Conference Agenda

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Session Overview
Session 22: Mould growth and related issues
Thursday, 26/Aug/2021:
2:00pm - 3:30pm

Session Chair: Dr. Petter Wallentén, Lund University
Location: Room 2 - Room 011, Building: 116

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2:00pm - 2:15pm

Influence of the mold growth on the crystallographic composition of hemp mortar

Dmytro KOSIACHEVSKYI1,2, Kamilia ABAHRI1, Anne DAUBRESSE2, Evelyne PRAT3, Mohend CHAOUCHE1

1Université Paris-Saclay, ENS Paris-Saclay, CNRS, LMT - Laboratoire de Mécanique et Technologie, 91190, Gif-sur-Yvette, France; 2Centre d’Innovation Parexgroup, 38070 St Quentin Fallavier, France; 3Sika Technology AG, Tüffenwies 16, 8048 Zürich, Switzerland

Nowadays the use of bio-based insulation composites is widely promoted in construction sector due to their environmental and economic benefits. Among different origins of the organic fibers present in France, hemp is interesting because of its availability and low price of raw material. Moreover, the use of the hemp mortar allows to decrease the carbon footprint and represent advantageous hygrothermal properties. Nevertheless, the use of such materials claims the consideration of different factors that could lead to the degradation of the material or their properties. Among them the microbiological contamination is one of the most important degradation factor. For example, molds are known for their ability to modify locally the composition of hemp mortar by decreasing the pH level. That’s why the main objectives of the present work are, first, to expose the hemp mortar to the favorable for mold growth conditions, second, to investigate the proliferation of the mold filaments inside the hemp mortar sample and, then, to analyze the crystallographic composition. Experimentally, hemp mortar samples were exposed to high level of relative humidity during 1 year until the mold growth, the SEM observation allowed to follow the inside growth and to identify the depth of the mold growth and finally using a XRD analysis the composition of the contaminated hemp mortar was studied. The obtained results reveal that molds growth occurs not only on the surface but also in the depth. Nevertheless, as the mold growth started only after 8 months of high humidity exposure, a good resistance of studied hemp mortar towards molds was noted. Furthermore, the mineralogical composition analysis of the contaminated hemp mortar shows the hydrates responsible for durability remained. These results consist of data for better forecast on the durability of the hemp mortars.

2:15pm - 2:30pm

Effects of different light wavelengths on mold growth in tomb

Xiaohan Zhou1, Yonghui LI1, HOKOI Shuichi2

1Southeast university, China, People's Republic of; 2School of Architecture Internationalization Demonstration, Southeast University, Nanjing, China

With a history of more than 1,000 years, the two mausoleums of Southern Tang Dynasty are the largest and oldest imperial tombs found in the middle and lower reaches of the Yangtze River in China. Since it opened in 1984, the building materials and murals inside the tomb have been severely damaged by mold. Field investigation found that the mold growth on the wall illuminated by the light in the tomb was more flourishing than that in the area without the light. Lighting in the tomb is inevitable for the exhibition. Therefore, the purpose of this study is to clarify the effects of light, particularly different light wavelengths on the growth of mold in the tomb, to provide the theoretical basis for the lighting design in the tomb chamber. This study is divided into two parts: in-situ experiment and laboratory experiment. In the in-situ experiment, four kinds of light wavelengths (white, red, blue, and green) were set in the tomb chamber to observe the difference of mold growth on the mural wall(FIG.1). Six dominant molds were collected from the field for the laboratory experiment. In the laboratory experiment, the spore mixture was placed in the inorganic salt medium under the condition of 25℃ and 95%RH, and the difference of mold growth was observed under four kinds of lights (white, red, blue and green). The results show that each light has a different effect on the composition of the microbial community in the tomb. Also, the blue light inhibited the growth of mold both in the field and in the laboratory.

2:30pm - 2:45pm

Development of moisture reference years for assessing long-term mold growth risk of wood framed building envelopes

Lin Wang, Maurice Defo, Abhishek Gaur, Michael Lacasse

National Research Council Canada, Canada

It has been well recognized that climate change will significantly influence the durability performance of building envelopes. Constructing moisture reference year is the most commonly used approach when assessing the durability performance within a specific time period, for example, a 30 years timeframe that is generally recommended for climate change impact assessment. Traditionally, the moisture reference year development was generally focused on correlating the climate indexes with the building performance indexes, then the year that is ranked on the top (the worst year or the 90 percentile year) in the investigated time period could be selected as moisture reference year. However, the moisture reference year selected based on climate indexes cannot reflect the uncertainty of climate change, specifically how the years with different moisture severity levels are distributed. Additionally, the hygrothermal simulation based on the year with a specific moisture severity level may not able to reflect the actual durability performance of the building envelopes, particularly the mold growth risk for wood framed building envelopes. This paper is trying to develop the moisture reference years that are able reflect the uncertainty of climate change and can be used for assessing the long-term mold growth risk of wood framed building envelopes through stochastic analysis. The moisture reference years are developed based on 15 climate data sets of a 31-year timeframe extracted from CanRCM4. Latin hypercube sampling method is employed to sample the representative years with different levels of moisture index. The sampling is repeated for 15 times to generate 15 sets of moisture reference years, whose length is much shorter than 31 years. The developed moisture reference years can be used for assessing the long-term mold growth risk of wood framed building envelopes, which is significantly influenced by the pattern of the years’ distribution.

2:45pm - 3:00pm

Case study of fungal growth on newly cast concrete decks

Sofie Marie Kristensen1, Anne Pia Koch1, Julie Koch Sheard2, Ulf Thrane3

1Danish Technological Institute, Department of Building and Environment, Denmark; 2Unafilliated, Copenhagen, Denmark; 3Danish Technological Institute, Department of Wood and Bio Based Materials, Denmark

In several cases, The Danish Technological Institute has experienced widespread fungal growth on newly cast concrete decks, with a moisture barrier and floating flooring. The reason for fungal growth is usually due to an inadequate drying period. Prior to mounting the floors, existing recommendations require that the relative humidity of air in equilibrium with the concrete, measured in the middle of the concrete deck, should not exceed 85-90% RH. However, if the relative humidity of the air between the concrete deck and the floor exceeds 75% RH, fungal growth can be established even though the pH in the concrete is high.

In this study, six randomly picked apartments in a newly built apartment complex, were chosen for a case study of fungal growth on newly cast concrete. Sampling for fungal growth was conducted with a combination of contact agar plate sampling and sticky tape samples. The survey showed high relative humidity well above 75% RH at the surface and observation of fungal growth. After cleaning of the concrete surface, the concrete decks were set to dry, and moisture and fungal growth were retested.

The study demonstrates that certain species of fungi can grow very well on newly cast concrete if the relative humidity at the surface is above 75% RH and the surface is dusty. The study also demonstrates that a few samples on the surface often will be representative for the whole floor. The study finds that there is a need to revise the existing guidelines for acceptable moisture content in the concrete before mounting the floor. This might have an impact on the entire building process and/or the design of the floor construction. The study also finds that there is a need for a guideline for measuring moisture and fungal growth on newly cast concrete.

3:00pm - 3:15pm

Impact of moisture and mould growth on a CLT structure using weather protection

Charlotte Svensson Tengberg1,2, Åsa Bolmsvik2

1Chalmers University of Technology, Sweden; 2Skanska Sweden, Sweden

Timber buildings are gaining market shares around the world, mainly due to antici­pated environmental benefits. The use of cross laminated timber, CLT, is increasing. Using a new technical solution raises new questions, one of them concerns moisture aspects. How should the construction phase be handled in order to achieve sustainable buildings, with respect to built-in moisture and microbiological damages? It is critical to know how a material should be treated to obtain real sustainable constructions built for the future. There are field studies concerning hygrothermal conditions of timber structures during construction, however mould growth is rarely included. However, it is observed that mould growth can occur during construc­tion when exposed to outdoor conditions. There are few studies on hygrothermal conditions using weather protection and a lack of documented experiences combining hygrothermal condi­tions, mould growth potential and weather protections when using CLT. The possibilities and necessity of using full weather protection are being debated in the building industry as well as in the research community, due to lack of knowledge of the combined effects. How does weather protection during the construction phase affect the hygrothermal conditions and the risk of mould growth in a CLT structure? To investigate these issues, a case study of a weather protected six-storey CLT building was performed. The hygrothermal conditions was monitored during the construc­tion period, both indoors and outdoors, and samples for mould on the CLT elements were ana­lysed at the end of the period. The results on mould growth are analysed together with simula­tions of mould growth using actual hygrothermal conditions. Theoretical conclusions show the weather protection gives significantly improved conditions and resulting in lower potential of mould growth compared to outdoor conditions. The results also show that there are lessons to be learned concerning planning of the construction site.

3:15pm - 3:30pm

Moisture safety in ventilated cathedral roofs

Gabriel Odén1, Gustav Månhardt2, Petter Wallentén3, Martina Stockhaus1

1PE Teknik & Arkitektur AB; 2Structor Bygg Malmö AB; 3Lund University, Sweden

Cathedral roof are commonly used when constructing small houses in Sweden. In contrast to roof constructions above a cold attic, where frequent moisture damage has been noted, the parallel roof is difficult to access for inspection. Furthermore, Swedish building regulations sets high demands regarding moisture safety, although there are no clear guidelines for their compliance. Hence, designing a cathedral roof must be done with great care. Previous studies, investigating moisture safety in cathedral roofs, applies a constant air exchange in the ventilated air cavity. This study analysed a cathedral roof ventilated from eave to eave, examining the relevance of considering the variation in cavity air flow caused by different cavity designs when conducting coupled heat and moisture calculations. The model took into account wind and buoyancy as driving forces and used hourly climate data as input. The accuracy of moisture safety assessments using blind calculations (without knowledge of measurement results) in WUFI Pro (2019) was also studied. Comparing measurements with calculations showed high similarity using both a model with constant cavity air flow, and higher similarity when using a model with varying air flow. The study indicated that it is possible to get improved similarity with measurements when pinpointing important parameters such as initial moisture content and material transport coefficients.Varying cavity design had low impact on moisture safety within predefined design values.

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