Environmental assessment of materials, components and buildings: Building-specific considerations, open-loop recycling, variations in assessment results and the usage phase of buildings

The building sector is a major contributor to the environmental loads generated by the society. The recognition of this fact by the sector and a general strive toward a sustainable society have lead to a focus on different tools that can be used to enhance the environmental performance of the sector and the society. Life Cycle Assessment (LCA) is one of these tools. The LCA methodology was initially developed for assessments of short-lived consumer products. The increasing interest in using the LCA methodology in the context of the building sector has initiated a development of the methodology to be able to consider the specific characteristics and considerations of the building sector. These are specific for the building sector, but not always unique. Examples of characteristics and considerations are: the long service lives of buildings, that each building is unique, the functional output is not always a physical product but rather a service. These have implications on several elements in the LCA methodology. The influenced elements that are dealt with in this thesis are in particular the modeling of the system, the functional unit, boundary setting, life cycle scenarios, scenarios and inventory of the usage phase and allocation procedures. Buildings and constructions are commonly not static systems. The systems are rather dynamic in the sense that the system will provide different services based on the same physical structure during its service life. To be able to model the dynamic system, sequential life cycle thinking is introduced and a list of topics is derived. The list of topics is a structured presentation of issues that are of interest in the pursuit of a flexible LCA methodology. The goal is to find out if a methodological approach is suitable for modeling dynamic systems with a functional unit that is based on the provided service rather than the physical building. Boundary setting, life cycle scenarios, allocation procedures, predicted service life and the modelling of the usage phase are all elements of the LCA methodology that have a potential to influence the result of an LCA in a significant way. The potential influence has been monitored based on the results of three case studies, which have been elaborated further to be able to estimate the magnitude of the potential influence. There is a multitude of available allocation procedures presented and used in different contexts. The procedures are developed based on different considerations and with different intended applications. Two alternative allocation procedures are presented in this thesis. The first is a procedure developed with multi recyclable materials in mind and it is based on the recyclability of materials and products. The second procedure is quite recently developed and it is based on a combination of economic parameters and recyclability. The importance of the usage phase for buildings and constructions has previously been recognised. The main contributors to the environmental loads generated during the usage phase are energy use, maintenance and emissions from products. It is, however, not very common to consider the usage phase in assessments conducted on materials and components, even though it is stipulated in e.g. ISO 14025 that the whole life cycle should be considered. A proposal of a model to estimate the environmental loads is, therefore, presented.