Modelling mould growth in domestic environments using relative humidity and temperature

The objective of this work was to compare the hygrothermal responses and the moisture performance of four wood-frame walls as predicted by four hygrothermal (HAM) simulation tools, namely: DELPHIN, WUFI, hygIRC and COMSOL. The four wall systems differ only in their cladding type; these were fibreboard, vinyl, stucco and brick. Three Canadian cities having different climates were selected for simulations: Ottawa, Ontario; Vancouver, British Columbia and Calgary, Alberta. In each city, simulations were run for 2 years. Temperature and relative humidity of the outer layer of OSB sheathing were compared amongst the four simulation tools. The mould growth index on the outer layer of the OSB sheathing was used to compare the moisture performance predicted by the respective hygrothermal simulation tools. Temperature profiles of the outer layer of the OSB sheathing were all in good agreement for the four HAM tools in the three locations. For relative humidity, the highest discrepancies amongst the four tools were found with stucco cladding where differences as high as 20% could be found from time to time. Mould growth indices predicted by the four HAM tools were similar in some cases but different in other cases. The discrepancies amongst the different HAM tools were likely related to: the material property processing, how the quantity of wind-driven rain absorbed at the cladding surface is computed and some implementation details. Despite these discrepancies, The tools generally yielded consistent results and could be used for comparing the impacts of different designs on the risk of premature deterioration, as well as for evaluating the relative effects of climate change on a given wall assembly design.

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The influence of weather on the quality of tropical legume pasture during the dry season in Northern Australia. II. Moulding of standing hay in relation to rain and dew

Australian Journal of Agricultural Research ◽

10.1071/ar9810589 ◽

1981 ◽

Vol 32 (4) ◽

pp. 589 ◽

Cited By ~ 5

Author(s):

RL McCown ◽

BH Wall

Keyword(s):

Relative Humidity ◽

Leaf Litter ◽

Bulk Sample ◽

Dry Season ◽

Northern Australia ◽

Mould Growth ◽

Tropical Legume ◽

Dry Tropics

Naturally desiccated legume pasture is valuable forage in the dry season but is very vulnerable to moulding, which drastically reduces its acceptability to cattle. At a network of sites in the wet-dry tropics of Australia, trends in mouldiness of standard leaf 'litter' samples were monitored in relation to rain, dew, and rates of drying. Although heavy dews occurred frequently at some sites, only the immediate top layer of fallen leaf moulded. This had a very small effect on the mouldiness of the bulk sample. Appreciable moulding occurred only after at least 2 mm rain, but in some cases there was no mould growth after over 10 mm rain; the amount of rain accounted for only 23 % of the variation in mouldiness. The duration of wetness of the leaf litter, as indicated by the duration of 95 % relative humidity 10 cm above the ground after rain, accounted for 91 % of the variation in mouldiness. At the more humid sites, material which was exposed for several weeks before rain moulded more rapidly after rain than did recently exposed material, even though at the time of rain there were no visible differences. Differences in causation of moulding of conventional hay and of 'standing hay' are discussed.

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Measurements behind Internal Insulation on Solid Masonry Walls with Different Orientations and Degrees of Repair in a Danish Multi-story Building

E3S Web of Conferences ◽

10.1051/e3sconf/202017201008 ◽

2020 ◽

Vol 172 ◽

pp. 01008

Author(s):

Lies Vanhoutteghem ◽

Britt Haker Høegh ◽

Thor Hansen

Keyword(s):

Relative Humidity ◽

Moisture Content ◽

Energy Use ◽

Wood Decay ◽

Large Temperature ◽

Mould Growth ◽

Insulation System ◽

Measurement Results ◽

Heritage Buildings ◽

Story Building

Internal insulation is used in many heritage buildings to ensure a better indoor environment and reduce energy use. This article describes measurement results from installing an internal insulation system in a Danish multi-story building. The internal insulation system consists of a fully glued vapour tight insulated plasterboard. To reduce the risk for wood decay and mould growth at the wooden beam ends in the floor construction, a 100-200 mm uninsulated gap was left above and below the floor construction. Measurements include the effect of orientation, degree of façade repair and influence of indoor moisture content. Results show in general acceptable hygrothermal conditions behind the insulation system. However, a gradual increase in relative humidity at sun-exposed walls was registered due to ‘summer condensation’. The degree of surface repair also showed an influence on relative humidity levels during this period. At the uninsulated gap above the floor, a higher moisture content indoor resulted in a higher relative humidity, though without exceeding the threshold for mould growth. However, a large temperature range was registered. The influence of the uninsulated gap on reducing the risk of wood decay and mould growth at the beam ends could therefore not unambiguously be confirmed.

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A Field Study of Mould Growth for Institute Higher Education Library Buildings in Malaysia

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.567.553 ◽

2014 ◽

Vol 567 ◽

pp. 553-558

Author(s):

Ngah Abdul Wahab Suriani ◽

Nurul Izma Mohammed ◽

Mohd Faris Khamidi ◽

Nazhatulzalkis Jamaludin

Keyword(s):

Higher Education ◽

Relative Humidity ◽

Literature Review ◽

Field Study ◽

Visual Inspection ◽

Field Studies ◽

Mould Growth ◽

Indoor Climate ◽

Assessment Technique ◽

Result Show

This paper is part of a PhD field study that focuses on the importance of conducting a visual inspection and evaluation of the indoor climates in libraries. Libraries contain a large amount of stored books that require a stable relative humidity to guarantee its preservation. Mould can survive and grow when indoor relative humidity is high and fungus is present all the time in the air that we breathe. Recording data through visual inspection and field studies. Its recorded the indoor relative humidity, temperature and lighting to assess mould growth problems. The assessment technique for this paper is based on guidelines survey and literature review. Visual inspection found few symptoms of mould growth that related to the amount of moisture appeared when the relative humidity in the library increases. Finally, the recording data for temperature and relative humidity demonstrate the result show that the stable indoor climate in the library building.

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The effect of temperature and relative humidity on population growth of three Liposcelis species (Psocoptera: Liposcelidae) infesting stored products in tropical countries

Bulletin of Entomological Research ◽

10.1017/s0007485300050562 ◽

1990 ◽

Vol 80 (3) ◽

pp. 353-358 ◽

Cited By ~ 46

Author(s):

D.P. Rees ◽

A.J. Walker

Keyword(s):

Relative Humidity ◽

Population Growth ◽

Geographical Distribution ◽

Cereal Grains ◽

Effect Of Temperature ◽

Stored Products ◽

Mould Growth ◽

Pest Status ◽

Rice Grains ◽

The Tropics

AbstractThe effect of a range of temperatures (15–42°C) and relative humidities (40–80%) on growth of populations of Liposcelis entomophilus (Enderlein), Liposcelis bostrychophilus Badonnel and Liposcelis paetus Pearman infesting a rice-based medium was investigated. These species are often found infesting stored cereal grains in the tropics. Both L. entomophilus and L. bostrychophilus bred most rapidly at 30°C, 70–80% r.h. Neither survived at temperatures of 36°C and above. In contrast, L. paetus bred most rapidly at 33–36°C, 70% r.h., and was able to breed at 42°C, 80% r.h. No species survived humidities below 60%. As well as consuming mould growth, Liposcelis spp. also caused visible damage in rice grains. Implications of these findings in the understanding of pest status and geographical distribution of severe outbreaks of Liposcelis spp. are discussed.

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Monte Carlo Simulation to Evaluate Mould Growth in Walls: The Effect of Insulation, Orientation, and Finishing Coating

Advances in Civil Engineering ◽

10.1155/2018/8532167 ◽

2018 ◽

Vol 2018 ◽

pp. 1-12 ◽

Cited By ~ 6

Author(s):

Ricardo M. S. F. Almeida ◽

Eva Barreira

Keyword(s):

Monte Carlo ◽

Relative Humidity ◽

Case Studies ◽

Prediction Models ◽

Growth Models ◽

Untreated Wood ◽

Mould Growth ◽

Indoor Climate ◽

Growth Phenomenon ◽

One Year

Mould growth can have severe consequences both on the health of occupants and on constructions’ durability. Mould growth is a very complex process that depends on many factors such as temperature and relative humidity, presence of nutrients, and exposure time. Several mould prediction models, which allow estimating mould growth in building components and performing risk analysis, are available in the literature, such as the updated VTT model or the Biohygrothermal model. A Portuguese typical wall configuration was used for a sensitivity analysis. The importance of insulation (with and without insulation), orientation (north and south), and finishing coating (gypsum-based rendering, medium density fibreboard (mdf), and untreated wood) for the mould growth phenomenon was tested using both the updated VTT model and the Biohygrothermal model. A total of 12 case studies were investigated. The influence of indoor climate was evaluated by simulating 200 scenarios previously generated using the Monte Carlo method. Each of the scenarios has been applied to the 12 case studies, and 2400 hygrothermal simulations were carried out. Initially, the case studies were simulated using WUFI 1D since both mould growth models require the superficial temperature and relative humidity as input. Simulations were carried out for a one-year period. The updated VTT model produced results (mould index—M) ranging between 0.4 (gypsum-based rendering, insulated, and south oriented wall) and 5.9 (untreated wood, noninsulated, and north oriented wall) and the Biohygrothermal model (mould growth) between 10.1 and 406.4 mm for the same case studies. Despite that the effect of the orientation of the wall could be identified, the importance of insulation and nature of substrate was more evident. Although the two models produced overall comparable results, some differences could be found, creating the opportunity to discuss their strengths and weaknesses as well as their sensitivity to the input parameters.

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Risk for Mould Growth on Hemp-Lime at Different Relative Humidity

10.4028/www.scientific.net/cta.1.588 ◽

2022 ◽

Author(s):

Sanne Johansson ◽

Kristin Balksten ◽

Paulien Brigitte Strandberg-de Bruijn

Keyword(s):

Relative Humidity ◽

Building Materials ◽

Microbial Growth ◽

Mould Growth ◽

European Climate ◽

Northern European ◽

Critical Relative Humidity ◽

Different Temperatures ◽

Critical Moisture ◽

Hemp Shiv

Microbial growth often thrives in humid conditions, at high relative humidity. Moulds are complex organisms; many types of mould are able to survive strong variations in humidity and temperature, such as those on building façades. For some building materials a critical relative humidity is determined, which functions as a theoretical threshold; at this (or lower) relative humidity microbial growth will likely not occur. Hemp-lime is a building material that consists of hemp shiv (the woody core parts of the hemp stem) and building lime. It is a material that can be used for walls, and even though it has been used for more than 20 years, thusfar little is known about its critical moisture levels for microbial growth. The aim of this research was therefore to determine at what relative humidity microbial growth occurs on carbonated hemp-lime material, and to study if there is a protective influence of a carbonated lime binder on the hemp shiv. The objective was to study microbial growth on hemp shiv, hemp-lime and on hemp with a thin layer of lime at three relative humidity (75 %, 85 % and 95 %) and at two different temperatures (15°C and 23°C); conditions that could occur naturally in a hemp-lime façade exposed to high rain loads in a northern European climate. Hemp shiv seems to have a relatively low resistance to microbial growth, similar to that of wood. However, because the hemp is protected by lime it can withstand much higher relative humidity without microbial growth occurring on the material. The critical moisture level for hemp-lime seemed to occur between 75 and 85 % RH, while the material was completely without microbial growth at 75 % RH. The lime had a protective effect on the hemp and acted as a mould inhibitor, both over time and with varying temperature and humidity.

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PACKAGING: III. EFFECT OF MOULD GROWTH AND AGEING ON THE WATER-VAPOUR TRANSMISSION OF PACKAGING MATERIALS

Canadian Journal of Research ◽

10.1139/cjr46f-013 ◽

1946 ◽

Vol 24f (2) ◽

pp. 117-122 ◽

Cited By ~ 2

Author(s):

C. G. Lavers ◽

W. I. Illman

Keyword(s):

Relative Humidity ◽

Cellulose Acetate ◽

Water Vapour ◽

Transmission Rate ◽

The Other ◽

Packaging Materials ◽

Metal Foil ◽

Mould Growth ◽

Coated Materials ◽

Laminated Materials

Packaging materials were dusted with mould spores and stored in a cabinet at 95° F. and 95 to 100% relative humidity for periods of one to eight weeks.M.S.T. and M.S.A.T. "Cellophane" were attacked only slightly by mould, but deterioration of the heat-sealing, moisture-proof lacquer occurred during storage under conditions suitable for optimum mould growth. Moulds grew abundantly on M.S.Y.T. Cellophane. Wax-coated materials supported abundant mould growth, and their water-vapour transmission values increased when wax peeled from the surface of the sheet. The transmission rate of laminated materials having metal foil as one layer was not greatly affected by mould growth or delamination of the other layers. Abundant mould growth developed on most samples of kraft, and on glassine. Very little mould developed on cellulose acetate, Pliofilm, or vinyl-film.

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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 ◽

10.1080/17480272.2018.1424239 ◽

2018 ◽

Vol 14 (3) ◽

pp. 129-141 ◽

Cited By ~ 6

Author(s):

Solrun Karlsen Lie ◽

Geir I. Vestøl ◽

Olav Høibø ◽

Lone Ross Gobakken

Keyword(s):

Relative Humidity ◽

Material Properties ◽

Mould Growth

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High Air Relative Humidity and Lighting Modes Govern Mould Growths on Damp Soil Ruins’ Surface in High-Humidity Regions

E3S Web of Conferences ◽

10.1051/e3sconf/202017223010 ◽

2020 ◽

Vol 172 ◽

pp. 23010

Author(s):

Yonghui Li ◽

Weilun Zhang ◽

Ruobin Wu ◽

Xinyuan Dang ◽

Shuichi Hokoi

Keyword(s):

Relative Humidity ◽

Environmental Variables ◽

Inhibitory Effect ◽

High Humidity ◽

Mould Growth ◽

Two Factors ◽

Hygrothermal Environment ◽

Growth Differences ◽

High Humidity Environment ◽

Humidity Environment

Mould growth, caused by favourable hygrothermal environment like high relative humidity, proper temperature and other environmental variables, is one of the most severe hazards to soil ruins in high-humidity regions. Nevertheless, the effects of these variables on mould growth under extremely high humidity conditions remain elusive. In our previous research, samples from Wenzhou Qiaolou soil ruin were used to estimate the effects of two factors, ventilation and lighting modes, in unison. Based on that, a subsequent analysis has been conducted to assess mould growth differences with air relative humidity and lighting modes. We found that the extremely stable high-humidity environment (99.9%) had a significantly inhibitory effect on mould growth of damp surface of soil ruins. This paper also gives suggestions on the management of soil ruin exhibition halls in high-humidity regions.

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