Microclimate and Mould Growth Potential of Air Cavities in Ventilated Wooden Façade and Roof Systems—Case Studies from Norway

Abstract

Harsh climatic conditions in the Nordic countries are being worsened by climate change, which increases the moisture load on building façades. New types of defects are being observed in air cavities in well-designed and well-built wooden façades and roofs. More knowledge is required on the microclimatic conditions in air cavities and roofs, and their implications for organic growth and biological deterioration. The present study collects and presents sensor data from three buildings in Norway. Collected air temperature, air humidity, and wood moisture data are compared to mould growth criteria found in scientific literature, building physics software, and national and international standards. The data shows great differences in air cavity microclimates between the case buildings and between different sensor positions within the instrumented air cavities. Air cavity temperatures are found to be lower than exterior temperatures for a substantial portion of the time. For tall buildings, the vertical positioning of a sensor influences the data more than the orientation of the façade. All three buildings feature monitoring positions with both acceptable and critically high levels of moisture to indicate mould risk. There is great variation in the estimated risk of mould growth according to the different criteria. The study indicates that the coastal climate in the south-west of Norway presents a challenge in terms of resilient building design to avoid mould growth in the ventilated air cavity.

Risk of Fungal Growth in Nearly Zero-Energy Buildings (nZEB)

“…Excessive ventilation, on the other hand, can cool the inside layer of the cladding, causing condensation and, thus, mold formation. The air cavities showed higher annual temperature amplitudes for long periods than the external air, which occurs to a greater extent for the ZEB Laboratory [35]. Furthermore, poorly designed or faulty installed wind and air barriers in external walls can lead to water condensation in the construction [34].…”

“…New buildings may face problems of built-in moisture in the envelope due to construction techniques that use materials with high moisture content, water damage incidents, or poorly executed construction details, combined with the lack of regulations and control [8,34]. Ingebretsen et al [35] analyzed the microclimatic conditions in air cavities and roofs by collecting wood moisture, air temperature, and humidity data for three case buildings in Norway. Even though significant differences are registered between case buildings and the position of the sensors, there was a risk for mold formation in all analyzed buildings.…”

“…Even though significant differences are registered between case buildings and the position of the sensors, there was a risk for mold formation in all analyzed buildings. In particular, the authors [35] highlight the critical issues related to ventilated cavities. Insufficient cavity ventilation can prevent structures from drying out, increasing humidity levels and leading to mold growth.…”

Damage Assessment of Pine Wood Facades in the First Years of Service for Sustainable Maintenance

“…For instance, the moisture content of wood elements may influence the results of ultrasonic waves, sclerometric, and resistance tests [22,25,26]. This could be especially crucial in areas with climate changes with moisture increase [27,28] and in areas with harsh conditions, such as near the sea where the moisture level is extremely high.…”

Innovative, Modular Building Facades - as a Tool to Counteract The Effects of and to Prevent Climate Change

“…Modern material technologies based on the ability of plastics to respond to changes in the environment; use of dynamic, multifunctional façades that integrate the building's external and internal environments and use of smart tools make it possible to develop façade systems for future buildings, often mimicking biological processes using heuristic methods and parametric design [21,5]. Searching for modern materials and design techniques, subjecting existing engineering solutions to analyses, conceptualising, looking for new ideas, prototyping and implementing optimal methods are integral to the creation of new inventions that are an answer to the problems of the modern world [1,14].…”