Nano TiO2 modified photocatalytic wood in urban architecture

The use of timber has a long tradition in Norwegian building design but has had its limitations in urban architecture due to technical deficiencies regarding biodegradation and fire safety. During the last years, however, Norwegian architects have been showing a strong interest to use wood as façade material for public buildings, such as kindergartens or schools, and in tall residential buildings. This development is mainly driven by two factors: firstly, the political will to increase the use of timber as construction material especially in urban areas due to the environmental credentials of wood. Secondly, the real estate prices in larger Norwegian cities are among the highest in the world, consequently, more multi-story buildings are built. Increasing the competitiveness of wood by overcoming its technical weaknesses is an important step to successfully implement wood as the preferred choice of façade material in urban architecture. In this regard, it is crucial to address a) color stability and b) fire safety. The project aims at developing a wood modification method based on nano titanium dioxide (TiO2) and siloxanes. The applied TiO2 is photocatalytically active and will produce under the influence of daylight highly reactive radicals. The photocatalysis will suppress the growth of microorganisms and result in clean naturally weathered silvergrey facades. The treatment with siloxanes will provide water-protection to the wood and therewith keep the moisture levels lower than favored by mould or decay fungi, assisting the photocatalysis during periods without UV light. Both, the TiO2 and the siloxanes, will covalently and therewith permanently bind to the wooden substrate, resulting in a durable product and adding the benefit of an enhanced flame retardance. In addition, the nano titanium dioxide (TiO2) and siloxanes will combat air pollution. In summary, this innovation has great potential to significantly extend the use of wood in urban architecture.