Silva’s commitment to supplying consistent and high quality timber products is reflected in our latest cladding material - ThermoWood®. Our extensive supply network has led us to source the finest ThermoWood® available from Lunawood, one of the world's leading producers of this innovative timber product.
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, Lunawood 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, Lunawood 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.
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
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.
Recommended end use applications
- Exterior/Interior cladding
- Outer doors
- Shutters/ louvres
- Environmental constructions
- Sauna and bathroom furnishing
- Flooring
- Garden furniture
Logging Selection Process
Only the finest raw materials are used which best suit Thermowood production in terms of type and quality. The timber species chosen are exclusively Redwood, that have fewer knot characteristics. The knots which do exist in the timber are sound and tight due to their structure, for a superb performing exterior cladding material.
In Nordic forest logging processes, trees are cut into three sections; Butt Log, Middle Log and Top Log. Silva's ThermoWood is produced from the top or middle log for a high quality, consistent product, with only the centre of the log used to ensure live-intergrown knots.
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 moisturized 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.
Silva Timber offer a prefinishing service in either a translucent finish, or stained to any colour imaginable, ready for immediate onsite installation. Contact us for more information.
How to order
There are a number of ways to order ThermoWood® from Silva Timber:
Sawn Boards
ThermoWood® can be supplied in sawn boards (25 x 100mm, 25 x 125mm, 25x150mm) for machining or further processing.
Standard Cladding Profiles
We offer a range of popular cladding profiles ‘off the shelf’ for immediate delivery. Click here to view our range
Custom Profiles
We can machine custom profiles to your specification. This process takes up to 14 days from receipt of order to delivery to your site.
ThermoWood® is also available prefinished with solid or translucent stains, and fire treated to British Regulation standards.
For more information please contact our customer support team on 0151 495 3111 (Cheshire) or 01895 271 300 (W. London).
Silva Timber's ThermoWood® is modified to Thermo-D (Durability) standards. Biological durability is an essential characteristic for end use applications in this treatment category. 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.
Summary of the effects of the Thermowood process on wood properties:
| Property |
Thermo-D |
| Treatment Temperature |
212oc |
| Weather Resistance |
++ |
| Dimensional Stability |
++ |
| Bending Strength |
- |
| Colour Darkness |
++ |
ThermoWood® Manufacturing Process
Thermal modification of timber is a clean, ecological process which enhances the properties of the wood. The process is completely 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 moisturized to the desired level.
PDF Downloads
ThermoWood Handbook
ThermoWood Main Properties
ThermoWood Technical Instructions
ThermoWood Installation Instructions
Quality requirements are set by Lunawood for ThermoWood® in order to take responsibility for the care of the environment. To ensure this, the quality chain goes all the way from the source of the raw materials to the end consumers. No chemicals are used in the manufacturing process of ThermoWood®, providing a strong basis for the ecological soundness of the product. Applied correctly, heat and steam are sufficient to turn wood into a durable and impressive construction material. At the end of its life span, thermowood can be burned and turned into bio fuel or recycled.
This product carries Programme for the Endorsement of Forest Certification (PEFC)
The PEFC Council is an independent, non-profit, non-governmental organisation founded in 1999 which promotes sustainably managed forests through independent third party certification. The PEFC provides an assurance mechanism to purchasers of wood and paper products that they are promoting the sustainable management of forests.
PEFC works throughout the entire forest supply chain to promote good practice in the forest and to ensure that timber and non-timber forest products are produced with respect for the highest ecological, social and ethical standards. Thanks to its eco-label, customers and consumers are able to identify products from sustainably managed forests.
Silva Timber meets the requirements for PEFC Chain of Custody within the BM TRADA Certification Limited Scheme for TRADA - Trak chain of custody certification.
Certificate number: BMT-PEFC-0319
