Mapping of biogenic carbon flows in the forest-based value chains in Sweden

The sawmill and wood industry sector is characterized by a high proportion of the use of domestic raw materials, where only around 2% of the timber comes from imports. 2950 kt of carbon is exported, which can be compared to the domestic use (including for energy purposes) of 8720 kt of carbon. Of the primary raw material used in the sawmills, 28% ends up in sawn spruce (2280 kt of carbon) and 18% in sawn pine (1460 kt of carbon). The sawn timber is then sent to the construction trade or for further processing within the wood manufacturing industry into various construction products, as well as to the furniture industry. The remaining portion of the wood raw material in the sawmills becomes by-products that go to energy production or to the pulp and paper industry.

From the Swedish wood manufacturing industry, there is a flow consisting of by- and residual streams where the majority becomes return wood chips (RT chips) that are either burned in their own boilers for heat production at the industry or sent to heating or combined heat and power plants. The amount of RT chips that enter the Swedish power and heating plants annually amounts to 1300 kt of carbon. The difference between what goes into the wood manufacturing industry and what is energy recovered in the form of primarily RT chips is bound in long-lived products such as wooden frames, building interiors, furnishings, and furniture, which are also partially exported.

The market for reuse and recycling of wood within the construction sector is still underdeveloped in Sweden, pilot studies are ongoing, and only small amounts of timber flow in this process. Since construction products often have functional and quality requirements that need to meet current building codes upon reuse, reuse is complicated, and the issue of responsibility also complicates matters. Regulations, test methods, new actors, and business models need to be developed.

There is a clear potential to use by- and residual streams from the wood value chain more efficiently considering the increasing competition for wood raw material from the forest. Two clear tracks

• Capture juvenile fibers from the breakdown and postprocessing processes in the wood value chain and coordinate flows into volumes that can be utilized for products instead of energy production. This requires coordination of more sectors than just the actors in the forest sector to find the right biogenic raw materials for energy production.

• Develop processes, methods, and business models that contribute to RT chips being used to a greater extent for products instead of energy production. A prerequisite for change is that both industry and society's energy supply (electricity and heat) can be managed with less energy from combustion of wood raw material.

Among the actors in the value chain, there is an understanding and even a willingness to make a transition, but above all, there is a lack of economic incentives to do so.

A further perspective, given the increasing competition for wood raw material from the forest, is to reflect on the volumes of exported wood, its use, resource efficiency and possible national need.

Today, there is a significant lack of detailed public statistics and data on the amount of sawn timber that goes into various types of products. The risk of disclosing company- that data collected by, for example, SCB (Statistics Sweden) cannot be published officially. Not all companies report data either. Statistics are available for flows upstream for sawmill production and downstream for distribution. Individual companies in the value chain have good knowledge of their internal flows. Statistics for product categories within wood manufacturing are specified at the product level and not in the level of detail for the input material. The low resolution makes it difficult to compile reliable statistics for flows of wood-based material. For energy and heat production, statistics are available via Energiföretagen (Swedish Energy Companies) and industry organizations. However, there is currently poor knowledge about the material flows that go to RT chips, which then go to combustion. A further perspective, given the increasing competition for wood raw material from the forest, is to reflect on the volumes of exported wood, its use, resource efficiency and possible national need.

Floor vibrations – Implications of the new EC5? This report presents the design methodology principles for the revised section for the control of vibrations in wooden floors, as well as the proposal for dividing timber floors into performance levels and quality selection, as found in Eurocode 5 With the aim of presenting how different floors commonly used in Sweden performs with respect to the new methodology, the results from a limited parameter study are presented. A total of eight different floor types were examined, including floor structures with load-bearing beams made of structural timber, glulam, LVL, and I-joists. The study also looked at rib joists with T-beams made of glulam combined with an LVL board, as well as floor structures with a load bearing CLT board. The following parameters were varied to study effect on the stiffness of the structures: • the centre distance between beams • the web height of the beam cross-section for rib-floor slabs, • thickness of load bearing CLT board. The maximum span for each floor structure was decided by finding the maximum span for each floor structure which meets the ultimate limit state and the serviceability limit state conditions, both with respect to deformations and vibrations for residential and office buildings set by the new EC5. The stiffness of each floor was then increased to study the effect of stiffness on the performance levels. Response factors were calculated for each case. Note! Direct comparison of the floor structures is not possible since the calculations are based on different span widths for each floor type. Since the calculations are based on each floor type’s unique conditions, it is not possible to compare the floor structures directly. Instead, comparisons must be made based on how a variation in stiffness affects the performance level of each individual floor type. The parameter study shows that for the light floor structures with discrete beams, spacing the beams closer changes the response factor slightly but it typically stays within the values for performance level V, i.e. between 24 and 36. For the other floor structures, rib floor and CLT, increasing the stiffness resulted in a larger change in performance and some floors changed floor performance level. The performance levels and quality choices introduced in the new methodology for checking vibrations in timber floors, makes it easier and clearer for clients and builders to achieve a consensus on what vibration comfort to expect in the finished building. This is an opportunity to reduce the risk of complaints and avoid having to take action to correct a perceived lack of quality. The current advice in the national annex for the Eurocode EKS12 specifies that the deflection for a 1 kN point load is limited to 1.5 mm, which corresponds to the upper deflection limit for performance level V. Performance level V is the worst performance level allowed for the quality choice ‘Economy’ for offices and homes in multi-family buildings. This means that the proposal on quality choice does not provide any tightening compared to the Swedish requirement in EKS12. However, the fact that performance level VI is allowed for dwellings in single-family houses with an upper limit value for deflection of 2.0 mm suggests that the proposal mitigates the requirement contained in EKS12.

Korslimmat trä (KL-trä) för byggnadsändamål är en produkt som togs fram i Centraleuropa i mitten av 1990-talet. Syftet med förstudien är att i samverkan utforska förslag för hur en framtida resurseffektivare KL-träprodukt kan utformas. Målet är att ta fram underlag för utveckling och genera en samling kring frågan. Det finns en medvetenhet för de omvärldsfaktorer som påverkar byggandet med KL-trä. Det finns en ökad efterfrågan på trä i byggsektorn och det finns ett dynamiskt tänkesätt för att ersätta betong med KL-trä. Ökad användning av skogsråvara, global uppvärmning och minskad tillgång via begränsningar i skogsbruk väcker frågor. Vilken råvara har vi i framtiden, vilka trädslag och hur ser tillgången ut? Det resulterande materialet har analyserats utifrån de olika perspektiven som representeras av intressentgrupperna i värdekedjan för byggande med KL-trä. Rapporten avslutas med projektidéer som framkom under arbetet med förstudien.

Cross-laminated timber (CLT) for house construction is a product that was developed in Central Europe in the mid-1990s. The purpose of this study is to collaboratively explore proposals for how a more efficient CLT product can be designed for the future. The goal is to produce a basis for development and generate a consensus around the issue. There is an awareness of the environmental factors that affect design with CLT. In addition, an increased demand for wood in the building sector has resulted in a dynamic mindset to replace concrete with CLT. Increased use of forest raw materials, global warming and reduced access via restrictions in forestry raise questions such as: What raw materials will we have in the future? Which tree species will be available? How large will the supply of raw materials be? The resulting material has been analysed based on the different perspectives represented by the stakeholder groups in the value chain for building with CLT. The report concludes with project ideas that emerged during the work on the feasibility study.

The limitations in performance of band-pass filters to accurately process rapid decaying signals in lower frequency bands is an obstacle for some measurements within building acoustics. For instance, it would be beneficial to be able to accurately measure reverberation times down to the 20 Hz one-third octave band for impact sound in timber buildings. Here, it is tested whether calculations with FFT with small incremental steps may be a way to achieve discrete frequency time signals with faster performance than traditional band-pass filters. The tests show that incremental FFT gives accurate estimations of the reverberation time corresponding down to 0.1 s at 20 Hz with a spectral resolution of 2 Hz. Using the one-third octave limits it is possible to form approximate one-third octave band results. It is seen that accurate estimations of reverberation time are achievable for BT⩾0.5 (T=0.1 seconds for the 20 Hz one-third octave band) and possibly even lower, if the dynamic range in the interrupted noise signal is sufficient. The higher one-third octave results show to work as well. A disadvantage with the method is that during short reverberation times (0.1 s) there is a severe spectral leakage to the side bands. Also, the method requires higher dynamic range decay signals compared to band-pass filtered signals. If a one-third octave resolution is requested, a dynamic range of 50 dB or greater is preferable. With a coarse resolution of e.g., 10 Hz and having no averaging into one-third octave bands, it is possible to measure short reverberation times (0.1 s) with signals having close to the same dynamic range used in classical band-pass filtered reverberation time measurements. © 2022 The Author(s)

The most popular single-number quantities (SNQs) of impact sound insulation in Europe are L’n, w and L’nT, w. They are based on measurements within 100-3150 Hz. Recently, it was proposed that the measurements should be extended down to 25 Hz for wooden floors, and L’nT, w+CI, 25 should replace L’nT, w. The purpose of this study is to analyze which of the two SNQs, Ln, w or LnT, w+CI, 25, predicts the annoyance of natural impact sounds better for wooden floors. We conducted a psychoacoustic experiment, where 52 participants rated the annoyance of 75 impact sounds. As stimuli, five types of natural impact sounds were used. They were recorded for 15 different wooden floors built in an impact sound insulation laboratory, where also their SNQs were measured. Based on correlation analysis, Ln, w explained annoyance of natural impact sounds equally well or better than Ln, w+CI, 25, depending on impact sound type Therefore, based on perception, it seems to be sufficient to conduct measurements within 100-3150 Hz for wooden floors and assess their sound insulation using L’nT, w or L’n, w © 2023 First author et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 3.0 Unported License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

In a Finnish-Swedish consortium project, a large amount of sound insulation tests was conducted for several intermediate floors in laboratory conditions to serve various scientific research questions. The dataset contains 30 wooden and 8 concrete constructions which are commonly used between apartments in multistorey buildings. Impact sound insulation was determined according to ISO 10140-3 standard using both tapping machine and rubber ball as standard sound sources. Airborne sound insulation was determined according to the ISO 10140-2 standard. The data are special since they have a broad frequency range: 20−5000 Hz. Data are reported in 1/3-octave frequency bands and the single-number values of ISO 717-1 and ISO 717-2 are also reported. Detailed construction drawings are available for all reported constructions. The data are highly valuable for research, education, and development purposes since all data were obtained in the same laboratory (Turku University of Applied Sciences, Turku, Finland), and all the constructions were built by the same installation team. © 2023 The Authors

Wooden floors usually have worse impact sound insulation (ISI) at low frequencies than concrete floors having the same rating level. Rating level is usually expressed by single-number quantities (SNQs), such as weighted normalized impact sound pressure level Ln,w. Psychoacoustic research among wooden floors is very limited although a controlled laboratory experiment is the strongest method to point out the most adequate SNQs to be declared for the floors. The purpose of our study was to determine how four standardized SNQs of ISO 717-2, Ln,w, Ln,w + CI, Ln,w + CI,50, and LiA,Fmax,V,T, and a recently proposed SNQ, Ln,w + CI,25, are associated with the annoyance of natural impact sounds transmitted through wooden floors. Fifteen floors were built in the laboratory based either on cross-laminated timber (heavy) or open box wood (light) slabs. Different coverings and suspended ceilings were applied on these slabs. The ISI was tested within 25–3150 Hz using both tapping machine and rubber ball. Thereafter, five natural impact sounds were recorded for each floor: rubber ball drops, steel ball drops, walking, jumping, and chair pushing. Fifty-two people rated the annoyance of these 75 recorded natural impact sounds in psychophysics laboratory. Annoyance was best associated with Ln,w for all the five impact sound types. That is, measurement of ISI within 100–3150 Hz is sufficient from subjective point of view. All four SNQs based on tapping machine explained annoyance better than the SNQ based on rubber ball. Our results can significantly guide the future research, development, and regulations of wooden floors.

During the last years the interest in multi-storey timber buildings has increased and several medium-to-high-rise buildings with light-weight timber structure have been designed and built. Examples of such are the 8-storey building Limnologen in Växjö, Sweden, the 9-storey Stadthaus in London, UK and being constructed at the moment, the 14-storey building Treet in Bergen, Norway. These are all light-weight and flexible structures which raise questions regarding the wind induced vibrations. For the building in Norway, the calculated vibration properties of the top floor are on the limit of being acceptable according to the ISO 101371 vibration criteria for human comfort. This paper will give a review of building systems for medium-to-high-rise timber buildings. Measured vibration properties for some medium-to-high-rise timber buildings will also be presented. These data have been used for calculating the peak acceleration values for two example buildings for comparison with the ISO standards. An analysis of the acceleration levels for a building with double the height has also been performed showing that designing for wind induced vibrations in higher timber buildings is going to be very important and that more research into this area is needed. © 2015 by ASME.