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In research, concepts are being developed and evaluated as to how buildings and entire urban districts can be sensibly refurbished in an economic and energy-efficient manner. These concepts, which are based on targeted and economically interrelated steps, can also help find suitable locations, remove barriers and initiate quality assurance processes. In addition there is the use of software-supported tools to optimise the planning processes.

More than 50 researchers gathered in Aachen on 24 and 25 November 2016 to discuss these topics. At the event, pioneering projects were presented and the implementation of such concepts was then discussed in five parallel workshops in regards to various aspects.

A report on the event by Uwe Friedrich and Johannes Lang

An exemplary renovation is provided by the extensive refurbishment of the Freiburg-Weingarten housing estate. Sebastian Herkel from Fraunhofer ISE presented the research project. The intention is that the primary energy consumption of all energy services in this housing estate shall be reduced by 30 per cent relative to the present situation. The Freiburger Stadtbau housing association is refurbishing its densely developed housing estate from the 1960s and 1970s, whereby innovative renovation concepts are being implemented and scientifically evaluated with individual buildings. The initial results from the monitoring and resulting optimisation are now available.

Exemplary refurbishment of a housing estate

“The sum of the measures implemented in Weingarten is exemplary for sustainable, energy-efficient urban renovation,” explained Herkel. Using the example of a 16-storey high-rise building, refurbishment to the passive house standard was also demonstrated. The measures taken at the same time for improving the residential public realm and the only moderate increase in rents following the renovation were decisive for the tenants’ acceptance of the project and satisfaction. The average rent in this district is still 30 per cent below the comparison values listed in the local rent level index. The cooperation between the housing association and the energy supplier and the participation of the tenants can be regarded as successful. An energy-efficient heat supply for the district is still under construction. Much of the room heating is to be provided via a modular CHP system.

© Markus Löffelhardt

Assessing economic efficiency in a methodically sound manner

Prof. Dr. Thomas Lützkendorf from the Karlsruhe Institute of Technology (KIT) presented research results on the economic efficiency of energy-optimised buildings with a view to already calculating the lifecycle costs during the planning phase. The topic is complex because it involves different building types, different usage scenarios, construction and utilisation costs as well as a comprehensive consideration of all costs incurred in the lifecycle of buildings. In addition to the costs, the yields and the benefits of buildings or energy efficiency-related modernisation measures are also of interest, again over time. The method also enables planning variants to be compared with one another.

“A comparison of different alternatives based on costs presupposes functional equivalence. If this is not the case in terms of the comfort or user acceptance, then the benefits must also be included in the calculation in addition to the costs. Accordingly, not only disbursements but also payments received are summed up,” explained Lützkendorf.

On the basis of many model projects, Lützkendorf was able to show that the construction costs of energy-optimised non-residential buildings are commensurate with the usual costs according to the BCI building cost index. The usage costs, however, are below the usual values according to OSCAR, an annual report on the typical operating costs of office real estate.

© BINE Informationsdienst

Consequences for the housing and real estate market

The energy efficiency characteristics and features will in future play a role as additional evaluation variables in rental price indexes. With comparison rents differentiated according to the energy efficiency, Lützkendorf sees an incentive for refurbishing buildings according to ambitious energy efficiency criteria, i.e. the “energy efficiency fitness” of buildings becomes a price-setting factor.

A good energy efficiency status also helps to increase the value of buildings when valuing real estate. This is because the “energy efficiency properties” and the “remaining duration of use” also flow into the calculation in accordance with Section 6 (5) ImmoWertV (German Real Estate Valuation Ordinance).

Literature tip

EnOB’s “Performance von Gebäuden” (Performance of buildings) technical book (in German) explains the fundamental principles and methods for measuring and assessing building performance. Findings from many research and demonstration projects illustrate the performance concept.

Further information on the technical book is available at...

Passive cooling for historical books

The comprehensive renovation of an individual building, the Luitpoldhaus belonging to Nuremberg City Library, in particular posed considerable challenges in regards to the energy optimisation and indoor environment. This is because it had to suitably accommodate the valuable collection of old manuscripts, incunabula, prints and maps. Prof. Wolfram Stephan from Nuremberg University of Technology presented the specially developed energy concept and the results of the scientific evaluation.

It is based on the use of renewable energy sources such as groundwater and largely passive cooling and component activation. The aim was to largely dispense with using active technology. A humidity control system was also introduced to take into account the moisture storage capacity of the book collections during operation of the air-conditioning systems. The refurbishment aimed to undercut the 2007 Energy Saving Ordinance for New Buildings (EnEV Neubau 2007) that was applicable at the start of the project by 30 per cent. It was also intended that the costs for energy and water should not increase despite the considerable expansion of the area. The refurbished building was scientifically evaluated on the basis of a two-year measurement programme. The energy targets were indeed fully achieved. Remarkable is that the passive cooling concept also works well in this building.

© Stadt Nürnberg

Innovative ventilation unit proves itself

A special ventilation unit with adiabatic evaporation cooling and sorptive dehumidification was specially developed and tested for the reading room, offices and exhibition space. Despite the necessary optimisation of the cooling devices, groundwater well pump and controllers, the calculated set values for the relative indoor air humidity were maintained with the exception of just a few summer days. The indoor air temperature was even maintained throughout the year.

Further details on the refurbishment concept and the system technology are available at ...

Additional storeys and refurbishment to create a CO2-neutral housing estate

Another pioneering project for the renovation of a residential complex is the Lilienstrasse Nord housing estate in Munich. The renovation of the typical 1950s housing estate, with the focus on providing structural thermal insulation, had been planned for a long time. The aim was to add additional storeys to the buildings, significantly improve the thermal insulation and make the energy supply CO2-neutral. In addition to the various, partly innovative thermal insulation measures on the building envelope, the use of innovative building services components is particularly noteworthy. Johann Dreher from the responsible housing association, Wohnungsbaugesellschaft GWG München, presented the project and the results from the first years of operation.

Because the residential complex cannot be supplied with district heating, it was decided to use a gas-engine heat pump, including a peak-load condensing gas boiler, in combination with a solar thermal system for providing heat. The room-based heating is controlled using the Geniax decentralised pump system. Anodic oxidation provides energy-saving legionella protection.

© Fraunhofer IBP (vor Sanierung) und GWG München (nach Sanierung)

Reliability and economic efficiency of the building services components

Johann Dreher reported on the difficulties with the gas-engine heat pump in this project. Although it has the potential to achieve very high efficiency values (COP) at low supply temperatures, the prototypical character of the unit, which is not available on the market, meant that the performance of the gas-engine heat pump remained significantly lower than expected despite the considerable efforts made in the project. For this reason, the desired CO2 neutrality was not achieved.

The research project also investigated the economic efficiency of the building services technology deployed. In terms of housing economics, this is achieved when series products can be procured at market prices comparable to alternatives. This is currently not the case for either the gas-engine heat pump or the Geniax heating pump system. According to Dreher, the anodic oxidation can only become economical when prices fall.

Workshops with keynote presentations

© BINE Informationsdienst

The Project Manager Meeting focussed on discussing individual topic areas in five parallel workshops, which were held in two sessions:

1. Implementation obstacles

Why are buildings and districts not being energy-efficiently modernised more often and in a more targeted fashion? The reasons why tried and tested concepts, systems and technologies for energy-optimised buildings and districts are not used or remain as isolated solutions are numerous:
For Prof. Dirk Müller from the Institute for Energy Efficient Buildings and Indoor Climate at RWTH Aachen University, the municipalities have considerable scope for action and influence, which however they have not yet sufficiently exploited. And, above all, the low energy prices mean that there is a lack of economic pressure and motivation to implement energy-efficient solutions.

With a keynote presentation about the “Three per cent project”, researchers formulated the success factors and obstacles for the energy-optimised renovation of buildings or districts. The aim of the project is to analyse obstacles in building refurbishment and to develop tailor-made refurbishment plans for various model districts. Using specially developed planning instruments, this should enable municipalities to specifically leverage previously unused renovation potential and increase the annual refurbishment rate. After all, the EU Building Directive stipulates a three per cent annual renovation rate for the existing building stock, whereby this figure persistently remains at around one per cent in Germany.

Energy-efficient refurbishment measures are perceived as a complex issue by most of the participants. This is because they often involve complicated legal frameworks, the decisions made in refurbishment projects remain partly intransparent, and the stakeholders lack information. Psychological factors, such as the topic’s lack of social relevance or personal motivation, also play a role. Added to this is the objective investor-user dilemma, which makes investments in energy efficiency more difficult because investors receive an insufficient return depending on the constellation. In addition to tailor-made refurbishment roadmaps as well as early and comprehensive communication with all stakeholders, new financing models could also help to overcome these difficulties.

New financing options and initiatives

Financing concepts range from co-operative solutions, crowd funding and green or climate bonds to contracting, leasing or tenant electricity models. All stakeholders should be approached according to their interests, informed at an early stage and involved in the planning processes.

The municipalities could also play an active role. There could be a much greater consideration of innovative concepts and technologies in district concepts and their value added potential recognised. This would also be “worthwhile” in terms of the positive publicity it generates. By offering new services and business models, the energy suppliers –especially the municipal utilities – could also get involved in the implementation in districts as partners of the municipalities, owners and tenants, and thus participate in the local energy transition.

2. Economic refurbishment concepts

Improved political and local framework conditions, as well as high-quality concepts, can promote the economic viability of refurbishment projects and their transferability.

“Difficult framework conditions, such as opaque funding programmes or constantly changing legal requirements, make planning processes and decision-making more difficult,” said Carsten Beier from the Fraunhofer Institute UMSICHT in his keynote presentation. “Local conditions also contribute when small-scale building and ownership structures prevail and there is a lack of clear contact partners,” added Beier. He said that knowing their interests and motives is essential, particularly if they are partners from the housing or energy supply sectors who have already anchored climate protection and energy efficiency in their corporate philosophy or have already developed their own business models.

Conceptual quality can also promote economic refurbishment concepts, for example their transferability to other buildings or the ability to deploy standard methods, such as the block-wise renovation of empty buildings. For broad implementation, it is therefore also important to find typical housing estate areas and successfully renovate them. A catalogue of the technical possibilities could help here to limit the organisational and planning costs with similar initial conditions.

New concepts for minimally invasive refurbishment also provide a promising approach for limiting the cost of refurbishment. Different concepts with prefabricated facade and window modules, which are largely mounted from the outside, are currently being tested.

3. Electricity balancing in districts

In the German energy sector, spatial units are compiled together into so-called balancing groups. For these, balances of the required and available energy can be generated, for example based on load forecasts. The liberalisation of the German electricity market, i.e. the free choice of electricity supplier independent of the network operator, required a regulation for billing the electricity transmitted through third-party networks. With the German “Data Exchange and Volume Balancing” (DuM) Directive, the first binding framework for the automated balancing group billing of electricity as a medium was established in 2005. This has now been incorporated into the current “Market rules for the implementation of balancing group billing for electricity” (MaBiS).

“Such rules for electricity balancing are also becoming increasingly important for energy-efficient district projects,” said Dr. Peter Bretschneider from Fraunhofer IOSB. “This is because the liberalisation of the electricity market has created new contractual relationships and processes as well as new market roles, such as for the connection user or electricity customer, or for the connection recipient as the owner of the building or property connected to the grid of the network operator.”

In a keynote presentation he outlined the requirements for electricity balancing in districts that could be regulated and implemented through the use of possible guidelines for the energy-efficient use of electricity.

The subsequent discussion between researchers and practitioners was concerned with quite fundamental issues: What needs to be done in order to make refurbishment economically viable? Is an energy transition in the heating sector (Wärmewende) at all possible in conurbations? And how can a sensible use of energy in districts be made possible?

Decentralised load management

It was felt that the comprehensive use of smart electricity meters would provide a major opportunity. For load management in districts, certain technologies for smart metering and electricity storage are already usable but not yet economically viable. Rigid framework conditions in Germany were mentioned as particular barriers in this regard. In the United States, for example, comparatively simpler regulations exist than in Germany. Added to this is the lack of business models for the innovative use of technology in districts, the frequent lack of data, insufficient measurement of low voltage and the still insufficient technical and economic importance attached to flexibility potential – i.e. possibilities for load balancing – at the low voltage level. Here more use needs to be made of the potential provided by coupling individual buildings. Their inclusion in district energy concepts could promote superordinate supply solutions such as local heating networks.

Tenant electricity models as an option

By way of example, the role of tenant electricity models for energy-efficient building and district solutions was discussed. Tenant electricity models are special energy supply constellations, similar to conventional contracting. These are concerned with supplying tenants or apartment owners with electricity from a decentralised generation system – usually a CHP unit or photovoltaic installation, which is sensible in apartment buildings with 20 residential units or more as part of refurbishment that is being carried out anyway. Such a decentralised power supply in residential real estate is eligible for remuneration under the current German Cogeneration Act. The low-interest loans as well as additional repayment subsidies from the KfW 40-Plus funding for energy-efficient buildings can also be used. The generated tenant electricity (or district electricity) does not have to be routed via public grids. This is why grid usage charges and concession fees are dispensed with, and the EEG levy will also be reduced from 2017 onward. However, tenant electricity models are currently often not economically viable as margins are low and costs are high. In addition, there are other problems such as short contract periods, tenant changes or the lack of willingness by tenants to participate in such solutions.

Simultaneity as an efficiency factor

The use of the so-called simultaneity factor was recommended for supplying heat to urban districts. When designing electrical systems, this factor takes into account that in thermal engineering systems the power consumed is usually less than the installed capacity, whereby the extent to which this is the case depends on the mode of operation or how the buildings and districts are used. This approach appears to be particularly useful when the local heating provision is characterised by competing potential. This is the case for example in the city of Wolfsburg, where the use of industrial waste heat from the VW factory competes with the municipal utility company’s supply strategy for providing heat for Wolfsburg by means of efficient CHP plants.

4. Tools for optimised planning processes

In his keynote presentation, Prof. Christoph van Treeck from RWTH Aachen University explained the necessity of a continuous, digital flow of information, starting from the design and execution to the operation and use of buildings. “The driving force is the increasing digitisation of planning processes, the technological trend away from isolated sub-models to multi-scale solutions and, ultimately, the development of international model standards,” said van Treeck. He said that the next logical step would be to synchronise Building Information Modelling (BIM) and Computer-Aided Facility Management (CAFM) so that a digital flow of information becomes possible throughout all phases of a building or property. However, he explained that there is still some need for structuring processes, interfaces and the data organisation. To exaggerate the point: “Will the caretaker ultimately have access to the data for the installed pump?”

It would also be conceivable with such data integration that existing concepts, such as the energy requirement certificate, are thereby replaced. Digital building models could be implemented for which relevant energy efficiency values were defined in the planning and which have to be proven each year during the operation.

Central simulation platform as an ecosystem

Current state-of-the-art simulation tools are often singular tools that can only be partially integrated into general planning processes. Van Treeck advocates the creation of a central platform for research and software development based on the US Department of Energy’s EnergyPlus and Tools Directory energy software. It could provide the basis and ecosystem for open-source concepts and cooperative tool development, and support the development and dissemination of new software and tools as well as their integration into standard design platforms. Van Treeck considers the structures emerging in the EnTool project as a first step towards this goal. A change in the funding strategy, away from the development of individual “experimental” approaches towards a central, structured development platform based on the US model, was, however, viewed critically by many of the participants. It was agreed, however, that a roadmap needed to be developed for further developing software for designing and operating buildings.

Software users in focus

The later users, architects and specialist designers are rarely involved to any great extent during the development of planning software and tools. For this reason, many tools require software-savvy experts to use the programs, which therefore often fail to meet the expectations and the planning reality of the users in the design offices. This is astonishing, since the success of software-supported tools depends heavily on the user-friendliness and user orientation.

In the workshop it became clear that, although the expert roles will change in the course of broad-based digitisation, specialist simulation and software experts will continue to be indispensable. There will therefore continue to be a justification for specialist experts and expert systems in the application of highly complex tools. Basic and advanced training and qualifications are important for planning practice. This way, acceptance and trust can also be created for specialist or complex tools.

5. Quality assurance processes for the construction phase

In her keynote presentation, Heike Erhorn-Kluttig from Fraunhofer IBP presented disturbing figures on the topic: According to a study by BauInfoConsult, in 2014 the “failure costs” in construction amounted to 10 per cent of the industry turnover and thus 9.9 billion euros. 545 architects and processors were asked for their assessment in this regard. This situation has hardly changed in the past few years – reason enough therefore to tackle the issue of “quality assurance processes” in a workshop.

Firstly, current results from QUALICHeCK were presented. This EU project focuses on the quality assurance for energy-efficient buildings. The intention is to improve not just the planning processes and the calculation quality but also the implementation on the construction site. Within the project, more than 70 critical situations were identified during the construction phase alone in regard to ensuring the high-quality implementation of energy-efficient buildings. Concepts shall therefore be developed in order to systematically prevent the resulting quality deficiencies.

The participants discussed existing quality assurance concepts and processes and recommended further necessary measures and steps, for example in the training and certification field, as well as for monitoring and sanctioning.

Measures for consistent quality assurance

The workshop participants also identified the causes for the various quality deficiencies. Unclear construction specifications, inadequate skills among the participating actors, critical economic conditions – for example in the case of tenders – as well as the lack of monitoring of the processes were mentioned here. In particular, there had also been experience with faulty implementations when parameterising building automation and control technology, sensor systems and hydraulic systems.

By way of conclusion, possible quality assurance measures were compiled and discussed, and areas identified where further measures are necessary. This concerns training and certification as well as monitoring and sanctioning.

Additional training and certification measures could concern, for example, the training of commissioning managers – similar to the LEED certification procedure. The coupling of training and certification measures with an insurance system was also advocated, as is the case, for example, with the retrofitting of injected insulation within cavity walls in the UK. There, the Cavity Insulation Guarantee Agency provides guarantees as cross-company insurance when certified and registered installers are commissioned.

A project at the TU Braunschweig was presented. There, researchers have developed a systematic documentation and quality assurance procedure for building automation which enables both functional tests and performance measurements of building technology according to HOAI LPH 8 and performance checks in the context of building certifications. The software-supported process is now commercially marketed by Synavision GmbH.

The contractor declaration required by the German Energy Saving Ordinance (EnEV) was also discussed. With this, the contractor declares that the work on the construction site has been executed in accordance with the information in the energy performance certificate. Although this declaration is not necessary under liability law, the instrument was positively evaluated because it makes clear to the building contractors that they are responsible for the correct execution in each individual case.

Also desired was a specially developed process definition for the commissioning test, similar to that practised with LEED certification. This service should only be granted to experienced and certified contractors who have demonstrated their competence.

The manufacturers of components and systems can also contribute to quality assurance by improving and developing more fault-tolerant products and by developing more user-friendly instructions for using them. For example, there is already a connection-tolerant radiator where the supply and return can be connected as desired.

Cross-project support research

The Project Manager Meeting takes place twice a year. It is used for sharing information and experiences as well as the presentation of new research projects and analyses from the accompanying research. This time the meeting was held at the E.ON Energy Research Centre at RWTH Aachen University, whose institutes and working groups are involved in various energy research projects. It was the first meeting with the new “Energy in buildings and districts” scientific support research network, which commenced work at the beginning of the year.

Prof. Dirk Müller outlined the four main areas of the cross-project support research: Research issues relating to buildings and districts as well as their energy provision shall be developed based on project experiences and discussions. In addition, data-based trend analyses will enable current technical developments and future-oriented technologies to be identified in the district and building sector. A cross-project analysis of all the research topics is also aimed at answering the question as to how single solutions can be combined into an efficient overall system. In addition, a revised reporting system aims to ensure greater transparency and more widespread replication of the research results. Findings from the research projects are decisive for this.

More details on the scientific support research

© RWTH Aachen, E.ON ERC

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