Norwegian Institute of Wood Technology

Oslo, Norway

Norwegian Institute of Wood Technology

Oslo, Norway
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Nore K.,Norwegian Institute of Wood Technology | Meloysund V.,Standards | Aanensen P.,Norwegian Institute of Wood Technology
WCTE 2016 - World Conference on Timber Engineering | Year: 2016

This paper describes the process, discussions, reasoning and proposed provisions in the enquiry draft of the Norwegian execution standard. Execution is for the time being, briefly handled in the structural timber standards, except in some countries. One purpose of an execution standard is to reduce the number of building defects and accidents caused by poor execution and failures on building sites. The standard promotes structured communication, linking the designer and the contractor. This execution standard also includes requirements on general handling and temporarily storing of timber products and elements. Moisture influence on timber structures needs special attention. Documenting the moisture history and preventing rapid moisture changes are vital in securing high quality timber structures. The modern building site often involves mounting of prefabricated elements or stacking and connecting modules. Controlling the tolerances during and after assembly of all timber components will be of importance in order to document the building process. The execution standard for timber structures will improve the building process, reduce the building defects and secure skilled craftsmanship.

Nyrud A.Q.,Norwegian Institute of Wood Technology | Strobel K.,Arup | Bysheim K.,Norwegian Institute of Wood Technology
WCTE 2016 - World Conference on Timber Engineering | Year: 2016

Focus groups were carried out in Austria, Finland, France, Norway, and Sweden to understand building professionals' and laypeoples' perceptions of building materials and wellbeing in indoor environments. Focus groups asked participants to share their opinions and experiences related to seven main topics: choosing interior materials, naturalness, naturalness for building materials, wellbeing in the indoor environment, wood materials, cleanabililty, and ethics and environment. This report presents a summary of responses and a preliminary analysis of common themes and priorities among participants. Participants from each of the countries generally held similar views. The appropriateness of interior materials was seen as dependent on building type and context, with a greater preference for natural materials, particularly wood, in residential construction. Different stakeholders had different priorities relating to cleanability and environmental aspects which were often assessed as being in opposition to cost and general aesthetics.

Sortland M.-L.,Norwegian University of Life Sciences | Thiis T.K.,Norwegian University of Life Sciences | Kraniotis D.,Norwegian Institute of Wood Technology | Nore K.,Norwegian Institute of Wood Technology
WCTE 2016 - World Conference on Timber Engineering | Year: 2016

Variations in micro climate induce shrinkage and swelling of wooden beams. The dimensional changes depend of the orientation of the annual growth rings and the moisture content of the beams. This causes laminated timber to experience different deformations than solid wood. A producer of element buildings with joists of laminated wood, have experienced deformations and sloping of the floor structure in several buildings, and believe that these might be caused by moisture. This paper combines in-situ measurements with simulations and a laboratory experiment, to make a survey of where in the buildings these problems are most likely to occur, and to estimate how much deformation the producer can expect in these areas. The results show that the largest deformations occur in a bedroom facing north, with low solar radiation and high moisture gradients between indoor and outdoor climate. In this room, a 13 % difference in moisture content is measured between the head joist and inner joist, with the sensor installed one meter from the edge of the floor system. This results in an estimated height difference of almost 8 mm, a value higher than the tolerances for finished surfaces. The producer will improve their construction accordingly.

Thiis T.K.,Norwegian University of Life Sciences | Burud I.,Norwegian University of Life Sciences | Kraniotis D.,Norwegian Institute of Wood Technology | Gobakken L.R.,Norwegian Forest And Landscape Institute
Energy Procedia | Year: 2015

Mold growth on the surface of wooden façades is usually dealt with by using surface treatment such as paint with fungicides. However, new developments in architecture are moving towards less use of coating, and more use of untreated wooden claddings. Mould growth is well understood and described, and several models for predicting mould growth on building materials exist. It is commonly known that mould growth is directly controlled by the climate which the wood is exposed to. Several authors identify humidity, temperature and time as the main drivers of mould growth. However, most of the current growth models developed are based on laboratory measurements at stable climatic conditions. Consequently, these models are less suitable for prediction of mould growth on exterior surfaces exposed to rapidly changing weather conditions. This paper analyses the effect of variations of meteorological data on the mould growth on wooden claddings. An experimental setup of wood samples was exposed to outdoor conditions and hourly weather conditions as well as the mould growth at different intervals were measured. The measurements were supplied with 1-D Heat And Moisture (HAM) simulations to provide a more accurate estimate of the conditions on the surface of the samples. The purpose of the analysis was to evaluate if an existing mould growth model might be applicable also for predicting outdoor mould growth. Several profiles of temperature and moisture were continuously monitored on different locations of an eight-story building made from Cross Laminated Timber (CLT). The results from the analysis of the samples of wood cladding were used to model the mould growth on different locations of the building. Also the drying effect of wind around the building was studied. The study shows that there is large variation of potential mould growth on the façade of the building. © 2015 The Authors.

Hoibo O.,Norwegian University of Life Sciences | Nyrud A.Q.,Norwegian Institute of Wood Technology
Journal of Wood Science | Year: 2010

Information about people's preferences as to wood products is of relevance to several decision makers in the forest sector. Studies revealing consumer preference provide information that can be used for marketing and manufacturing of wood products, but these also provide information of relevance to designers and decision makers involved in building design and construction processes. Previous studies show that the overall harmony of the visual surface is correlated with preference. In this study, perceived visual homogeneity is modeled for five copper-impregnated and five organic biocide-impregnated decking materials with different visual quality. The models are based on visual variables. Homogeneity is a function of material-dependent variables (dry knots, knot shape, and splay knot), production-dependent variables (stain), and surplus color, which is a combination of both wood property and treatment. The results imply that homogeneity is influenced by both wood properties and treatment. Producers of decking should, while maintaining a focus on using high-quality raw material, also focus on producing a product with an unstained appearance. © 2010 The Japan Wood Research Society.

Alfredsen G.,Norwegian Forest And Landscape Institute | Flaete P.O.,Norwegian Institute of Wood Technology | Militz H.,University of Gottingen
International Wood Products Journal | Year: 2013

Acetylation appears suited to provide adequate protection against biological attack for materials derived from non-durable wood species. But still there are unanswered questions related to resistance against fungal decay. The paper summarises existing knowledge related to fungal deterioration of acetic anhydride modified wood and also highlights future research opportunities. In addition, statistical analyses based on previously published decay fungi studies were performed to quantify what factors contribute most to the performance (calculated as test sample/ control). The results showed that weight per cent gain can explain approximately 50% of the performance for acetic anhydride treated wood. Others of the applied variables, like wood species or type of fungus, can reduce the variance in performance by additional 15%. Based on the surveyed literature the degree of cell wall bulking in combination with lowering of the equilibrium moisture content seems to be the primary mode of action. © 2013 IWSc, the Wood Technology Society of the Institute of Materials, Minerals and Mining.

Sharapov E.,Volga State University of Technology | Mahnert K.-C.,Norwegian Institute of Wood Technology | Militz H.,University of Gottingen
European Journal of Wood and Wood Products | Year: 2016

Scots pine (Pinus sylvestris) was thermally modified and its residual strength after cyclic bending was tested. Asymmetric sinusoidal cyclic oscillations at 20 Hz frequency and load ratio p = 0.3 were conducted. The variables of the experiment were the thermal treatment temperature (160, 190 and 220 °C), the number of bending oscillations (103, 505 × 103 and 106) and the equilibrium moisture content at target climates of 20 °C and 35, 65 and 95 % relative humidity (RH). The results showed that all input variables were insignificant for the residual modulus of elasticity. The initial moisture content of the specimens before fatigue testing and the maximum thermal modification temperature were identified as main influence on the residual modulus of rupture. The cyclic creep deflection significantly increased with increasing number of loading and initial specimen moisture content. © 2016 Springer-Verlag Berlin Heidelberg

Ulvcrona T.,Swedish University of Agricultural Sciences | Flaete P.O.,Norwegian Institute of Wood Technology | Alfredsen G.,Norwegian Forest And Landscape Institute
European Journal of Wood and Wood Products | Year: 2012

Various oils can be used to lower the equilibrium moisture content and increase the service life of Scots pine wood products. The aim of this study was to investigate effects of the lateral wood zone on the brown rot resistance of untreated and linseed oil-impregnated Scots pine wood in a laboratory test (EN 113). Significant differences were found in the mean mass losses of treated and untreated specimens taken from three lateral heartwood zones, but not between specimens taken from sapwood. The treatment had no significant effect on sapwood, although it seems to have some positive effect on the durability of heartwood, apparently due to interactive effects with the high extractives contents of heartwood. © Springer-Verlag 2012.

Nore K.,Norwegian Institute of Wood Technology | Kraniotis D.,Norwegian Institute of Wood Technology | Bruckner C.,Norwegian Institute of Wood Technology
Energy Procedia | Year: 2015

The interaction of the wood surface and indoor climate has been of increasing interest the last decade. The fluctuating air humidity reacts with the wood surface to seek equilibrium moisture content. This reaction is crucial when experiencing a sauna. The instant heat contribution of the latent heat from the released damp when pouring water on the oven gives the intense perceptible sauna experience. This paper shows a set of measurements and calculations conducted in a Norwegian sauna. One sauna event includes in three parts. The heating of the sauna, increasing the temperature and drying out the wood. Then when visiting the sauna is, with the changes between warm and cold, like taking a cold bath in between being heated in the sauna. Usually also this heating includes pouring water on the oven. The physics around this moistening of the sauna is of special interest in this paper. Finally, the visitors leave the sauna and it cools down. The focus in this paper is on the increase of temperature when pouring water on the oven in the sauna. Different moisture protocols are ran with varying amounts of moistening. The protocols follow real sauna experiences. Surface temperature is carefully measured and recalculated. The key role of the wood surface sorption, providing this latent heat phenomenon, is presented in the results. The sensible heat increase is not due to the change of humidity, as often stated. The heat conductivity is actually higher in dry air compared to moist air. The damp transport energy from the sauna oven through high enthalpy in the air. The damp is absorbed in the dried wood surface and consequently emits latent heat energy back to the room. That is, the surfaces becomes substantial heating panels. The heat release due to wood surface sorption is an extreme employment of the potential of the latent heat. The authors believe that this effect may be significant also in other cases, with smaller water potentials. This is elaborated in the paper. © 2015 The Authors.

Glase G.,Norwegian Institute of Wood Technology | Nore K.,Norwegian Institute of Wood Technology
World Conference on Timber Engineering 2012, WCTE 2012 | Year: 2012

Cross laminated timber (CLT) elements are usually designed for performance regarding mechanical load, strength and stiffness, and structural fire performance, in addition to its aesthetical qualities. A modified CLT element combining the structural capacity with acoustic dampening has been developed in Norway. The modification converts the element into a Helmholz-resonator. In order to use the acoustic element as a structural element, several test elements have been studied on shear performance and compared with standard CLT elements. The shear performance of the connection between acoustic and standard CLT has also been tested.

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