Green Roofs

There are two main families of technological greenery systems (TG): green roofs (GR) and vertical greening systems (VGS). Referred to as roof gardens, horizontal systems have historically been the first form of integration of vegetation into the built environment. They are vegetated surfaces (green canopy) endowed with a substrate of organic material (soil). From a technological point of view, GR are divided into intensive and extensive, according to the depth of the substrate (which feeds the vegetation) and the use of the roof. Some authors add a semi-intensive category, with characteristics in between the two main ones.⁶

Intensive GR generally have a considerable substrate depth (more than 15–20 cm [5.91–7.87 in.]), a wide variety of plants (similar to ground-level landscapes), high water retention capacity (over 50%), high capital costs ($25/sq. ft. [0.09 m²]), and heavy weight (180-500 kg/m² [37-102.5 lb./sq. ft.]).⁷ Depending on the soil depth, the plant selection is wider and can include small trees, shrubs, and bushes.^8,9 However, the greater weight of the roof can require additional structural reinforcement, and the richness of the vegetation requires a higher level of maintenance, with drainage and irrigation systems that increase the technical complexity and associated costs.¹⁰ Typically intensive GR are designed for human recreation purposes and, thanks to plant variety, can improve biodiversity.¹¹ 

Extensive green roofs are characterized by a thinner depth of substrate layer (less than 15 cm [5.91 in.]), thus only limited types of plants, including grasses, mosses, herbs, and a few succulents can be used and irrigation is not required unless periodically. As a consequence, they are more economic, very lightweight, and the construction process is technically simple. Generally, they are not accessible. In comparison with intensive green roofs, they perform worse in terms of energy savings and storm water management. On the contrary, intensive ones can decrease runoff by 85% when compared to traditional roofs.¹² 

In highly urbanized areas, apart from improving stormwater management, GR provide different ecosystem services: they increase regulation of building temperature, sound insulation,¹³ heat island control,¹⁴ and restoration of biodiversity.¹⁵ In particular, energy saving is due to different mechanisms ¹⁶:

• shading: vegetation provides an additional layer that shades the roof, blocking part of the incoming solar radiation;

• evapotranspiration: plant transpiration and soil evaporation cool the surface of the plants;

• decreased heat flux toward the interior of the building and the urban heat island, etc.;

• thermal inertia: the substrate increases the roof thermal mass, delaying and reducing incoming heat fluxes;

• thermal insulation: the substrate and drainage layers increase the heat resistance of the roof by providing an additional layer. 

Despite its high initial cost, in the long term, green roofs are an economical option considering their energy savings, but they are often chosen by developers purely for aesthetic reasons. This is generally due to a lack of research on different aspects of vegetative roofs and the premature introduction of products into the market.¹⁷

Biology of Mosses 

Among the world of plants, bryophytes are the second largest group, exceeded only by the Magnoliophyta– the flowering plants (350,000 species). There are between 18,000 and 23,000 species of bryophytes worldwide ³³ where they occur in every location that is habitable by photosynthetic plants. However, bryophytes cover three systematic phyla: hornworts (Anthocerotophyta), liverworts (Marchantiophyta) and mosses (Bryophyta).³⁴ The last group includes the most part of bryophytes suitable for applications. For this reason, mosses are the sole bryophytes treated in this review. (Fig. 1).

Mosses are small (rarely larger than a few centimeters) and unable to produce lignin (they cannot become woody). The most important ability of mosses is that when they are completely hydrated after dry periods, they quickly resume their metabolism after rewetting. This peculiarity, named poikilohydry, makes them particularly resilient and is in part the result of totipotency – the ability of any cell of an organism to dedifferentiate and then differentiate into a new plant.³⁵ All bryophytes are to some extent totipotent: they can regenerate from fragments, or even single cells, making them great survivors. Peat moss (genus Sphagnum) is one of the most important genus of plants, and certainly the most important peat producer in the world, locking away an enormous amount of carbon and holding vast quantities of water ³⁶: peat moss is essentially a huge sponge. Mosses growing on trees (i.e., epiphytes) have been known as great indicators of air pollution for a long time.³⁷ Mosses show a vast range of specific sensitivity and visible symptoms to pollutants greatly exceeding that of higher plants.³⁸

What distinguishes mosses collectively from all other land plants (ferns, conifers, and flowering plants) is that their life cycle is dominated by gametophyte generation rather than sporophyte generation; that is, by the haploid or sexual phase (when gametes are produced), as opposed to the diploid, spore-producing phase.³⁹ In contrast, all other land plants are dominated by the sporophyte generation, with the gametophyte much reduced, often to just a few cells. In other words, the leafy green part that one sees in the main plant, which is mainly photosynthetic, is the gametophyte in bryophytes, whereas it is the sporophyte in all other land plants. The bryophyte sporophyte is usually reduced to a spore-producing, stalked capsule that remains attached to the gametophyte, and is dependent on it for sustenance. In addition, many mosses produce specialized asexual reproductive organs, such as gemmae, which circumvent the sporophyte generation entirely, simply replicating the gametophyte parent.

From an ecological point of view, mosses are important because with limited needs, they manage to settle in environments where most land plants are unable to survive (for example, mosses colonize stones and trunks).⁴² The most interesting aspect is that mosses are also common in a city in the joints of floors, on roofs, and on walls; in short, mosses are easily adaptable organisms in urban habitats. Aside from the extreme case of peat moss, most moss species act to some extent as sponges, taking up water rapidly, holding it, and releasing it only slowly. They are efficient colonizers and stabilizers of bare substrates (e.g., soils) and they can serve as hosts for blue-green algae (cyanobacteria), which have an important role in nitrogen (N) fixation.⁴³ A spore less than 100 μm [1/250 in.] in diameter can provide sufficient energy for a new moss to get started. Water is clearly needed by mosses, but rather than maintaining hydration, they are able to become metabolically inactive, exercising an ectohydric strategy that holds water in capillary spaces while they dry slowly. Being small itself seems to be a strategy to conserve water.⁴⁴

Additionally, they provide habitats for other organisms: seedbeds for vascular plants, shelter and food for small invertebrates, nesting material for birds and small mammals, etc. A type of mire (i.e., bogs) in particular, forms entire ecosystems fundamentally dependent on mosses (peat moss). Despite their small size, the role of mosses in the ecosystem may be significant: even though it is a largely overlooked field of study, recently ecologists are increasingly recognizing that mosses can no longer be ignored. For example, peat moss alone may be the genus that sequesters more carbon than any other on Earth, and the role of mosses in housing small organisms that ultimately increase the diversity of their predators could be vital.

Since ancient times, mosses have been used as insulation both for dwellings (Fig. 2) and in clothing. Because it is so dense and has a tight root system, moss acts as an excellent insulator. Traditionally, dried moss was used in some Nordic countries and Russia as an insulator between logs in log cabins, and tribes of the northeastern United States and southeastern Canada used moss to fill chinks in wooden longhouses. Circumpolar and alpine people have used mosses for insulation in boots and mittens. Ötzi the Iceman had moss-packed boots. 

The capacity of dried mosses to absorb fluids has made their use practical in both medicinal and culinary uses. Peat moss, and many other mosses for that matter, are extremely spongy and hold large amounts of water. In the case of peat moss, it can be literally squeezed, drinking the water that comes from it. Since it is acidic, bacteria do not tend to grow in it. Finally, dried moss is extremely flammable, whereas when it is alive, it is waterproof.

This first line of research concerns the use of moss in the specific field of building technology, in particular the envelope. Two main themes are identified. The first has a specific name, “bioreceptive design,” which consists of designing building components and materials that are able to host biological plant life such as mosses, lichens, etc. directly thanks to their chemical and physical properties. The second item concerns the use of moss grown on substrates used for the building envelope in technological greenery, such as green roofs or living wall systems.

This research revealed that MPC panels, even though very porous, had good structural integrity during structural tests but they did not perform well when exposed to the action of freeze-thaw, thus inappropriate for long-term outdoor exposure in continental climate. Moreover, after one year, there was no sign of biological growth of mosses on MPC panels, and all tests confirmed that both residual chemical surface properties and porosity created an unexpected inhibitor for growth in a single annual cycle on the MPC panels. Further test demonstrated that more time (2 years) was necessary for these panels to become bioreceptive, possibly to allow uncured chemicals in the material to be washed out.

On the contrary, the behavior of the OPC (Ordinary Portland Cement) panels in urban environments demonstrated that certain moss types are capable of growing on them because, despite initial high alkalinity, OPC has a gradual decrease of pH when carbonized over time, which makes it gradually more bioreceptive. Thus the goal turned out to be the offset of the carbon footprint of OPC, which is the cheapest and most available material in the construction industry.

The tests revealed that algae and moss growth occurred in specific areas of OPC panels that had no porosity and, therefore, offered water catchment areas in horizontal crevices. As a consequence, surface morphology plays a vital role in creating bioreceptivity on concrete panels.⁵⁶

A third installation in December 2020 was a smaller wall made of 10 GRC limestone corkcrete panels made of a mix of OPC and cork aggregates, and integrated in a building extension at Merchiston Park in Edinburgh. The underpinning research was underway with the University of Coimbra (Prof Fernando Branco) and the Technical Institute of Tomar (Dr Lurdes Belgas) as well industrial partners Amorim (ACC) in Portugal, where additional mixes of natural and expanded cork were investigated as an alternative aggregate. The aim was to promote the growth of lichens along with mosses and test the long-term carbon offset by the photosynthetic activity of the plants. When compared with the slow growth on MPC panels, Corkcrete samples proved to be more bioresponsive, even hosting moss and lichen after a single winter cycle.⁵⁷

Following the same principles, other researchers worked to develop bio-integrated systems using surface geometry in an ordered and systematic manner as a design variable to facilitate moss growth on concrete panels.⁵⁸
The research followed a top-down approach where, first, designs were developed based on a literature review and field surveys, then the fabricated panels were validated through practical experimentations and finally, a general design guideline was provided. The resulting guideline indicates the macrogeometries that performed best and allows countless options of surface morphology that can be used to create a self-sustaining bioreceptive concrete façade panel. In 2022, Marc Ottelé, who is among the authors in this paper, launched a TU Delft spin-off called “Respyre” and has developed an innovative – patent pending – bioreceptive concrete solution. After hardening, the bioreceptive concrete’s surface accommodates the growth of moss thanks to its porosity and water retainment, micropore texture, acidity, and nutrients that are included in the mixture.

It is a low-cost, low-maintenance, versatile, and lightweight system, with interesting performance in terms of water management and surface temperature reduction (up to 14 °C [57.2 °F]). Several moss species, that is, Homalothecium sericeum, Barbula unguiculata, Pseudoleskea incurvata, Grimmia pulvinate, and Hypnum cupressiforme, were selected, based on their ability to tolerate the abiotic stresses of urban environments, as the most suitable for the development of the greening system. Four different configurations of the panel were designed, with dimensions of 80 × 80 cm [31.50 × 31.50 in.], and all consisting in: 

• an elastic belt, supporting and anchoring to the building surface;

• a layer of the selected material, comprising a thin waterproof membrane with the function of isolating the wet panel from the building surface;

• a micro-perforated channel, inserted in a slot obtained by stitching between Layers 2 and 4;

• one or two layers of the selected material depending on the configuration.

The advantages of these solutions are the reduced cost of the panels compared to the systems on the market and the no need for pruning, which could allow a wide integration in densely urbanized areas. 

 The most famous application of mosses in façade is the City Hall in Reykjavík (1987-92). A scientific paper is deserving of this since it has worked well for thirty years. 

 “The wall was constructed from reinforced precast concrete elements with a lava finish. The lava was laid in a flat bed and concrete (with a retarder) poured over. The careful selection of the lava is important to ensure porosity, frost resistance, and appearance (somewhere between natural and artificial). Before the concrete hardened completely the elements were raised and the cement slurry washed from the lava. Carbon dioxide was blown over the surface to balance the ph of the elements. The moss was harvested locally to ensure that it would flourish in the climate of application. Our tests took two years.” (Studio Granda.67) (Fig. 6.)

 Another example of application is visible in the Prada building in Tokyo by Herzog & de Meuron (2000-2003). The external access and plaza are covered by moss wall on oblique surfaces like a vegetal carpet that covers the anteroom of the building (Fig. 7). In this case, the moss was treated like a textile and sewn directly onto the stone surface. This realization is an ideal continuation of an earlier (1998-2003) moss application by Herzog & de Meuron in the extension project of Aarau Fine Art Museum (Switzerland) where, on the contrary, the architects used a different technique for cultivating mosses (see Fig. 5). Spores were injected directly into tuff-like limestones, following the French biologist Michel Chiaffredo who developed this technique as an ecological means of cleaning and rehabilitating beaches that had been polluted by oil spills.

Today companies that sell lightweight and easy to install exterior live moss wall panels are active also in the USA. For example, in Pennsylvania, Moss Acres (https://mossacres.com/) and Moss Walls (https://mosswalls.com/), which refer to the same owners. They produce and sell a low-maintenance living exterior rain screen system that features moss grown on a capillary water retention mat. It is backed with a masonry backer panel, available in around 1.2 m [3.94 ft.] wide rolls, and has an installed cost of around a quarter of the price of traditional living plant walls. A third company in North Carolina is called Mountain Moss (https://www.mountainmoss.com/). Held by bryophytic botanic Annie Martin, they sell moss wall mats based on flexible material in sizes of approximately 1×1 m [3.28×3.28 ft.] or 1×2 m [3.28×6.56 ft.]. This last company seems to be very active in publications, seminars, and specialistic courses.

In the same years, a more holistic approach has been followed by Green City Solutions GmbH, a German start-up founded by P. Sänger and Zhengliang Wu, in collaboration with Splittgerber V., Alfred Wiedensohler (Head of the Department of Experimental Aerosol and Cloud Microphysics, Leibniz Institute for Tropospheric Research, Leipzig), the Institute of Air Handling and Refrigeration Dresden (University of Dresden), the University of Leipzig and the University of Applied Science in Dresden. The team developed a self-supporting biofilter called CityTree that has been adopted in more than twenty cities in Europe in central areas as street furniture and has been supported by the EUHorizon2020 funding for its research and development. CityTree is a 3 m × 0.6 m x 4 m [9.84 × 1.97 × 13.12 ft.] (length x width x height) urban infrastructure, with the two largest vertical sides covered with combi-hydroponic cultures of mosses, predominantly of Amblystegium varium and Leucobryum glaucum types. The second species was located toward the outer surface of the panel because of its hardiness and ability to withstand sunlight, whereas the first was toward the inner side as it thrives on reduced direct sunlight.⁷² The planting concept consists of variously structured plants with smooth and raw surfaces, needles and hair, tall and small leaves. Moss is used as an optimal substrate in which vascular plants flourish. The chosen structures of the vascular plants are able to reduce wind speed and PM 10 particles. 

Irrigation is provided by a fully automated self-regulated system, according to temperature and relative humidity measurements, to ensure the highest efficiency for moss cultures. CityTree collects atmospheric pollutants through two distinct mechanisms: via spontaneous deposition of particles and gases onto the moss surfaces (passive mode) and via impaction and interception of aerosols when the air is forced to flow across the panel using a ventilation system (filtration mode or active mode). Panels are specifically designed to force airflow (in active ventilation mode) through the layers of moss, ruling out airflow leaks through the metal joints of the structure. Being permeable to air and with their mesh-like texture, mosses can capture atmospheric particulate matter by impaction and deposition when flowed with ambient air. Air flow is forced into CityTree by an internal venting system. Consequently, the particles of the fraction PM 5.5 and PM 0.1 are attracted, bounded, and converted into phytomass by the moss. Thus, all fractions of fine dust are fixed and unable to get back into the air. The systems’ living components lead to an excellent fixing of nitrogen oxide compounds because of their better quality and vitality.

The energy for Internet of Things (IoT) technology and automatic irrigation systems is supplied by photovoltaic panels and only a few hours per year are required for maintenance. Since ground anchoring is not required, CityTree can be placed anywhere, especially in city centers where there are no possibilities for planting new trees and consequently there is a high concentration of air pollutants (Fig. 9). CityTree is aligned and planted depending on the prevailing wind direction, the exposure to pollutant emitters, and the sun. Therefore, an algorithmic analysis is carried out to achieve excellent effectiveness. 

By courtesy of intelligent selection and positioning of the used plant matter, the so-created planting concept leads to a nitrogen oxide reduction up to 10/15% and a fine dust reduction up to 20/25%. Thanks to IoT technology, CityTree performance in terms of pollution reduction is fully traceable. Anyway, the results are strongly affected by the actual urban context, where a detailed survey is necessary to map the PM and NOx concentration at street scale.⁷³ Finally, in terms of circular economy, due to the growth of the plants and the possible pyrolysis of the clippings within five years the CityTree binds more carbon dioxide than it requires for production. Pyrolysis converts the cutting waste and thus prevents the carbon dioxide from re-entering the atmosphere. 

Despite these few promising applications, use of mosses in technological greenery is only at the beginning. 

Further research is urgently needed and should be addressed on the following three main topics:

(1) market research should be applied for designing new modules of systems that integrate mosses and provide a more appealing aesthetics; indeed mosses are proven to be plants well suitable for LWS due to their lightness, low cost, and low maintenance, and for green roofs too;

(2) appearance modification and durability of plants during the seasons years should be tested in accordance with user expectations;

(3) research species which are more suitable for specific functions, in combination with local geographic and climatic conditions, in order to protect biodiversity.

Among a high diversity of species, only a few mosses have been used in technological greenery. This is a clear limitation, especially if the use is intended outside under different climatic conditions. Indeed, research should be addressed to explore more suitable species to a specific regional climate (or even better, to the near future change of regional climate), but an assessment of species ranges is strictly recommended to avoid the risk of introducing a possible invasive alien plant (i.e., a moss outside its natural range and harmful to the local biodiversity). The selection of moss species is therefore a crucial way for developing technological greenery that is efficient and attractive to the market, but scientific research is currently on potential candidates ⁷⁶ and few studies are directly based on comparative experiments among moss species.⁷⁷ Species selection is linked to develop and test cultivation methods on a broad-scale for moss.⁷⁸ 

However, harvesting from the wild appears to be the most widely used method of commercially offering mosses, but this repeated practice may adversely affect rare species and deplete ecosystems in the long term. For the latter reasons, limitations for the harvesting of moss in nature was introduced by international (e.g., Habitats Directive, 92/43/EEC: species in Annex V, i.e. Leucobryum glaucum and Sphagnum spp.) or national laws (e.g., Lombardy Region in Italy: “the harvesting of lichens, mosses and sphagnum for commercial purposes is prohibited”).

Aleffi, Michele, Roberta Tacchi, and Cortini C. Pedrotti, C. “Check-List of the Hornworts, Liverworts and Mosses of Italy.” Bocconea 22 (2008).

Anderson, Malcolm, John Lambrinos, and Erin Schroll.

“The Potential Value of Mosses for Stormwater Management in Urban Environments.” Urban Ecosystems 13, no. 3 (2010). 

Baik, Jong Jin, Kyung Hwan Kwak, Seung Bu Park, and Young Hee Ryu.

“Effects of Building Roof Greening on Air Quality in Street Canyons.” Atmospheric Environment 61 (2012). 

Bellini, Oscar Eugenio, Giuseppe Ruscica, and Vittorio Paris. “Towards a New Ecology of Shared Living.

Technological Greenery and the Internet of Nature,” AGATHÓN | International Journal of Architecture, Art and Design, 11 (2022). 

Bellomo, A. Pareti Verdi, Nuove Tecniche. Edited by Sistemi Editoriali- Esselibri Simone, 2009.

Besir, Ahmet B., and Erdem Cuce. “Green Roofs and Facades: A Comprehensive Review.”
Renewable and Sustainable Energy Reviews. (2018). 

Bombelli, Paolo, Ross J. Dennis, Fabienne Felder, Matt B. Cooper, Durgaprasad Madras Rajaraman Iyer, Jessica Royles, Susan T.L. Harrison, Alison G. Smith, C. Jill Harrison, and Christopher J. Howe. “Electrical Output of Bryophyte Microbial Fuel Cell Systems Is
Sufficient to Power a Radio or an Environmental Sensor.” Royal Society Open Science 3, no. 10 (2016). 

Brandão, Carolina, Maria do Rosário Cameira, Fernanda Valente, Ricardo Cruz de Carvalho, and Teresa A. Paço. “Wet Season Hydrological Performance of Green Roofs Using Native Species under Mediterranean Climate.” Ecological Engineering 102 (2017). 

Cascone, Stefano. “Green Roof Design: State of the Art on Technology and Materials.”
Sustainability 11, no. 11 (2019). 

Clymo, R. S., and P. M. Hayward. “The Ecology of Sphagnum.” In Bryophyte Ecology, edited by A. J. E. Smith, 229–89. Dordrecht (The Neth.): Springer, 1982.

Cruz de Carvalho, Ricardo, Zulema Varela, Teresa Afonso do Paço, and Cristina Branquinho.

“Selecting Potential Moss Species for Green Roofs in the Mediterranean Basin.”

Urban Science 3, no. 2 (2019). 

——, Teresa Afonso do Paço, Cristina Branquinho, and Jorge Marques da Silva.

“Using Chlorophyll a Fluorescence Imaging to Select Desiccation-Tolerant Native Moss Species for Water-Sustainable Green Roofs.” Water 12, no. 6 (2020). 

Cruz, Marcos, and Richard Beckett. “Bioreceptive Design: A Novel Approach to Biodigital Materiality.”

Architectural Research Quarterly 20, no. 1 (2016).

——. Poikilohydric Living Walls. Edited by Yeoryia Manolopoulou, Barbara Penner and Phoebe Adler.

London: The Bartlett School of Architecture, 2022.

Davis, M. J. M., M. J. Tenpierik, F. R. Ramírez, and M. E. Pérez. “More than Just a Green Facade: The Sound Absorption Properties of a Vertical Garden with and without Plants,” Building and Environment 116, May (2017).

Donateo, Antonio, Matteo Rinaldi, Marco Paglione, Maria Gabriella Villani, Felicita Russo, Claudio Carbone, Nicola Zanca, et al. “An Evaluation of the Performance of a Green Panel in Improving Air Quality, the Case Study in a Street Canyon in Modena, Italy.”
Atmospheric Environment 247, February (2021). 

Dunnett, Nigel and Noel Kingsbury. Planting Green Roofs and Living Walls. Portland OR, USA: Timber Press, 2008.

Fletcher, Michael. Moss Grower’s Handbook, An Illustrated Beginners Guide to Finding, Naming and Growing over 100 Common British Species. Reading, UK: Seventy Press, 1991.

Garabito, Daniel, Roberto Vallejo, Eduardo Montero, Javier Garabito, and Javier Martínez- Abaigar.

“Envolventes Verdes de Edificios Con Briófitos. Una Revisión Del Estado Actual de la Cuestión” [Green Building Envelopes with Bryophytes. A Review of the State of the Art] Boletín de la Sociedad Española de Briología 47–48 (2017).

Glime, Janice M. “Bryophyta - Bryopsida. Chapt. 2-7.” Bryophyte Ecology. Volume 1.
Physiological Ecology 1, June (2013).

——. Review of Lichens, Bryophytes and Air Quality, by Thomas H. Nash III and Volkmar Wirth (Berlin: J. Cramer, 1988), The Bryologist 92, no. 3 (1989).

Guillitte, O. “Bioreceptivity: A New Concept for Building Ecology Studies.” Science of the Total Environment 167 (1995). 

Harmens, Harry, David Norris, and Gina Mills. “Heavy Metals and Nitrogen in Mosses: Spatial Patterns in 2010/2011 and Long-Term Temporal Trends in Europe.” ICP Vegetation Programme Coordination Centre, Centre for Ecology and Hydrology, Bangor, UK, 2013.

Haughian, Sean, R. and Jeremy L. Lundholm. “The Moss Machine in Action: A Preliminary Test of a Low-Cost, Indoor Cultivation Method for Mosses.” Evansia 36, no. 4 (2020).

Hodgetts, Nick. A Miniature World in Decline: European Red List of Mosses, Liverworts and Hornworts. Brussels, Bel.: IUCN, 2019. 

Janhäll, Sara. “Review on Urban Vegetation and Particle Air Pollution - Deposition and Dispersion.” Atmospheric Environment. Elsevier, 2015. 

M. Amir A. K., Yasuo Katoh, Hiroshi Katsurayama, Makoto Koganei, and Makoto Mizunuma.
“Effects of Convection Heat Transfer on Sunagoke Moss Green Roof: A Laboratory Study.”

Energy and Buildings 158 (2018). 

Kosareo, Lisa and Robert Ries. “Comparative Environmental Life Cycle Assessment of Green Roofs.” Build and Environment 42, no. 7 (2007). 

Manso, Maria, and João Castro-Gomes. 2015. “Green Wall Systems: A Review of Their Characteristics.”

Renewable and Sustainable Energy Reviews 41 (January 2015). 

——, João Castro-Gomes, Bárbara Paulo, Isabel Bentes, and Carlos Afonso Teixeira.

“Life Cycle Analysis of a New Modular Greening System.” Science of the Total Environment 627, June (2018).

Manso, Sandra. “Bioreceptivity Optimisation of Concrete Substratum to Stimulate Biological Colonisation.” (2014). https://www.researchgate.net/publication/262938554.

Mazzali, Ugo, Fabio Peron, and Massimiliano Scarpa. “Thermo-Physical Performances of Living Walls via Field Measurements and Numerical Analysis.” WIT Transactions on Ecology and the Environment 165 (2013). 

Mustafa, Kazi Fahriba, Alejandro Prieto, and Marc Ottele. “The Role of Geometry on a Self-Sustaining Bio-Receptive Concrete Panel for Facade Application.” Sustainability (Switzerland) 13, no. 13 (2021). 

Nagase, A., Katagiri, T., & Lundholm, J. “Investigation of Moss Species Selection and Substrate for Extensive Green Roofs.” Ecological Engineering 189 (April 2023).

Oberndorfer, Erica, Jeremy Lundholm, Brad Bass, Reid R. Coffman, Hitesh Doshi, Nigel Dunnett, Stuart Gaffin, Manfred Köhler, Karen K.Y. Liu, and Bradley Rowe. “Green Roofs as Urban Ecosystems: Ecological Structures, Functions, and Services.” BioScience 57,
no. 10 (2007).

Ottelé, Marc, Katia Perini, A. L.A. Fraaij, E. M. Haas, and R. Raiteri. “Comparative Life Cycle Analysis for Green Façades and Living Wall Systems.” Energy and Buildings 43, no. 12 (2011). 

Pan, Lan and L. M. Chu. 2016. “Energy Saving Potential and Life Cycle Environmental Impacts of a Vertical Greenery System in Hong Kong: A Case Study.” Building and Environment 96, 1 February (2016).

Pérez, Gabriel, Julià Coma, Salvador Sol, and Luisa F. Cabeza. “Green Facade for Energy Savings in Buildings: The Influence of Leaf Area Index and Facade Orientation on the Shadow Effect.” Applied Energy 187 (2017).

—— and Katia Perini, eds. Nature Based Strategies for Urban and Building Sustainability.
Oxford, UK: Butterworth-Heinemann, 2018. 

Perini, Katia, Paola Castellari, Dario Gisotti, Andrea Giachetta, Claudia Turcato, and Enrica Roccotiello.

“MosSkin: A Moss-Based Lightweight Building System.” Building and Environment 221, August (2022). 

——, Marc Ottelé, A. L.A. Fraaij, E. M. Haas, and Rossana Raiteri. “Vertical Greening Systems and the Effect on Air Flow and Temperature on the Building Envelope.”

Building and Environment 46, no. 11 (2011). 

Rajandu, Elle, Tiina Elvisto, Hanna-Liisa Kappel, and Marko Kaasik. “Bryophyte Species and Communities on Various Roofing Materials, Estonia.” Folia Cryptogamica Estonica, 58 (2021).

Rayner, John P., Claire Farrell, Kirsten J. Raynor, Susan M. Murphy, and Nicholas S. G.
Williams. “Plant Establishment on a Green Roof under Extreme Hot and Dry Conditions: The Importance of Leaf Succulence in Plant Selection.” Urban Forestry and Urban Greening 15 (2016). 

Rowe, D. Bradley. “Green Roofs as a Means of Pollution Abatement.” Environmental
Pollution 159, nos. 8–9 (2011).

Schuster, R. M., ed. New Manual of Bryology, vol. 1 (1983): 1 -626; vol. 2 (1984): 627-1295. Nichinan, Jap.: Hattori Botanical Laboratory. 

Shaw, A. Jonathan and Bernard Goffinet. Bryophyte Biology. Cambridge, UK: Cambridge University Press, 2000.

Shenk, George. Moss Gardening: Including Lichens, Liverworts, and Other Miniatures.
London: Timber Press, 1997.

Splittgerber, V. and P. Saenger. “The CityTree: A Vertical Plant Wall.” WIT Transactions on Ecology and the Environment 198, June (2015).

Wageningen University, “PlantPower - Living Plants in Microbial Fuel Cells for Clean, Renewable, Sustainable, Efficient, In-situ Bioenergy Production.” Final Report Summary.