Abstract

     The rate at which buildings are renovated across Europe is expected to increase in the upcoming years. However, selecting renovation solutions for residential buildings is still a challenging task due to the participation of multiple stakeholders, lack of clear decision-making procedures, and diverse effects resulting from the renovation alternatives. Most of the existing approaches do not consider multiple stakeholders and focus mainly on weighting criteria and performing simulations to quantify alternatives’ performance. Therefore, this paper presents a more complete Multi-criteria decision-making (MCDM) framework to support the decision-making process in renovation. To illustrate and validate the framework, it is implemented in two case studies based on a five-story building located in Spain. Each case includes five stakeholders. Two weighting settings are analysed to study the robustness and sensitivity of the proposed approach. The main contributions correspond to: 1) an MCDM enabling the participation of multiple stakeholders using the Pairwise comparison method; supporting the setting of objectives and criteria, promoting a comprehensive evaluation of the alternatives; and facilitating the integration of criteria weights and alternatives’ performance through the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method; and 2) the validation of the proposed framework, especially the implementation of TOPSIS to evaluate renovation alternatives. Promoting the setting of objectives and criteria can enable discussions and encourage a broader and more complete analysis of renovation alternatives. In the two case studies, stakeholders included social aspects and assigned in total weights around 20% to this category. The Pairwise comparison and TOPSIS methods integrated the perspectives of stakeholders with different interests and the alternatives’ performance to obtain a shared view of the renovation and a final ranking of the alternatives to differentiate them accordingly and make a better-informed decision.

Introduction

     In Europe, building renovation rates are expected to increase due to the large number of existing buildings that require to be renovated. Around 75% of existing buildings are considered inefficient according to current standards [1]. 85–۹۵% of the existing building stock will still be standing in 2050 [2]. Typically, in residential renovation projects, complex governance and ownership structures, legal structures, and other challenges impact the initiation and execution of the renovation activities [3]. Some of these aspects lead towards complex decision-making processes to select the final renovation solution. Strategies and tools need to be developed to support stakeholders to overcome these barriers.

     In the building renovation field, there is a lack of consensus regarding the main criteria, applicable renovation methodologies, and tools to support the decision-making process [4]. Despite the involvement of multiple stakeholders in such projects, most of the existing approaches are limited to cases where the decision is made by a single stakeholder. Nevertheless, in these projects, additional stakeholders such as tenants and building managers may get involved [5], influencing the decision-making process. Around 49% of the housing stock in Europe corresponds to multi-family units, and the average share of rented units is 30%, reaching levels around 70% in countries such as Germany [3]. Therefore, a decision-making strategy in the context of residential renovation should support the participation of multiple and diverse stakeholders, which may have different rights and obligations [6].

Conclusion

     Residential renovation projects encounter different scenarios and particularities that require a better-structured decision-making approach to select suitable renovation solutions that fulfil the requirements of the project and stakeholders involved. This paper presented an approach that enables the participation of multiple stakeholders through the Pairwise comparison method, supports the objectives and criteria setting based on a predefined comprehensive decision tree and complementary activities, and integrates the criteria weights and alternatives’ performance through the TOPSIS method. Firstly, the implementation of the Pairwise comparison allows gathering the preferences of stakeholders with different interests to obtain a gathered perspective of the problem. The first weighting setting showed that following the perspective of only one of the stakeholders can lead to different results in the ranking of the renovation alternatives. Secondly, promoting the setting of objectives and criteria can enable discussions and encourage a broader and more complete analysis of renovation alternatives, including social-related issues. In the two case studies, besides economic and environmental aspects, stakeholders selected social and technical elements to evaluate the renovation alternatives, assigning in total weights around 20% to this category. Since each renovation project encounters specific requirements, the flexibility of the proposed framework to include new goals and criteria in the decision tree proved to be relevant. Stakeholders included new criteria according to their requirements. Thirdly, the inclusion of the TOPSIS method enabled the integration of the stakeholders’ perspective and alternatives’ performance to make a better-informed decision, especially in complex cases where the effects resulting from the different renovation alternatives are not easy to differentiate. Different weighting settings showed that TOPSIS allows considering the importance of the criteria in combination with the alternatives’ performance to differentiate renovation alternatives and rank them accordingly to facilitate the analysis by the stakeholders involved. Finally, even though the proposed approach was implemented in two specific cases, it can be applied in other scenarios including single or multiple stakeholders, playing different roles in the decision-making process.