Project: VOC-optimised cross laminated timber from pine wood and indoor air quality in cross laminated timber buildings
Cross laminated timber (CLT) is a frequently used constructive wood material, whose importance in Europe and Austria is increasing due to the increasing solid wood construction. Currently CLT is mainly produced from spruce wood. However, the availability of spruce is limited due to increased competition and a decline in the available raw material potential. At the same time, the demand for solid wood such as CLT is increasing.
In order to meet this growing demand, new raw material sources for the production of CLT are needed. Pine wood, which has both excellent properties and a high untapped raw material potential, could be a meaningful alternative. However, pine is a wood species which is extremely rich in resin and therefore contains a high amount of extractives. This leads to increased emissions of volatile organic compounds (VOC). For this reason, pine wood has so far only been used to a limited extent in solid wood construction. In order to satisfy the increasing demand for cross laminated timber in solid wood construction, and to make pine, in addition to spruce, usable for this product in the future, the CLT production process was adapted accordingly in this project.
It could be shown in the project that, taking into account also economic considerations, process-technical possibilities exist to achieve the reduction of VOC emissions from pine CLT by means of targeted control of the parameters drying temperature and drying duration.
- Already an increase in the drying temperature from 70 °C to 85 °C and a prolongation of the drying time from 1.8 to 5.4 day for pine wood raw material led to a reduction of up to 68 % in VOC emissions from the CLT elements produced thereof. In addition, a 60% reduction in VOC emissions was achieved for drying times of only 1.8 days using high-temperature drying at 110 °C.
- VOC emissions were also reduced by 41-68 % by gluing the pine wood surface. For 3-layer CLT (pine/pine/spruce), a combination of gluing and the orientation of the spruce layer to the interior side of the room led to a VOC reduction of over 90 %.
- For pine wood raw material with low resin content, the combination with spruce as hybrid-CLT could thus replace pure spruce-CLT in the future. For resin-rich pine wood material, the use of a combination of hybrid-CLT and drying at higher temperatures (min. 85 °C) and/or a longer drying time is necessary.
- The reduction of emissions by 20 % by increasing the drying temperature from 70 °C to 85 °C was demonstrated in a 6-month long-term test setting in model rooms that correspond to the European reference room.
The results of the project will enable the use of pine wood for future CLT production and will also provide findings for industries and interest groups of the solid wood sector, but also for planners, architects and customers.
Collective Research – FFG, 2017–2020
Wood K plus – Kompetenzzentrum Holz GmbH
Fachverband der Holzindustrie Österreich
Stora Enso Wood Products
KLH Massivholz GmbH
Mayr-Melnhof Holz Gaishorn GmbH
Binderholz GmbH Holzindustrie
Dr. Cornelia Rieder-Gradinger
The PineXLAM project "VOC-optimised cross laminated timber from pine wood and indoor air quality in cross laminated timber buildings" was financed with funds from the Austrian research promotion agency FFG and the participating company partners.
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