ThermoWood® Cladding - Thermally Modified Wood
Silva's 21 x 119mm Tongue & Groove ThermoWood® profile offers a slender looking cladding board with a subtle v-joint allowing for a slight shadow line.
ThermoWood® Cladding Properties:
- Improved durability against decay
- Resin removed
- Reduced splitting strength
- Slightly reduced bending strength
- Improved dimensional stability
- Consistent colour throughout the timber
- Chemical-free, entirely natural manufacturing process
- Reduced equilibrium moisture content
ThermoWood® is produced using a chemical-free natural process. By heat treating only the finest Scandinavian Redwood to enhance the chemical and physical properties of the timber, ThermoWood® offers an exceptional cladding material with outstanding durability, stability and insulation characteristics.
Along with enhanced physical properties, the treatment also results in an attractive, consistent, deep brown tone for a beautiful appearance. Due to it's stability, Thermowood also takes and retains finish well, allowing for translucent or solid colour stains to be applied to create unique and striking buildings.
Silva's ThermoWood® is produced from Finnish PEFC Certified wood in accordance with strict and specific classification requirements. The consistent, high quality nature of production is based on a logistics supply chain stringently managed from forest to final product.
Suitable for commercial and residential buildings, ThermoWood® meets the requirements of Durability Class 2 (BS EN 350), carries European Standard CE Mark certification and is recognised by the Building Research Establishment (BRE) which endorses a 30 year service life when used for cladding.
Thanks to an improved durability against decay, ThermoWood® is well suited to projects facing harsh weather conditions. The attractive appearance and exceptional dimensional stability also makes the timber an ideal choice for internal cladding.
Silva Timber's ThermoWood® is modified to Thermo-D (Durability) standards, enhancing an essential characteristic for external end use applications. The average tangential swelling and shrinkage due to moisture for Thermo-D class treated wood is 5-6%, Thermo-D class ThermoWood® is classified as durable accoring to the EN113 standard - meeting Class 2 requirements.
The treatment used to enhance the dimensional stability and physical properties of ThermoWood are unfortunately not without drawbacks.
As a result of the increased temperate during the heat-treatment process some polymer bonds within the wood substrate (cellulose, hemicelluloses and lignin) are affected. Lignin in the wood becomes especially prone to UV degradation and if not protected, the wood cells (mainly composed of cellulose) will become faded and loose, and subsequently the erosion of the wood surfaces is inevitable - leading to accelerated weathering and loss of ThermoWood's original lustre, an issue for all thermally modified timber on the market.
Therefore, proper finishing and coating of heat-treated wood is an essential step in ensuring the longevity of the wood in both exterior and interior applications.
Sansin Test Results
Under the direction of Dr. Nenad Vidovic, the Sansin Research & Development team conducted extensive testing of Sansin's core line up of products in a variety of heat-treated wood applications. Sansin's test results confirmed that without suitable coating, heat treated wood is not weather resistant and particularly susceptible to UV degradation. Initial fading, greying, cracking on untreated samples was observed between 7-21 days after outdoor exposure. Erosion of exposed heat treated wood is found to occur up to 4 times faster than non-heat treated wood.
There are a wide range of wood protection finishes available from Silva Timber to help protect ThermoWood from the outset. For the optimal performance, Silva Timber recommend protecting ThermoWood with Sansin SDF HT using our pre-finishing service.
Sansin SDF HT is specially formulated for thermally modified timber to provide high resistance to UV degradation and natural weathering.
Recommended end use applications
- Exterior/Interior cladding
- Outer doors
- Shutters/ louvres
- Environmental constructions
- Sauna and bathroom furnishing
- Garden furniture
ThermoWood® Manufacturing Process
Thermal modification of timber is a clean, ecological process which enhances the properties of the wood. The process is completely natural and chemical free, using only high temperatures and steam to transform and control the timber's characteristics.
During the thermal modification process, timber is treated with high temperature (+212oc). Water vapour is used as a protective gas and heat conductor, enabling heating of the wood beyond its auto-ignition temperature. By heating the wood to 212oc, resistance to decay and dimensional stability are greatly enhanced, creating the Thermo-D properties suitable for exterior and interior cladding materials.
Thermal modification can be divided into three phases:
1: Temperature of the wood is raised, then dried
2: Thermal modification takes place - Moisture content of wood is dropped to close to zero, and then heated to 212oc.
3: The treated wood is cooled down and moisturised to the desired level.
ThermoWood® Finish & Treatment
ThermoWood's dimensional stability provides an ideal exterior cladding material. With improved resistance to decay and weather conditions, ThermoWood® holds an unbeatable advantage in outdoor use. As with all timber, ThermoWood will naturally weather to a silvery-grey colour with prolonged exposure to the elements if left untreated.
To maintain the longevity and appearance of ThermoWood® , it is recommended to apply a surface treatment for added UV protection such as a penetrating oil, translucent finish or solid colour stain.