Due to the growing population, the revived trend of living in urban areas and the scarcity of building plots, the idea of vertically extending existing residential buildings is gaining popularity in Belgium. Timber frame constructions are appropriate due to their light weight and lack of point loads. This article aims to assess (1) the potential environmental impact reduction of light-weight timber frame constructions for rooftop extensions by changing composition and dimensions and (2) the effect of biogenic carbon. Timber frame walls and roofs are analyzed based on the life-cycle assessment method. Starting from the current building practice in Flanders, various parameters are assessed. The effect of using I-joists instead of solid studs, of adjusting the center-to-center distance between the studs and of changing materials for different layers is analyzed. The results showed a limited environmental impact reduction of using I-joist instead of solid studs and of adjusting the center-to-center distance. Changing the composition of the walls and roofs in terms of materials can lead to a total life-cycle environmental reduction of 22% and 14%, respectively. If biogenic carbon accounting is integrated in the assessment method, based on the ILCD method, the total life-cycle environmental impact is reduced by up to 35% and can lead to significant differences in the preferred choice of timber frame composition.

The emphasis in this research is on affordable and innovative semi-prefabricated ‘open-renovation-systems’ for extending residential buildings. Based on an existing LCA (life cycle assessment) and LCC (life cycle costing) methodology, two methodological issues in evaluating renovation interventions are assessed: (1) the allocation of the environmental impact of the existing structures and materials to the life cycle before and after renovation and (2) the energy calculation method. An existing semi-prefabricated ‘open-renovation-system’ for a rooftop extension is assessed both on element and building level from an environmental and financial life cycle perspective.

Purpose The built environment consists of a huge amount of infrastructure, such as roads and utilities. The objective of this paper is to assess the life cycle financial and environmental impact of road infrastructure in residential neighbourhoods and to analyse the relative contribution of road infrastructure in the total impact of neighbourhoods. Methods Various road sections are analysed based on an integrated life cycle approach, combining life cycle costing and life cycle assessment. To deal with complexity, a hierarchic assessment structure, using the principles of the “element method for cost control”, is implemented. Four neighbourhood models with diverse built densities are compared to gain insight in the relative impact of road infrastructure in neighbourhoods. Results and discussion The results reveal important financial and environmental impact differences between the road sections analysed. Main contributors to the life cycle financial and environmental impact are the surface layer and electrical and piped services. The contribution of road infrastructure to the total neighbourhood impact, ranging from 2 to 9 % of the total cost, is relatively limited, compared to buildings, but not negligible in low built density neighbourhoods. Conclusions Good spatial planning of the neighbourhood is recommended to reduce the amount of road infrastructure and the related financial and environmental impact. The priority should be to design denser neighbourhood layouts, before decreasing the financial and environmental impact of the road sections.

Ongoing research in Europe related to sustainable renovation mainly focuses on improving the energy performance of buildings. These studies have a limited scope regarding sustainability as operational energy is often the only focus. A screening of current practices in Flanders moreover shows that renovations are often limited to small interventions, whereby a long term vision is missing. We are convinced that a more integral approach is necessary to strive for sustainable renovation. This research aims at supporting the construction sector in the challenge for an increased renovation rate with more in depth transformations of the existing housing stock in Flanders. The objective is moreover to stimulate a transition from energy-focused renovations towards integral sustainable renovations from a life cycle perspective. In this context, the research aims among others at developing a number of affordable and innovative ‘open-renovation-systems’, with the focus on interventions such as splitting, combining, wrapping and extending residential buildings. To compare and analyze these renovation systems, a method to evaluate the environmental and financial impact of the renovation interventions over their whole life cycle is being developed. This evaluation method is based on the LCA (life cycle assessment) and LCC (life cycle costing) methodology. This paper focuses on two methodological issues in evaluating the environmental impact of renovation interventions: the allocation of the environmental impact of existing structures and materials to the life cycle before and after renovation, and the role of the estimation of the building lifespan (before and after renovation) in decision taking. The results of the analyzed case study show that the chosen allocation approach does not influence the overall conclusions regarding renovation or demolition followed by new construction. However, the case study reveals that the estimation of the second building lifespan can affect the results in a significant manner.