Tall Timber and Fire Safety: Mjøstårnet, Brumunddal
Session: G: Façade Engineering Award & Life Safety Design Award
Leif Tore Isaksen
Fire & Risk Engineer, Sweco Structures AB
Mjøstårnet with a height of 85.4 meters was previously named the worlds tallest timber building in the world (May 2019), and recently surpassed by The Ascent in Milwaukee in July 2022 (86.6 meters). The building is located in Brumunddal, Norway. The main fire risk in this building is the height, combined with wooden materials in the load bearing system, and wooden facades. Sweco developed calculation methods for modeling a full duration of a fire in wooden constructions. When the mass of surface contributing to the fire is small enough, it can be verified that charring stops. This is not the result one finds from Eurocodes, using the constant charring rates. Using a developed process to verify whether the fire will stop, or continue charring, it could be determined whether a reduction to the area of wooden surfaces contributes to fire. This makes it possible to design a building with combustible materials which resist a burnout.
The fire testing was conducted by Rise Fire and research AS (independent organization) who are Norway's fire technical competence center. Together with their Swedish division, RISE Safety and Transport - Fire Research in Borås are one of the largest research organization on fire. To ensure robustness of the design at Mjøstårnet, Sweco provided numerous guidelines for fire protection and safety.
Wood is one of the most sustainable and environmentally favorable construction materials available. This is due to its absorption of carbon dioxide while growing, is a renewable material, lasts a long time, can be recycled and reused, is great at retaining heat, its waste is 100 percent biodegradable, and it has a positive effect on your physical and mental health. Besides its many other benefits, timber as a construction material is especially suitable due to its low weight and ample prefabrication possibilities and can be designed to meet fire and risk safety standards.