Bewertung der Ressourceneffizienz von Baukonstruktionen : Entwicklung und Anwendung eines Bewertungssystems

Struck, Franziska; Flamme, Sabine (Thesis advisor); Walther, Grit (Thesis advisor); Greiff, Kathrin (Thesis advisor)

Aachen : RWTH Aachen University (2023)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2023


The construction sector is responsible for a large consumption of energy and raw materials,which results in large amounts of waste and emissions. Consequently, construction elements(walls, roofs etc.) that are resource-efficient during their entire life cycle are needed. Resourceefficiency is defined as the quotient of the benefit of a construction element (e. g., its propertieslike sound and fire protection or thermal insulation) and the resource input required fora construction element over its life cycle. Three resources are taken into acount: energy, rawmaterials and the resulting impact on ecosystems. Existing legislation has already achievedprogress in the area of energy. However, there is a need for improvement in the areas of rawmaterials and ecosystems, as political goals fixed in legislation are insufficient and raw materialsare regulated exclusively through waste legislation.The construction sector is responsible for 63% of raw material consumption, 40% of energyconsumption and 35% of CO2-emissions in Germany. This high resource consumption resultsfrom the construction and use of buildings and infrastructure facilities over their whole life cycle.In addition, large amounts of waste are generated at the end of the life cycle: 55% of all Germanwaste is construction and demolition waste. Consequently, resource consumption must be reducedand optimized over the entire life cycle. This requires construction elements (walls, roofs,etc.) that are resource-efficient over the entire life cycle. Resource efficiency is defined as thequotient of the benefit of the construction (e. g., its properties like sound and fire protection orthermal insulation) and the resource input required for a construction element over its entirelife cycle. Resources in this context are energy, raw materials and the resulting impact onecosystems. Existing legislation has already achieved progress in the area of energy. However,there is a need for improvement in the areas of raw materials and ecosystems, as political goalsfixed in legislation are insufficient and raw materials are regulated exclusively through wastelegislation.To increase resource efficiency, architects and civil engineers must be able to use resource-efficientconstruction elements when planning buildings or designing construction products. To this end,resource efficiency must be assessable as objectively as possible. Evaluation should, furthermore,consider the entire life cycle and the level of construction elements. An approach at thislevel is crucial because at this stage planning decisions are made and system manufacturersdesign their products. Moreover, refurbishments require the replacement of individuel elements.The whole life cycle is important, as effects of different life cycle phases can influence eachother, e. g., low material requirements in manufacturing vs. lack of recyclability at end of life.In addition, the particular conditions of construction compared to other products shouldbe considered: Buildings are created through a process of interaction of different actors andmany construction products have long lifetimes so that developments in e. g. manufacturing orrecycling processes are likely to occur during their life cycle.Currently, there are three methods for assessing resource efficiency (ESSENZ, VDI 4800and Fritz). However, these have not been developed for the construction sector or cannot beused for the assessment of the element level. Consequently, a new evaluation system for theresource efficiency of construction elements throughout their full life cycle must be developed.This evaluation system should build on existing approaches. Thus, already existing models wereanalyzed and evaluation criteria were derived. In addition to the aforementioned models assessingresource efficiency, models rating sustainability, individual resource aspects, individual life phases (e. g., recyclability) or other levels of observation (e. g., building level) were included.34 criteria were considered relevant for the resource efficiency of construction elements. Subsequently,indicators were selected that can be evaluated as objectively and transparently aspossible, as they are, for example based on norms. Such indicators were identified for 23 criteria.The other criteria had to be excluded due to a lack of indicators. The evaluation is based onfive-level tables containing specific threshold values or conditions to reach a certain score.Two construction element catalogs (for inner walls and floors), containing over 100 elementseach were created. All necessary indicators were calculated for these elements and thresholdvalues were derived using a percentile-based calculation method. Today’s construction elementsachieve points and differences in resource efficiency are visible, but there is also an incentive toimprove. An Excel tool was developed to assure user-friendlyness.Afterwards, the resource efficiency of interior wall and floor elements were determined, using the developed evaluation system. In six use cases, each comparing construction element shaving the same benefit, the resource efficiency was calculated. In this manner, the most resource efficient construction element can be selected for a specific application, e g., in a construction project. By analysing the evaluation results, factors influencing resource efficiency were identified. The most important factors are a long service life and the reuse of the constructions. The construction method and the requirements for a building structure, on the other hand, have a lesser influence. Current drywall elements and construction elements without requirements are more resource-efficient than solid construction elements or construction elements with high sound and fire protection requirements. The individual construction design is, however, crucial. For individual applications, solid construction elements can be more resource-efficient, and a construction that does not meet any requirements is not always more resource-efficient than a construction that meets high requirements. In sum, taking resource efficiency into consideration leads to an increase of resource efficiency, as for each application construction elements with very different scorings could be chosen. A transfer of the evaluation system to exterior walls and flat roofs shows that it is applicable regardless of the type of construction (exterior, interior, horizontal and vertical construction elements. The evaluation system can also be transferred to the assessment of multiple uses. Overall, the evaluation system developed enables a quantification of resource efficiency so that designs can be compared and results communicated. In addition, deficits of the designs can be identified enabeling product developers to improve their construction element. Planners can consciously use resource-efficient construction elements in new buildings and renovations. Building owners can demand resource efficiency for their project, e. g., in tenders. The need fore source-efficient materials and disposal methods can be made clear using the rating system and communicated to manufacturers and disposal companies. In this way, all agents involved in the life cycle can influence the resource efficiency of a construction element. The developed evaluation system shows which constructions are particularly resource-efficient or have a need for improvement. It can contribute to increasing the resource efficiency of construction elements throughout their entire life cycle.


  • Forschungskolleg VERBUND.NRW [080053]
  • Division of Mineral Resources and Raw Materials Engineering [510000]
  • Chair of Anthropogenic Material Cycles and Institute of Processing, Coking, and Briquetting [512110]
  • Chair of Operations Management [813510]