Cities today face a combination of global challenges, including climate change, biodiversity loss and rapid urbanization. While urban areas disrupt natural ecosystems, they also hold untapped potential for biodiversity due to their lower management intensity compared to agricultural land. At the same time, the built environment is one of the largest contributors to global biodiversity loss, underscoring the urgent need to integrate nature into cities. Retrofitting existing buildings with nature-based solutions (NBS) offers a more sustainable alternative to demolition and reconstruction, particularly in densely built environments. Among NBS, Vertical Greening Systems (VGS) offer high spatial potential on building envelopes but remain underutilized, partly due to limited knowledge of their biodiversity impact and feasibility on existing buildings. Current methods for assessing structural feasibility are highly detailed and often expensive, therefore not suitable for early design phases. Additionally, VGS suppliers rarely provide insight into biodiversity performance or adaptation to existing structures, complicating system selection.

This thesis addresses the need for a practical framework to support the decision-making of VGS implementation on existing urban office buildings during the feasibility phase of enhancing a building's biodiversity performance. It aims to reduce the knowledge and feasibility gap by structuring the exploration process based on biodiversity indicators, building characteristics and structural potential. The objective is reflected in the main research question:
"How can a framework be developed to support decision-making on the feasibility and selection of VGS for existing Dutch office buildings aiming to enhance urban biodiversity?"

To answer the main research question, a multidisciplinary research approach was applied, structured around four core components of the developed framework. First, an exploratory literature review was conducted to classify VGS based on key distinctive physical features. This typology serves as a foundation for the entire study. Second, the biodiversity performance of the classified VGS types was assessed through a Multi-Criteria Analysis (MCA). Biodiversity indicators were derived from empirical literature and weighted based on the preferences of selected animal groups acting as ecological stakeholders. This resulted in a relative biodiversity ranking of VGS types. Third, a set of building indicators was developed by analyzing the key features of the VGS types and linking them to architectural characteristics commonly found in Dutch office buildings constructed between 1960 and 1990. This resulted in the definition of four representative building typologies to support suitability assessments. Fourth, the structural feasibility of VGS was addressed by analyzing Dutch design guidelines for existing concrete structures and validating a simplified estimation method for excess capacity in facade-supporting slabs and beams, using a parameter study. These steps together form the basis of the framework that supports VGS selection during the feasibility phase. Finally, the framework is verified through an illustrative case study.

The findings of this thesis show that all VGS types included in the study contribute to urban biodiversity, although to varying extents depending on their physical characteristics. The indicators most relevant to biodiversity performance are plant coverage, plant diversity, substrate size and substrate orientation. For assessing VGS suitability, building height, shape, facade geometry, glass percentage and facade type proved to be key characteristics. While the framework enables general recommendations based on these factors, detailed assessments remain necessary for project-specific implementation. Furthermore, the parameter study validates the use of excess capacity factors as a viable method for estimating structural feasibility in early phases, although some outliers from the parameter study have been translated into practical warnings for the framework. These are mainly related to the design of shear reinforcement and the calculation of its resistance, as this approach has evolved significantly over the years.

The resulting framework enables users to explore the implementation of VGS during the feasibility phase of enhancing a building’s biodiversity performance. By relying on basic, broadly applicable parameters, it remains adaptable to a wide range of office buildings, while still offering structured guidance on the feasibility of different VGS types. The framework is built around the expected level of structural knowledge available in the feasibility phase and provides, for each level, either a graph or a formula to estimate structural excess capacity. This estimate can then be compared to the weight ranges identified for the different VGS types, offering insight into their structural feasibility. Based on the building’s exterior, relevant characteristics can be derived that allow the building to be classified within one of the predefined office building typologies. These same characteristics are used to identify VGS recommendations for each typology. By combining the structurally feasible options, the architecturally suitable systems, and the biodiversity ranking, the framework supports well-informed decision-making for both the feasibility and selection of VGS implementation. Its application to a hypothetical case demonstrates that the framework functions as intended. Future application to real-world buildings would further validate its robustness and enhance its relevance for practical use, especially for architects, engineers, and municipalities seeking to green the urban environment.

Urbanization has significantly altered the built environment, leading to increased urban heat and the loss of green spaces, which are being replaced by buildings, which in its turn retain more heat inside the city. Climate change causes extremer weather, resulting in heavier rainfall and urban floodings, for which cities are often unprepared. Incorporation of nature into the vertical buildings surfaces has the potential to address these challenges. A promising solution for creating these vertical green areas are porous concrete façades. Although research into this application has been performed for several years, a widespread implementation remains limited. A demountable, quick-to-install solution could assist the broader implementation of green solutions in urban areas. This research investigates the feasibility of such a demountable system.

Noise pollution has become a significant environmental concern in urban areas. Low-frequency sounds, especially those coming from aviation activities present a major difficulty among noise sources, due to their ability to travel long distances and easily penetrate different structures. In response to the growing need for mitigating such environmental challenges, green roof structures are becoming an increasingly effective potential. Green roof systems provide several environmental benefits, including thermal insulation, enhanced air quality and stormwater attenuation that have been extensively studied. However, the potential of these systems to mitigate low-frequency noise pollution remains underexplored.
This study aims to investigate the acoustic absorption capabilities of green roof systems, emphasizing their role in reducing noise pollution and the importance of certain sustainability aspects. To achieve this, the use of resonance absorbers is being investigated, focusing on integrated Helmholtz resonators targeting low-frequencies. Initially, acoustic measurements are conducted to assess the acoustic performance of five different green roof systems provided by SemperGreen. Based on the measurements’ results, different integrated resonator design concepts are developed and evaluated systematically in order to find the most optimal solution. FEM numerical simulations are performed in COMSOL Multiphysics by modeling a large impedance tube to assess the impact of different resonator configurations on the green roof system’s overall acoustic performance.
The findings of the study demonstrate that the integration of Helmholtz resonators in the growing medium layer can improve the acoustic performance of the system at lower frequencies, however within a particular limited range. As a final step, optimization strategies including the introduction of cross-structure fins in the resonators’ neck or adding a secondary neck alongside the primary one are explored as potentials to broaden the absorption peaks. From the findings it can be concluded that the development of more acoustically efficient green roof systems is feasible; however, further experimental validation is required to confirm and refine the proposed solutions.

Plants can capture particulate matter (PM) on leaf surfaces, helping to reduce PM concentration in the air. In urban areas, limited space is available to increase vegetation cover, but climbing plants require little space to grow. This is why this study investigates the PM capturing capacity of different climbing plants in an urban environment. The PM was collected on the leaves of six plant species and was quantified using two experimental methods. In the gravimetric method, leaves were washed in an ultrasonic cleaner, after which the water was filtered to determine the weight of PM_coarse, PM₁₀, and PM_2.5 that was on the leaves. For the Environmental Scanning Electron Microscope (ESEM) method, images were taken of the leaf surfaces at 125x, 250x, and 500x magnifications and the particles of
different size fractions were counted.

The results indicated that there is no statistically significant difference between the amount of PM that Hedera helix, Trachelospermum jasminoides, Wisteria sinensis, Parthenocissus quinquefolia, plastic ivy, and Rynchostegium confertum captured. They suggest that the epicuticular wax layer of plants plays an important role in long-term PM capture, with H. helix and T. jasminoides showing trends towards higher PM capture and retention, and that mosses like R. confertum have potential for efficient PM collection. A comparison of the two experimental methods indicated that the gravimetric method could be used to determine surface PM retention of different plants, whilst the ESEM method could be used to analyse particles in the wax layer and for more precise analysis of the plant leaves.

Environmental noise is a pervasive and significant issue in urban areas, negatively affecting the health and well-being of both residents and wildlife. Despite efforts under the European Noise Directive to reduce noise from sources such as road, rail, air traffic, and industrial activities, around 20% of the EU population still lives in areas where noise levels exceed health-based guidelines. The dense infrastructure and reflective surfaces in urban environments amplify noise levels, highlighting the urgent need for effective noise reduction strategies.

Vertical Greenery Systems (VGSs) can effectively reduce urban noise pollution when implemented thoughtfully. State-of-the-art VGS designs commonly incorporate multi-layer structures comprising a bearing wall, substrate layer, and foliage layer. This research aimed to optimize such VGSs in the early design stages to enhance their noise mitigation capabilities. Among the available generic models, the Transfer Matrix Method (TMM) offers the most comprehensive approach for modelling the acoustic characteristics of these structures. TMM allows for the modelling of acoustic properties on both sides of a one-dimensional fluid-like layer using effective, frequency-dependent parameters encapsulated within a 2 × 2 matrix. The total transfer matrix of the VGS results from the product of its individual layer transfer matrices.

It was established that to accurately evaluate the acoustic effectiveness of multi-layered VGSs, it is imperative to concentrate on the performance resulting from the superposition of layers under specific boundary conditions, rather than analysing individual layer parameters in isolation. This approach recognizes that there is no definitive answer regarding which specific components demonstrate superior performance. Instead, the intricate nature of superposition underscores the necessity for systematic experimentation with various component combinations and the manipulation of extrinsic variables, such as layer thicknesses, to optimize VGS performance.

In this research, the TMM was utilized to develop a tool for evaluating the acoustic performance of VGS designs, suitable for deployment during the early phase of the design process. The tool includes a comprehensive material library that allows stakeholders to explore various design options, making the approach more adaptable. It enables the evaluation of VGS design feasibility by examining the normal incidence weighted sound absorption coefficient and its corresponding absorption class. Additionally, the tool serves as a framework for conducting further analysis on the long-term environmental impact and economic viability of VGSs.

The pressing challenges of climate change and the increasing surplus of concrete waste is making it increasingly important to fully recycle concrete in a sustainable way. Since cement is by far the component that contributes most to the environmental footprint of concrete, it is of great importance to investigate the potential of upcycling secondary cementitious materials. Modern recycling techniques such as the Smart Liberator make it possible to efficiently separate the coarse and fine fractions in concrete waste. It also makes is possible to produce a fine powder fraction that shows potential to replace primary cement, which helps to mitigate CO2 emissions. This study explores to which extent recycled concrete fines (RCF), obtained from advanced recycling technologies such as the Smart Liberator, can replace ordinary Portland cement (OPC) in mortar mixtures. It is assumed that the RCF consist mostly of cementitious materials. The aim of this study is to assess the performance of RCF when replacing OPC in different mortar mixtures. Several treatment methods were applied to enhance the reactivity of the RCF.
To be able to assess the performance of the RCF as replacement of ordinary Portland cement at mortar level, three reference mortar mixtures, made from CEM I, CEM II/B-V and CEM III/B, were prepared for comparison. Portland cement with strength class 52.5 R was used in for preparation of the reference mixtures. The used RCF were the 0-63 μm fraction obtained from the Smart Liberator. It is expected that the RCF are from CEM III origin based on documentation from the company Rutte Groep. However, due to limited stock, some of the mortar mixtures had to be prepared with a different type of RCF, consisting of RCF with a CEM I and CEM III origin that were mixed in a 1:1 ratio. The OPC in the reference mixtures was replaced with RCF at 50%, 75% and 100% ratios.
Grinding, carbonation, conventional heating and flash calcination were applied as treatments to enhance the reactivity of the RCF. Thermogravimetric analyses were used to assess the effects of the treatments on the decomposition of the compounds of the RCF. Mortar prisms made with treated and untreated RCF were tested for flexural and compressive strength after 28 days of curing, and their performance was compared to the reference mortars.
The results showed that the untreated RCF performed best when used in combination with blast furnace slag. This combination was the only one in which a 100% replacement resulted in measurable strengths and the measured strengths at the other replacement ratios were the highest, reaching up to 70% of the compressive strength of the reference prisms at 50% replacement. This indicates that the RCF are a suitable activator for blast furnace slag.
The effects of the treatments differed in the different mixtures and also varied across the replacement ratios. Grinding of the RCF improved their performance at the 50% and 75% replacement ratios in the CEM I variant, while their performance in the CEM II and CEM III variants was similar to or lower than the untreated RCF. The same conclusions are drawn from the results after carbonation. Heating of the RCF up to 900 °C for 30 minutes in a regular chamber furnace resulted in better results for the CEM I variants at all replacement ratios, while no significant improvements were measured for the CEM II variants. For the CEM III variants, only the 75% replacement ratio had a significant improvement. Lastly, flash calcination resulted in the most significant improvements for the CEM I and CEM II variants at all replacement ratios. For the CEM III variants, flash calcination significantly improved the strengths at the 100% and 75% replacement ratio, but not at the 50% replacement ratio. Since this does not align with each other, it is necessary to reconfirm these results.
As a conclusion, this study demonstrated that untreated RCF shows potential to BFS, while flash calcination is the most promising treatment for boosting RCF reactivity across most mixtures. Conventional heating also showed potential, especially for CEM I. However, grinding and carbonation had mixed results, with limited benefits for BFS combinations due to carbonation effects. Future research should confirm these findings and explore ways to optimize the treatment methods.

The urban heat island effect is a well-known and pressing problem in cities today related to urbanisation. It is the phenomenon of an increased ambient air temperature in cities compared to the surrounding rural areas. The use of nature-based solutions has been proposed as a way to help solve this problem. These interventions use nature and biodiversity to improve urban sustainability. By replacing materials that accumulate a lot of heat, the urban heat island effect is tackled. One way of doing this is by making use of so-called bioreceptive concrete on our facades, which allows for the biological growth of mosses to take place on the concrete substrate itself, without requiring any additional systems or maintenance.
This master thesis aimed to quantify the evaporative cooling effect of these moss-covered concrete facades on the urban environment. The research objective was to measure and model the amount of cooling resulting from the evapotranspiration of moss, by analysing water uptake and release, as well as the temperature decrease of a façade surface as a result of evaporation.
Laboratory experiments were conducted to examine the evaporation rates of various moss species under controlled ambient conditions. Bryum capillare displayed the highest water uptake, water retention, and drying time, with the ability to take up 32.4 g of water per 83 x 83 mm surface area. This is equivalent to 4703 g of water per square meter or 470 kg/m3 volumetric weight. Pleurocarpous mosses showed a range of 27 to 27.4 g of water uptake, corresponding to 3919 to 3977 g of water per square meter or 392 to 398 kg/m3. The concrete itself absorbed 21.1 g of water, which is equal to 3063 g of water per square meter or 204 kg/m3 for the 15 mm thick sample that was tested.
Evaporation rates were found to be higher immediately after a watering event, with variability observed between different moss species. Highest variability was 5.56 g/h for Eurhynchium striatum versus 1.86 g/h for Syntrichia ruralis. However, after a certain time, most mosses exhibited similar evaporation rates. The exception was Bryum capillare, which consistently maintained a higher evaporation rate. This moss, growing in cushion form, demonstrated enhanced drought avoidance due to a reduced surface-to-volume ratio and additional capillary spaces for water retention. The highest levels of evaporation were observed in all moss species under conditions of high temperature (25°C) and low relative humidity (50% RH).
Field testing involved monitoring the temperature of two bioreceptive concrete façade panels, one covered in moss and the other left bare. On sunny days, when panel temperatures exceeded 15 to 20 °C, and the panels were dry, the moss panel temperature was 0 to 5 °C lower compared to the bare concrete panel. This temperature difference was attributed to the lower albedo of the moss (0.07 – 0.11) compared to the concrete (0.10 – 0.40). The moss absorbs more solar radiation and prevents it from reaching the surface beneath it. Infrared camera measurements confirmed that the dry moss surface temperature was about 2 to 3 °C warmer than the concrete panel surface due to lower albedo of the moss. On rainy or cloudy days minimal temperature differences were observed between the panels. Additionally, the moss acts as an insulation layer, trapping the air between its leaves, keeping the material behind it cooler. The potential implications of this additional insulation layer on top of the facade remain to be investigated. Based on its specific heat capacity and heat conductivity, it could help with heat gain in winter and cooling gain in summer. It is hypothesised that moss has a lower thermal mass than concrete, potentially facilitating quicker heat dissipation at night and contributing to reduced building surface temperatures.
Watering the panels significantly reduced surface temperatures, with the moss panel being 2 to 5 °C cooler than the concrete panel when wet. The moss exhibited higher water absorption and longer water retention compared to the porous concrete, enabling more evaporation resulting in lower façade temperatures. This cooling effect persisted for approximately two and a half hours after a 40 ml watering event, equivalent to a 1 mm rain event at low wind speeds. These findings indicate that applying moss on a concrete facade cools the surface temperature of a façade compared to a bare concrete façade.
A non-stationary model based on the energy balance of the facade system was calibrated using field testing data. This model provides accurate temperature profiles under different weather conditions. Evaporation modelling was calibrated using water events but could be improved by implementing a water balance. By computing the irrigation, precipitation, evaporation, throughflow and runoff in a dynamic balance, the evaporation and temperature profiles would become more accurate.
The model is used to simulate a heat wave and the thermal behaviour of the façade after rain events with different intensities. A 1 mm rain event decreases the surface temperature of the façade with a few degrees but the effect does not last for a very long time. A 10 mm rain event decreases concrete surface temperature up to 10 °C initially, and the effect lasts for a few hours. The length and intensity of cooling can be extended through the application of moss on a façade. Then, for a 10 mm rain event, the initial temperature reduction is equal to 15 °C. To increase this effect, the pore volume of the concrete could be increased. Also, a moss species should be cultivated on the concrete which grows in cushion form, is desiccation tolerant, and has natural protection against UV light.
The thesis concludes that applying bioreceptive concrete on facades has the potential to mitigate the urban heat island effect by maintaining cooler temperatures for an extended time following rain events depending on their severity. This approach replaces materials that accumulate and radiate excessive heat. To quantify the effect of bioreceptive concrete as a mitigation strategy more accurately, a computational fluid dynamics (CFD) model could be made to predict the ambient temperature decrease of the air in front of a bioreceptive facade.
By investigating and quantifying the evaporative cooling effect of moss-covered concrete facades, this thesis contributes to the understanding of nature-based solutions. The findings highlight the potential benefits of incorporating bioreceptive concrete in building facades to mitigate the urban heat island effect and improve thermal comfort in urban areas.

The Dutch construction sector has the task in the coming years, to build around 1 million new houses in the Netherlands, most of which will have to be built in urban areas. Together with existing (inter)national crises such as the climate change crisis and biodiversity loss crisis, this means the sector will have to think differently to not jeopardise the liveability of our cities. One way of doing this is to create more Nature-based Solutions in these urban areas, but the perception is that this is an expensive solution. By using the framework from Ecosystem Accounting, the benefits these Nature-based Solutions can give us, are monetised to show that the perception of it being expensive is wrong. The aim for this research was to see how Ecosystem Accounting can be used in procurement procedures to create more Nature-based Solutions.

With the double diamond approach, this study was split into two sections. In the first section of the research, a literature study and stakeholder interviews were used to find the most important themes for clients and contractors to have an ambition for Nature-based Solution. These themes were: biodiversity, climate adaptation, health & wellbeing and aesthetic value. In the second section, a new literature research combined with key informant interviews indicators for these themes were found. A total of four indicators (Vegetation layer score, shadow cover, air quality and soil quality) and five services (rainwater regulation service, local climate regulation service, health service of nature, visual amenity service of nature and visual amenity service of water) were found.

For effective use of the framework, three moments in time are important. In the ambition phase Ecosystem Accounting can be used to formulate the ambition of a project. In the tender phase (depending on the amount of design freedom in the contract) EA can be used as a requirement or as a MEAT-criterium. To assure that the plans are realised, the control phase should not be forgotten either.

Green roofs can play an important role in reducing problems in urban areas by being flexible, multifunctional and adaptable. These features of nature have proven effective in combating climate change and contribute to human well-being. Previous research has shown that green roofs can sometimes be cost-effective, but the benefits included in cost-benefit analyses are fragmented and an absence of a learning curve in the literature regarding green roofs is discernible. This research focuses on how to determine the economic value of the benefits of green roofs and what methodologies are used to do so. There is also a need to bridge the gap between research on costs and benefits and research on external costs of production materials. This research contributes to bridging this gap by creating a full life-cycle cost-benefit analysis of a green roof by mapping and analysing current methodologies. This research contributes to sustainable development and in it serves as a starting point to determine the utilisation of green roofs with the pursuit of sustainable urban development.

The aim of the current graduation project is the investigation of the potential of using hempcrete for the construction of residences in the Netherlands. The research focuses on the prefabricated block form of the material and investigates different aspects that can play a major role and eventually affect the choice for the selection of the material in building applications. Such aspects are: the regulation and performance proofing requirements which are associated with the application of an unstandardised material, the application methods, the strengths and limitations related to the nature of material, the current industry barriers, its hygrothermal, energy and environmental performances according to the Dutch building regulation in comparison to popular industrialised materials in the Netherlands and the related costs. The compared industrilised options were two: the Aerated Autoclaved Blocks, which account for an industrialised option with equivalent properties as these of the hempcrete blocks, and the option of Sand-lime bricks in combination with Fiberglass insulation, which is currently a widely used construction option in the Netherlands. Dynamic hygrothermal simulations were performed in WUFI software, whereas available EPDs were used for the investigation of the environmental impacts of the materials under scrutiny in a life cycle analysis. Available literature, interviews with parties characterised by different roles and high experience regarding the use of biobased materials in the building industry were also used as a means for the completion of the current graduation project.
Apart from the available literature, the research methods followed in the current graduation project were influenced by the results of the performed interviews, which indicated aspects that could be further explored. The results of the research show that in terms of performances, the material is able to satisfy the requirements of the modern Dutch building regulation and therefore the later does not account for the reason behind the limited propagation of the material in the Dutch building industry. Nevertheless, the current Dutch regulation is currently a barrier that discourages the international material supply and disregards important properties of hempcrete as its moisture buffering capacity and specific heat capacity which can play an important role. The Sand lime brick option has been proved more competitive in comparison to the Autoclaved Aerated option, as hempcrete outperformed its industrialised version AAC in the vast majority of the analyses performed in the current study. Hempcrete shows a better moisture buffering capacity and environmental footprint. The hygrothermal performances of hempcrete blocks were also proved beneficial in the condensation analyses, where even hempcrete walls with lower thermal resistance still reached the same performances as the better thermally designed SL walls. Hempcrete design of the residence exhibited slightly lower energy performances, which can be attributed to the lower volumetric heat capacity of the material.

The climate emergency calls for a global shift towards a low-carbon economy, to preserve natural resources and biodiversity, while limiting global warming and its consequences. This project focuses on the impact of distribution centres, intended for the storage of commercial goods. Warehouses are characterised by large flexible spaces and simple structural systems, most often with steel or concrete frames aiming at efficiency and low costs. The aim of this research is to create a sustainable single-storey warehouse with a significantly lower environmental impact compared to reference designs with steel and concrete frames. Considering a new-build project with no reuse of existing elements, a meaningful target for embodied carbon reduction is set to 50% of the environmental impact score of reference steel and concrete warehouse designs.
A selection of sustainable design strategies are investigated, giving insight into which actions designers shall take in priority to effectively reduce the embodied carbon of a warehouse. Reducing upfront emissions (LCA modules A1-A3) requires looking into short-term sustainability measures like reducing material use or using low carbon alternatives wherever possible. Replacing fossil-based products by renewable carbon sequestering materials like timber or other biobased alternatives contributes to lowering the impact of a building, by storing biogenic carbon for the lifespan of these elements. A sustainable use of wood presumes that its design lifespan is at least equal to forest rotation periods to maintain or increase the forest timber stock, combined with sustainable forest management practices. Biogenic carbon storage may be extended by designing for long-term reuse or recycling. Greening the envelope of a building takes advantage of ecosystem services provided by vegetation, like improving air quality, enhancing thermal performance or supporting biodiversity. Many systems can be applied on facades and roofs, depending on project-specific requirements (plant species, layout, load-bearing capacity), to effectively introduce vegetation in the built environment.
The first design step investigates the embodied carbon reduction potential of substituting steel or concrete by timber in the load-bearing frame of a warehouse. Reference steel and concrete structures are selected, and baseline timber designs are created with similar geometrical characteristics and stability systems, to compare their environmental impact on a fair basis. The second design step of the research aims at further reducing the impact of not only the frame, but also other parts of the timber warehouse (foundation pads, floor slab, envelope). Big ticket items responsible for the most impact are identified and tackled in priority: in both timber designs, the floor slab and envelope are responsible for the largest share of embodied carbon. Based on the results of design steps 1 and 2, the 50% embodied carbon reduction target can be achieved by substituting steel or concrete in the frame by timber (-31%), replacing sandwich panels on steel supports by biobased materials in the envelope (-13%), and reducing the floor slab thickness by 50mm (-7%), when considering only fossil emissions. If biogenic carbon storage is accounted for, using biobased materials in the frame (-65%) and in the envelope (-58%), without modifying the floor slab, results in a carbon positive warehouse design. These results are only valid assuming long-term carbon storage in biobased materials, supported by circular design measures. Greening the envelope also contributes to making warehouses more sustainable, provided that benefits from ecosystem services outweigh environmental costs from additional materials.

Due to global warming, in the construction sector there is aimed for a transition towards the circular economy. The past years, many utility buildings were demolished, consisting of a concrete structure. This results in concrete rubble which is often down- or recycled. For new construction projects, new concrete elements will be produced. However, instead of producing new concrete structural elements, potentially concrete structural elements can be reused. Therefore, this research focuses on the reuse potential of in-situ concrete elements whose can be dismantled from demolition projects of utility buildings. In order to stimulate structural engineers to reuse concrete structural elements in practice, this research presents the Reusability Tool. This tool assesses the reuse potential of in-situ concrete structural elements based on structural safety, environmental impact, and economic impact.

Based on an extensive desk research, interviews with experts from the field, and a case study, the processes of three circular strategies are analysed: reusing, upcycling, and downcycling. These processes are made operational in the Reusability Tool. Based on input information about the analysed structural element, the Reusability Tool assesses the element on structural safety, environmental impact, and economic impact. This assessment result in an advised circular strategy for the element: reuse, upcycling, or downcycling.

The Reusability Tool is validated by a case study and feedback sessions with structural engineers. The Reusability Tool is a user friendly tool which can be used to assess the reuse potential of in-situ concrete structural elements from utility buildings, and will prevent valuable elements to get lost. The tool can give insight in the reuse potential in an early design stage of a future project, and can form the basis for further investigations.

The impacts that the construction industry has on the environment has become an element of concern worldwide. The EPA (Environmental Protection Agency) claims that building activity has the potential to dramatically alter land’s surface (Sikra, 2017). This is mostly because many construction projects include destroying vegetation and digging, which extensively pollutes the area’s surroundings. Additionally, due to their high embodied energy contents, construction materials like concrete, aluminum, and steel are directly to blame for significant amounts of CO2 emissions. Uncomfortably, building activities account for one-sixth of world freshwater consumption, one-quarter of global wood consumption, and one-quarter of global waste. They also consume half of all natural resources that are taken from the environment. 40% of drinking water contamination, 50% of landfill waste, 23% of air pollution, and 50% of climate change are all caused by the building industry (Sikra, 2017). And these are just some of the aspects in which the construction industry is involved, but it is enough to realise that solutions are needed to heal planet Earth and in fact contribute positively to it.

One approach to this problem is to leave room for nature to manifest and express itself and then to be inspired by it. Natural creatures are an example of living and thriving on Earth by striking a balance between themselves and the surroundings. They are constantly integrating and optimizing themselves in order to produce life-friendly settings (Oguntona and Aigbavboa, 2017). The lessons that can be learned from nature are summarised in Bio-mimicry Life’s Principles. One of them suggests how natural organisms evolved with the logic of optimising rather than maximising by developing a multi-function design (De Pauw et al., 2010a).

This report deals with two key principles: sustainability and multi-functionality. The aim is to develop a methodology that allows, in an objective manner, the identification of the best tailored building strategy in terms of maximisation of the level of sustainability achievable with one single solution.

The project follows 6 steps: research, development, investigation and improvement, validation and testing. The methodology is designed within Microsoft Excel and integrates the sustainability criteria of LEED green building rating system, a program for assessing the green level of buildings that is already widely used internationally. The LEED program appears in all project phases but particularly in the research, development and validation phase. The latter is conducted by the method of comparing data obtained from the tool in Excel with verified data from LEED-certified projects. After the development phase, it emerges that the tool while based on a well-structured, widely used and tested program such as LEED, is prone to subjectivity. Much of the time is therefore devoted to making sure that the tool is project-dependent and not user-dependent. As for the investigation and improvement phases, these are carried out by means of a survey built in Google Forms. Finally, the process of testing the tool is performed by applying it to a real case which is offered by the engineering and architecture company OneWorks. It is the General Aviation terminal at Orio al Serio airport (Bergamo, Italy).

To conclude, time is a crucial aspect when it comes to reducing the impact on the environment. So, this thesis aspires to provide a new methodology that can help designers, engineers and architects to shorten the time it takes to choose the best tailored strategy in terms of sustainability and multi-functionality.

The Paris agreement’s mechanisms for 2050 represent a challenge for the world to achieve Net-zero emission and climate resilience. Retrofitting the existing stock is a critical step in every nation to achieve these goals. The building sector has a significant role in the Net-zero emission transition. The ambitions for retrofitting the Netherlands´ by 2030 and 2050 bring the need to explore new products taking sustainability and circular economy as the basis of design. This research explores the application of a “cradle to cradle” design approach to redesign a sandwich panel currently used as a renovation strategy to wrap existing dwellings in The Netherlands. The research in performed from the perspective of a façade company in the national market.

The current product manufactured by the company is not studied with the end of its service life in mind and is designed mainly with fossil fuels related products. Also, the time component is detached from the product, and scenarios where the materials are “processed and disposed” or “mined and reused” are not considered. The research explores three different façade concepts that contrast with a traditional linear production based mainly on fossil fuels. The analysis brings a set of 24 options, each with three circularity scenarios. The conclusions reveal that the environmental impacts and success of a “cradle to cradle” design strategy has a close relationship with the number of years the existing dwellings will be used. By reusing the existing dwellings for prolonged times (50 and 100 years), the best option for the company is to develop a biobased sandwich panel relying on renewables and materials with low environmental impacts but as an efficient “cradle to grave” strategy. However, for a shorter span of usage in the existing stock (25 years), the best option is a “cradle to cradle” strategy where the resources are taken back to the technical cycle combined with reduced usage of materials for the cladding system.

Some of the technical recommendations suggested are to test the biobased panel for a mechanical test. Afterward, develop the construction details for connections in foundation, windows, and doors to finally build a 1:1 mock-up to be tested for meteorological degradations and durability. Also, further analysis is needed for a financial case for the scenarios where materials are used after a first cycle. Finally, further research is needed to develop fully biobased matrixes to biocomposite fully biodegradable, allowing them to get back into a biological cycle.

As cities are getting denser and larger, space for conventional green features is diminishing. Cities without green alienate people from nature, deteriorate ecological systems and directly harm personal well-being. Limited open areas and many sealed surfaces in today’s cities raise the need for a renewed green space approach that fits in an increasingly dense and compact urban landscape; an approach in which green space is not limited to large open spaces at ground level, but one where greenery is truly integrated with built structures. The concept of compact urban green space (CUGS) is introduced in this study to refer to green space compatible with this approach. Too often, current CUGS on buildings and in small spaces solely serves aesthetic purposes and is treated as mere (architectural) decoration. This attitude results in pragmatic but disconnected interventions with little added value to ecology and well-being.
This study puts forward that urban planners and landscape architects should embrace these new and unconventional green spaces, because, when planned and designed from a larger social-ecological perspective, compact urban green space can functionally solve several urban challenges simultaneously while also improving ecological quality and human well-being. This graduation project explores the qualitative aspects of small green spaces that result in major improvements in ecological resilience and personal well-being. It is concluded that CUGS can provide quality for people and nature. E.g. by encouraging stewardship of local communities and allocating space for natural processes.
A pattern language approach is used to better understand the relations between a variety of CUGS patterns across different scales. Novel CUGS patterns, such as rooftop landscapes, bioreceptive building envelopes and topographic building blocks are tested in the spatial and ecological context of Rotterdam. The resulting spatial framework for the city centre guides the development of future CUGS. A design experiment performed in the neighbourhood of the Wijnhaven Eiland shows that multidimensional green structures and networks can improve well-being and ecological resilience in Rotterdam when they add value at different scale levels and are fundamentally integrated into the design of the city.

Noise pollution is a growing health concern in cities, especially in busy streets with parallel reflective facades, known as urban street canyons. Here, high flows of vehicular traffic generate a broadband noise, with high noise levels in the low-frequency (LF) spectrum. In the canyons, noise decays slowly due to multiple reflections. To counter this, vertical greening systems (VGS) can be applied as multi-disciplinary solutions. Not only can these systems attenuate noise, they can also e.g. decrease the urban heat island effect and increase biodiversity. Yet, the shortcoming of VGSs is the lack of LF-absorption. Hence, the following research question was asked: “How can the acoustic absorption of vertical greening systems in urban street canyons be improved, especially for low-frequency noise?” Four concept designs were developed consecutively, and evaluated on the basis of design criteria. These criteria included specifications on acoustic absorption, manufacturability, and durability. The final design consisted of a living wall system (LWS) based on hydroponic rock wool, with a parallel array of Helmholtz resonators integrated in its structure. This array was added to increase the LF-absorption of the VGS below 250 Hz. The Helmholtz cavity volumes were not physically subdivided, but rather filled with a locally reactive material with a low flow resistivity, to enforce propagation that is normal to the surface. Additionally, plants can also absorb sound in the visco-thermal boundary layer around their organs, depending on the leaf area density. It was found that sciophytes (shade-loving plants) had most acoustic potential due to their large leave surfaces. Analytical, experimental, and numerical validation was performed. A Matlab script was developed that applied Delany-Bazley-Miki equations in an equivalent fluid model, and a transfer-function approach for the multi-layer complex impedance. The design yields near-unity absorption for f>500 Hz. The resonators extended the LF-absorption (a>0.5) down to 80 Hz. Impedance tube and reverberation room measurements demonstrated that piercing the porous substrate layer with the Helmholtz resonator necks can yield a combined acoustic absorption. Finally, acoustic simulations showed that applying the proposed LWS to the facades in a reference urban street canyon in Rotterdam can substantially decrease sound levels, both inside the street canyon, as well as in the adjacent courtyard canyon. However, the window-to-wall ratio of the facade largely determines to what extent sound levels can be decreased, since vertical greenery cannot be applied in front of windows.

Bioreceptivity in building envelopes is a new type of facade greening system which thrives to improve the urban climate. In this type of facade greening the building envelope acts as a mediating layer between indoor and external conditions. This research focuses on the impact of the implementation of bioreceptive facade panels in the urban climate of The Netherlands; this includes designing in the urban climate and measuring what benefits these plants can bring, and how they can contribute to their own existence in their habitat.

The built environment is and will be the place in which most of the people live and its expansion is unavoidable due to urbanization. However, such a phenomenon will increase further the already high material consumption in the building industry, as well as the waste generation. A development that rises many concerns in modern society and, thus, various solutions are investigated. One of the suggested solutions is the "living in a bottle" project from Ir. P. de Ruiter. The aim of this project is the use of computational design and additive manufacturing to produce mono-material building structures out of one recyclable material. PET GROWN is part of the above-mentioned project and investigates whether a self-sustaining, mono-material and multi-functional green roof system, 3d-printed out of rPET, is possible. The selection of a green roof module as a case study, is based on the green roof feature to reduce heat flow and UV radiation reaching the structure, two parameters in which PET is sensitive. With regards to the module, the study focuses on the replacements of the multiple material layers in a green roof, with one single material by using additive manufacturing. During research, design variants are developed, by using computational tools, and evaluated according to requirements related to functionality and 3d-printabiltiy. Then, the most suitable variants are selected and developed further to form the final project. The study highlights the influence of additive manufacturing in all its design steps, as well as, its advantages and limitations. In the end, the final outcome this study is a mono-material green roof design that fulfills most of the functional requirements of an extensive green roof.

Bio-receptivity is a natural growth of small plant species on stony surfaces with minimum external influence. It is commonly found around us on old buildings, crevices and corners, damp and moist areas. Bio-receptivity has always been viewed as a negative phenomenon in the public eye due to its random and shabby growth conditions. However, this phenomenon co-exists on building surfaces establishing a hybrid relationship, which poses several advantages on the building life-cycle. Apart from being a protective coating, its environmental benefits, like CO2 reduction in air, air purification through dust removal and cooling effect through evapotranspiration, has been known and researched through decades, but has not been brought into practice in the building industry. This research chooses to use geometry as a design variable to engineer self-sustaining moss growth on concrete panels in an ordered and systematic manner. The exercise is an attempt to not only address the functional aspect of Bio-receptivity but also its aesthetic quality which is vital to influence the perception of people and promote mass use of this new type of sustainable concrete material. The primary intend of the research is to gain a thorough understanding into the concept of Bio-receptivity and identify the governing factors responsible for the relationship between the small plant species and stony materials. Saxicolous moss like Tortula muralis and Grimmia Pulvinata are found to be the most common moss types growing on limestone base stony materials and is further utilized in the practical experiment. The research is conducted in a top-down approach, where first the designs are developed in an ordered system taking into consideration the growth structure of moss in nature and the influencing environmental characteristics, next the designs are fabricated into prototypes exhibiting the appropriate material properties and then validated through series of practical experimentation and CFD simulations to justify the influence of geometry; based on the comparative analysis of the results a general design guideline is provided for a self-sustaining Bio-receptive concrete facade panel. A real-time visual representation of Bio-receptive panel is presented as per the guidelines and an economically viable and technically feasible facade system is proposed to facilitate its commercial use on buildings/facades.

The construction, operation and maintenance of buildings consume more than 40% of primary energy in most countries. Out of this 40%, a large portion is related to the operational phase involving heat losses through a buildings envelope. To reduce this loss, several materials have been developed to reduce the thermal transmittance through a façade, even though they carry a heavy environmental burden. Furthermore, the unregulated and rapid expansion of urban environments led to a considerable amount of problems. Among them, the urban heat island effect demands special attention as it has been responsible for an increase of the energy consumption to higher mortality rates. In part, the use of materials with high thermal admittance is responsible for these effects. Vertical green systems have shown to be a potential solution to improve, among others, the thermal demands of buildings and to mitigate the urban heat island effect. However, due to the uncertainty associated with their design process and operation, the implementation of vegetation as a construction material in an urban setting is often overlooked. Therefore, an in-depth study of their performance under different configurations and climate conditions is needed.

The optimization study was based on the parametrization of a green façade and a living wall system which aimed to identify their response under variable initial conditions. A analysis of the essential parameters in the vegetation model was performed. Consequently, the leaf area index showed the highest effect, followed by the substrate thickness, leaf angle distribution, leaf surface albedo and finally by the moisture content of the substrate layer. Furthermore, a state-of-the-art computational work flow was developed through the integration of ENVI_met, Rhino/Grasshopper and modeFRONTIER, in combination with Python 3 scripting, to evaluate the performance of vertical greenery systems. The evaluation focused on the heat transmission through the façade of a single building, in comparison to a reference model. The work flow allowed the study of the impact of each parameter in the behavior of the system and led to the development of several design guidelines. The optimized result was tested in an urban setting to evaluate its potential as a mitigation strategy for the urban heat island effect.

The largest reduction in thermal transmission took place in equatorial, fully humid climate due to the low vapor pressure deficit; while the lowest in a temperate climate during winter conditions, suggesting the lower efficiency of the systems under cold weather. Furthermore, living wall systems have a significantly higher performance in comparison to green façades. On the other hand, the latent heat release associated with the evapotranspiration process has a strong correlation with the leaf area index, given the simultaneous action of the aerodynamic and bulk surface resistance. The optimized configuration of the vegetation was then derived based partly on this correlation. Moreover, the leaf angle distribution displayed a high correlation with the solar zenith angle and the leaf surface albedo with the intensity of the solar radiation and the ambient temperature. Additionally, among the substrate properties, the substrate thickness indicated a large potential in reducing heat transmission.

The effects of vertical green systems in an urban setting suggested an improvement of the environmental conditions. While the leaf area index is directly related to the decrease of wind speed and evaporative cooling, the leaf surface albedo influenced the amount of reflected shortwave radiation in a façade. Furthermore, the highest cooling potential was observed in desert climates as a result of the high vapor pressure deficit with temperature drops of up to 0.25 C.

The outcome of this research indicates that an optimized vertical greenery system is a suitable replacement for artificial insulating materials as a passive alternative to reduce energy demands in buildings. Indicating a decrease in heat transmission from 8% to 50% of the original heat flux. Furthermore, the findings of the urban study suggests that a decrease in the ambient temperature and an overall reduction of the negative impacts related to the urban heat island effect is possible.