Threshold values for mould growth: Critical moisture level of 21 different building materials

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 ◽

10.1016/j.buildenv.2014.07.002 ◽

2014 ◽

Vol 81 ◽

pp. 404-409 ◽

Cited By ~ 34

Author(s):

Pernilla Johansson ◽

Annika Ekstrand-Tobin ◽

Gunilla Bok

Keyword(s):

Building Materials ◽

Test Method ◽

Moisture Level ◽

Mould Growth ◽

Critical Moisture

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Laboratory study to determine the critical moisture level for mould growth on building materials

International Biodeterioration & Biodegradation ◽

10.1016/j.ibiod.2012.05.014 ◽

2012 ◽

Vol 73 ◽

pp. 23-32 ◽

Cited By ~ 82

Author(s):

Pernilla Johansson ◽

Annika Ekstrand-Tobin ◽

Thomas Svensson ◽

Gunilla Bok

Keyword(s):

Laboratory Study ◽

Building Materials ◽

Moisture Level ◽

Mould Growth ◽

Critical Moisture

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Predicting mould growth on building materials- the PJ-model

E3S Web of Conferences ◽

10.1051/e3sconf/202017220001 ◽

2020 ◽

Vol 172 ◽

pp. 20001

Author(s):

Pernilla Johansson ◽

Thomas Svensson

Keyword(s):

Building Materials ◽

Dynamic Models ◽

Technical Specification ◽

Field Studies ◽

Moisture Level ◽

Mould Growth ◽

Limit Values ◽

Ongoing Work ◽

Previous Round ◽

Development And Validation

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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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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Validation of critical moisture conditions for mould growth on building materials

Building and Environment ◽

10.1016/j.buildenv.2013.01.012 ◽

2013 ◽

Vol 62 ◽

pp. 201-209 ◽

Cited By ~ 58

Author(s):

Pernilla Johansson ◽

Thomas Svensson ◽

Annika Ekstrand-Tobin

Keyword(s):

Building Materials ◽

Mould Growth ◽

Critical Moisture ◽

Moisture Conditions

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Implications of Building Material Choice on Outdoor Microclimate for Sustainable Built Environment

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.650.82 ◽

2015 ◽

Vol 650 ◽

pp. 82-90 ◽

Cited By ~ 1

Author(s):

D. Kannamma ◽

A. Meenatchi Sundaram

Keyword(s):

Thermal Comfort ◽

Building Material ◽

Building Materials ◽

Climatic Factors ◽

Outdoor Environment ◽

Outdoor Thermal Comfort ◽

Physical Factors ◽

Physiological Equivalent Temperature ◽

Material Choice ◽

The Impact

The climatic conditions in a man-made urban environment may differ appreciably from those in the surrounding natural or rural environs.... each urban man-made buildings, roads, parking area, factories......creates around and above it a modified climate with which it interacts [1].Outdoor thermal comfort has gained importance in thermal comfort studies especially in tropical countries. In country like India, culturally the activities are spread both indoors and outdoors. Therefore the need for ambient outdoor environment gains importance. As there are many factors that contribute to outdoor thermal comfort (climatic factors and physical factors), this study aims in analyzing the impact of building material contribution, in an institutional courtyard. In order to understand the thermal contribution of various building materials and to suggest material choice to designers, ENVIMET is used for simulation purpose. The outdoor thermal comfort index employed in this study is PET (Physiological Equivalent Temperature), calibrated using RAYMAN.

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Removing NOx Pollution by Photocatalytic Building Materials in Real-Life: Evaluation of Existing Field Studies

Journal of Photocatalysis ◽

10.2174/2665976x02666210308151731 ◽

2021 ◽

Vol 02 ◽

Author(s):

Pernille D. Pedersen ◽

Nina Lock ◽

Henrik Jensen

Keyword(s):

Air Pollutants ◽

Building Materials ◽

Evaluation Criteria ◽

Real Life ◽

Ambient Air ◽

Well Being ◽

Good Health ◽

Objective Evaluation ◽

Field Studies ◽

Hazardous Air Pollutants

: The NOx gasses (NO and NO2) are among the most important air pollutants, due to the toxicity of NO2, as well as the role of NOx in the tropospheric oxidation of Volatile Organic Carbons (VOCs), contributing to the formation of other hazardous air pollutants. Air pollution is one of the biggest health threats world-wide, hence reducing NOx levels is an important objective of the UN sustainable development goals, e.g. #3, “Good health and well-being” and #11 “Sustainable cities and communities”. Photocatalysis using TiO2 and light is a promising technique for removing NOx along with other pollutants, as demonstrated on laboratory scale. Furthermore, a long range of real-life test studies of varying scales have been conducted during the past two decades. The results of these studies have been conflicting, with some studies reporting no effect on the ambient air quality and others reporting significant reductions of NOx level. However, the studies are very difficult to compare and assess due to the very different approaches used, which consequently vary in quality. In this review, we aim to develop a set of objective evaluation criteria to assess the quality of the individual studies in order to simplify the interpretation and comparison of the existing studies. Moreover, we propose some guidelines for future test-studies. Furthermore, the approaches and main conclusions from 23 studies are independently assessed and discussed herein.

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On the Issue of Safe Use of Fiber Cement Materials in the Buildings and Structures

Occupational Safety in Industry ◽

10.24000/0409-2961-2021-7-35-41 ◽

2021 ◽

pp. 35-41

Author(s):

N.I. Konstantinova ◽

◽

N.V. Smirnov ◽

O.V. Krivoshapkina ◽

O.I. Molchadskiy ◽

...

Keyword(s):

Building Materials ◽

Protective Coatings ◽

Fire Hazard ◽

Thermal Exposure ◽

Test Methods ◽

Test Method ◽

Sand Mixture ◽

Industrial Buildings ◽

Experimental Complex ◽

Combustible Materials

Fiber cement finishing materials are widely used in the construction of industrial buildings and structures due to the complex of valuable operational properties. In the Russian market there are fiber-cement panels with a variety of design solutions for their coloring and application of protective coatings. Fiber cement board is a strong and moisture-resistant composite material made from a cement-sand mixture, reinforcing cellulose fibers and special additives. Not being a non-combustible material, the fiber cement boards in accordance with the current mandatory requirements, as a decorative, finishing and facing material for walls and ceilings have restrictions on their use. Existing domestic requirements regarding the methodology for assessing the combustibility of fiber cement products largely narrow the field of using these materials. Therefore, it is advisable to develop the proposals for amending the test methods and the regulatory framework governing their fire-safe extended scope. In the course of this work execution, the main provisions of the regulatory and methodological framework that establish the requirements for the fire-safe use of fiber cement materials are analyzed. Experimental complex studies of fire hazard properties of various types of samples of the fiber cement finishing panels and slabs were carried out. It is established that fiber-cement materials belong to the class of the least fire-hazardous materials. Advisability is determined concerning the introduction to the national regulatory practice of GOST R «Building materials. Test method for fire hazard under thermal exposure with a single burner (SBI)». Classification parameters of the group of non-combustible materials NG2 were established to amend GOST R 57270—2016 (method 1). Classification parameters of the group of non-combustible materials NG2 for making changes in GOST R 57270—2016 (method 1) are established. Proposals were developed to expand the scope of application of the materials and products made of fiber cement as enclosing structures, partitions, and decorative finishes (cladding) in the buildings and structures.

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