Climate-Neutral Buildings: A Herculean Task … But Achievable

Steinbeis experts implement carbon-neutral pilot projects

In 2018, the EU Commission presented its plan for a climate-neutral Europe at a summit in Katowice, Poland. In 2020, the plan was adopted and coined the European Green Deal, laying down targets for net-zero climate-damaging greenhouse gas emissions by 2050. This provides a solid basis for reliable long-term planning in European countries, particularly when it comes to the economy. The future goal of low carbon emissions, across all sectors of the economy, goes hand in hand with a transformation process, which will require annual investments totaling hundreds of billions of euros. The scale of this investment is considerable, but as Steinbeis expert Professor Dr.-Ing. Manfred Norbert Fisch explains, the consequences of damage to the climate resulting from doing nothing would likely be far graver.

The German government has set binding limits on permissible carbon emissions generated by the energy industry, manufacturing, buildings, transportation, and agriculture. Under the new regulations, greenhouse gas emissions must be reduced by at least 55% by 2030 versus 1990. The building sector should reduce two-thirds of climate-damaging emissions by 2030 and ensure existing buildings are as good as climate-neutral by 2050.

 

In Germany, 2014 emissions stood at around 900 million metric tons of CO₂, or roughly 11 metric tons of CO₂ per inhabitant per year. Regarding the source of emissions, around 120 million tons of carbon were directly attributable to buildings. Indirect carbon emissions caused by the use of materials and resources during construction and renovations – as well as imported “final energy” (attributable to building occupants using resources such as electricity) – are attributed to the energy  and industry sector.

CO₂ polluters: new buildings and renovation

According to calculations made by Manfred Norbert Fisch and his colleagues at energieplus, the Steinbeis Innovation Center, assessed according to “principles of origin,” every year a significant proportion of indirect emissions (also known as gray emissions) are caused when buildings are constructed or renovated. Every year, the building sector expands by an area of around 80 million square meters, generating about 60 million tons of CO₂. Roughly 50 million square meters of buildings are renovated per year. The resources required to do this – and the release of climate-damaging emissions – result in around 10 million tons of CO₂ per year. This is a considerable amount, but significantly lower than for new buildings.

According to the German government’s climate protection plan, by 2030 net local emissions from buildings should be reduced by 50 million tons of CO₂ per year, i.e. 42% versus 2014. With new buildings being added over the next decade, and the additional carbon emissions they generate, existing buildings will therefore need to be “decarbonized” by at least 55%. The new buildings that will be constructed by 2030/2050 will also heighten pressure to cut energy use in existing buildings, although in absolute terms they will have little impact on the carbon reduction goal. Tightening energy performance regulations applicable to new buildings (under the 2020 Building Energy Act) is insignificant when it comes to the climate protection targets for 2050. Gray carbon emissions will already decrease by 2030 with de-carbonization of the energy sector and industry, as well as potential reductions in the number of new buildings.

“The building sector is facing a herculean task, with a whole host of overlaps with energy-relevant sectors of industry. Based on our recommendations, I believe that the desired climate neutrality is feasible, however,” believes Steinbeis expert Manfred Norbert Fisch. The heating requirements of private households, commerce, trade, services, and industry are around 670 TWh p.a. for heating rooms and roughly 130 TWh p.a. for producing hot water. Together, that corresponds to around 32% of the total heating requirements covered by final energy, which is roughly 2,500 TWh p.a. In 2020, the share of this covered by renewables was only 14.5%. At 42%, the contribution made by renewables to gross domestic electricity consumption is already much better.

To accelerate changes in heating habits and the decarbonization of buildings, energy refurbishments will need to accelerate to more than 2% per year, fossil fuels (oil and gas) will need to make way in the market for electric heat pumps, the expansion of wind and PV farms will need to accelerate, and a progressive start needs to be made with the development of green district heating.

The CO₂ label – a key performance index for buildings

The experts at the energieplus Steinbeis Innovation Center have been proposing the introduction of a carbon assessment system for buildings for years. By distinguishing between CO₂ (A)emissions (caused by new buildings or renovations) and CO₂(B) emissions (caused by the operation and use of buildings), a calculation basis is provided for evaluating circumstances from a holistic perspective.

The CO₂(A) value is calculated at the point of construction or renovation based on fundamental building mass and the related carbon scores of materials catalogued in eco-databases. A multi-story residential building with solid walls would achieve a score of between 700 and 1,000kg of CO₂ per square meter of net floor area (CO₂/m² _NFA). For a renovation, the score would be less then 200kg CO₂/m² _NFA.

The CO₂(B) value is based on annual net end energy performance when the building is in use (according to German building energy regulations). Electricity used by occupants is added to this number. CO₂(B) decreases over time as a result of the ongoing decarbonization of electricity, district heating, and gas supplies, as well as the increasing use of solar energy in existing buildings. The CO₂(B) value for existing buildings constructed after 1995 is 40 to 60 kg CO₂/m² p.a. In the future, new buildings and renovations should be expected to achieve below 20kg CO₂/m² p.a. Progressive decarbonization of electricity from the grid may make it possible to achieve a CO₂(B) value under 10 kg/m² p.a. by 2030. The Steinbeis team recommends regularly updating readings taken for the CO₂(B) label – at least every five years, based specifically on the current carbon performance of fossil energy and renewables for the share of final energy imported to or exported from the building. It also recommends that data be compiled in a central database to create a reliable carbon emissions register for existing buildings, which could also be used for tax assessments.

Impressively climate-neutral pilot projects

In 2009, the Steinbeis experts applied the concept of a building acting as a power generation plant to a single-family house called the Berghalde in Leonberg in the state of Baden-Wuerttemberg[1]. The success of the project spoke for itself: Since 2012, more than 40 Effizienzhaus Plus homes have been based on this concept, as part of a funding initiative target called Zukunft Bau (“the future of construction”). The ambitious goal was to be carbon-positive and positive in terms of annual end energy consumption. The aim was also to test required construction and building technology.

The Steinbeis experts have drawn on their experience with the planning, construction, and operation of the first model projects to compile a list of Effizienzhaus Plus planning recommendations[2]. “Our building projects are based on a holistic approach: economic optimization during the life cycle, through the reduction of energy consumption, and through the efficient use of renewables,” says Fisch, summarizing the work carried out at the energieplus Steinbeis Innovation Center. This approach goes beyond Efficiency First thinking and is fundamentally based on open technology systems.

The Steinbeis experts also succeeded with the Aktiv-Stadthaus project in Frankfurt. This initiative, for the first ever climate-neutral apartment building, was also funded through the Zukunft Bau program. Completed in 2015, the eight-story building houses 74 apartments covering an area of 6,634 m² (net floor area). During the first two years of occupation, technical and sociological monitoring took place[3]. The Aktiv-Stadthaus building is based on Electricity Only principles. Room heating and hot water are provided by an electrical heat pump (120 kW_th). A heat exchanger covering an area of approximately 100m² was fitted in a sewage canal in the adjacent street (Speicherstrasse) to provide heating. To minimize domestic electricity use, the apartments were equipped by the landlord with ultra-high-efficiency household appliances.

Electricity consumption is covered by photovoltaic modules integrated into the facade (120 kWp) and roof (250 kWp). There is a 250 kWh storage system to boost solar electricity self-supplies. The battery works in conjunction with a charging management system to reduce peaks during power feed-in and operate the system in harmony with the grid. Monitoring confirmed that the carbon footprint estimate during planning (value CO₂(B) was achieved. Roughly a third of carbon emissions were caused by the heat pump using electricity to cover demand for room heating and hot water. The lion’s share of this demand, 55%, was generated by building occupants. On average, solar energy and the share of energy generated by the building per year stood at around 47%. At around 18 kWh/m² p.a., electricity consumption (including energy used for ventilation equipment) was around 20% below demand levels defined during planning (Effizienzhaus Plus standard). During the first two years of occupation, the annual carbon footprint was neutral. Electricity required to run the building and the amount of electricity used by occupants – roughly 0.9t CO₂ p.p. per annum – was almost offset by carbon credits awarded for feeding in surplus solar electricity. The building provided an impressive demonstration that climate neutrality is even possible for an eight-story apartment building under actual occupancy scenarios.

 

Building refurbishments are a decisive factor in achieving climate protection targets. The Steinbeis experts developed a concept for the comprehensive renovation of the Riederwald housing estate in Frankfurt, which dates back to the 1960s, based on Virtually Climate-Neutral requirements. Following the renovation, the building envelopes met KfW 55 standards. Heating is provided by electric heat pumps that use vertical geothermal probes in combination with ambient air heat exchangers as a heat source. The roofs lie east to west and are covered with as many PV units as possible. Carbon emissions, including those accounted for by occupants, were successfully reduced by 60%. When the new system went live in 2016, they stood at approx. 17kg CO₂/m² p.a. As electricity supplied by the grid is gradually decarbonized, the CO₂(B) value will reduce to less than 10kg CO₂/m² p.a.

These projects demonstrate that climate-neutral buildings and housing districts are possible with the existing technology , but it will still be important to invest in R&D in the coming years. Being climate-neutral is not possible being cost-neutral, and the Green Deal will require extensive financial resources and effort. This makes it all the more important to summon up the courage and increase acceptance among society for the aims of achieving climate neutrality as well as develop a social fair balanced finanzing for all humans.

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Recommendations for the real estate industry

Real estate industry stakeholders need to become active and develop medium-term strategies for climate-neutral building portfolios. The Green Deal gives them a reliable planning foundation for this. Based on its experience implementing the model climate-neutral buildings project, the energieplus Steinbeis Innovation Center has drafted the following recommendations for buildings:

• Building envelope
  • New buildings – residential building: Effizienzhaus EH 55, non-residential building: EH 70
  • Renovation – residential building: EH 70, non-residential building: EH 100
  • Consider gray energy based on outline provided with the label
• Energy supply
  • • Avoid fossil fuels
    • New buildings: no gas, no gas cogeneration units, no exhaust gas stack required
    • Electrical heat pumps
    • Transfer systems, if possible with low-temperature surface heating
    • Buffer storage and energy management system (EnMS)
    • Maximum use of roofs for solar panels
    • Energy storage: 1 kWh/kWp
• Optimized operation Based on technical monitoring systems (non-residential)

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Contact

Prof. Dr.-Ing. Manfred Norbert Fisch (author)
Steinbeis Entrepreneur
Steinbeis Innovation Center: energieplus (Braunschweig)

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References
[1] Fisch, M. N.; Wilken, T.: Climate-Neutral Housing – The Berghalde Single-Family House. Published by: Univ. Prof. Dr. M. Norbert Fisch, ISBN 978-3-9820898-0-5
[2] Fisch, M. N.; et. al.: Effizienzhaus Plus – Planning Recommendations. Published by: BBSR, Bonn, ISBN 978-3-87994-293-0
[3] Nusser, T.; Mahler, B.: Final report on energy monitoring of the Aktiv-Stadthaus building in Frankfurt, 2018. Steinbeis Transfer Center: EGS, Stuttgart

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