By Dineo Phoshoko
Thermally modified wood (thermory wood) is a beautiful, sustainable timber material produced using chemical-free heat treatment. Timber iQ looks at two projects where thermory wood was used.
Thermal modification enhances the wood’s durability and stability properties, thereby expanding the range of applications in which the wood can be used, particularly outdoors. The most popular external uses include decking, screening and façade cladding. The attractive appearance, removal of resins and formaldehydes and zero chemical content make this timber very suitable for both interior and exterior applications.
Case study 1: Tswalu Reserve Kalahari Motse Camp refurbishment
The ash was specifically selected for its durability and thermal stability, due to the extreme temperatures and very low humidity conditions experienced year-round in the region. Credit: Savile Row
A major part of the work done on the project was the decking. For this, 150mm of thermory ash decking was used for decking on the main building. Credit: Savile Row
The Tswalu Kalahari Reserve is a private game reserve situated in South Africa’s Northern Cape province. It is also South Africa’s largest private game reserve, covering an area of over 114 000 hectares. There are nine suites at the Motse Lodge, and the private Tarkuni has five suites.
In September 2018 Savile Row was commissioned by Tswalu to redesign Motse Camp which required a much-needed upgrade. The nine suites, public areas, spa, gym and back-of-house spaces were extensively altered and refurbished to what is now a luxury lodge standard. The project was undertaken on November 2018 and was handed over on 13 June 2019.
A major part of the work done on the project was the decking. For this, 150mm of thermory ash decking was used for decking on the main building. For the individual legae and spa front decks, thermory ash decking with a width of 95mm was used. The ash was specifically selected for its durability and thermal stability, due to the extreme temperatures and very low humidity conditions experienced year-round in the region. Both decking widths were fixed by means of clips along the side so as to maintain a clean timber look.
The budget was increased for the decking portion of the project in order to accommodate the thermory product rates, as it was unanimously agreed by the project team and client that the specification was indeed best suited for the harsh climatic environment. Having a natural timber finish was essential to maintaining the overall high end yet environmentally appropriate finish for the lodge.
The project timeline was most probably the biggest challenge encountered by the building team for this project. The five-month shut-down period was predetermined well in advance of the actual confirmation of the scope of the project. What was initially planned as a soft refurbishment by the lodge, became a more substantial remodelling of interior and exterior spaces when the Savile Row team was appointed. This placed extreme pressure on the building team to ready the site, and subsequently made the decking preparation work and installation very difficult.
The remoteness of the site was also a major contributor to the complexity of the project with a large tented contractor camp being required to accommodate the large team required to execute the project within the condensed timeline.
Despite the challenges experienced in the execution of this project, the cohesive way in which the client, building and design teams worked together to ensure the best possible outcome of the project was incredible. After six months of dedication and hard work, the project was handed over to a satisfied client who also endorsed the use of high-quality finishes throughout the lodge.
Case study 2: Tuluei Lodge – Khwai Private Game Reserve
The Tuluei Lodge client was very pleased with beautiful finishes created by the thermory pine supplied by renewable sources. Credit: Tegs Timbers
The second project featured where thermory wood was used is the Khwai Private Game Reserve in Botswana’s Okavango Delta. The reserve has various lodges and camps including the Tuluei Lodge, where the project took place.
Different variations of thermory timber were used during the Tuluei Lodge project. For the decking, flooring and panelling, thermory pine was used. Credit: Tegs Timbers
The Tuluei Lodge client was very pleased with beautiful finishes created by the thermory pine supplied by renewable sources. Credit: Tegs Timbers
Tuludi Camp is set in the extensive Khwai Private Reserve, some 200 000 hectares of pristine wilderness. Accommodation is 7 tree-house style rooms, set under shady leadwood trees. The rooms (60m²) all have high, pitched canvas roofs in the bedroom area, thus making a light and airy space. The tree houses all boast separate dressing and sleeping areas, an en suite bathroom, indoor and outdoor showers, and bathtubs. The tree houses are all connected by wooden boardwalks which wind through the leadwood trees, and are, in turn, connected to the main area.
During the project, extensive work was done on the panelling, decking and flooring for the tented bush lodge. Different variations of thermory timber were used during the project. For the decking, flooring and panelling, thermory pine was used. Structural treated pine was used for the supporting structure of the lodge.
One of the major challenges experienced during this project includes the team working under extreme weather conditions. Temperatures in the area reached highs of up to 40°C, which made working conditions close to unbearable. Another significant challenge was the remoteness of the project site. Fortunately, the client assisted with logistics arrangements by transporting the project’s material and supplies for the project.
In the end, everything came together with the project being completed in June 2019. The client was very pleased with beautiful finishes created by the thermory pine supplied by renewable sources. The installers were also very impressed with the ease of working with thermory pine.
Thermory wood: Alternative wood treatment methodThe method of treating wood with high temperature to make it more durable was discovered centuries ago. Studies on the possible benefits of thermal modification of wood began as early as the 1930s in Europe and US. Decades later, the Technical Research Institute of Finland became interested in the idea and as a result, the technique was developed, innovated and enhanced into the 21st century and for the past 20 years, world-renowned architects and designers have relied on thermally modified wood to provide the ultimate expression of excellence for their exterior and interior projects. With unsurpassed stability, performance and rot resistance, combined with its captivating beauty and elegance, thermally modified wood provides a sustainable alternative to timbers sourced from endangered tropical rainforests. The process of transforming the timber is totally chemical free. Every fibre of the wood is modified. In special kilns, lumber is slowly heated to approximately 215°, while controlling the moisture content through means of steam. Under the influence of high temperature, the chemical and physical properties of wood undergoes permanent change. The end phase of the process is cooling down and re-moisturising to bring the timber to the normal equilibrium moisture content of 5-7%, which is suitable for machining, installing and using. Thermo-treatment changes wood’s chemical composition. The depolymerisation of lignin under influence of high temperature reduces the length of chains of cellulose. In other words, most of the wood sugars are cooked out, eliminating the food source for bacteria and insects. The side effect of this process is change of the colour of the wood through the entire thickness of each piece. The colour becomes more sated and homogeneous on all sections and the grain of the wood effectively comes to light. The effect of valuable breeds of wood is reached. However, the main effect is increase of biological durability. Thermo-treated wood does not require any chemical protection from rot. The high heat eliminates conditions for occurrence and duplications of a fungus or microorganisms. Bio-damaging agents are destroyed. According to tests thermally modified hardwoods (such as American and European ash) gain durability class 1 (over 25 years’ service life outdoors), and thermally modified softwoods (such as Scots Pine or Radiata) have class 2, which means 15-25 years of carefree lifespan outdoors. Being equal to tropical timbers in durability, thermally modified wood considerably outplays them in dimensional stability. As the result of thermal modification, cellular structure of the wood is altered to reduce movement related to moisture absorption. Equilibrium moisture content of thermory wood is reduced by 50% compared to untreated wood, and this difference remains after years of exposure, therefore we can say, equilibrium moisture content of thermory wood is permanently reduced. Swelling and shrinkage of wood strongly depends on the absorption qualities of the wood, and in thermory wood it is reduced 5-10 times for hardwoods and 2-3 times for softwoods. Thanks to its high resistance to heat and moisture, thermory is a perfect match for the applications, where wood materials would normally fail – around pool areas, at waterfronts, in rooms with high humidity. Decreased equilibrium moisture content reduces thermal conductivity. A thermory wooden deck will always be much cooler in hot summer days than any other decks. Resins are almost fully removed, which makes the timber very suitable for decorative coatings. Depending on the type of coating, it would last 5-15 years without the look changing too much, thanks to the rot resistance and stability of the wood under it. Thanks to thermal modification, architects and builders all over the world have been exposed to a different way of using timber in construction. Thermally modified wood has proven its worth in different climatic conditions all over the world. |
