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

Abstract:

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.

• Periodical: Construction Technologies and Architecture (Volume 1)
• Pages: 588-594
• DOI: https://doi.org/10.4028/www.scientific.net/CTA.1.588
• Online since: January 2022
• Authors: Sanne Johansson, Kristin Balksten, Paulien Brigitte Strandberg-de Bruijn*
• Keywords: Hemp-Lime, Lime, Microbial Growth, Moisture, Mould, Relative Humidity

References

[1] Arizzi, A., Brümmer, M., Martín-Sanchez, I., Cultrone, G., Viles, H., 2015. The Influence of the Type of Lime on the Hygric Behaviour and Bio-Receptivity of Hemp Lime Composites Used for Rendering Applications in Sustainable New Construction and Repair Works. PLoS One 10, 1–19. https://doi.org/10.1371/journal.pone.0125520.

DOI: 10.1371/journal.pone.0125520

[2] Boutin, M.-P., Flamin, C., 2013. Examination of the Environmental Characteristics of a Banked Hempcrete Wall on a Wooden Skeleton, by Lifecycle Analysis: Feedback on the LCA Experiment from 2005, in: Amziane, S., Arnaud, L. (Eds.), Bio-Aggregate-Based Building Materials. ISTE Ltd and John Wiley & Sons, Inc, London, p.317.

DOI: 10.1002/9781118576809.ch9

[3] Evrard, A., De Herde, A., Minet, J., 2006. Dynamical interactions between heat and mass flows in Lime-Hemp Concrete. Res. Build. Phys. Build. Eng.

[4] Gaylarde, C.C., Morton, L.H.G., 1999. Deteriogenic biofilms on buildings and their control: A review. Biofouling 14, 59–74. https://doi.org/10.1080/08927019909378397.

DOI: 10.1080/08927019909378397

[5] Grant, C., Hunter, C.A., Flannigan, B., Bravery, A.F., 1989. The moisture requirements of moulds isolated from domestic dwellings. Int. Biodeterior. 25, 259–284. https://doi.org/https://doi.org/10.1016/0265-3036(89)90002-X.

DOI: 10.1016/0265-3036(89)90002-x

[6] Gravesen, S., Nielsen, P.A., Iversen, R., Nielsen, K.F., 1999. Microfungal contamination of damp buildings--examples of risk constructions and risk materials. Environ. Health Perspect. 107 Suppl, 505–508. https://doi.org/10.1289/ehp.99107s3505.

DOI: 10.1289/ehp.99107s3505

[7] Greenspan, L., 1977. Humidity fixed points of binary saturated aqueous solutions. J. Res. Natl. Bur. Stand. - A Phys. Chem. 81A(1), 89–96.

DOI: 10.6028/jres.081a.011

[8] Johansson, P., Ekstrand-Tobin, A., Svensson, T., Bok, G., 2012. Laboratory study to determine the critical moisture level for mould growth on building materials. Int. Biodeterior. Biodegradation 73, 23–32. https://doi.org/https://doi.org/10.1016/j.ibiod.2012.05.014.

DOI: 10.1016/j.ibiod.2012.05.014

[9] Johansson, S., 2005. Biological Organisms on Building Facades, in: 7th Symposium on Building Physics in the Nordic Countries. Reykjavik, Iceland, p.719–724.

[10] Marceau, S., Glé, P., Guéguen-Minerbe, M., Gourlay, E., Moscardelli, S., Nour, I., Amziane, S., 2017. Influence of accelerated aging on the properties of hemp concretes. Constr. Build. Mater. 139. https://doi.org/10.1016/j.conbuildmat.2016.11.129.

DOI: 10.1016/j.conbuildmat.2016.11.129

[11] Mattsson, J., 2004. Mögelsvamp i byggnader - Förekomst, bedömning och åtgärder. Mycoteam förlag, Oslo.

[12] Nielsen, K.F., Holm, G., Uttrup, L.P., Nielsen, P.A., 2004. Mould growth on building materials under low water activities. Influence of humidity and temperature on fungal growth and secondary metabolism. Int. Biodeterior. Biodegrad. 54, 325–336. https://doi.org/10.1016/j.ibiod.2004.05.002.

DOI: 10.1016/j.ibiod.2004.05.002

[13] Walker, R., Pavia, S., Mitchell, R., 2014. Mechanical properties and durability of hemp-lime concretes. Constr. Build. Mater. 61, 340–348. https://doi.org/10.1016/j.conbuildmat.2014.02.065.

DOI: 10.1016/j.conbuildmat.2014.02.065