Journal of Sustainable Architecture and Civil Engineering

Guest Editor Preface

Targo Kalamees — Mon, 19 Feb 2024 00:00:00 +0200

It is a great pleasure that I preface this special issue of the Journal of Sustainable Architecture

and Civil Engineering, which comprises invited papers submitted to the 5th Forum Wood Building

Baltic, organized between 27 – 28 February 2024 in Tallinn, Estonia.

The Forum Wood Building Baltic 2024 conference was a fantastic opportunity for scientists and

practitioners to meet and exchange experiences and to learn from the best within the field. The

conference was organized by Tallinn University of Technology, the Estonian Academy of Arts and

Forum Holzbau in collaboration with Estonian Association of Civil Engineers and Estonian Woodhouse Association.

Revitalizing Modernist Districts: Neighbourhood Level Mass-Renovation with SOFTacademy Project

Murel Truu, Lauri Lihtmaa, Mariliis Niinemägi — Mon, 19 Feb 2024 00:00:00 +0200

This article discusses the neighbourhood-level renovation potential in Tallinn's modernist privately owned apartment blocks, with the aim of addressing the global need for deep renovation. The analysis considers international directives, national policies and municipal objectives, highlighting the focus of current renovation initiatives on apartment buildings. The discourse drives the ongoing conflict between energy-focused renovation and the preservation of spatial quality, relevant especially for the countries that favour partial renovation over the complete transformation of a building. It analyses the emerging impact of the New European Bauhaus (NEB) initiative, emphasizing the need to balance technical energy investments with cultural and aesthetic considerations in wider neighbourhoods.

Shifting the focus to Tallinn, the article deals with the challenges of modernist mass production housing districts, recognizing their technical structure, current decay and socio-economic limitations. The European Renovation Wave strategy and upcoming energy efficiency requirements are seen as catalysts for neighbourhood revitalization, prompting the exploration of innovative models to transform these neighbourhoods into liveable and functional spaces. The discussion unfolds within the NEB compass, emphasizing the core values of beauty, sustainability, and cohesion.

Practical considerations for the transformation of Tallinn districts are discussed, including spatial regulations, the complexity of ownership and the different perspectives of apartment owners. As a solution, the SOFTacademy approach is introduced, proposing a collaborative model establishing both the hardware and software elements for NEB driven renovation of neighbourhoods. In terms of hardware solution, prefabrication and modularity is used both for renovating the buildings as well as reinventing the courtyards around them. While the physical rejuvenation of the neighbourhoods is the key to NEB transformation, the shift depends as much from the software solutions.

The results outline a process for initiating neighbourhood-level renovations, emphasizing the importance of consulting with owners, creating blueprints, and entering into cooperative agreements.

Circular Renovation of an Apartment Building with Prefabricated Additional Insulation Elements to Nearly Zero Energy Building

Eero Nigumann, Targo Kalamees, Kalle Kuusk, Peep Pihelo — Mon, 19 Feb 2024 00:00:00 +0200

Construction and demolition waste constitute more than one-third of the total waste generated in the European Union. The pursuit of sustainable renovation must progress further to encompass elements that ensure reuse or recyclability. A fundamental transformation, involving extensive renovation and a transition to circular renovation practices, is indispensable in effectively addressing the pressing challenge of decarbonization for the entire building stock in Europe. In this study, we have developed a circular deep renovation solution using prefabricated modular external additional insulation elements to achieve a nearly Zero Energy Building (nZEB). Circular prefabricated modular external additional insulation elements were formulated, manufactured, and installed. The potential for disassembly and reutilization of materials was developed and demonstrated for both a prototype and the complete deep renovation. The analysed prefabricated modular solutions exhibited greater potential for circularity compared to the traditional External Thermal Insulation Composite System (ETICS) due to their superior demountability and reusability characteristics. The overall cost of the renovation, which included the installation of a new heating system, replacement of water and sewer pipes, addition of 50 kW photovoltaic (PV) panels on the roof, installation of new balconies, addition of a balanced ventilation system with heat recovery, and replacement of the electricity system in common areas, amounted to 505 €/m². Following the deep renovation, the Energy Performance Value was measured to be 92 kWh/(m²·a), resulting in an EPC class of A. This implies that the building now meets the requirements for nZEB in accordance with Estonian legislation, with no performance gap.

Technical State, Renovation Need and Performance of Renovation Solutions of Estonian Wooden Log Houses

Alois Andreas Põdra, Gert Air Allas, Aime Ruus, Elo Lutsepp, Targo Kalamees — Mon, 19 Feb 2024 00:00:00 +0200

The wooden log house serves as a prevalent architectural archetype in rural regions of several Nordic and Baltic countries. To ensure the long-lasting nature of these buildings, proper maintenance is imperative. However, in order to meet the evolving expectations of residents and minimize the environmental impact, a deep renovation is currently required. To successfully achieve the goals of this renovation wave and effectively address the personal needs of the homeowners, it is crucial to develop systemic renovation solutions that can be offered through a digital renovation passport. Consequently, the purpose of this study is to identify common damages, renovation requirements, and evaluate current renovation practices. The findings will serve as a crucial resource for the development of a digital renovation passport. In our study, we utilize rural wooden log houses (comprising 208 houses, 4 years of data) as our research subject. The building elements that are most in need of renovation are the external walls, roofs, and foundations, which require renovation in 77%, 63%, and 63% of the buildings, respectively. The primary cause of damage to the vulnerable structures is excessive moisture. Additionally, decay in the foundation can be attributed to factors such as erosion of mortar, frost, insufficient plinth height, inadequate foundation depth, and inadequate moisture protection. Recommendations provided by consultants primarily focus on restoring and preserving the dwellings' original architectural appearance. As a result, they are deemed insufficient in terms of improving energy performance and indoor climate. This lack of comprehensive consultation is concerning as it fails to consider the potential for cost efficiency, minimizing disruption to occupants, and achieving a comprehensive end result. The absence of recommendations for enhancing indoor climate, energy efficiency, general living quality, and reducing the building's carbon footprint performance the necessity for such renovation solutions and the importance of educating professionals and homeowners. The study's novelty lies in the establishment of statistical probabilities for damages and their causes, as well as the assessment of renovation and maintenance needs and the quality of existing recommendations. Results are scaled to the Estonian building stock, showing the renovation need on national scale. The findings can be incorporated into the digital renovation passport, along with specific renovation goals related to a given house.

Bioinspired Living Coating System for Regenerative and Circular Architecture

Anna Sandak, Karen Butina Ogorelec, Ana Gubenšek, Faksawat Poohphajai — Mon, 19 Feb 2024 00:00:00 +0200

Surfaces of exposed materials are affected by biotic and abiotic degradation processes. They often are protected by architectural coatings that not only provide a decorative layer but also enhance integrity of the material structure. Common surface treatments often include mineral oil binders and other ingredients that are known to have a negative impact on the environment. To address these issues, an alternative bioinspired concept for materials protection based on engineered fungal biofilm is under development. This paper presents the first results related to the bioreceptivity of building materials and the initial steps of natural biofilm formation.

This research concluded that fungal colonisation and the variability of microorganisms is influenced by the type of material and climate condition at the exposure site. Fungal infestation was lower on protected materials (e.g., with commercial coatings). Samples from the eastern and western exposure exhibited the highest fungal colonisation, whereas samples from the northern and southern exposure exhibited the least growth. Furthermore, the samples in close spatial proximity were colonized by different fungal microbiota. It was determined that Aureobasidium sp. is the dominant species in the early phase of colonisation.

In the following steps, a bioactive protective coating system that works in synergy with nature will be developed. Based on the initial results Aureobasidium appears to be a viable candidate as an active, living component of a new nature-inspired coating system. The novel protection concept is based on three interrelated components – bioinspiration as a driving force for materials design, bio-based ingredients, and living fungal cells that will provide self-healing and bioremediation capacity. The living coating will be designed to protect various architectonic materials, including porous materials such as biomaterials, concrete, stone, and non-porous, as well as plastics, and metals. The ultimate goal is to advance the development of engineered living materials that interact, adapt, and respond to environmental changes.

Assessment on Strength and Stiffness Properties of Aged Structural Timber

Maarja Kauniste, Alar Just, Eero Tuhkanen, Targo Kalamees — Mon, 19 Feb 2024 00:00:00 +0200

Despite the growing popularity of wood and wood-based products in the construction industry, there has been insufficient focus on assessing the condition, preservation, and potential reuse of existing timber. While numerous standards evaluate the quality of freshly sawn timber, there is currently no standardized system for assessing the strength properties of aged and reused timber. The lack of these guidelines is also one of the reasons the results obtained in numerous research are often fluctuating, and we cannot draw clear conclusions. The matter is further complicated by the lack of data on old in-situ wood and its exploitation, which would help to evaluate its condition. Consequently, there is a real practical need to assess the condition of old timber to avoid unnecessary demolition and the loss of valuable and structurally sound building material.

What sets this study apart from others is that, in addition to destructive testing, the 4-point non-destructive (ND) bending tests were conducted on all four faces of test specimens. This provided an opportunity to assess the wood visually and then find connections to associate external characteristics with real properties. This methodology aimed to determine whether it is feasible to visually assess the most practical way to use wooden elements in construction. If this question arises, which face of the beam would be better suited for the tension side and which for the compression side? The old timber used in testing originated from an old library building located on Vaksali Street, Tartu, Estonia and is estimated to be about 120 years old.

This paper investigates and compares the collected data with a Nordic standard for grading fresh-sawn timber and two established Italian standards for visually assessing aged timber. This comparison contributes to developing a standardized framework for future visual assessments. ND and destructive four-point bending tests were performed to validate and find appropriate visual characteristics to determine the strength and stiffness of the timber elements. The primary goals of this study were first to compare the results obtained from existing ND methods with actual results and secondly to provide guidelines for better visual grading of wood in the future, based on Nordic Standard INSTA 142 (2010) and Italian standards UNI 11119 (2004) and UNI 11035 (2010)

Contrary to previous research conclusions, the visual assessment results yielded unexpected outcomes. The results show that the grading standards significantly underestimated the real strength of the wood, and even more, none of the visual assessments overestimated the real strength of the specimens. Therefore, based on prior research and the findings derived from this study, there is evident a substantial potential for extensive development and optimization within this field.

Bending and Vibration Behaviour of CLT-Steel Composite Beams

Noah Böhm, Achim Vogelsberg, Bertram Kühn — Mon, 19 Feb 2024 00:00:00 +0200

A strengthening of cross-laminated timber (CLT) by a composite effect with steel girders can widen the application of CLT ceilings to spans over 8 m. Most possible shear connectors are not stiff enough to ensure a completely rigid composite. At present, it has not been sufficiently clarified how the elastic bending behaviour is affected by the influences of the flexibility of continuously and discontinuously shear connectors, the number of transverse layers of the CLT and the span width. Thus, 4-point bending tests and vibration tests were performed with different cross-section configurations and two different shear connectors in continuous and discontinuous spacing in spans of 8.10 and 10.80 m. To date, no comparable bending tests have been carried out in these spans, with more than five CLT-layers and discontinuously arranged shear connectors.

The composite beams deformed linear-elastically until the yield strength of the steel was reached. The composite effect increased the elastic bending stiffness up to twofold compared to no composite. Increasing the span resulted in a higher bending stiffnesses. The elastic bending stiffness of the composite beams with shear studs was significantly lower than with fully threaded screws.

For a worthwhile composite effect, both materials should contribute a balanced share of the stiffness. A larger share of the CLT in the bending stiffness compared to the steel girder created a higher elastic limit load capacity but an equivalent bending stiffness. It is necessary to discuss which cross-sectional configurations are appropriate in terms of load bearing capacity, economic efficiency and sustainability.

To assess the practical application potential in spans between 8 and 12 m, the tests were additionally evaluated for the equivalent load level for the serviceability limit state of office or industrial buildings. For spans of 8.10 m, the limits according to EC5 for the initial deflection of L/300 and fundamental frequency of 8 Hz can be met. For spans of 10.80 m, only less strict deflection limits are achieved. However, by increasing the degree of composite through more shear connectors, compliance with the limit values mentioned could already be possible with the cross-sections tested.

In case of fire, it may be sufficient to consider only the CLT with the reduced cross-section method (EN 1995-1-2) for load transfer, even for longer fire durations.

Prefab Light Clay-Timber Elements for Net Zero Whole-Life Carbon Buildings

Mon, 19 Feb 2024 00:00:00 +0200

"Net zero whole life carbon" is an ambitious climate target that refers to neutralizing and offsetting the entire LCA-based carbon footprint of a building, including both operational and embodied greenhouse gas emissions. Especially in the Northern climate, viable building envelope structures must, therefore, provide good thermal insulation and low embodied emissions. Carbon offset is typically based on excess on-site renewable energy or purchased carbon offsets disconnected from the building and the site. Viable strategies for carbon neutrality start by minimizing material-related and energy-related CO₂e emissions. As a result, new kinds of building envelope structures have been recently introduced in the academic literature and experimental building projects.

Traditional construction materials, such as timber and clay, have been sourced locally and processed manually, providing good results for the embodied emissions in life cycle assessment. Recent studies on clay-based construction materials have concluded that more research on clay as a construction material is needed, in particular considering its environmental performance.

One specific concern in the Northern climate is that the weather conditions limit clay construction outdoors and prevent industrial-scale application of these solutions. The methods of prefabrication can address these issues.

This study introduces the critical technical and environmental properties of a new prefabricated wall element based on a combination of light timber frame and light clay. In a hybrid light clay-timber structure, a mixture of clay and hemp shives is cast between the timber studs. On the one hand, the novelty of this wall structure is the prefabrication that enables industrial applications and upscaling without the limitations of weather conditions. On the other hand, the study assesses the climate impact of a light clay-timber wall element : cradle-to-gate emissions, thermal insulation, and the climate benefits outside the system boundary (carbon handprint) reported in the D-module of the LCA framework.

The study also shows that natural materials require a different approach than synthetic materials from industrial processes. There may be variations in the properties of hemp and clay, especially when local sourcing is prioritized for better environmental performance. Moreover, the mixing and installation processes have a significant impact on the final properties and the performance. We show that constructing a light clay wall is a knowledge-intensive process that may result in very different technical properties.

A Numerical Study of Methods to Improve Moisture Safety of Ventilated Wooden Roofs

Klaus Viljanen, Laurina Felius — Mon, 19 Feb 2024 00:00:00 +0200

The hygrothermal performance of highly insulated, prefabricated wooden roof structures is likely to deteriorate due to the low heat flux to the ventilation cavity. This article evaluates the possibility to improve the moisture safety of such roofs in a Nordic climate by using different control methods for the ventilation rate of the roof and by using thermal insulation above the roof sheathing. The results support the use of adaptive roof ventilation as it decreases the probability of mould growth in the roof. The use of thermal insulation above roof sheathing decreases the probability of mould growth only slightly in a roof with elevated amount of built-in moisture.

On-Site Application of End-Grain Bonded Timber Under Low Curing Temperatures

Dio Lins, Steffen Franke — Mon, 19 Feb 2024 00:00:00 +0200

The end-grain bonding of timber components using the Timber Structures 3.0 technology (TS3) is an advancing construction method in timber engineering. This technology allows the realisation of any plate size by bonding plates on-site where low temperatures influence the performance. Therefore, investigations are underway to evaluate the influence of the low temperatures on the curing process. Additionally, research is in progress to discover techniques to reduce any adverse effects of low curing temperatures on the mechanical properties of the bond. The implementation of particular measures, such as the inclusion of milled heating wires into the joint and the pre-heating of the joint with a hot air blower, has been identified as advancing the potential for grouting even in the face of low external temperatures, as recent research has indicated.