VOLUME 55, ISSUE 4/2014

For the release of formaldehyde from products requirements exist to keep the level below the reference point of 0.1 ppm even under normal conditions. Mainly solid wood or plywood is used for the sauna interior. Presently there is insufficient information about the release of formaldehyde at temperatures typical for saunas. In addition there has been a lack of test procedures respectively appropriate equipment for the determination of formaldehyde in low concentrations at temperatures up to 90 °C. For the investigations the gas analysis system referring to the DIN EN 717-2 (1994) within the analytical method needed to be modified. The results show that typical sauna woods meet a gas analysis value of 0.4 mg/m²h at 90 °C, which is the criterion of evaluation. Pine and oak wood showed higher release levels as the results of higher contents of fatty acids in case of the pine wood respectively acetyl groups in case of the oak wood. A significantly increased release of formaldehyde was found at temperatures of 40 °C and above. Regarding the release of formaldehyde, plywood manufactured with formaldehyde-free glue showed large differences between various products depending on the type of plywood. For those products gas analysis values between 0.1 mg/m²h and 1.7 mg/m²h were found. The cause might be the glue formula. It is supposed that the high differences of the subsequent formaldehyde releases at higher temperatures might be the result of the action of catalysts. Further investigations on other materials shall confirm the preliminary findings.

An innovative light weight material based on wood and natural binders is presented. Starting materials are fine residues of the wood processing industry, which are foamed with wheat flour in a complex fermentation process. The resulting raw mixture can then be shaped and baked. After drying, the element is processed by conventional methods. The resulting porous material has a low density of about 340 kg/m³ and can be laminated with different materials. The raw material has good fire resistance properties and is distinguished by a very high sound absorption coefficient. Potential product applications are acoustic elements, pin boards and inner layers for doors.

In current studies concerning modern box-type windows, the influences of the prevailing flow conditions on the thermal performance are, among others, investigated. The present work discusses basic mechanisms of heat transfer and the importance of turbulent flows as well as ways of gaining knowledge by standard-based methods. With the help of the CFD method the prevailing flow conditions are analysed and the results interpreted.

Proof of efficacy of wood preservatives against blue stain in Europe is usually achieved by laboratory testing according to EN 152 (2011), in combination with either an artificial pre-conditioning or a half-year natural weathering. Uncertainty exists whether this laboratory test is also suitable to predict service life of a wood preservative. In this study five specially designed test-products were comparatively evaluated in laboratory tests after preconditioning in a QUV and after natural weathering. Laboratory test results were then compared to a six year performance of naturally exposed wood treated with the respective products. Results show that a laboratory test according to EN 152 (2011) in combination with a QUV pre-conditioning puts a severe stress on anti-blue stain products. Those products passing the test without allowing any blue stain on the wood surface performed also perfect for four years in service and showed only minor staining after six years.

As part of quality assurance in the manufacturing process of buildings and to ensure the operability and safety in the building use, knowledge of the material moisture is of great importance. Sensitive textile structures for application areas of timber and concrete construction may be integrated into the building, allowing a permanent moisture control. It turns out that in the timber with the aid of the developed sensor textiles using the TDR and the DPW method, critical increases in moisture content can be reliably detected in components.

Since the middle of the 20th century several studies concentrate on the mathematical description of the cutting process of wood. In order to resolve this problem, empirical as well as analytical approaches were applied. Despite extensive research until now still no practical as well as a complete description of the interaction process of wood cutting exists. For this reason the aim of the following work is bringing together different approaches to develop an accurate and yet user-friendly explanation of cutting forces in wood, likewise in the metal working industry. Basic requirement is the consistent use of the general definitions. Therefore this part of the work deals with the geometric principals of the cutting process. Furthermore previously developed models, especially empirical models, are presented. Additionally assets and drawbacks of the analytical models are discussed.

Strength graded structural timber with rectangular cross sections needs CE-labelling on the EU market. The criteria and requirements for assessment of conformity and labelling of preservative treated structural timber against biological attack are regulated by EN 15228 (2009). As the assessment and verification of constancy of performance according to EN 14081-1 (2011) in regard of durability requires AVCP system 2+, a notified body needs to be involved. For practical use of preservative treated timber the German regulations “Bauregelliste” and “Liste der Technischen Baubestimmungen” have to be observed. As CE-marking of treated timber provides no indication of use class, which is decisive, it could be useful for the German market to include an additional statement according to DIN 68800-3 (2012) on delivery documents.