Partnerskapets innovasjoner

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Verktøy og veiledere for klimatilpasning

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Pilotprosjekter

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Spesialister i klimatilpasning

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Hygrothermal Simulation of Interior Insulated Brick Wall - Perspectives on Uncertainty and Sensitivity

Energy retrofit of existing masonry buildings has become attractive to meet demands for reduction in energy consumption. Retrofit may, however, introduce moisture risk that needs to be assessed. Hygrothermal simulation analysis is often conducted in this respect. Nevertheless, hygrothermal simulation of interior insulated bare brick masonry exposed to driving rain can be challenging due to the many aspects involved that determine heat- and moisture-transport behavior, and which should be addressed by an applied model. The present study highlights uncertainty encountered when establishing a hygrothermal simulation model. Furthermore, different modeling choices or simplifications are studied to determine impact on results. As a check of realism, results of 2D simulations are compared to results of a previous laboratory experiment of masonry wall segments subjected to severe rain wetting and subsequent drying. Rain absorption is modeled conservatively, attempting simulation results to envelope experiment results. Conservative results were not achieved for a relative humidity sensor placed on the masonry interior without inclusion of a “leaky” mortar joint. Simultaneously, the conservative approach underestimated drying experienced by the relative humidity sensor in two of three experiment wall segments. Regarding beam-end moisture content, the modeling approach conservatively enveloped experiment results in 3D but not in 2D.publishedVersio

Determining the Vapour Resistance of Breather Membrane Adhesive Joints

Due to increasingly stringent requirements, tapes and adhesive joints are a commonly used method to ensure tightness and energy efficiency in modern building envelopes. Previous studies have researched and tested properties such as the strength and tightness of adhesive joints. So far, water vapour resistance has been neglected. This article aims to determine the vapour resistance and shed light on possible consequences of vapour-tight adhesive joints in breather membranes used in roof assemblies. Laboratory measurements of vapour resistance were conducted according to NS-EN ISO 12572:2016, known as the cup method. Eleven products of breather membranes were tested. Results from the laboratory measurements were used to evaluate the impact of vapour-resistant adhesive joints related to the drying of built-in moisture. The simulation programs WUFI 2D and WUFI Mould Index VTT were used to model scenarios for moisture transport and risk for mould growth. Laboratory results show that the vapour resistance of breather membrane adhesive joints varies from 1.1 to 32 m in sd-value. Three of the tested products have a vapour resistance larger than 10 m, while four products have an sd-value less than 2.0 m. The sd-values of the membranes themselves range between 0.027 and 0.20 m. All tested adhesive joints are considerably more vapour tight than the Norwegian recommended value for breather membranes (<0.5 m). However, the mould growth analysis shows that the risk of mould growth is low in most practical cases, except when using adhesive joints with the highest vapour resistance in roofs assembled during autumn.publishedVersio

Montana Kaimin, March 5, 1993

Student newspaper of the University of Montana, Missoula.https://scholarworks.umt.edu/studentnewspaper/9619/thumbnail.jp

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

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.publishedVersio

Vapour resistance of wind barrier tape: Laboratory measurements and hygrothermal performance implications

In the building industry, the interest into adhesive tape to achieve a more tight and robust building envelope has increased rapidly in recent years. With an increasing demand for energy efficiency in buildings, national building authorities are strengthening building requirements to mitigate and adapt to future climate impacts. This paper studies the water vapour permeability of adhesive tape for building purposes. A water vapour permeable wind barrier is essential to enable drying of the external side of the building envelope. Laboratory measurements have been conducted to evaluate how the drying conditions of the wind barrier layer are affected by the use of wind barrier tape. The results show that all the wind barrier tapes tested can be defined as significantly more vapour tight than the wind barrier itself. The wind barrier used as reference was found to have an sd-value of 0.03 m while tape ranged between 1.1 and 9.24 m. To ensure adequate drying and minimize the risk of moisture damages, the wind barrier layer should be vapour open. In an investigated construction project, the amount of tape constitutes 13% of the area of the building’s wind barrier. Further simulations need to be conducted to accurately determine the drying conditions and the following consequences.publishedVersio