet the requirements for this class? 

Ingo Krümmel: Yes, thicker walls in the sense of more insulation. Besides the insulation thickness, even the thermal conductivity of the building materials is relevant: the higher the density, the lower the heat loss. Modern insulated windows minimise energy consumption and heat loss.

Aiming for the 55 EE standard was quite ambitious in my opinion. One of the ways we managed to achieve it was by using advanced building management technology to automatically control the building’s cooling system based on the outside temperature. We also recover heat from waste thermal emissions generated by the building’s ventilation system. 

DMG: What part does our photovoltaic system play in terms of energy efficiency class?  

Ingo Krümmel: In favourable conditions, the photovoltaic system will be completely sufficient to supply the building, including the heat generator, with its own electricity. Despite that, it only plays a minor role in “EE” categorisation. The City of Hamburg doesn’t consider the overall impact in this regard, but has adopted a two-pronged approach: the installation of photovoltaic systems is now required by law for roof renovations and new builds. The renewable energy rating is essentially determined by the additional use of renewable energies, i.e. heat pumps, solar thermal collectors, etc.

For this building, we opted for a hybrid solution by installing a heat pump system in combination with an efficient condensing boiler system. This is only used when necessary, if outside temperatures are very low. The use of heat pumps significantly reduces the consumption of fossil fuels. It also reduces costs associated with purchasing natural gas and significantly cuts down on CO2 emissions. This all pays off in the long term – both environmentally and financially. 

DMG: Was thought given to environmentally friendly materials during the design process? 

Ingo Krümmel: The supporting structure, prefabricated columns and girders consist of steel composite with 90 % recycled steel content.  

But when it comes to business spaces, we always prioritise materials that require low maintenance. We asked ourselves: what would it cost to maintain and preserve the value of the building in the long term? This thought process often automatically leads to more sustainable measures, but the underlying motivation is different: materials for the building shell were chosen primarily in terms of their durability, care and maintenance requirements, and value retention. We chose aluminium frames for windows, doors and other transparent façade components with industrially finished surfaces, as well as robust designs for movable elements such as windows and doors, thus minimising the need for repairs and maintenance. 

We are also creating an extensive green roof system. Green roofs have a considerable impact on urban climate. They cool and absorb CO2. In summer, they absorb heat, preventing it from being transferred to the building. And the building gains an extra layer of insulation at the same time. Moreover, green roofs store rainwater and release it more slowly into the environment, thereby relieving Hamburg's rainwater reservoirs, which are now too small to cope with extreme rainfall. Green roofs therefore also accumulate rainwater and prevent flooding. 

DMG: Thank you very much for taking the time for this detailed and informative interview.