HEKLA SAUNAS · POSH SPAS GUIDE

Why HEKLA uses Thermo-Aspen.

The timber inside a sauna repeatedly moves between heat, cooling and moisture. HEKLA uses thermally modified woods because stability and comfort matter as much as appearance.

Baked with heat and steam

Thermo-Aspen starts as natural aspen. It is thermally modified at high temperature in a controlled low-oxygen process using heat and steam rather than chemical preservatives. The treatment changes the timber through its full thickness rather than applying a surface stain.

Why that matters in a sauna

Dimensional stability

Thermal modification reduces the amount of moisture the wood takes up. That means less expansion and contraction through repeated heating and cooling cycles, helping panels and benches hold their shape.

Comfort against skin

Aspen has relatively low thermal conductivity and a smooth, low-resin surface, which makes it a natural choice for benches and backrests that contact bare skin.

Colour and finish

The process deepens pale aspen into a warm caramel/brown tone throughout the board. Scratches therefore do not reveal a completely different surface colour in the way a dark surface stain can.

Low aroma

Unlike strongly scented timbers such as cedar, aspen has a mild neutral smell. That suits customers who want the sauna aroma to come from heat, steam or their chosen oils rather than the timber itself.

Thermo-spruce outdoors

HEKLA also uses thermally modified spruce, particularly in Barrel structures and outdoor framing. It applies the same principle — greater stability and moisture resistance for material exposed to the changing British climate.