The Natural Greying of Lunawood Thermowood

The thermal modification process gives Lunawood a distinctive brown color and a natural weather resistance for all climatic conditions without harmful chemicals. However, the brown color will start to fade over time due to the effect of the weather conditions. As it does, the wood will begin to turn grey gradually. The color can vary from a platinum silver to a lighter rustic tone depending on the construction and the climate conditions. This natural process allows architects and builders to achieve a beautiful, weathered façade with minimal maintenance and low lifecycle costs.

The thermal modification alone gives a freedom not to do a separate surface treatment  or a maintenance for the wood,  this rule applies when the installation is done correctly, according to the official installation instructions.  With these examples, we want to show how graying looks like in practice with its many different variations.

Graying of Thermowood requires sufficient air circulation

At all stages of the construction process, the manufacturer’s installation instructions should be followed to achieve a long-lasting and sustainable end-result. The functionality of Lunawood products is guaranteed by sufficient air circulation behind the facade and terrace boards. This is done with a ventilation gap and a sufficient distance from the ground. Thanks to sufficient air circulation, the humidity does not weaken the graying and the exterior grey cladding lasts longer.

Grey cladding with low-maintenance – even without any surface treatment

Thermal modification makes Lunawood exceptionally durable, and correct installation allows the timber to be used without any surface treatment. This makes Lunawood an especially sustainable choice: no regular maintenance with oils, tints or paints is required, and no preparatory work is needed. As a result, resources are saved throughout the product’s lifecycle. When left untreated, Lunawood cladding weathers naturally and evenly to a soft silver-grey over time.

If the original warm brown tone is preferred, Lunawood can also be maintained to retain its appearance. Applying a tinted or pigmented wood oil, wax, wood-protecting stain, varnish or paint containing UV protection helps preserve the surface colour.

Gradually towards the silver gray wood surface

When left untreated, Lunawood cladding ages naturally, transitioning from its original brown tone to a soft silver-grey surface over time. This gradual colour change is a defining visual characteristic of Lunawood Thermowood and part of its natural expression.

The greying happens due to physical and biological processes that take place within the top layer of the wood, and is driven by exposure to sunlight and moisture. UV radiation gradually alters the surface of the wood, while environmental factors such as dirt particles and natural deposits contribute to the formation of a silver-grey patina. As a natural material, Lunawood weathers individually, resulting in subtle variation between boards and giving façades a lively, authentic appearance that blends harmoniously with its surroundings.

How fast does Thermowood turn gray?

The duration of the weathering — or greying — process can vary widely. For example, it depends on the application: whether it’s used on a façade or decking, and how much the surface is exposed to UV radiation. Wood decking turns grey faster than cladding because it receives more direct sunlight and moisture. During the summer months, the decking typically reaches a grey tone within just a few months. Shading from surrounding trees, structures, or solar shades also influences how quickly graying occurs. The process happens gradually and can take up to few years for the façade, but the end result is well worth the wait.

Key Takeaways: Natural Greying of Lunawood Thermowood

• Lunawood Thermowood greys naturally over time without chemical treatments due to UV radiation and moisture.
• The silver-grey patina develops gradually, and the end result varies by climate, exposure and application.
• Excellent technical performance of Lunawood — including durability and dimensional stability — remains unchanged when naturally weathered.
• No surface treatment or regular maintenance is required when the product is installed correctly.
• Proper ventilation and correct installation of the cladding ensure long-lasting performance and appearance.