**5. Road-mapping**

### **5.1 Introduction**

A technology roadmap is an instrument to outline the expected future development and the boundary conditions of such development. The application of roadmaps built on the hypothesis that the future does not simply happen but can be constructed with a view towards a desirable future [7]. A roadmap helps to align short-term targets with long-term goals and directions [8]. The roadmap also helps to understand the context of technical developments better. A technology roadmap will document the current context and will draft the desired future performance. It will then develop a pathway from the current situation towards the intended future performance. In the original form, a roadmap requires a graphical representation and the time axis to depict the required steps in their sequence towards the desired state. Today, besides the graphical representation, table structures and narratives are used in the development and communication of roadmaps. Such roadmap is not static-once developed and then applied until the end of its time frame- but a roadmap design requires mechanisms for its review and continuous improvement [7].

As instruments for planning for the future and for directing the development towards the desired state, roadmaps have been used on various levels in management, economy and policy contexts. Policy roadmaps and sector roadmaps are used widely today to understand the contexts and requirements of transformation processes on the larger scale of countries or worldwide. In companies, roadmaps are used for product planning, the development of capabilities and strategic knowledge assets and to align activities between departments towards a coordinated goal. Phal et al. [7] list various types of roadmaps as given in **Table 1** and their specific purposes, and obviously, roadmaps can be used for further applications.


#### **Table 1.**

*Types and purposes of roadmaps, cited from Phal et al. [7, p. 16].*

A multilevel approach is required involving the identification of technologies and the technological context, the assessment of its compatibility and the complementary of various technologies and the integration of the technologies into the system as well as the implementation of first implementation instances to introduce new technologies and concepts into a market [9].

Often technology roadmap designs are structured with the layers such as the science layer, the technology layer, the application layer and the market layer (S-T-A-M framework) [7], each addressing one aspect of a product's life cycle. On a higher level of technology application in the design of a governance framework, the layers social context, technology context, economic context, environmental context, political context, legal context and infrastructural factors could be used. A roadmap can be designed to fit the needs of the specific application. In this chapter, a retrofit plan for a low-emission building is to be promoted with layers along with the main components of the energy balance and the elements of the energy concept.

#### **5.2 Applications of roadmaps**

Rockström et al. [8] suggest a global roadmap for rapid decarbonisation. The authors remark the model-based decarbonisation strategies often fall short of capturing transformative change and the dynamics of development involving disruption, innovation and nonlinear change in human behaviour. Therefore, they suggest drafting a roadmap towards the achievement of global decarbonisation based on simple principles, such as halving the anthropogenic carbon dioxide emissions every decade. Such a goal will serve as guide rail with increasing ambition every decade to achieve the required change in steps until the long-term goal is reached.

However, the simpler the roadmap to guide policies, the lesser its use to achieve the goal in the field. We need to translate the goals on the global policy level to national goals in every country and sector goals in every sector in every country. Ultimately, these goals must be applied in every facility and case of the building sector for every existing and newly built building. Rockström et al. [8] structure their

**37**

**Figure 2.**

*building performance.*

*Road-Mapping for a Zero-Carbon Building Stock in Developed and Developing Countries*

actions are aligned and are in the best case supportive to each other.

first movers in the solar industry in Germany and later worldwide.

contribute to transformative change together.

roadmap framework and suggest developing narratives in the dimensions innovation, institution, infrastructure and investment to understand the required conditions and steps in the various sectors. These narratives could be reviewed and newly aligned to the actual development in regular steps. The narratives developed in the various sectors by the sector stakeholders and experts can be used to align actors and organisations to achieve a common goal through trans-sectoral transformation. In consequence, not only one broad roadmap is required, but countless individual roadmaps are required towards delivering the individual share to the solution. Since all these individual roadmaps are directed towards the same common goal,

Benefits can be realised through an interplay of the roadmaps on the various levels. For instance, in many situations, the first movers are essential to start the required market transformation, but these first movers often face disadvantages, such as pioneering costs, reluctance in the market and the investment in early technology generations. In such situations, a roadmap on a higher level can provide security for first movers' investment and activity [1], so that the early majority can follow, and the application is taken up by the mainstream. The long-term framework of the German feed-in tariff is an example of such support. Since the feed-in tariff was guaranteed for 20 years, investors were willing to invest in an early generation of solar photovoltaic systems, which in turn provided the market for

**Figure 2** depicts the scheme of a layered integrated implementation roadmap towards zero-carbon building performance in 2050. Only the aligned interplay between the layers will allow the stakeholders on the building layer to implement near-zero-emission buildings effectively and to align their efforts towards the same goal. Formulation and communication of the specific roadmaps will allow the individual layers' stakeholders to link into the activity of the other layers in order to

In the context of building's design and the broader field of urban development, a more elaborate narrative of a desirable future defined by a framework of sustainable qualities and performance characteristics can be formulated. Such a narrative

*Schematic depiction of the layers of an integrated implementation roadmap framework towards zero-carbon* 

*DOI: http://dx.doi.org/10.5772/intechopen.92106*

#### *Road-Mapping for a Zero-Carbon Building Stock in Developed and Developing Countries DOI: http://dx.doi.org/10.5772/intechopen.92106*

roadmap framework and suggest developing narratives in the dimensions innovation, institution, infrastructure and investment to understand the required conditions and steps in the various sectors. These narratives could be reviewed and newly aligned to the actual development in regular steps. The narratives developed in the various sectors by the sector stakeholders and experts can be used to align actors and organisations to achieve a common goal through trans-sectoral transformation.

In consequence, not only one broad roadmap is required, but countless individual roadmaps are required towards delivering the individual share to the solution. Since all these individual roadmaps are directed towards the same common goal, actions are aligned and are in the best case supportive to each other.

Benefits can be realised through an interplay of the roadmaps on the various levels. For instance, in many situations, the first movers are essential to start the required market transformation, but these first movers often face disadvantages, such as pioneering costs, reluctance in the market and the investment in early technology generations. In such situations, a roadmap on a higher level can provide security for first movers' investment and activity [1], so that the early majority can follow, and the application is taken up by the mainstream. The long-term framework of the German feed-in tariff is an example of such support. Since the feed-in tariff was guaranteed for 20 years, investors were willing to invest in an early generation of solar photovoltaic systems, which in turn provided the market for first movers in the solar industry in Germany and later worldwide.

**Figure 2** depicts the scheme of a layered integrated implementation roadmap towards zero-carbon building performance in 2050. Only the aligned interplay between the layers will allow the stakeholders on the building layer to implement near-zero-emission buildings effectively and to align their efforts towards the same goal. Formulation and communication of the specific roadmaps will allow the individual layers' stakeholders to link into the activity of the other layers in order to contribute to transformative change together.

In the context of building's design and the broader field of urban development, a more elaborate narrative of a desirable future defined by a framework of sustainable qualities and performance characteristics can be formulated. Such a narrative

#### **Figure 2.**

*Schematic depiction of the layers of an integrated implementation roadmap framework towards zero-carbon building performance.*

*Zero-Energy Buildings - New Approaches and Technologies*

**Purpose Description**

Long-range planning (foresight)

Programme planning

**Table 1.**

Knowledge and asset planning

new technologies and concepts into a market [9].

*Types and purposes of roadmaps, cited from Phal et al. [7, p. 16].*

**5.2 Applications of roadmaps**

A multilevel approach is required involving the identification of technologies and the technological context, the assessment of its compatibility and the complementary of various technologies and the integration of the technologies into the system as well as the implementation of first implementation instances to introduce

Process planning Supports the management of knowledge, focusing on the knowledge flows

Integration planning Focuses on the integration and/or evolution of technology, and how different technologies combine to form new technologies

Product planning A common type of roadmap, aligning technology and product strategy, typically including more than one generation of product Capability planning More suited to service-based enterprises, focusing on the insertion of technology

Strategic planning Includes a strategic dimension, supporting the evaluation of different opportunities

horizons (e.g., industry, science and policy' foresight roadmaps)

Typically developed at the sector or national level incorporating longer time

Focuses on the implementation of strategy, to support the management of integrated R&D programmes. This type is more closely related to project planning

Focus on aligning knowledge assets and knowledge management initiatives with

necessary to support a particular process area, such as new product development

into organisational capabilities

business objectives

methods (Gantt charts)

or threads typically at the business level

Often technology roadmap designs are structured with the layers such as the science layer, the technology layer, the application layer and the market layer (S-T-A-M framework) [7], each addressing one aspect of a product's life cycle. On a higher level of technology application in the design of a governance framework, the layers social context, technology context, economic context, environmental context, political context, legal context and infrastructural factors could be used. A roadmap can be designed to fit the needs of the specific application. In this chapter, a retrofit plan for a low-emission building is to be promoted with layers along with the main

components of the energy balance and the elements of the energy concept.

Rockström et al. [8] suggest a global roadmap for rapid decarbonisation. The authors remark the model-based decarbonisation strategies often fall short of capturing transformative change and the dynamics of development involving disruption, innovation and nonlinear change in human behaviour. Therefore, they suggest drafting a roadmap towards the achievement of global decarbonisation based on simple principles, such as halving the anthropogenic carbon dioxide emissions every decade. Such a goal will serve as guide rail with increasing ambition every decade to achieve the required change in steps until the long-term goal is reached. However, the simpler the roadmap to guide policies, the lesser its use to achieve

the goal in the field. We need to translate the goals on the global policy level to national goals in every country and sector goals in every sector in every country. Ultimately, these goals must be applied in every facility and case of the building sector for every existing and newly built building. Rockström et al. [8] structure their

**36**

can then give direction for the required development and the communication and alignment of strategies.

In this sense, following the global goal, the requirements set in the Paris Agreement, it is the aim to reduce the carbon emissions of the German building stock towards 0 kg CO2 emissions till 2050. Such a time perspective provides 30 years to reduce the emission of the building stock by improving the building performance and the performance of the energy infrastructure. However, the activities towards the desired performance must be planned in order to make effective use of the given time. Long-term goal setting will provide security to the market but will also create the required pressure. It will allow all the stakeholders to plan and to start the individual transformation process and will avoid overwhelming the stakeholders by abrupt changes.

It is possible today to evaluate the performance of buildings before they are built, and the performance of different configurations of retrofit measures can be assessed for the development of a retrofit plan, for example through computational simulation studies. To calculate the future performance, the assessor has to make predictions on the development of economic parameters, such as system costs, energy tariffs and operation cost and environmental impacts, such as the composition of the energy mix and the resulting CO2 emissions.

In case a roadmap approach is applied as part of a governance framework or for performance assessment in a subsidy scheme, these predictions can be defined by the operating body to support the designers and assessors of the individual building projects. Such a definition of the evaluation context is an example, where the country-level roadmap and the building-level roadmap are interlinked. By defining and providing such context information on a higher layer with the mid-term and long-term perspective, the assessment for single building projects but also higherlayer policy interventions can be supported on the lower layers.

In this context, the German sustainable building council has issued a framework for "carbon-neutral buildings and sites" [10]. Herein, carbon accounting rules, rules for CO2 reporting and carbon management rules (or a climate protection roadmap) are provided. The framework sets current and future individual performance targets of a building or a group of buildings by assessment of the current annual carbon emissions and the target carbon emission of <0 kg CO2 emission in 2050. The target values in between are retrieved by simple linear interpolation between the current values and the targeted value, as shown in **Figure 3**. If the building performance remains below this line, and the retrofit roadmap is followed, the building can be labelled "carbon-neutral by 2050".

Such a roadmap framework will allow preparing for planned future enhancement of the technical installations in the given time frame until the most ambitious target is reached. Since it sets performance targets in terms of carbon emissions, the framework is not restrictive to any technology and operation strategy.

It will allow identifying technology fields that require or allow the installation of advanced solutions immediately and to schedule the retrofit of other solutions in the building's life cycle. For example, the client could decide to install doubleglazed windows today but to schedule the installation of triple-glazed windows in the next renovation cycle in 2040 after the technical lifetime of the first set of windows. At that time, triple-glazed windows might be better available in the local market. Another example could be a building concept that relies on natural ventilation first to reduce the initial cost of construction, but that is prepared for retrofit of a controlled ventilation system with heat recovery in future when such systems are better available from local suppliers. For other technologies with long technical lifetimes, high-performance solutions should be implemented from the beginning. In any case, login effects must be avoided, so that high-performance solutions can

**39**

that time.

**Figure 3.**

*buildings and sites" [10].*

*Road-Mapping for a Zero-Carbon Building Stock in Developed and Developing Countries*

be implemented at a later time in the building's lifetime. Therefore, roof spaces must be designed suitable for solar collectors and shafts must be provided to run the required cables and pipes (see **Figure 1**). For some solutions, road-mapping also

*Roadmap to the climate-neutral building stock. Reproduced from DGNB "Framework for carbon-neutral* 

Architects and engineers can model the building and its future performance under the local conditions and test and develop such design variants in the computational thermal building simulation model today. In contrast to the usual application of computational simulation models, the optimisation target is first set to <0 kg CO2 emission with the anticipated boundary conditions of 2050. A building concept with the desired performance and design qualities in 2050 is developed, and the design is detailed, although not all planned systems are to be installed at the time of first construction. The design is then reduced step by step and solutions for the later retrofit towards 2050 performance are developed. The technical systems are evaluated based on their technical lifetime and the required maintenance, and replacement cycles are considered in roadmap development, thereby retrofit, and energy upgrade steps are scheduled in the period till 2050. The performance of each retrofit step is simulated and evaluated with the anticipated boundary conditions at

In order to apply such a roadmap approach, the assessor will need to make predictions of the development of economic parameters, such as installation costs, energy tariffs and operation costs. The assessor will also have to make predictions on future technical development, the technical and economic lifetime of systems, as well as on the development of the market context. Parameters such as labour cost for installation and maintenance work as well as the available skills for technology installation and maintenance need to be considered. Many of these required assumptions can be provided by central bodies, such as the government, administrations, funding institutions or professional associations to support strategic road-mapping on building level towards the international climate protection goals. Such central generation and provision of required data would reduce the individual degrees of freedom in modelling and thereby make the modelling results more comparable. The boundary conditions can be supplied from higher layer

gives hints where leapfrogging of inferior technologies is required.

**5.3 Modelling for building assessment**

*DOI: http://dx.doi.org/10.5772/intechopen.92106*

*Road-Mapping for a Zero-Carbon Building Stock in Developed and Developing Countries DOI: http://dx.doi.org/10.5772/intechopen.92106*

**Figure 3.**

*Zero-Energy Buildings - New Approaches and Technologies*

tion of the energy mix and the resulting CO2 emissions.

layer policy interventions can be supported on the lower layers.

can be labelled "carbon-neutral by 2050".

alignment of strategies.

stakeholders by abrupt changes.

can then give direction for the required development and the communication and

It is possible today to evaluate the performance of buildings before they are built, and the performance of different configurations of retrofit measures can be assessed for the development of a retrofit plan, for example through computational simulation studies. To calculate the future performance, the assessor has to make predictions on the development of economic parameters, such as system costs, energy tariffs and operation cost and environmental impacts, such as the composi-

In case a roadmap approach is applied as part of a governance framework or for performance assessment in a subsidy scheme, these predictions can be defined by the operating body to support the designers and assessors of the individual building projects. Such a definition of the evaluation context is an example, where the country-level roadmap and the building-level roadmap are interlinked. By defining and providing such context information on a higher layer with the mid-term and long-term perspective, the assessment for single building projects but also higher-

In this context, the German sustainable building council has issued a framework for "carbon-neutral buildings and sites" [10]. Herein, carbon accounting rules, rules for CO2 reporting and carbon management rules (or a climate protection roadmap) are provided. The framework sets current and future individual performance targets of a building or a group of buildings by assessment of the current annual carbon emissions and the target carbon emission of <0 kg CO2 emission in 2050. The target values in between are retrieved by simple linear interpolation between the current values and the targeted value, as shown in **Figure 3**. If the building performance remains below this line, and the retrofit roadmap is followed, the building

Such a roadmap framework will allow preparing for planned future enhancement of the technical installations in the given time frame until the most ambitious target is reached. Since it sets performance targets in terms of carbon emissions, the

It will allow identifying technology fields that require or allow the installation of advanced solutions immediately and to schedule the retrofit of other solutions in the building's life cycle. For example, the client could decide to install doubleglazed windows today but to schedule the installation of triple-glazed windows in the next renovation cycle in 2040 after the technical lifetime of the first set of windows. At that time, triple-glazed windows might be better available in the local market. Another example could be a building concept that relies on natural ventilation first to reduce the initial cost of construction, but that is prepared for retrofit of a controlled ventilation system with heat recovery in future when such systems are better available from local suppliers. For other technologies with long technical lifetimes, high-performance solutions should be implemented from the beginning. In any case, login effects must be avoided, so that high-performance solutions can

framework is not restrictive to any technology and operation strategy.

In this sense, following the global goal, the requirements set in the Paris Agreement, it is the aim to reduce the carbon emissions of the German building stock towards 0 kg CO2 emissions till 2050. Such a time perspective provides 30 years to reduce the emission of the building stock by improving the building performance and the performance of the energy infrastructure. However, the activities towards the desired performance must be planned in order to make effective use of the given time. Long-term goal setting will provide security to the market but will also create the required pressure. It will allow all the stakeholders to plan and to start the individual transformation process and will avoid overwhelming the

**38**

*Roadmap to the climate-neutral building stock. Reproduced from DGNB "Framework for carbon-neutral buildings and sites" [10].*

be implemented at a later time in the building's lifetime. Therefore, roof spaces must be designed suitable for solar collectors and shafts must be provided to run the required cables and pipes (see **Figure 1**). For some solutions, road-mapping also gives hints where leapfrogging of inferior technologies is required.

#### **5.3 Modelling for building assessment**

Architects and engineers can model the building and its future performance under the local conditions and test and develop such design variants in the computational thermal building simulation model today. In contrast to the usual application of computational simulation models, the optimisation target is first set to <0 kg CO2 emission with the anticipated boundary conditions of 2050. A building concept with the desired performance and design qualities in 2050 is developed, and the design is detailed, although not all planned systems are to be installed at the time of first construction. The design is then reduced step by step and solutions for the later retrofit towards 2050 performance are developed. The technical systems are evaluated based on their technical lifetime and the required maintenance, and replacement cycles are considered in roadmap development, thereby retrofit, and energy upgrade steps are scheduled in the period till 2050. The performance of each retrofit step is simulated and evaluated with the anticipated boundary conditions at that time.

In order to apply such a roadmap approach, the assessor will need to make predictions of the development of economic parameters, such as installation costs, energy tariffs and operation costs. The assessor will also have to make predictions on future technical development, the technical and economic lifetime of systems, as well as on the development of the market context. Parameters such as labour cost for installation and maintenance work as well as the available skills for technology installation and maintenance need to be considered. Many of these required assumptions can be provided by central bodies, such as the government, administrations, funding institutions or professional associations to support strategic road-mapping on building level towards the international climate protection goals.

Such central generation and provision of required data would reduce the individual degrees of freedom in modelling and thereby make the modelling results more comparable. The boundary conditions can be supplied from higher layer

roadmaps and agreed and consolidated research results. For instance, the German Ministry of Construction has recently provided new test reference year datasets for the current climate conditions, but also for the climate in 2050 including the predicted climate change effects to be used in thermal simulation studies for future situations [11].

### **5.4 Application in the building sector**

An example for the application of roadmaps is the "individual renovation roadmap" (individual Sanierungsfahrplan, iSFP) as it is currently introduced by the German Federal Ministry for Economic Affairs and Energy (BMWE) for the application in energy-retrofit projects in Germany [12]. In future, an iSFP will be the basis for a financial support scheme for the retrofit of building projects in Germany. Before isolated retrofit measures are planned, an individual renovation roadmap is drafted to define the intended development of the building's functions and performance. In this way, it is possible to avoid lock-in effects and to make use of synergies in the energy system of the building. The method is explained in detail in the "Handbuch für Energieberater" [12] in relation to the existing building assessment framework in Germany.

Also, the subsidy schemes in Germany support the preparation for renewable energy retrofit. In one programme, investment grants are provided for "renewable ready" condensing boiler systems in case these systems are prepared for later renewable energy integration with prepared additional fittings for necessary piping and functions in the control system. Investment grants are paid to the investor if the renewable energy system is installed within 2 years after the installation of the heating system.

Also, the US Department of Energy has developed a "Zero Energy Ready Home" [13] building labelling system, which builds on top of the existing and forthcoming low energy building requirements and requires the client to prepare for the later retrofit of renewable energy systems. Within the scheme, the client has to demonstrate that the maximum allowable loads of the roof structure are sufficient for the installation of PV solar collectors, that the conduits run from the roof to the dedicated location of the inverter and that the inverter can be connected to the electrical panel and circuit breakers are prepared for installation.

Since in many situations, the current building practice is too remote from the intended performance, such as plus-energy performance or zero-carbon performance, a roadmap approach will be instrumental for the development of the building stock in many countries.

#### **5.5 Steps in the individual renovation roadmap**

In summary, the following will draft the steps in the integrated and the individual renovation roadmap. The concept is illustrated in **Figure 4**. It is suggested to develop narratives and technical concepts for the state of the art, the goal in 2050, the situation today and of intermediate steps.

#### *5.5.1 State of the art*

In the development of roadmaps for a zero-emission building in a specific context, state of the art needs to be reviewed and currently available advanced options for retrofit are to be listed. Thereby the commonly used technologies, as well as the local and international front runner technologies, need to be addressed to benchmark the current and the possible future performance.

**41**

*5.5.2 2050*

**Figure 4.**

*layers.*

*Road-Mapping for a Zero-Carbon Building Stock in Developed and Developing Countries*

The review of state-of-the-art technologies will inspire the designers for the design of the building today and envision the developments of potential key

*Illustration of individual renovation roadmap under the influence of the integrated implementation roadmap* 

technologies in future. Thereby, a front-runner technology review and the review of technology development, which are currently still on the low end of the technology-

The performance goal defines the "2050" narrative and the intended performance. In the case of the DGNB roadmap to climate-neutral building stock, it is a

readiness level scale of research projects, are very informative.

*DOI: http://dx.doi.org/10.5772/intechopen.92106*

*Road-Mapping for a Zero-Carbon Building Stock in Developed and Developing Countries DOI: http://dx.doi.org/10.5772/intechopen.92106*

*Zero-Energy Buildings - New Approaches and Technologies*

**5.4 Application in the building sector**

assessment framework in Germany.

building stock in many countries.

*5.5.1 State of the art*

panel and circuit breakers are prepared for installation.

**5.5 Steps in the individual renovation roadmap**

the situation today and of intermediate steps.

mark the current and the possible future performance.

situations [11].

heating system.

roadmaps and agreed and consolidated research results. For instance, the German Ministry of Construction has recently provided new test reference year datasets for the current climate conditions, but also for the climate in 2050 including the predicted climate change effects to be used in thermal simulation studies for future

An example for the application of roadmaps is the "individual renovation roadmap" (individual Sanierungsfahrplan, iSFP) as it is currently introduced by the German Federal Ministry for Economic Affairs and Energy (BMWE) for the application in energy-retrofit projects in Germany [12]. In future, an iSFP will be the basis for a financial support scheme for the retrofit of building projects in Germany. Before isolated retrofit measures are planned, an individual renovation roadmap is drafted to define the intended development of the building's functions and performance. In this way, it is possible to avoid lock-in effects and to make use of synergies in the energy system of the building. The method is explained in detail in the "Handbuch für Energieberater" [12] in relation to the existing building

Also, the subsidy schemes in Germany support the preparation for renewable energy retrofit. In one programme, investment grants are provided for "renewable ready" condensing boiler systems in case these systems are prepared for later renewable energy integration with prepared additional fittings for necessary piping and functions in the control system. Investment grants are paid to the investor if the renewable energy system is installed within 2 years after the installation of the

Also, the US Department of Energy has developed a "Zero Energy Ready Home" [13] building labelling system, which builds on top of the existing and forthcoming low energy building requirements and requires the client to prepare for the later retrofit of renewable energy systems. Within the scheme, the client has to demonstrate that the maximum allowable loads of the roof structure are sufficient for the installation of PV solar collectors, that the conduits run from the roof to the dedicated location of the inverter and that the inverter can be connected to the electrical

Since in many situations, the current building practice is too remote from the intended performance, such as plus-energy performance or zero-carbon performance, a roadmap approach will be instrumental for the development of the

In summary, the following will draft the steps in the integrated and the individual renovation roadmap. The concept is illustrated in **Figure 4**. It is suggested to develop narratives and technical concepts for the state of the art, the goal in 2050,

In the development of roadmaps for a zero-emission building in a specific context, state of the art needs to be reviewed and currently available advanced options for retrofit are to be listed. Thereby the commonly used technologies, as well as the local and international front runner technologies, need to be addressed to bench-

**40**

*Illustration of individual renovation roadmap under the influence of the integrated implementation roadmap layers.*

The review of state-of-the-art technologies will inspire the designers for the design of the building today and envision the developments of potential key technologies in future. Thereby, a front-runner technology review and the review of technology development, which are currently still on the low end of the technologyreadiness level scale of research projects, are very informative.

#### *5.5.2 2050*

The performance goal defines the "2050" narrative and the intended performance. In the case of the DGNB roadmap to climate-neutral building stock, it is a total annual carbon-emission of 0 kg. Also, the technical configuration of the building and the boundary conditions for the calculation need to be specified in order to be useful for the building owner. The configuration able to achieve the intended performance can be determined through computational simulation. The technical description is the target for the successive retrofit.

#### *5.5.3 Situation today*

Today's state of the building is either in case of building retrofit projects the current condition of a building at the time of assessment or it is the state of a new building at the time of construction in case of a newly built building. This condition is documented as the starting point for roadmap development.

In order to design a "climate-neutral by 2050" building, it is advisable to determine the 2050-configuration first and then to subtract the elements until construction is technically and economically feasible at the current time. The subtraction of elements can be due to financial constraints, or due to technical availability or market maturity or also due to changing demand. Obviously, it is not possible to predict the future precisely, but the road-mapping approach will help to avoid login effects and allow for the design of future-proof buildings.

### *5.5.4 Intermediate steps*

The intermediate steps are defined by the current state and the intended state in 2050. In the method introduced earlier, these intermediate steps are determined by subtraction components from the high-performance configuration. In this process, the technical lifespans of the building components and service systems are considered. For example, double-glazed windows installed in 2020 are exchanged for triple-glazed windows at the end of their lifespan in 2040 to achieve the intended performance in 2050.
