MV
M.I.A. Veeger
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1
How moss affects urban temperatures
The effects of moss on the thermal dynamics of an urban cementitious surface
Urban surfaces often exhibit higher temperatures than natural ones, increasing heat stress in urban inhabitants. Plants can provide a solution due to their cooling effect. Whereas this has been investigated in vascular plants, this study is the first to investigate the influence of three moss species (Grimmia pulvinata, Ptychostomum capillare, and Brachythecium rutabulum) attached to a cementitious surface on air, surface, and substrate temperatures. They were compared to bare mortar, mortar covered with the climbing plant Hedera helix, and a moss–climber combination under varying weather conditions. Moss was found to affect temperatures in three ways. Firstly, moss increased surface temperatures in direct sunlight, with an average daytime increase of +1.5 °C to +4.1 °C compared to bare mortar. Secondly, moss exhibited insulating properties, dampening the heat flux to and from the underlying substrate. This reduced heat transfer to the substrate during warm days, limiting heat gain, but also reduced heat transfer from the substrate at night, leading to average nighttime temperatures inside the substrate that were higher (+3.0 °C to +3.8 °C) than in the bare samples. Finally, when moss was hydrated, an evaporative cooling effect could be observed, but it lasted only a few hours after watering. These findings suggest that moss could be a net positive in colder seasons or climates, but that under warmer conditions, it is best to keep moss hydrated or shaded during sun-exposed periods. Therefore, a moss-climber combination appears promising, combining the thermal insulation, acoustic and air-quality benefits of moss with the shading effect of climbing plants.
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Urban surfaces often exhibit higher temperatures than natural ones, increasing heat stress in urban inhabitants. Plants can provide a solution due to their cooling effect. Whereas this has been investigated in vascular plants, this study is the first to investigate the influence of three moss species (Grimmia pulvinata, Ptychostomum capillare, and Brachythecium rutabulum) attached to a cementitious surface on air, surface, and substrate temperatures. They were compared to bare mortar, mortar covered with the climbing plant Hedera helix, and a moss–climber combination under varying weather conditions. Moss was found to affect temperatures in three ways. Firstly, moss increased surface temperatures in direct sunlight, with an average daytime increase of +1.5 °C to +4.1 °C compared to bare mortar. Secondly, moss exhibited insulating properties, dampening the heat flux to and from the underlying substrate. This reduced heat transfer to the substrate during warm days, limiting heat gain, but also reduced heat transfer from the substrate at night, leading to average nighttime temperatures inside the substrate that were higher (+3.0 °C to +3.8 °C) than in the bare samples. Finally, when moss was hydrated, an evaporative cooling effect could be observed, but it lasted only a few hours after watering. These findings suggest that moss could be a net positive in colder seasons or climates, but that under warmer conditions, it is best to keep moss hydrated or shaded during sun-exposed periods. Therefore, a moss-climber combination appears promising, combining the thermal insulation, acoustic and air-quality benefits of moss with the shading effect of climbing plants.
Growing moss on bioreceptive concrete using a novel two-step approach
The effects of light, water, and species selection
Bioreceptive concrete supports biological growth on its surface, but natural colonisation takes years, and indoor cultivation followed by outdoor translocation often results in poor long-term survival. This research aimed to develop a method for rapidly establishing a moss layer on bioreceptive concrete while ensuring long-term persistence and survival. The developed method comprised a two-step approach. First is the rapid establishment of moss on bioreceptive concrete indoors. Then, it is hardened and translocated outdoors. Findings indicate that the most effective method for growing moss on concrete indoors is to grow them at low light intensity (70 μmol m−2 s−1 full-spectrum), while watering daily for the first six weeks. Subsequently, watering can be gradually reduced to once every 4 days, inducing drought hardening. This resulted in significant coverage and growth for both acrocarp (Mcoverage = 15.1 %; Mgrowth = 11.2 mm) and pleurocarp species (Mcoverage = 51.7 %; Mgrowth = 15.5 mm). Finally, after outdoor translocation, the moss should be covered with a light-blocking cloth for a 3-month period to allow for adaptation to UV and high light intensity conditions. When applying this method to moss species (mixtures), it was found that T. muralis showed slow indoor growth but the best adaptation to outdoor conditions on both north- and south-facing surfaces. Contrarily, both P. capillare and B. rutabulum displayed faster growth under indoor conditions but showed poor surface adhesion when translocated outdoors, which can, in some cases, be improved by using species mixtures. This research is a first step towards identifying the factors influencing moss growth and survival on bioreceptive concrete in the built environment.
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Bioreceptive concrete supports biological growth on its surface, but natural colonisation takes years, and indoor cultivation followed by outdoor translocation often results in poor long-term survival. This research aimed to develop a method for rapidly establishing a moss layer on bioreceptive concrete while ensuring long-term persistence and survival. The developed method comprised a two-step approach. First is the rapid establishment of moss on bioreceptive concrete indoors. Then, it is hardened and translocated outdoors. Findings indicate that the most effective method for growing moss on concrete indoors is to grow them at low light intensity (70 μmol m−2 s−1 full-spectrum), while watering daily for the first six weeks. Subsequently, watering can be gradually reduced to once every 4 days, inducing drought hardening. This resulted in significant coverage and growth for both acrocarp (Mcoverage = 15.1 %; Mgrowth = 11.2 mm) and pleurocarp species (Mcoverage = 51.7 %; Mgrowth = 15.5 mm). Finally, after outdoor translocation, the moss should be covered with a light-blocking cloth for a 3-month period to allow for adaptation to UV and high light intensity conditions. When applying this method to moss species (mixtures), it was found that T. muralis showed slow indoor growth but the best adaptation to outdoor conditions on both north- and south-facing surfaces. Contrarily, both P. capillare and B. rutabulum displayed faster growth under indoor conditions but showed poor surface adhesion when translocated outdoors, which can, in some cases, be improved by using species mixtures. This research is a first step towards identifying the factors influencing moss growth and survival on bioreceptive concrete in the built environment.
Evaluating mosses on bioreceptive concrete
Effective sound absorbers?
Moss-covered bioreceptive concrete is a novel green vertical structure which can be applied to a wide variety of structures due to its low structural and maintenance requirements. One of the potential benefits of using moss-covered concrete is its ability to absorb sound, the extent of which is currently unknown. Therefore, the effectiveness in attenuating (urban) noise of six moss species in different hydration states was assessed and compared to bare concrete and other vertical green structures. Results show that using moss-covered concrete increases sound absorption compared to bare concrete in nearly all situations. The best-performing mosses overall were acrocarp species, particularly P. capillare, which reached a peak sound absorption coefficient of 0.86 and an average of up to 0.48 (50–6400 Hz). Its results are also relatively constant across hydration states. On the other hand, G. pulvinata outperformed P. capillare when dry, but not when hydrated or wet. The pleurocarp species showed the lowest sound absorption. Finally, the thickness of the moss layer has a minor impact on absorption. The acrocarp moss species compare favourably to (in)direct vertical green structures using climbing plants, whereas the sound absorption of the pleurocarp species is slightly lower. However, the sound absorption of moss-covered concrete is significantly lower than that of vertical green structures using a growing substrate (Living Wall Systems), as the substrate provides the bulk of the absorption in this case. In conclusion, the moss-covered bioreceptive concrete presents a viable alternative to (in)direct green structures, although benefits are mostly limited to frequencies above 1000 Hz.
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Moss-covered bioreceptive concrete is a novel green vertical structure which can be applied to a wide variety of structures due to its low structural and maintenance requirements. One of the potential benefits of using moss-covered concrete is its ability to absorb sound, the extent of which is currently unknown. Therefore, the effectiveness in attenuating (urban) noise of six moss species in different hydration states was assessed and compared to bare concrete and other vertical green structures. Results show that using moss-covered concrete increases sound absorption compared to bare concrete in nearly all situations. The best-performing mosses overall were acrocarp species, particularly P. capillare, which reached a peak sound absorption coefficient of 0.86 and an average of up to 0.48 (50–6400 Hz). Its results are also relatively constant across hydration states. On the other hand, G. pulvinata outperformed P. capillare when dry, but not when hydrated or wet. The pleurocarp species showed the lowest sound absorption. Finally, the thickness of the moss layer has a minor impact on absorption. The acrocarp moss species compare favourably to (in)direct vertical green structures using climbing plants, whereas the sound absorption of the pleurocarp species is slightly lower. However, the sound absorption of moss-covered concrete is significantly lower than that of vertical green structures using a growing substrate (Living Wall Systems), as the substrate provides the bulk of the absorption in this case. In conclusion, the moss-covered bioreceptive concrete presents a viable alternative to (in)direct green structures, although benefits are mostly limited to frequencies above 1000 Hz.
Moss species for bioreceptive concrete
A survey of epilithic urban moss communities and their dynamics
Research into bioreceptive materials is gaining increased interest. However, while advances are being made on the material side of bioreceptivity, the underlying ecology of urban mosses is still underexposed. This research aimed to determine how the local environment affects the species composition of urban epilithic moss communities and assess which moss species are most suitable for the colonisation of pristine (bioreceptive) concrete surfaces, leading to recommendations for moss species selection to designers and engineers of bioreceptive structures. We conducted a field survey of 137 moss communities on concrete in the Dutch cities of Amsterdam, Rotterdam and The Hague. A total of 26 different species were found, of which the acrocarp species Tortula muralis, Grimmia pulvinata, Ptychostomum capillare, and Orthotrichum diaphanum and the pleurocarp species Brachythecium rutabulum, Hypnum cupressiforme, and Rhynchostegium confertum acted as most common pioneers and also formed a part of the climax community. We found some positive associations between acrocarp species but negative associations between acrocarp and pleurocarp species. Local environmental factors only played a small role in the community composition at a species level; however, when comparing acrocarp and pleurocarp species, the former preferred more exposed sites, whereas the latter preferred more shaded habitats. As such, we recommend that bioreceptive concrete structures use acrocarp pioneers for exposed locations and pleurocarp pioneers for more shaded locations.
...
Research into bioreceptive materials is gaining increased interest. However, while advances are being made on the material side of bioreceptivity, the underlying ecology of urban mosses is still underexposed. This research aimed to determine how the local environment affects the species composition of urban epilithic moss communities and assess which moss species are most suitable for the colonisation of pristine (bioreceptive) concrete surfaces, leading to recommendations for moss species selection to designers and engineers of bioreceptive structures. We conducted a field survey of 137 moss communities on concrete in the Dutch cities of Amsterdam, Rotterdam and The Hague. A total of 26 different species were found, of which the acrocarp species Tortula muralis, Grimmia pulvinata, Ptychostomum capillare, and Orthotrichum diaphanum and the pleurocarp species Brachythecium rutabulum, Hypnum cupressiforme, and Rhynchostegium confertum acted as most common pioneers and also formed a part of the climax community. We found some positive associations between acrocarp species but negative associations between acrocarp and pleurocarp species. Local environmental factors only played a small role in the community composition at a species level; however, when comparing acrocarp and pleurocarp species, the former preferred more exposed sites, whereas the latter preferred more shaded habitats. As such, we recommend that bioreceptive concrete structures use acrocarp pioneers for exposed locations and pleurocarp pioneers for more shaded locations.
Bioreceptive concrete
State of the art and potential benefits
Implementing nature in cities has great potential to improve urban liveability by providing ecosystem services, which can help mitigate heat stress, improve air quality, attenuate noise, and reduce rainwater run-off. However, widespread adoption of urban nature and green building typologies is still limited due to their costs, environmental impact, and space constraints. Bioreceptive concrete can form the basis of a new green building typology, where the concrete mixture is adjusted to allow for biological growth, specifically mosses, to occur on its surface.
This literature review aims to give an overview of the current state of the art on bioreceptive concrete as a material in general and specifically the (potential) ecosystem services provided by the mosses growing on this bioreceptive concrete.
This review shows that bioreceptivity can be achieved in concrete in several ways, including minor adjustments to standard concrete recipes. While quantitative data on the ecosystem services provided by mosses in an urban context is still limited, potential gains appear significant. The main challenges lie in the durable long-term development of mosses on the bioreceptive concrete and the valuation through quantification of the ecosystem services they provide. However, moss-receptive concrete shows promise as a new green building typology if these challenges are bridged. ...
This literature review aims to give an overview of the current state of the art on bioreceptive concrete as a material in general and specifically the (potential) ecosystem services provided by the mosses growing on this bioreceptive concrete.
This review shows that bioreceptivity can be achieved in concrete in several ways, including minor adjustments to standard concrete recipes. While quantitative data on the ecosystem services provided by mosses in an urban context is still limited, potential gains appear significant. The main challenges lie in the durable long-term development of mosses on the bioreceptive concrete and the valuation through quantification of the ecosystem services they provide. However, moss-receptive concrete shows promise as a new green building typology if these challenges are bridged. ...
Implementing nature in cities has great potential to improve urban liveability by providing ecosystem services, which can help mitigate heat stress, improve air quality, attenuate noise, and reduce rainwater run-off. However, widespread adoption of urban nature and green building typologies is still limited due to their costs, environmental impact, and space constraints. Bioreceptive concrete can form the basis of a new green building typology, where the concrete mixture is adjusted to allow for biological growth, specifically mosses, to occur on its surface.
This literature review aims to give an overview of the current state of the art on bioreceptive concrete as a material in general and specifically the (potential) ecosystem services provided by the mosses growing on this bioreceptive concrete.
This review shows that bioreceptivity can be achieved in concrete in several ways, including minor adjustments to standard concrete recipes. While quantitative data on the ecosystem services provided by mosses in an urban context is still limited, potential gains appear significant. The main challenges lie in the durable long-term development of mosses on the bioreceptive concrete and the valuation through quantification of the ecosystem services they provide. However, moss-receptive concrete shows promise as a new green building typology if these challenges are bridged.
This literature review aims to give an overview of the current state of the art on bioreceptive concrete as a material in general and specifically the (potential) ecosystem services provided by the mosses growing on this bioreceptive concrete.
This review shows that bioreceptivity can be achieved in concrete in several ways, including minor adjustments to standard concrete recipes. While quantitative data on the ecosystem services provided by mosses in an urban context is still limited, potential gains appear significant. The main challenges lie in the durable long-term development of mosses on the bioreceptive concrete and the valuation through quantification of the ecosystem services they provide. However, moss-receptive concrete shows promise as a new green building typology if these challenges are bridged.
A bioreceptive material allows for biological content (biofilms) to grow on it, without necessarily affecting the material itself. If a bioreceptive concrete could therefore be integrated into a building façade, it could lead to green façades that do not need additional technical systems. As part of previous research by the authors, a promising bioreceptive concrete mixture was formulated. The aim of this research is to develop this concept by using the previously developed mixture to create a bioreceptive concrete façade panel prototype, made using commonly available materials, that can direct where the biological growth takes place. The latter is done by combining the bioreceptive concrete with a non-bioreceptive (UHPC-based) concrete in the same panel, through a two-stage pouring process. A biofilm was developed on this prototype panel and results show that full coverage of the bioreceptive parts of the panel can be achieved within two weeks under optimal growing conditions and biological growth can be directed. However, exterior survivability is an issue for now. The concept of bioreceptive façades therefore shows promise, yet further investigation into improving exterior survivability is necessary, while further research into the underlying ecology, material, economics, and climate effects is also necessary.
...
A bioreceptive material allows for biological content (biofilms) to grow on it, without necessarily affecting the material itself. If a bioreceptive concrete could therefore be integrated into a building façade, it could lead to green façades that do not need additional technical systems. As part of previous research by the authors, a promising bioreceptive concrete mixture was formulated. The aim of this research is to develop this concept by using the previously developed mixture to create a bioreceptive concrete façade panel prototype, made using commonly available materials, that can direct where the biological growth takes place. The latter is done by combining the bioreceptive concrete with a non-bioreceptive (UHPC-based) concrete in the same panel, through a two-stage pouring process. A biofilm was developed on this prototype panel and results show that full coverage of the bioreceptive parts of the panel can be achieved within two weeks under optimal growing conditions and biological growth can be directed. However, exterior survivability is an issue for now. The concept of bioreceptive façades therefore shows promise, yet further investigation into improving exterior survivability is necessary, while further research into the underlying ecology, material, economics, and climate effects is also necessary.
Making bioreceptive concrete
Formulation and testing of bioreceptive concrete mixtures
Increased urbanisation will put an increasing strain on our green spaces, which is expected to have a significant effect on our physical and mental health, as well as the health of our ecosystems. As such it is important to integrate more green spaces in our urban fabric. One way of doing this is by making use of so-called bioreceptive concrete on our façades and other structures, which allows for biological growth to take place on the concrete substrate itself, without requiring any additional systems or maintenance. However, the challenge is to create an
affordable concrete mixture that is sufficiently bioreceptive for biological growth to take place. As such, in our research we test four possible measures to make concrete more bioreceptive: changing the aggregate to CEC (crushed expanded clay), adding bone ash to the mixture, increasing the wcf (water cement factor) and using a surface retarder on the concrete. Of these measures, changing the aggregate to CEC (p = 0.024), the addition of bone ash (p = 0.022) and the use of a surface retarder (p < 0.001) were found to significantly increase bioreceptivity. Increasing the wcf factor, however, was not found to significantly increase bioreceptivity (p = 0.429). It was also found that whereas it was previously though a pH below 10 is necessary for biological growth to take place, this does not appear to be the case. Although further research under natural conditions is necessary, the creation of an inexpensive bioreceptive concrete looks to be feasible.
...
Increased urbanisation will put an increasing strain on our green spaces, which is expected to have a significant effect on our physical and mental health, as well as the health of our ecosystems. As such it is important to integrate more green spaces in our urban fabric. One way of doing this is by making use of so-called bioreceptive concrete on our façades and other structures, which allows for biological growth to take place on the concrete substrate itself, without requiring any additional systems or maintenance. However, the challenge is to create an
affordable concrete mixture that is sufficiently bioreceptive for biological growth to take place. As such, in our research we test four possible measures to make concrete more bioreceptive: changing the aggregate to CEC (crushed expanded clay), adding bone ash to the mixture, increasing the wcf (water cement factor) and using a surface retarder on the concrete. Of these measures, changing the aggregate to CEC (p = 0.024), the addition of bone ash (p = 0.022) and the use of a surface retarder (p < 0.001) were found to significantly increase bioreceptivity. Increasing the wcf factor, however, was not found to significantly increase bioreceptivity (p = 0.429). It was also found that whereas it was previously though a pH below 10 is necessary for biological growth to take place, this does not appear to be the case. Although further research under natural conditions is necessary, the creation of an inexpensive bioreceptive concrete looks to be feasible.