Tall Timber Facades- Identification of Cost-effective and Resilient Envelopes for Wood Constructions

The interest for the use of timber in urban construction is increasing steadily over time. In order to further develop the marked timber facades play an important role, since they have to be reliable, durable, and functional and ideally prefabricated offsite. The focus of this project is the analysis and understanding of the moisture interaction of timber based facades with special emphasis to moisture safety. In particular tall timber façade structures are exposed to moisture ingress due to higher wind loads and consequently larger amounts of wind driving rain. There, it is a challenge to protect the timber material from excessive moisture accumulation, and therefore provide the boundary condition for the facades functionality without damage over the lifetime of the buildings. Furthermore, it is much more difficult to access the facades of tall buildings for inspection and repair. The risk of moisture damages in buildings is to a large extend underestimated in the planning, design and quality assurance. Especially for timber buildings a high frequency of moisture damages is a large risk when considering the competition to other building materials. Therefore, a safety concept that is comparable to the safety concept for mechanical calculations will be developed within this project in order to design the facades and safely prohibit moisture damage. The design decisions that have to be supported by the safety concept are related to the choice of material, design alternatives and geometries. The safety concept will be implemented by a risk analysis tool (“RIFA”) that can be utilised also by engineers without particular expert knowledge about risk assessment. The methodology will also be used to establish best praxis standard solutions for different applications of timber based materials in facades. This will be done in close collaboration with the projects industry partners.

The interest for the use of wood in urban buildings is growing. In order to preserve and develop the chances on the market, wood construction must be reliable, durable, flexible and strong in off-site production/prefabrication. To fulfil most of these req uirements a prolonged moisture-safety is necessary, which is in the focus of this project. With an increasing height of timber buildings the challenge is increasing to provide dry conditions for the expected lifetime of the building. Tall buildings are pa rticularly exposed to high wind pressures combined with driving rain (WDR). Additionally, large buildings require longer times of construction in which the structural elements are especially exposed to moisture. Last but not least inspection, maintenance and repair possibilities are limited in high rise structures. Compared to the every time aware fire safety and static questions, the risk of moisture damages is today dramatically underestimated in planning and building processes and in quality management . This may lead to an image risk for timber buildings, if damages will increase in future. Therefore "safety concepts", similar to safety concepts in static calculations, are necessary to improve construction and prevent damage by moisture. The variety o f options and configurations of the building envelope and the diversity of the effects of the external and the internal climate need assistance in the selection of material and design options. For this, based on risk analysis methods, a risk facade tool ( RIFA tool) will be developed that will enable planner and producer to make substantiated decisions for specific constructions. In addition, the tool is used to create a guideline for Tall Timber Facades - envelope constructions, which are developed togeth er with industry partners for practical application.