The Experts below are selected from a list of 7530 Experts worldwide ranked by ideXlab platform
Pernilla Johansson - One of the best experts on this subject based on the ideXlab platform.
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Predicting Mould Growth on building materials- the PJ-model
'EDP Sciences', 2020Co-Authors: Pernilla Johansson, Thomas SvenssonAbstract:Mould Growth in buildings is a complex process, affected by moisture and temperature, the properties of the building material as well as characteristics of the Mould fungi. The complexity poses challenges when assessing the risk of Mould Growth in buildings. Mathematical models are often used to predict whether Mould will grow in a part of building with expected RH and temperature conditions. The models can be described as static or dynamic. In a previous round-robin study, comparing results from models with observations from field studies, the outcome of the dynamic models evaluated depended on the user of the model. Also, the models often underestimated the risk of Mould Growth. A better agreement was found for static models, especially for the PJ-model. It is a part of a standardised technical specification (SIS-TS 41:2014) and has not previously been described as a model. The critical moisture level (RHcrit), determined by tests according to the method, is used as input. Thus, the subjectivity in the predictions is reduced. RHcrit is the lowest moisture level at which Mould can grow and is temperature-dependent. The PJ-model provides an equation to estimate RHcrit at typical temperatures in buildings. If RH in a building section exceeds the limit values at the current temperature, Growth is predicted. This paper describes the PJ-model version 1.0, some of the extensive work performed during the development and validation of the model and the ongoing work to refine the model to include considering transient conditions and measurement uncertainties
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Threshold values for Mould Growth: Critical moisture level of 21 different building materials
'EDP Sciences', 2020Co-Authors: Pernilla Johansson, Gunilla Bok, Lukas Lång, Carl-magnus CapenerAbstract:The susceptibility for Mould Growth varies among different building materials. One way to describe the susceptibility is the lowest RH at which Mould can grow on a specific material, the critical moisture level (RHcrit). Determining RHcrit for materials provide the basis for material choice in designs where moisture and temperature conditions are known. In this study, RHcrit of 21different products were determined according to SIS-TS 41:2014/SPMet 4927. This test method is developed based on the results of a variety of laboratory studies and validated by field studies. Test specimens were inoculated with a suspension containing spores from six different Mould fungi and were then incubated in moisture chambers at four levels of RH at 22 °C. After 12 weeks specimens were analysed for Mould Growth. RHcrit was determined based on the lowest RH at which Mould grew on the specimens. RHcrit varied among different products, even between product belonging to a similar group of material, for example, calcium silicate boards or gypsum boards. The results show, and confirm, previous findings that it is not possible to estimate RHcrit for a specific product based on material group. Instead, each product must be tested
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an innovative test method for evaluating the critical moisture level for Mould Growth on building materials
Building and Environment, 2014Co-Authors: Pernilla Johansson, Annika Ekstrandtobin, Gunilla BokAbstract:Abstract The critical moisture level (RH crit ) for Mould Growth, that is the lowest relative humidity (RH) at which Mould can grow, varies between different materials. The factors that most affect Mould Growth, RH and temperature, also vary in different parts of a building. One way of preventing the Growth of Mould in buildings is therefore to choose building materials that can withstand the expected conditions, materials that have a higher critical moisture level than the highest expected RH. It is thus crucial that data are available to allow the correct choice of materials to be made. In this paper an innovative laboratory test method for determining the RH crit of a material is described and discussed. The results from testing of a material according to the method gives information to make the correct choices. The method is developed based on the results of a variety of laboratory studies and has been validated by field studies.
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the effect of cyclic moisture and temperature on Mould Growth on wood compared to steady state conditions
Building and Environment, 2013Co-Authors: Pernilla Johansson, Annika EkstrandtobinAbstract:Abstract Moisture and temperature are the two key environmental parameters that determine the possibility of Mould Growth on building materials. The time that the material is exposed to these elements is also crucial. The natural environmental conditions of relative humidity and temperature are seldom constant over prolonged time periods in a building. Instead, they vary over time, with fungi encountering both favourable and unfavourable conditions; such variable conditions affect Mould Growth. This paper reports findings from a laboratory study in which Mould Growth at alternating RH (between 90% and 60%) or temperature conditions (between 22 °C and 5 °C) was studied and compared to steady state conditions. Fluctuating RH led to slower Mould Growth, and when the period of unfavourable/favourable conditions was longer (1 week), Growth was affected more than if the duration of these conditions was short (12 h). When alternating the temperature weekly between 22 °C and 5 °C, with a mean of 13 °C, the Mould Growth rate was lower compared to when the temperature was held constant at 22 °C. The Mould Growth under fluctuating temperature conditions was comparable to when the temperature was kept constant at 10 °C.
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validation of critical moisture conditions for Mould Growth on building materials
Building and Environment, 2013Co-Authors: Pernilla Johansson, Thomas Svensson, Annika EkstrandtobinAbstract:Abstract Materials that are stored or used in damp conditions may be subject to Mould Growth. However, all materials are not equally susceptible; for each specific material, there is a critical moisture level for Mould Growth. If this is exceeded, there is a risk that Mould fungi will develop on the material. This level can be determined in accelerated laboratory tests, at constant temperatures and relative humidity (RH) favourable to Mould Growth. Within a building however, these parameters are expected to vary from one part of the construction to another, and are seldom constant; there is fluctuation in temperature and RH due to seasonal or shorter-term variations. In this study, test pieces of the same materials tested in a laboratory environment were placed in three outdoor ventilated crawl spaces and three outdoor ventilated attics, where the temperature and RH varied, and Mould Growth on the test pieces was studied over 2.5 years. Material-specific Mould Growth curves were produced based on critical moisture levels, as determined in laboratory experiments under constant temperature and RH. When the actual conditions of RH and temperature exceeded these curves, there was Mould Growth on the test pieces if the time was sufficiently long. The conclusion from the study is that although conditions in laboratory studies are simplified and accelerated, the results serve well to indicate Mould Growth within a building construction.
Annika Ekstrandtobin - One of the best experts on this subject based on the ideXlab platform.
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an innovative test method for evaluating the critical moisture level for Mould Growth on building materials
Building and Environment, 2014Co-Authors: Pernilla Johansson, Annika Ekstrandtobin, Gunilla BokAbstract:Abstract The critical moisture level (RH crit ) for Mould Growth, that is the lowest relative humidity (RH) at which Mould can grow, varies between different materials. The factors that most affect Mould Growth, RH and temperature, also vary in different parts of a building. One way of preventing the Growth of Mould in buildings is therefore to choose building materials that can withstand the expected conditions, materials that have a higher critical moisture level than the highest expected RH. It is thus crucial that data are available to allow the correct choice of materials to be made. In this paper an innovative laboratory test method for determining the RH crit of a material is described and discussed. The results from testing of a material according to the method gives information to make the correct choices. The method is developed based on the results of a variety of laboratory studies and has been validated by field studies.
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the effect of cyclic moisture and temperature on Mould Growth on wood compared to steady state conditions
Building and Environment, 2013Co-Authors: Pernilla Johansson, Annika EkstrandtobinAbstract:Abstract Moisture and temperature are the two key environmental parameters that determine the possibility of Mould Growth on building materials. The time that the material is exposed to these elements is also crucial. The natural environmental conditions of relative humidity and temperature are seldom constant over prolonged time periods in a building. Instead, they vary over time, with fungi encountering both favourable and unfavourable conditions; such variable conditions affect Mould Growth. This paper reports findings from a laboratory study in which Mould Growth at alternating RH (between 90% and 60%) or temperature conditions (between 22 °C and 5 °C) was studied and compared to steady state conditions. Fluctuating RH led to slower Mould Growth, and when the period of unfavourable/favourable conditions was longer (1 week), Growth was affected more than if the duration of these conditions was short (12 h). When alternating the temperature weekly between 22 °C and 5 °C, with a mean of 13 °C, the Mould Growth rate was lower compared to when the temperature was held constant at 22 °C. The Mould Growth under fluctuating temperature conditions was comparable to when the temperature was kept constant at 10 °C.
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validation of critical moisture conditions for Mould Growth on building materials
Building and Environment, 2013Co-Authors: Pernilla Johansson, Thomas Svensson, Annika EkstrandtobinAbstract:Abstract Materials that are stored or used in damp conditions may be subject to Mould Growth. However, all materials are not equally susceptible; for each specific material, there is a critical moisture level for Mould Growth. If this is exceeded, there is a risk that Mould fungi will develop on the material. This level can be determined in accelerated laboratory tests, at constant temperatures and relative humidity (RH) favourable to Mould Growth. Within a building however, these parameters are expected to vary from one part of the construction to another, and are seldom constant; there is fluctuation in temperature and RH due to seasonal or shorter-term variations. In this study, test pieces of the same materials tested in a laboratory environment were placed in three outdoor ventilated crawl spaces and three outdoor ventilated attics, where the temperature and RH varied, and Mould Growth on the test pieces was studied over 2.5 years. Material-specific Mould Growth curves were produced based on critical moisture levels, as determined in laboratory experiments under constant temperature and RH. When the actual conditions of RH and temperature exceeded these curves, there was Mould Growth on the test pieces if the time was sufficiently long. The conclusion from the study is that although conditions in laboratory studies are simplified and accelerated, the results serve well to indicate Mould Growth within a building construction.
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laboratory study to determine the critical moisture level for Mould Growth on building materials
International Biodeterioration & Biodegradation, 2012Co-Authors: Pernilla Johansson, Annika Ekstrandtobin, Thomas Svensson, Gunilla BokAbstract:Abstract The susceptibility of building materials to Mould Growth varies. Some are tolerant to high relative humidity in the ambient air without Mould Growth occurring, while others are less tolerant, and Mould can grow in relative humidity as low as 75%. Within a building, constructions are exposed to different temperatures and relative humidities. To minimise the risk of microbial Growth, building materials should be chosen that are tolerant to the expected conditions. In this study, the critical moisture levels for ten building materials with a range of expected critical moisture levels (wood-based materials, gypsum boards and inorganic boards) were evaluated. Samples of the building materials were inoculated with spores from six species of Mould fungi ( Eurotium herbariorum , Aspergillus versicolor , Penicillium chrysogenum , Aureobasidium pullulans , Cladosporium sphaerospermum , Stachybotrys chartarum ) and incubated in test cabinets at specified temperature (10 °C and 22 °C) and relative humidity conditions (75–95%); Growth of Mould was analysed weekly for at least 12 weeks. One of the conclusions is that two similar building materials or products may have considerably different resistance to Mould Growth, and so the results from one type of building material cannot be applied to the other. Also, in order to compare results from different tests, it is important to use the same test method. It is also important to state the temperature at which the critical moisture level applies and how long the material is exposed to the temperature and relative humidity conditions during the test.
Gunilla Bok - One of the best experts on this subject based on the ideXlab platform.
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Threshold values for Mould Growth: Critical moisture level of 21 different building materials
'EDP Sciences', 2020Co-Authors: Pernilla Johansson, Gunilla Bok, Lukas Lång, Carl-magnus CapenerAbstract:The susceptibility for Mould Growth varies among different building materials. One way to describe the susceptibility is the lowest RH at which Mould can grow on a specific material, the critical moisture level (RHcrit). Determining RHcrit for materials provide the basis for material choice in designs where moisture and temperature conditions are known. In this study, RHcrit of 21different products were determined according to SIS-TS 41:2014/SPMet 4927. This test method is developed based on the results of a variety of laboratory studies and validated by field studies. Test specimens were inoculated with a suspension containing spores from six different Mould fungi and were then incubated in moisture chambers at four levels of RH at 22 °C. After 12 weeks specimens were analysed for Mould Growth. RHcrit was determined based on the lowest RH at which Mould grew on the specimens. RHcrit varied among different products, even between product belonging to a similar group of material, for example, calcium silicate boards or gypsum boards. The results show, and confirm, previous findings that it is not possible to estimate RHcrit for a specific product based on material group. Instead, each product must be tested
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an innovative test method for evaluating the critical moisture level for Mould Growth on building materials
Building and Environment, 2014Co-Authors: Pernilla Johansson, Annika Ekstrandtobin, Gunilla BokAbstract:Abstract The critical moisture level (RH crit ) for Mould Growth, that is the lowest relative humidity (RH) at which Mould can grow, varies between different materials. The factors that most affect Mould Growth, RH and temperature, also vary in different parts of a building. One way of preventing the Growth of Mould in buildings is therefore to choose building materials that can withstand the expected conditions, materials that have a higher critical moisture level than the highest expected RH. It is thus crucial that data are available to allow the correct choice of materials to be made. In this paper an innovative laboratory test method for determining the RH crit of a material is described and discussed. The results from testing of a material according to the method gives information to make the correct choices. The method is developed based on the results of a variety of laboratory studies and has been validated by field studies.
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laboratory study to determine the critical moisture level for Mould Growth on building materials
International Biodeterioration & Biodegradation, 2012Co-Authors: Pernilla Johansson, Annika Ekstrandtobin, Thomas Svensson, Gunilla BokAbstract:Abstract The susceptibility of building materials to Mould Growth varies. Some are tolerant to high relative humidity in the ambient air without Mould Growth occurring, while others are less tolerant, and Mould can grow in relative humidity as low as 75%. Within a building, constructions are exposed to different temperatures and relative humidities. To minimise the risk of microbial Growth, building materials should be chosen that are tolerant to the expected conditions. In this study, the critical moisture levels for ten building materials with a range of expected critical moisture levels (wood-based materials, gypsum boards and inorganic boards) were evaluated. Samples of the building materials were inoculated with spores from six species of Mould fungi ( Eurotium herbariorum , Aspergillus versicolor , Penicillium chrysogenum , Aureobasidium pullulans , Cladosporium sphaerospermum , Stachybotrys chartarum ) and incubated in test cabinets at specified temperature (10 °C and 22 °C) and relative humidity conditions (75–95%); Growth of Mould was analysed weekly for at least 12 weeks. One of the conclusions is that two similar building materials or products may have considerably different resistance to Mould Growth, and so the results from one type of building material cannot be applied to the other. Also, in order to compare results from different tests, it is important to use the same test method. It is also important to state the temperature at which the critical moisture level applies and how long the material is exposed to the temperature and relative humidity conditions during the test.
Staf Roels - One of the best experts on this subject based on the ideXlab platform.
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review of Mould prediction models and their influence on Mould risk evaluation
Building and Environment, 2012Co-Authors: Evy Vereecken, Staf RoelsAbstract:Abstract A reliable prediction of Mould risk in buildings is important to ensure a healthy environment and to avoid social and economical damage. Whereas previously the temperature ratio was often used to minimize the Mould risk, nowadays– more advanced – Mould prediction models can be found (e.g. isopleth systems, biohygrothermal model, ESP-r Mould prediction model, empirical VTT model). These models include the main influencing factors for Mould Growth: the surface temperature and relative humidity. However, they are based on either experiments or assumptions and some of them neglect a third important influencing factor: the exposure time. The current paper gives an overview of the different existing models and analyses the impact of the Mould prediction model on the Mould risk evaluation. To do so, the existing Mould prediction models are used to predict the Mould risk for different temperature and relative humidity courses. The Mould risk, the time until Mould Growth starts and the Mould intensity according to the existing prediction models are compared. Based on the obtained results, the influence of simplifications or shortcomings in the Mould prediction models is discussed.
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impact of wind driven rain on historic brick wall buildings in a moderately cold and humid climate numerical analyses of Mould Growth risk indoor climate and energy consumption
Energy and Buildings, 2009Co-Authors: Masaru Abuku, Hans Janssen, Staf RoelsAbstract:Abstract This paper gives an onset to whole building hygrothermal modelling in which the interaction between interior and exterior climates via building enclosures is simulated under a moderately cold and humid climate. The focus is particularly on the impact of wind-driven rain (WDR) on the hygrothermal response, Mould Growth at interior wall surfaces, indoor climate and energy consumption. First the WDR load on the facades of a 4 m × 4 m × 10 m tower is determined. Then the hygrothermal behaviour of the brick walls is analysed on a horizontal slice through the tower. The simulations demonstrate that the impact of WDR loads on the moisture contents in the walls is much larger near the edges of the walls than at the centre. The obtained relative humidity and temperature at the interior wall surfaces are combined with isopleths of generalised spore germination time of fungus Mould. The results show that WDR loads can have a significant impact on Mould Growth especially at the edges of the walls. Finally, for the case analysed, the WDR load causes a significant increase of indoor relative humidity and energy consumption for heating.
Lone Ross Gobakken - One of the best experts on this subject based on the ideXlab platform.
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surface Mould Growth on wooden claddings effects of transient wetting relative humidity temperature and material properties
Wood Material Science and Engineering, 2019Co-Authors: Geir I Vestol, Olav Hoibo, Lone Ross GobakkenAbstract:ABSTRACTEffects of climatic factors and material properties on the development of surface Mould Growth on wooden claddings were investigated in a laboratory experiment. Specimens of aspen (Populus ...
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surface Mould Growth on five modified wood substrates coated with three different coating systems when exposed outdoors
International Biodeterioration & Biodegradation, 2008Co-Authors: Lone Ross Gobakken, Mats WestinAbstract:Modified wood has potential for above ground use, but surface treatment might be a request in such applications. Three coating systems were applied on furfurylated Scots pine, acetylated Scots pine, heat treated Scots pine, oil heat treated Scots pine, heat treated Norway spruce, and eight reference wood substrates and exposed outdoors to evaluate their ability to resist surface Mould. Samples of the surface were taken for fungal identification to examine any relationship between treatment and fungal species. Both water-borne and solvent-borne coatings with various fungicides were included and the test was carried out according to EN 927-3. The degree of Mould Growth mainly varied with time and type of paint. Of the modified wood substrates furfurylated Scots pine had the lowest degree of Mould Growth and acetylated pine had the highest after 3.5 years. A brown semi-transparent acrylic paint had the lowest degree of Mould Growth after year 1, year 2.5 and year 3.5. Larch heartwood, copper-organic preserved pine and pine heartwood performed best as wood substrates. No differential patterns in susceptibility to various fungal species were detected on the surface of the coated wood substrates - Aureobasidium pullulans was the dominating species on all the wood substrates.