FAQ - What does the THOR Torrefaction process involve?
THOR Torrefied Wood™ is a natural heat treated solid wood cladding product that has a 60 year warranty against decay. Torrefaction is a 100% natural process that involves prolonged, high temperature treatment of wood reaching 200° C making it amazingly durable and stable.
Using proven Scandanavian heat treatment technology, Thor™ cladding is manufactured in Canada by Maibec®, one of North America’s leading manufacturers of factory finished timber cladding products. Silva Timber is the exclusive distributor of Thor™ cladding in the UK.
THOR Torrefied Wood™ cladding is available in a rebated bevel profile with a 25mm thick butt end. This tried and tested cladding profile is installed horizontally and creates a bold shadow-line where the boards overlap. Rebated bevel is quick and easy to install; the boards overlap neatly for an impeccable finish with no visible fasteners. Matching trim boards are also available.
The Key Benefits of Thermally Modified Timber Cladding:
Increased resistance to decay
Intensive heat treatment changes the chemical and structural composition of the wood and removes the natural food sources which significantly improve its resistance to fungal decay. THOR Torrefied Wood™ cladding does not require any further chemical protection.
Increased dimensional stability
The torrefaction process lowers the equilibrium moisture content of the wood meaning that the chance of it warping, shrinking or expanding will be significantly reduced.
Excellent water-repellence and weather protection
The change in the molecular structure as a result of the heat treatment process reduces the permeability of the wood. Even without a finish torrefied wood has excellent weather resistance.
Environmentally friendly
The 100% natural torrefaction process modifies the molecular structure of the wood to increase its durability and therefore extend its service life. The process also improves the woods thermal insulating properties. Wood torrefaction uses no harmful chemicals and water-based stains have low harmful volatile organic compound (voc) emissions.
Aesthetically appealing
Intensive heat treatment gives the wood a rich natural amber colour.
The Torrefaction Process
The torrefaction heat treatment process has been developed and patented by VTT Technical Research Centre of Finland. Here’s how it works:
Phase 1 - Temperature increase and high-temperature drying
Using heat and steam, the kiln temperature is raised rapidly to a level of around 100ºC. Thereafter, the temperature is increased steadily to 130ºC, during which time the high-temperature drying takes place and the moisture content in the wood decreases to nearly zero.
Phase 2 - Heat treatment
Once high-temperature drying has taken place, the temperature inside the kiln is increased to between 185ºC and 215ºC. When the target level has been reached, the temperature remains constant for 2-3 hours depending on the end-use application.
Phase 3 - Cooling and moisture conditioning
The final stage is to lower the temperature by using water spray systems; when the temperature has reached 80-90ºC, re-moisturising takes place to bring the wood moisture content to a useable level, 4-7%.
How does torrefaction affect the molecular structure of wood?
