• Energy Research

The reuse of existing materials in buildings can give a contribution to sustainable practices such as a balance in embodied energy, water, and emission reduction. However, it is not always possible to maintain the existing structural materials because some different technical variables could hamper their usability, namely seismic reinforcement needs, fire safety protection, conservation state, and new legal requirements. The paper follows a case study approach for assessing the technical and environmental performances of structural options for old building retrofitting works. All structural options were analyzed through the results of several categories of environmental impact. Some parameters of a retrofitting management system were also used to frame in a comprehensive way the technical constraints pertaining to building retrofitting works. The structural option choice was taken by the owner with the contribution of the design team and the construction manager of the construction project as well as the results of interviews with other construction professionals, considering the variables related to technical suitability and environmental impact. The results of the study show that the steel structure is the solution that best addresses the technical constraints of the building retrofit works and minimizes environmental impact. The results of the study also suggest that the consideration of other variables other than the technical ones can contribute to the effective functioning of the renovation subsegment of the building market. Some suggestions for further studies to enhance the results of this work are put forward.

The retrofitting works in old buildings require appropriate knowledge of the vernacular techniques. Previous researches have identified retrofitting works as more intrusive and using more unnecessary demolition materials than real needs. This study constitutes a new framework that focuses on the project management success of old building retrofitting in historical centres by developing a methodological system for this purpose. It uses a construction sector system approach, reviews legal requirements, framework specifications, recommendation practices and sustainable measures adapted to old building projects. It presents 50 parameters adapted to these works’ specificities that could be used by construction market stakeholders. The research uses a case study methodology divided in two parts. The first one involves the review of building retrofitting projects in historical centres, complemented by a questionnaire in the second part. The results of the projects review have shown little concern with the underlying sustainability aspects of retrofitting works in all project designs analysed. However, the questionnaire results have revealed a high interest and applicability of all parameters omitted in the project designs data. The study describes a useful management system in a toolkit format which might contribute to reduce uncertainty in the management of retrofitting projects in historical centres.

There is still a little recognition in policies that homeowners cannot be assumed as one homogeneous group when it comes to their decision for energy-saving renovation. The interest in energy efficiency varies among these homeowners depending not only on personal and contextual factors but also on everyday life activities and social practices. Some studies suggest that the homeowner’s life stage have a significant role in shaping this interest. This study aims to understand the influence of the homeowner’s age on the motivation for energy-related renovations of Portuguese owner-occupied single-family buildings and how this age is linked to the home-related and social practices that may encourage these renovations. A survey and a structured observation method were used. The younger Portuguese homeowners seem to be more environmentally conscious and adopt “little-by-little” energy renovations, even if less visible to the community. For the older, despite higher incomes, usual motivational arguments do not seem to work. If energy-related renovations are associated to some particular issues about aesthetics, indoor comfort conditions and sentimental meanings given to the home, these renovations are more likely to happen. However, both can be influenced by key moments in their life that trigger the renovation process. Keywords: Energy policy, Energy-related renovation, Homes, Homeowners, Social practice theory, User practices

Abstract The most recent studies point out that building users play a critical role in the decision-making process for the energy renovation of buildings as well as in energy use during the building life-time occupancy. Nevertheless, this important player has been poorly considered in the policies implemented. The homeowner, whose role has been passively induced to renovate accordingly with impositions of the regulations, is calling for himself a more active participation in the renovation process. The social dimension of the building renovation has been ignored. This study aims to highlight the role of the homeowner in the decision-making for energy building renovation investigating his motivations, needs, attitudes and daily routines. A selected group of Portuguese homeowners were interviewed. Also in Portugal, homeowners’ qualitative decisions and everyday life practices have a strong influence in the decision-making for building renovation.

Office buildings built before the pre-1960 age constitute a relevant group for analyzing the energy performance of the Portuguese building sector. A dynamic energy simulation was used to assess the energy performance of an existing office building located in the town of Bragança, Portugal. By using a staged renovation approach, two passive technologies applied to the building envelope and an efficient domestic hot water system were selected and a financial evaluation through the net saving (NS) method was undertaken to choose the best efficiency measures/packages for improving the building’s energy performance. Real discount rates of 3% and 1% were used in the financial evaluation. Considering the real discount rate of 3%, the results showed that only two out seven retrofit options had a positive financial return. By using the real discount rate of 1%, all retrofit options were found to be financially efficient. The results of the study corroborated those of earlier works that found that the financial profitability of energy renovation investments is very sensitive to the discount rate used in the analysis. The results of the study also suggested that the staged renovation approach used in the analysis is economically feasible, and that this approach is an alternative to one-step renovation approach to help to achieve the country´s energy and climate targets by 2030. Suggestions for future research conducted for office buildings in the different climate zones and other age groups in Portugal are proposed.

Given the high annual water consumption for non-potable uses (1112.08 m3, 65%) of an industrial building with a large roof area (4638 m2) located in the Northeast of Portugal, this study aims to evaluate the technical and financial feasibility of a rainwater harvesting system for these uses, considering the existing conventional roof (scenario 1) and adapting a green roof to the existing roof (scenario 2). This evaluation was based on the impact of the two scenarios on the building’s water savings. Under scenarios 1 and 2, the expected water savings were 64.47% and 59.43%, respectively. Therefore, the expected reduction in the annual water bill was €3867.07 + VAT (scenario 1) and €3564.63 + VAT (scenario 2). For scenario 1, considering a reservoir with 70 m3 for non-potable purposes, such as washing the building’s floor and use in industrial machines, and an initial investment of €41,109.13 + VAT, the single payback will be 11.29 years. The single payback for scenario 2 largely exceeded the lifetime of the green roof. However, as they are considered interesting solutions to reduce the negative externalities of industrial settlements, financial incentives could be proposed for the implementation of the green roof in this typology of buildings.

Office buildings built before the entry into force of the first thermal regulation in 1991 constitute a relevant group for analysing the energy performance of the Portuguese building sector. A dynamic energy simulation was used to assess the energy performance of an existing office building located in the town of Bragança, Portugal. Four energy efficiency measures were selected and a financial evaluation through the internal rate of return (IRR) method was undertaken to choose the best retrofit option for improving the building’s energy performance. An investment package consisting of the roof insulation and a new equipment for the domestic hot water system presented an IRR higher than the discount rate used in the analysis, and, thus, a positive financial return. The results of the study also suggest that the EU’s comparative methodology framework is not particularly suitable for assessing building retrofit investment at the private investor’s perspective and further refinement in the cost-effective approach to renovations is needed to help stimulate building’s energy renovation market. Suggestions for further studies conducted for office buildings in the different climate zones in Portugal are also proposed.