Lunawood Thermowood
LUNAWOOD THERMOWOOD is a beautiful, sustainable wood material produced by using natural methods, heat and steam. Thermal modification improves the wood’s properties, thereby expanding the range of applications in which the wood can be used. Thermowood is dimensionally stable, resistant to decay and resin free. It can be used inside or outdoors, in any climate. Lunawood is an non-toxic natural product which is easy to machine and install.
Process
Even the ancient Vikings knew that when building defensive fencing for fortifications, poles made from wood with a burnt surface were more durable than poles which had not been treated in any way. Studies on the possible benefits of thermal modification of wood began as early as the 1930s and 1940s in Europe and USA, but the manufacturing process never reached an industrial scale. Decades later, VTT (Technical Research Institute of Finland) became interested in the idea and as a result, the Thermowood process was patented and the brand was launched in Finland at the end of the 1990s.
The Lunawood thermal modification process uses only heat (ranging from 190-212°C) and steam. Lunawood end products are completely natural and free from chemical additives.
The Thermowood process respects the natural properties of wood. The patented production process is based on the gradual thermal modification of wood, wherein the chemical and physical properties of wood undergo permanent change. Thermowood is a registered trademark and may only be used by member companies of the International Thermowood Association. Lunawood is one of the association’s founding members. The quality of Thermowood production is monitored by an independent, external party.
The best raw materials
We use mainly Finnish PEFC-certified wood in our production that is sorted in accordance with our specific and strict requirements. The high and even quality of our production is based of a logistics chain that is carefully managed from forest to final product. Together with our suppliers, se select and use only the raw materials that are the best suited for our production in terms of type and quality.
Pine (Pinus Sylvestris)
Pine grown in the northern latitudes is our main raw material. We only use sound knotted wood to ensure the high quality of the final products. As a result, Lunawood is known for its top quality.
Spruce (Picea Abies)
The properties and quality requirements of the spruce that we use in production are similar to those of pine. Lunawood uses mainly spruce in the production of exterior cladding boards and other related products. In terms of production, knots are the main difference between pine and spruce: in spruce, the knots are smaller but relatively hard, which makes them break more easily during the processing.
Other species
The high quality of Lunawood Thermowood starts from the raw material. The main wood species modified are PEFC certified Scots pine and Norway spruce, which are graded in accordance with our specific and strict requirements. For Scots pine only sound knotted heartwood originated from top log is suitable for our products. The properties and quality requirements of the spruce that we use in production are similar to those of pine.
Good to know about Thermowood
The following will present some useful advice and recommendations on the use of Lunawood. The purpose of this information is to help you to enjoy all the many benefits of using Lunawood Thermowood.
- Durability
Durability
LunaThermo-D belonging to durability class 2 has a projected service life of 30+ years when resistance to decay is considered (BRE). This applies to exterior cladding and decking applications. However the decking material is subject to surface-wear and loading which decreases the reasonable expected service life to 15–20 years. Thermowood is not recommended for use in direct contact with the ground.
- Equilibrium moisture content
Equilibrium moisture content
After the thermal process the equilibrium moisture content of Lunawood is 4–7%. In outdoor use (+20 Celsius, RH 85%) the equilibrium moisture content of LunaThermo-D pine stabilizes at 10% (EN 13183).
- Fastening by hand
Fastening by hand
Thermal processing makes wood slightly more susceptible to splitting. For this reason we recommend using self-tapping screws with a coarse thread or predrilled holes before fixing. The screws should be stainless steel and suitable for fastening wood. When using nails, they should not be closer than 7 cm from the end of the board or use pre-drilled nail holes. When using a conventional hammer, it is advisable to use a nail punch for the last 2–3 mm. Tongue and grooved boards should be fastened using pre-drilled holes from over the top of the tongue so that the screw or thin nail is driven in at an angle of less than 40 degrees. In the installation the heart side should always be the weather-exposed face.
- Fastening – Gluing
Fastening – Gluing
Gluing of Lunawood Thermowood is possible. However the gluing and compression time may be 4–6 times longer compared to untreated wood. Always follow the glue manufacturers’ guidelines.
- Installation – Decking
Installation – Decking
When building a deck it is always recommended to keep the deck off the ground to improve the air circulation below. The gap between the boards should be at least 6 mm to secure air ventilation and promote drainage of rainwater. Any gap next to an adjoining wall should be at least 6 mm and the gap between two board ends should be 1-2 mm to allow for any movement.
- Installation – Cladding
Installation – Cladding
In claddings, ventilation should be provided behind the boards (min. 40 mm). Please also note that there should be at least 30 cm between the ground and lower edge of the cladding. Screws or nails can be used for mounting. They need to be stainless steel.
- Installation – Milling
Installation – Milling
If Lunawood is intended to be milled, the blades should be in good and sharp condition to ensure good end results. The light, fine-grained saw dust is readily extracted with no adhesion to the cutter blades. Furthermore, due to the fine-grained sawdust, it is recommended to use a respiratory protection mask.
- Installation – Planing
Installation – Planing
Lunawood can be planed with a normal planer or planing machine. Planing Lunawood gives its surface a superior quality. The planing machine should be adjusted for hardwood species and the planing speed is less than with untreated similar wood. The raw material after thermal processing may be convex and therefore the feed rollers should be adjusted accordingly to prevent the boards from splitting.
- Installation – Sanding
Installation – Sanding
Sanding may not be needed with Lunawood at all because the quality of the surface is so good after being planed and milled. However, if Lunawood is sanded the resin free material keeps your sandpaper in good shape for a longer period of time.
- Installation – Sawing
Installation – Sawing
Sawing Lunawood is just as easy as sawing ordinary wood. However, the blade should be a sharp, fine-toothed saw and the wood should be fed slowly.
- Surface treatment – Outdoors
Surface treatment – Outdoors
Lunawood Thermowood should be surface treated before installation or immediately after installation if the beautiful brown color is to be retained. Treating the boards with tinted or pigmented wood oil, wax, wood-protecting stain, varnish or paint – which contains a UV-filter – can retain the surface color. The surface treatment can be applied either before or immediately after installation using only a thin coat. Any excess should be wiped off. However, one should always follow the manufacturer’s recommended guidelines.
- Surface treatment – Indoors
Surface treatment – Indoors
Normal paints, wood oils, waxes, and varnishes can be used indoors. For saunas, paraffin oil can be used in addition to a surface treatment agent to emphasize the color of Thermowood and protect it from impurities.
- The use of Lunawood without surface treatment
The use of Lunawood without surface treatment
Lunawood recommends surface treatment for Thermowood always when the end use application is exposed to weather. With all wood materials it is typical that after time fine cracks and splinters appear on the surface. Though Thermowood has lower potential for these defects, they still exist and coating protects the wood from them.
- Strength
Strength
Bending strength properties are somewhat reduced with heat treatment class LunaThermo-D. Therefore it is not recommended to use Lunawood in load bearing structures without additional support; or without strength calculations being carried out on a case-by-case basis.
