Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2026
Authors
Geir Wæhler Gustavsen Philip Bester Van Niekerk Jonas Niklewski Christian Brischke Gry AlfredsenAbstract
This cross-country study examineed perceptions of maintenance for coated wooden cladding in residential buildings across Norway, Sweden, and Germany. As timber cladding gains popularity in European homes, understanding expectations around cleaning, recoating, and replacement intervals becomes increasingly important. An online survey gathered responses from over 3,000 participants aged 18–89, randomly selected from representative regional panels in each country. The survey focused on the perception of maintenance practices and intervals, while also collecting data on personality traits, risk aversion, and socioeconomic background. Perceived maintenance practices for coated timber cladding differed across countries, but individual characteristics were generally more influential than national context. Most respondents accepted longer cleaning intervals than recommended, while their preferences more closely aligned with guidelines for recoating. Acceptance of replacement intervals varied markedly by country. Longer acceptable maintenance intervals were associated with a higher preference for uncoated cladding, particularly in Germany and Sweden. Younger age, urban residence, limited experience, and selected demographic and personality traits were linked to more intensive maintenance preferences.
Abstract
Abstract This study assesses the economic feasibility and environmental profile of producing Irvingia-based wood adhesives on a small scale (30 ton/year) in South Africa. A detailed techno-economic analysis was conducted including operating cost estimation and sensitivity analysis of key input variables. The estimated production costs for three adhesive formulations ranged from R157.1/kg – R318.14/kg. The average production cost was R214.62/kg and was below the typical market price of R379/kg for synthetic wood adhesives. Raw materials especially kernels and modifiers were identified as the dominant cost drivers, whereas labour and electricity had minimal impact on unit cost. A carbon footprint assessment (CFA) was performed with cradle-to-gate boundaries to estimate greenhouse gas (GHG) emissions. Two raw material sourcing scenarios were considered. They included adhesive production from kernels and adhesive production directly from whole fruits (including on-site fruit dehulling). The cradle-to-gate CFA indicates that both scenarios have similar GHG emission profiles given equivalent process conditions, with most emissions arising from energy use and chemical additives rather than feedstock transport. A review of mechanical performance from prior studies showed that these bio-based adhesives met industry standard requirements. The results demonstrate that small-scale production of Irvingia adhesives is economically viable and environmentally sustainable, making it a promising alternative to synthetic adhesives for wood composite manufacturing in South Africa.
Abstract
This study (1) determined the differences between the dynamic vapor sorption (DVS) behavior of wood subjected to light (H2O) and heavy water (D2O) vapors at matching equivalent relative humidities (RHs) and (2) developed an in-situ method for studying the transmission-mode Fourier-transform infrared (FTIR) spectra of wood subjected to increasing RHs. The D2O-subjected wood was pre-deuterated so that the hydrogen bonding of the native wood with H2O was compared with the deuterium bonding that occurs with D2O for the DVS and FTIR studies. Fibrous Scots pine sapwood particles were used for the DVS experiments, whereas FTIR spectroscopy involved Scots pine sapwood earlywood microscopic sections placed inside a small RH chamber. The sorption isotherms and hysteresis plots of H2O and D2O showed statistically non-significant differences between the solvent vapors. However, larger practical differences were observed at higher RHs, with the H2O sorption isotherms having higher “equilibrium” moisture contents. The Gibbs free energies of sorption and desorption at equilibrium, as determined from the DVS data, showed statistically significant differences, suggesting that deuterium bonding is more thermodynamically favorable. The sorption and desorption rates obtained from the DVS samples generally indicate that H2O vapor subjection progresses initially at faster rates per RH level, without significantly affecting the total experimental time. The accessibility of the hydroxy groups increased somewhat with D2O between the before- and after-isotherm scenarios. In the FTIR spectra, H2O addition led to higher peak intensities and broader hydroxy band widths due to increased RH. The FTIR spectra for the D2O case had a decrease in the hydroxy band area, particularly in the width parameter, while the intensity and width of the formed deuteroxy peak grew as RH increased. The FTIR spectra also provided evidence of a successful hydrogen-versus-deuterium bonding comparison for the DVS study, as the intensities and band widths reverted to their original states after drying using a water-vapor-subjection method like that used in the DVS. Finally, it is hypothesized that deuterated wood is less hygroscopic than native wood, despite the thermodynamic favorability of deuterium bonding.
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Authors
Shumaila Khatri Hanne Kathrine Sjølie Kristina Bringedal Gedde Lizhen Huang Per Kr. Rørstad Roja Modaresi Lone RossAbstract
This report summarizes the main findings of the research conducted within the CircWOOD project during the period 2022-2026 and presents key recommendations for decision-makers towards wood reuse in the construction sector. CircWOOD aimed to enable and support a transition to a sustainable, competitive, and technologically optimized circular wood value chain through a transdisciplinary research approach. The project was carried out by five research institutions and universities, exploring technical, environmental, economic, and social dimensions in the value chain. Our research findings demonstrate potentials for wood reuse, while also highlighting a variety of practical and market-related challenges. The report presents eight key recommendations for policymakers, industry stakeholders, and other decisionmakers to drive wood reuse. Improving sorting systems and quality control for wood waste from construction and demolition activities and prioritizing deconstruction over demolition can enable reuse. Developing supporting infrastructure such as material banks, reuse centers, and logistics systems is also important. Wood reuse can create new opportunities for businesses, while continued research, better data, and AI can strengthen decision-making and support a more resource-efficient built environment.
Abstract
This study investigates the moisture-induced recovery of temporary property changes in thermo-mechanically densified (TMD) birch and aspen wood, compared to thermally modified (TM) wood. Both treatments were prepared under identical thermal conditions, differing only by compression in TMD. Dimensional stability, water vapour sorption, and Brinell hardness were assessed before and after repeated wetting and drying cycles to evaluate the effect of stress storage in the polymer matrix and its recovery during moisture exposure. The results indicate that both TMD and TM treatments induce a temporary reduction in moisture uptake, consistent with the formation of an annealed polymer structure. Water saturation and subsequent drying restored higher moisture content and reduced Brinell hardness in TMD wood, highlighting a moisture-driven recovery of the annealed polymer conformation. Notably, the decrease in hardness could not be attributed solely to the reduction in bulk density, indicating additional effects of polymer plasticisation. The presence of compression stresses during TMD appeared to enhance stress storage, thereby influencing the recovery of moisture-induced properties. Initial wood moisture content before TMD had little effect on the temporary reduction in moisture content, suggesting that annealing also occurs in dry states. These findings emphasise the need to account for moisture cycling in TMD wood’s service life. Future work should focus on the interplay between compression stresses and the annealing effect to reduce the temporary nature of the property improvements by TMD.
Abstract
Wood has many attractive material qualities, but it is susceptible to biological degradation by wood-decaying fungi. Moisture is one of the critical requirements for wood decay, but much remains unknown about moisture dynamics in decaying wood. To fill this knowledge gap, this study investigated moisture in Scots pine sapwood during decay caused by the brown rot fungus Coniophora puteana. Samples were exposed to decay in two time-series experiments; mass loss and moisture content were recorded over the course of decay, and the bound and free water populations in the samples were analysed using low-field nuclear magnetic resonance (LFNMR) relaxometry in both the decaying state and at full water saturation. Selected samples were also used for water vapour sorption measurements. The time-series decay tests showed that moisture content initially increased due to fungal activity but decreased over time when corrected for mass loss, contrary to the general belief that moisture content increases with decay. LFNMR revealed that bound water content increased on a decayed-mass basis in the decaying state and at saturation, but no increase was seen after correction for mass loss. Free water content followed gravimetric moisture content in the decaying state, but the saturated state measurements revealed an initial increase and subsequent decrease with mass loss. Degradation caused changes in hygroscopicity, but our data show that overall moisture content is regulated by fungal activity rather than by material properties. These findings highlight the complexity of water interactions during fungal degradation, offering valuable new insights into wood degradation mechanisms.
Authors
Kristina Bringedal Gedde Georgios Triantafyllidis Alessio Miatto Lone Ross Lizhen Huang Daniel Beat MuellerAbstract
Abstract The building sector accounts for a significant share of global material stocks and embodied greenhouse gas emissions. Material intensity (MI), defined as construction materials per unit floor area, is a key metric for understanding resource use and environmental performance. Existing approaches estimate MI for specific building types and cohorts but rarely explore additional factors that influence the structural element requirements. This study refines traditional methods by incorporating building geometry, number of floors, geographical context, construction methods, and regulatory changes, using Norwegian residential buildings as a case study. We focus on stud use in exterior walls to understand how their MI (kg/m 2 ) varies across buildings. Our correlation analysis reveals that construction year (ρ = 0.69) and energy efficiency standards (ρ = 0.51) are associated with higher MI of studs while building length shows a notable negative correlation (ρ = –0.38). Timber stud MI increases with footprint complexity and number of floors but decreases as building length and floor area grow. Snow load further contributes to increased stud MI. Studs' MI also varies across periods, reflecting changes in regulations and construction practices. These findings enhance our understanding of material use drivers in timber structures and provide a foundation for developing more nuanced building stock models to improve resource efficiency assessments and support targeted climate mitigation strategies.
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This paper presents a comprehensive study on lightweight cement-bonded composites containing pulp sludge (PS). The objective of the study was to evaluate how the incorporation of perlite (a lightweight volcanic glass aggregate) and lime mud (a pulp mill residue) influences composites’ properties including mechanical strength, insulation and fire resistance. Up to 50% of the cement binder was replaced with PS (by mass), and small fractions of cement (5–15%) were replaced with perlite or lime mud. A suite of analytical techniques, material characterization and mechanical tests with digital image correlation (DIC) for strain analysis were employed. X-ray analysis showed that the aggregates influenced the composite properties to a considerable extent due to their particle sizes and ability to form hydrated gels with cement. Adding 5% of perlite or lime mud yields optimal strength without compromising weight reduction whereas higher aggregate content (15%) led to reduced strength. The DIC system provided insights into strain distribution during loading, confirming enhanced toughness from the fibrous PS. The composites were significantly lighter (732–749 kg/m3) and showed about 30% lower thermal conductivity (0.17 W/mK) than pure cement composites (0.25 W/mK). The normal incidence sound absorption of the composites was about 0.3 at mid-high frequencies due to their compact structure. The composites demonstrated potential for use as sustainable, lightweight construction materials with good acoustic and thermal insulation, as well as acceptable load-bearing capacity for non-structural applications based on EN 634-1/-2 requirements for cement-bonded particleboards.