Feasibility Study for Energy-efficient Refurbishment of District Administration Office, Pforzheim, Germany

The district office I of the Enzkreis started operations in 1993 with building sections A to C. In 2006, it was expanded with section D. The complex is the largest energy consumer in the district's portfolio. In winter, there is a comfort issue, as users feel cold even when the room temperature is set to 21 °C and in summer, offices facing the north and south sides, and the atrium overheat.
The task was to identify specific measures for a possible refurbishment of the building complex that would take the ecological footprint into account. Transsolar analysed the existing building and surveyed the users' perception of comfort; thermal bridges were identified. The U-values for the windows are 3.2 W/m²K for the frames and 2 W/m²K for the glass. Although the heat requirement for the standard of the building envelope is low, there is a high primary energy requirement. The consumption values are 58 kWh/m²a for heating and 51.3 kWh/m²a for electricity. The high electricity consumption is primarily caused by lighting. The low heat demand can be explained by the fact that electrical devices in the rooms significantly contribute to heating. With global warming in mind, it is important to consider that offices are likely to become even more overheated in the future.
Transsolar simulated the building in its current state by combining four office space variants to record the refurbishment potential and to identify and analyse the possible solution variants.
Reducing electricity consumption would already reduce the comfort problem in summer. Airing the rooms overnight would be sufficient to eliminate the need for conventional cooling. The windows cause a large proportion of heat loss. In winter, the window surfaces are very cold and cause people to feel cold in the room, even though the room air temperature should be sufficient. To counter this problem, regulating the temperature to the operative room temperature or replacing the radiators with convectors could help. Upgrading the façade, including replacing the windows, is the only solution that also reduces the heating requirement. Changing the light sources to LEDs can reduce electricity consumption by 40 %. Switching to energy-saving workplace equipment and daylight control halves the primary energy requirement.
The identified greenhouse gas (GHG) emissions for the refurbishment amount to 413 t CO2, which corresponds to 59 kg/m² and 1876 MWh converted into primary energy. Window frames made of new aluminium generate 60% of the GHG emissions of the refurbishment, frames made of recycled aluminium or replacement of only the insulating glass would significantly reduce emissions. Refurbishment releases GHGs now, but operational emissions are released more slowly over the next decades. Emissions now are more critical to avoid reaching tipping points in climate change.
The time required for the amortization of GHG emissions depends on the assumptions for district heating. Using the emission factor for Pforzheim's district heating determined by the district office, an annual emission saving of 9.7 kg CO2e/m² is achieved, which amortizes after six years. However, if CO2-neutral heat is considered prospectively, the emissions from the renovation will only amortize in over 32 years. Future decarbonization of electricity will further extend the amortization period.
To become independent from energy supplies, geothermal energy is an option. By utilizing geothermal probes or the walls of the underground garage as a ground collector, a heating capacity that can cover approximately 80% of the demand is possible.
Photovoltaics on the roof, combined with facade-integrated white PV modules, can cover the electricity requirement on an annual balance. This would make the district office climate-neutral, if district heating is considered climate-neutral. Operating costs are reduced by 33% to 50%, depending on the variant.
Special funding opportunities for municipalities are available for renovation from KFW. Certification as a sustainable building according to BNB is also an option.