Author:
Université Libre de Bruxelles.
Note: opinions in the articles are of the authors only and do not necessarily reflect the opinion of the EU.
Although the potential of the retrofitting of existing buildings has been identified, guidelines come in the form of general suggestions, failing to address the diversity of each project. In practice, the detailed implementation of the measures must suit the individual project, in terms of the building’s existing condition, location, project specifications, budget and the client’s ambition and architect’s decisions.
The integration of all design aspects during the early retrofitting design phases is extremely complex, particularly as far as energy efficient design is concerned. Decisions taken during this stage can determine the success or failure of the design, as a decision made earlier can have a bigger impact with less effort. If the designer is provided with an indication of how efficient refurbishment options are, it is possible to apply them as part of an integrated strategy rather than try to add measures at later stages, after the strategy has been developed.
The methodology used have a common approach that could be replicated in any building stock as it is based on the analysis and characterisation of the existing building stock. Once the analysis is completed and the specificities of each stock are defined, different retrofitting scenarios are proposed to improve the energy efficiency.
The target group selected is buildings constructed between the years 1850 and 1930, in the Leopold Quarter.
The building stock built before 1940 in Brussels represents 60% of built areas and is responsible for 62% of the region energy consumption.
As it can be seen in Figure 2, the characterisation is limited to three factors that allow to delimit the different building typologies: date of construction, floor area, number of dwellings per building.
Fig. 1. Number of buildings by typology. Leopold Quarter.
Fig. 2. Building typologies classified by date of construction, floor area and dwellings per building in Leopold Quarter.
Each type of building is studied including a general description of the type (description of building situation, spatial organisation, internal circulation and staircase, building systems and materials, roof, façades and building materials), a description of the main characteristics (relation with public space, size of the plot, size of the building, volume, number of floors, height and width of the main façade…) and description of type variations.
By a deep analysis of the building typologies, the designer could have a better understanding of the particularities of the stock. After the building stock definition, a more practical approach is required.
The building stock is catalogued using the previous description and all the buildings of the area are classified using GIS tools, even if the refurbishment measures are developed for the whole stock. This will enable the implementation of a final database.
The filters system allows an easy comparison of the buildings facilitating the selection of those that will be consider as case of study.
Maps of every individual topic could be provided, depending on the interest of the user, as well as individual databases.
Fig. 3. Building catalogue
The first step to enable the evaluation of the different measures is to systematically compile and organise them, according to their building components. For an integrated refurbishment, all the key aspects of the building construction and systems need to be considered and included in the refurbishment measures.
After defining the different possible retrofitting measures, it is assessed how the measures contribute to the energy efficiency upgrade. The quantification of the energy efficiency upgrade is expressed as the reduction in energy demand prior to and after their application.
Fig. 4. Scenarios of envelope retrofitting
It is important to understand which retrofitting measures are applicable to every case, and what are the interactions between them.
Each project has different design process, as the parameters that affect decisions differ. Combining these processes creates a roadmap to refurbishment strategy design process.
The roadmap addressed each building component separately. The process is iterative and not necessarily linear, as some decisions affect other components as well.
Some European projects that also use the analysis of building typologies for optimal retrofitting as its research basis, are featured hereunder:
1. ReCO2ST – This project addressed the challenges of nZEBs refurbishment through a systemic 3 step approach:
Source: ReCO2ST project
2. OptEEmAL – Has developed an Optimised Energy Efficient Design Platform for refurbishment at district level. It has succeeded to deliver an integrated and systemic design based on an Integrated Project Delivery (IPD) approach for building and district retrofitting projects, reducing time delivery and uncertainties, resulting in improved solutions when compared to business-as-usual practices.
Source: OptEEmAL project
3. HAPPEN - has developed the MedZEB approach (Mediterranean Zero Energy Building), aimed to foster the market uptake of the deep energy retrofitting of the Mediterranean residential built environment, which is characterised by the following features:
4. ALDREN – proposed a transparent, consistent, common EU wide assessment framework to trigger more ambitious renovation projects through the inclusion of improved sustainability metrics in certifications and the use of decision-support protocols and tools.
The ALDREN framework is a major contribution allowing the Energy performance (EP) assessment of buildings to:
5. B³Retrotool - Sustainable retrofit of urban blocks and buildings in the Brussels Capital Region (BCR). Development of a multi-scale and multi-criteria pre-assessment tool.
B³-RetroTool aims at offering a new vision of Brussels Capital region (BCR) by approaching the retrofitting of the city from different scales and from an integrated multi-criteria and multi-scale approach.
Through a top-down and bottom-up approach, all the layers are meant to be linked horizontally so different scenarios of retrofitting are proposed and assessed by transversal heritage, environmental and energy concepts. The key is probably to consider these aspects in a non-compartmentalised, complementary way, to reach a global objective through a sustainable and responsible approach.
The research has focused on the definition of criteria for each of these scales to identify typologies and propose suitable urban or architectural interventions in each situation to preserve heritage value and chose relevant energy performances, materials and systems.
Source: B³-RetroTool
6. EPISCOPE - The overall strategic objective was to make the energy refurbishment processes in the European housing sector transparent and effective. This will help to ensure that the climate protection targets will be attained and that corrective or enhancement actions can be taken in due time. As a further step the scope was extended towards the elaboration of building stock models to assess refurbishment processes and project the future energy consumption. A main outcome is a concerted set of energy performance indicators which shall enable key actors and stakeholders on different levels to ensure a high quality of energy refurbishments, the compliance with regulations, to track and steer the refurbishment processes in a cost-efficient way and to evaluate the achieved energy savings.
Source: EPISCOPE project
7. TABULA - Residential building typologies have been developed for 13 European countries. Each typology consists of a classification scheme grouping buildings according to their size, age and further parameters and a set of exemplary buildings representing the building types.
The "TABULA WebTool" provides an online calculation of the exemplary buildings from all countries, displaying their energy related features and the possible energy savings by implementing refurbishment measures.
Source: TABULA WebTool
8. REZBUILD – The main goal is defining a collaborative refurbishment ecosystem focused on the existing residential building stock. The aim is widening the construction sector with the integration of innovation technologies to pave the way towards an annual renovation rate of 3% instead of the current rates lower than 1%. The technologies will be merged in a common decision making platform related to an innovative concept of refurbishment plan. The methodology interconnects on one hand, advanced refurbishment technologies and existing ones based on a decision tree strategy. On the other hand, it broadcasts all stakeholders involved in the housing renovation process from designers, refurbishment to private consumer and public / private owners.
Source: REZBUILD project
9. HEART - The Holistic Energy and Architectural Retrofit Toolkit (HEART) brings together different components and technologies that can transform existing buildings into smart buildings, thus contributing to the Renovation Wave in order to decarbonise Europe’s building stock.
Source: HEART project
