Thermally modified wood has become a go-to for architects and builders who want real wood on a facade without the upkeep worries. Here is what it is, where it works best, and what to plan for.
What is thermally modified wood?
Thermal modification changes wood using heat and steam in a controlled process. Lunawood, the Finnish producer we partner with, modifies slow-grown Nordic softwood using heat and steam only, with no chemicals at any stage.
The process removes resin from the wood and leaves it with an exceptionally low moisture content, according to Lunawood. The change runs through the whole board, not just the surface.
The benefits
- Stability. Thermal modification improves dimensional stability, so boards move less with changes in humidity.
- Durability. The process increases resistance to decay. Lunawood gives an expected service life for exterior cladding of up to 30 years.
- No chemicals. Heat and steam do the work, with nothing added to the wood.
- Carbon storage. Lunawood’s Environmental Product Declaration reports that its Nordic products store up to five times more carbon than is released during their production.
- Resin-free. With the resin removed, the wood suits interiors and even saunas.
Where to use it
Lunawood describes its products for facades, landscaping, interiors and saunas. In the Crisp program, Lunawood is used for:
- Exterior cladding
- Exterior soffits and ceilings
- Interior walls and ceilings
What to know before you specify
- It weathers. Left uncoated, thermally modified wood greys to a silver patina. Lunawood notes this is purely visual and does not affect durability or stability.
- Hairline cracks can appear. Weathering can cause small surface cracks, which Lunawood says do not affect the product’s durability.
- Skip linseed oil. Lunawood advises against linseed oil on its products, as it can promote fungal growth.
- Follow the installation guide. Ventilation, clearances and fixing matter. See the Lunawood requirements in our installation guide.
Lunawood at Crisp
Crisp is a Lunawood Partner. Our program includes Lunawood Fineline in seven colours and Lunawood Triple, a 3D cladding profile, in four colours. Every board is sealed on all six faces and delivered complete, with a gallon of touch-up stain in every order.
View Lunawood colours · Order samples
Sources: Lunawood Collection 2026 North America; Lunawood Environmental Product Declaration; Lunawood Installation Guide for Facades (11/2025); Lunawood ThermoWood Cladding Maintenance and Care Guide (2026).