1. LVL AS A CONSTRUCTION MATERIAL 1.12.3 Emissions and product safety Phenolic adhesives that are cured at high temperature and wood raw material both contain small quantities of free formaldehyde. In Europe, the formaldehyde emissions of LVL products are tested according to the standards EN 717-1 (chamber method) or EN ISO 12460-3 (gas analysis method). The Class E1 requirement according to EN 14374 corresponding to ≤ 0,1 ppm (EN 717-1) can be easily achieved with LVL products. LVL manufacturers commonly report significantly lower formaldehyde emission levels of ≤ 0,03 ppm, and this limit stated in the voluntary certification of some construction product associations to demonstrate the low emissions of their products. For example, the German Qualitätsgemeinschaft Deutscher Fertigbau (QDF) für Holzwerkstoffe QDF-Positivliste criteria states a formaldehyde limit of ≤ 0,03 ppm. For volatile organic compounds (VOC) a European classification is currently under preparation, but for the present different classification systems are used in different countries either voluntarily or based on legislation. For example, in Finland, LVL products are certified to show that they fulfil the M1 emission classification requirements of the Finnish Building Information Foundation RTS for building materials. The M1 classification criteria set limit values for total volatile organic compounds (TVOC), formaldehyde, ammonia, carcinogens and sensory evaluation 19. After curing at high temperature, the adhesive bond between the LVL veneers becomes an inert polymer that does not dissolve or react with other materials in the surrounding environment. It is safe and non-hazardous to humans and animals. Standard LVL products do not contain more than 0,1% of any of the Substances of Very High Concern (SVHC) listed in the Candidate List of the European Chemicals Agency, as these substances are not intentionally added to the products 20. Manufacturers continuously monitor the Candidate List for updates. LVL does not contain anything classified as hazardous waste, and has the following waste code in the consolidated European Waste Catalogue: - 17 02 01 Wood (Construction and Demolition Wastes) After use at the end of its life cycle, LVL can be utilized e.g. for bioenergy production 3. 1.12.4 Acoustics LVL members can be used in timber frame structures in similar ways to other wood members to achieve the required sound insulation levels. Sound insulation of timber structures is usually good at high and middle frequencies if the structures have careful detailing so that they are airtight. However, timber structures are light, which makes it challenging to design adequate sound insulation structures against low frequency sounds. Therefore, layered structures are necessary for airborne sound insulation of intermediate walls between apartments. In floor structures additional mass and resilient layers are needed to keep the impact sound level at low frequencies low enough. Despite the challenges of low frequencies, real-life feedback from people living in well-designed wooden multi-storey buildings has been positive. The buildings are considered silent and the room acoustics of wooden buildings is usually regarded to be comfortable. One reason for this is that the surfaces of timber elements are less dense compared to steel or concrete, which is beneficial for sound absorption. Robust perforated LVL panels can be used together with mineral wool insulation installed in cavities behind the panels for sound absorption, e.g., in sport halls and schools. The good impact resistance of these panels is also advantageous, e.g., in walls of halls for ball games. 1.12.5 Fire safety When wood burns, a layer of char forms on the wood surface. This char layer serves as protective thermal insulation, inhibiting further burning of the remaining wood cross section. This makes the behaviour of wooden structures in fire predictable and their resistance to fire can be calculated based on the charring rates defined in EN 1995-1-2 (Eurocode 5). The one-dimensional charring rate β0 of LVL is 0,65 mm/min, and the notional charring rate βn for beams and columns is 0,70 mm/ min when the characteristic density is ≥ 480 kg/m3. As LVL cross sections are typically thin, with a product thickness of max. 75 mm, they usually require additional protection to achieve the required fire resistance. This is usually achieved with gypsum plasterboard panelling directly onto the LVL members, or onto LVL frame structures with cavities that are left empty or filled with mineral wool insulation. Eurocode 5 provides instructions for calculating resistance to fire. The risk of flame spread is controlled by reaction to fire class classifications of construction products. The class for untreated LVL is D-s2,d0, which is the same as solid wood, where D is the combustibility class, s is smoke production and d is burning droplets. The classification may be improved with fire retardant treatments up to class B-s1,d0 for some structures, mainly in indoor applications. For more information about fire safety, please see Chapter 6. 1.12.6 Structures for seismic areas LVL structures can be used in seismic areas. Unless special assessments are made, LVL structures are intended to be used subject to static or quasi-static actions. In seismic areas the behaviour factor of LVL panels used for the design is limited to non-dissipative or low-dissipative structures (q ≤1,5), defined according to Eurocode 8 (EN 1998-1:2004 clauses 1.5.2 and 8.1.3 b) and to applicable national rules on construction work. LVL structures have low weight which reduces the design loads in seismic design. LVL-C panels are available in large sizes, so they can be used as robust panel bracing components to 46 LVL Handbook Europe
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