Lone Ross Gobakken

Carbon footprint including effect of carbon storage for selected wooden facade materials

Abstract The outer facade constitutes a substantial volume of the total consumption of materials used in a building and the need for maintenance of the facade makes it especially interesting from a life cycle perspective. The range of wooden materials and products used for facades has different impacts over the life cycle, but the analyses so far have not included a time-adjusted global warming potential (GWP). Wooden facade materials were assessed with respect to their life cycle carbon footprint based on the environmental product declarations (EPD) and adjusted according to EN15804. The results showed low impacts of untreated Scots pine heartwood (≈1 kg CO2-eq. per square meter [m2]), medium for thermally modified Scots pine, coated Norway spruce and oil/copper–organic preservative-treated Scots pine (1–5 kg CO2-eq. per m2) and high for furfurylated Scots pine and acetylated Radiata pine (5–10 kg CO2-eq. per m2). The results with time-adjustment showed that these methods have a potential large effect on the carbon footprint of wooden claddings. The inclusion of biogenic carbon flows and timing seems to be more important than the difference between the product when biogenic carbon is not included. This fact highlights the importance time-adjusted GWP would have for wood products EPDs.

Weathering kinetics of thin wood veneers assessed with near infrared spectroscopy

Wooden elements may be subjected to mechanical, environmental or biological alterations during their service life. The most susceptible parts of wood structural members are the exposed surfaces since they are subjected to ageing, weathering and/or decay. Knowledge of the influence of weathering factors and polymer degradation mechanisms is essential for understanding the weathering process of wood. The goal of this study was to investigate the degradation of thin wooden samples exposed to short-term weathering. Tests were performed through the European summer (July), which according to previous research is considered as the most severe period for weathering of wood micro-sections. Fourier transform near infrared spectroscopy was used for evaluation of chemical changes of wood samples. Three approaches for data evaluation are presented in this paper: (1) direct spectral interpretation, (2) a concept for calculation of a weathering index Wind and (3) kinetics of lignin changes in relation to the exposure direction for selected wavelengths. Observation of the effects of weathering will allow better understanding of the degradation process. The southern exposure site was slightly more affected by weathering than other sites. Results of this research will be used for future determination of the weather-dose response model and could be essential for predicting the future performance of timber facade elements.

Near Infrared Hyperspectral Imaging in Transmission Mode: Assessing the Weathering of Thin Wood Samples:

Untreated wooden surfaces degrade when exposed to natural weathering. In this study thin wood samples were studied for weather degradation effects utilising a hyperspectral camera in the near infrared wavelength range in transmission mode. Several sets of samples were exposed outdoors for time intervals from 0 days to 21 days, and one set of samples was exposed to ultraviolet (UV) radiation in a laboratory chamber. Spectra of earlywood and latewood were extracted from the hyperspectral image cubes using a principal component analysis-based masking algorithm. The degradation was modelled as a function of UV solar radiation with four regression techniques, partial least squares, principal component regression, Ridge regression and Tikhonov regression. It was found that all the techniques yielded robust prediction models on this dataset. The result from the study is a first step towards a weather dose model determined by temperature and moisture content on the wooden surface in addition to the solar radiation.

Progress of discoloration in green, freshly cut veneer sheets of black alder (Alnus glutinosa L.) wood

Abstract Black alder wood has a great potential for more wide-spread use in the woodworking industry. This study describes the colour changes that appeared the first few hours after cutting thin veneer sheets from fresh, unseasoned black alder wood. CIELab coordinates were recorded for 50 spots at time intervals from 0 to 140 minutes exposure of the fresh-cut surfaces. The most pronounced change was increased lightness developing from 20 to 60 minutes after cutting. A model for total colour change as function of exposure time was developed. Redness of veneer sheets increased only slightly, i.e. the expected transfer to orange discoloration of the surface did not occur. The reason for this was probably that part of the free water in the wood was squeezed out during veneer production. The findings of this study give useful information about the colour change that appeared directly after veneer cutting, advising to avoid excess water on wood surface and ensuring quick surface drying.

Hyperspectral near Infrared Imaging of Wooden Surfaces Performed Outdoors and Indoors

Hyperspectral near infrared imaging has been applied in a field study of fungal growth on a variety of wood substrates exposed in an outdoor environment over a six-month period. This study was performed as a follow up to a hyperspectral examination study of fungal growth on wood surfaces in a laboratory setting. Hyperspectral measurements were carried out both outdoors and indoors in order to explore the influence of the different light conditions. Segmentation of the mould growth on the wood surfaces was carried out using principal component analysis, spectral angle mapper and partial least squares-discriminant analysis. Growth curves showing the fungal growth over time were obtained for all the samples from the measurements performed outdoors. However, there are some challenges connected to studies of wood surfaces due to structures caused by growth rings, knots and sometimes cracks. These wood properties will cause a great variation in the spectra from the wood and also cause natural variation in the fungal growth. Determining specific classes in a classification model such as partial least squares-discriminant analysis is proposed as a way to overcome these issues. Moreover, the wood substrates exposed in an outdoor environment will have a colour change due to photodegradation of lignin, wetting/leaching of the upper layer of the wood surface and growth of a variety of wood discolouring fungi. Hyperspectral technology is a promising technique to study wood properties and we plan to carry out a study to be able to separate and model the different effects on colour degradation on wood surfaces.

Assessment and monitoring of aesthetic appearance of building biomaterials during the service life

Bio-based building materials offer a wide range of outlooks, from traditional rustic to modern design products. Recent development in the science of materials significantly improves their functional performance. However, when considering the use of bio-materials in outdoor environments, materials will deteriorate due to processes like weathering, oxidation, biodegradation, wear, and decay. Consequentially, biomaterials may lose visual appeal, leading to a perceived need for replacement even if the material is far from reaching functional failure. Visual assessment is the most direct method for evaluation of the aesthetic appearance of materials. However, it possesses a high degree of subjectivity when performed by an untrained person. On the contrary, measurement of surface properties with dedicated sensors provides objective values that might be related to the current state of the material in use. Recent developments in field of optics and electronics opens a new possibility to perform measurements in-situ. Colour-, gloss-, or spectro-photo-meters allow non-destructive measurements without particular sample preparation. Since all of the above techniques provide complementary information, the multi-sensor approach is more frequently suggested for applied research. The material state can be assessed regularly during service life. In this case, such measurement turns into monitoring. The paper illustrates examples of assessment and monitoring of biomaterials’ degradation due to weathering. Direct implementation of various sensors is demonstrated. A proposal for the approach of combining data provided by various sensing techniques with data mining is also presented.