A subtropical climate vegetated roof (SCV roof) is a type of

green building Green building (also known as green construction, sustainable building, or eco-friendly building) refers to both a structure and the application of processes that are environmentally responsible and resource-efficient throughout a building's li ...

practice that employs a planted soil media installed above a waterproof roof deck to obtain

environmental Environment most often refers to: __NOTOC__ * Natural environment, referring respectively to all living and non-living things occurring naturally and the physical and biological factors along with their chemical interactions that affect an organism ...

benefits and address

sustainability Sustainability is a social goal for people to co-exist on Earth over a long period of time. Definitions of this term are disputed and have varied with literature, context, and time. Sustainability usually has three dimensions (or pillars): env ...

concerns, similar to traditional

green roofs A green roof or living roof is a roof of a building that is partially or completely covered with vegetation and a growing medium, planted over a waterproofing membrane. It may also include additional layers such as a root barrier and drainage ...

located in northern continental United States. Soil media, plant palettes, and green roof systems that can adapt to the adverse weather conditions and physical characteristics of the humid, subtropical regions of the United States are utilized in the construction and design of subtropical climate vegetated roofs. Green roofs are used for various reasons including:

urban oasis An urban oasis is a public urban open space, open space, park, or plaza which is located in between buildings or formed by surrounding buildings in an urban setting. It can exist in any kind of culture. There are various sizes of urban oases. ...

, storm water mitigation,

carbon reduction Climate change mitigation (or decarbonisation) is action to limit the greenhouse gases in the atmosphere that cause climate change. Climate change mitigation actions include conserving energy and replacing fossil fuels with clean energy sour ...

energy conservation Energy conservation is the effort to reduce wasteful energy consumption by using fewer energy services. This can be done by using energy more effectively (using less and better sources of energy for continuous service) or changing one's behavi ...

, aesthetics, and therapeutic values depending on the

geographic location In geography, location or place is used to denote a region (point, line, or area) on Earth's surface. The term ''location'' generally implies a higher degree of certainty than ''place'', the latter often indicating an entity with an ambiguous bou ...

and the intended specific goals of the project. Most of the current green roof research pertains to northern parts of the continental United States, whereas, very limited research has been conducted in humid, subtropical regions. Although similar characteristics and principles exist, there are several differences between the two types of environmentally sound roofing systems. These differences are comparable to the differences found between regions of the United States in conventional

landscaping Landscaping refers to any activity that modifies the visible features of an area of land, including the following: # Living elements, such as flora or fauna; or what is commonly called gardening, the art and craft of growing plants with a goal ...

and gardening or the variations found in forms of landscaping. Plant species and landscaping methods utilized in northern parts of the United States are not suitable for humid, subtropical regions of United States due to the extreme temperatures and rain events that occur. This accounts for the most significant difference between a green roof in northern United States and a subtropical climate vegetated roof (SCV roof). A subtropical climate vegetated roof that is well designed according to the specific geographic locations climate can lower roof surface temperatures by as much 38° and depending on the amount of the event retain up to 88% of rainfall. An improperly designed subtropical climate vegetated (SCV roof) using incorrect soil media and plant species can fail by not achieving the intended goals. This roofing method also contributes towards growing the

green economy A green economy is an economy that aims at reducing environmental risks and ecological scarcities, and that aims for sustainable development without environmental degradation, degrading the environment. It is closely related with ecological econ ...

clean energy Energy is sustainable if it "meets the needs of the present without compromising the ability of future generations to meet their own needs." Definitions of sustainable energy usually look at its effects on the environment, the economy, and s ...

technology policies, and qualifies for Federal and local tax incentives, set in place by the United States government.

Technology and terminology

Compared with other parts of the United States, the number of vegetated roofs currently in the Southeast is significantly less. Vegetated roofs in humid subtropical regions rely on the same core green roof terminologies that are used throughout the world and other parts of the United States. Extensive, intensive, soil media, ballast, filter fabric, drainage layer, waterproof membrane are some of the core green roof component terms associated with SCV roofs. Regional terms, plant palettes, and technologies are forming to adapt to recent innovations and increased popularity of green roofs in the humid, subtropical regions of the United States. All forms of green roofs have the potential to retain

stormwater Stormwater, also written storm water, is water that originates from precipitation (storm), including heavy rain and meltwater from hail and snow. Stormwater can soak into the soil ( infiltrate) and become groundwater, be stored on depressed lan ...

on the roof surface and lower the

thermal loading Thermal shock is a phenomenon characterized by a rapid change in temperature that results in a transient mechanical load on an object. The load is caused by the differential expansion of different parts of the object due to the temperature chang ...

on buildings. Due to high temperatures, prolonged heat, and excessive amounts of precipitation, humid subtropical regions of the United States receive the greatest environmental benefits provided by SCV roofs, which are: reduced rainwater input into storm water retention systems during rainfall and increased energy performance ratings in buildings. SCV and green roofs increase energy efficiencies of buildings by stabilizing roof surface temperatures. In other regions of the United States, the greatest environmental benefits of green roof design may be different based upon the type of

climate Climate is the long-term weather pattern in a region, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteoro ...

the area possesses. Recent advancements in soil engineering and plastic technologies allow vegetated roofs the ability to adapt to different locations within the humid, subtropical region of the United States. Soil media

moisture content Water content or moisture content is the quantity of water contained in a material, such as soil (called ''soil moisture''), rock, ceramics, crops, or wood. Water content is used in a wide range of scientific and technical areas, and is expressed ...

and capacity levels can be regulated by using soil elements that adapt to the climate of each specific geographic location and client needs. The amount of moisture retained depends on the maximum moisture retention capacity, the permeability and the depth of the soil media. High density plastics permit SCV roof systems to withstand the weather elements and adjust to varying building types of the region. As defined by green roof industry standards, extensive green roofs have a soil media of less than 6 inches in depth and intensive green roofs have a soil media of more than 6 inches in depth. Most SCV roofs that are greater than 6 inches in depth are expensive and found on residential high rise structures, often containing

pool Pool may refer to: Bodies of water * Swimming pool, usually an artificial structure containing a large body of water intended for swimming * Reflecting pool, a shallow pool designed to reflect a structure and its surroundings * Tide pool, a roc ...

s and other amenities. An SCV roofs requires a unique soil media mixture to adapt to the harsh

weather conditions Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloudy. On Earth, most weather phenomena occur in the lowest layer of the planet's atmosphere, the ...

and physical characteristics of the southern United States. Expanded shall and

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolinite, ). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impuriti ...

are typically used to form a base and comprise up to 90% of some soil media mixtures used throughout the United States.

Perlite Perlite is an amorphous volcanic glass that has a relatively high water content, typically formed by the Hydrate, hydration of obsidian. It occurs naturally and has the unusual property of greatly expanding when heated sufficiently. It is an indu ...

vermiculite Vermiculite is a hydrous phyllosilicate mineral which undergoes significant expansion when heated. Exfoliation occurs when the mineral is heated sufficiently; commercial furnaces can routinely produce this effect. Vermiculite forms by the weathe ...

, ash, tire crumbs, sand,

peat moss ''Sphagnum'' is a genus of approximately 380 accepted species of mosses, commonly known as sphagnum moss, also bog moss and quacker moss (although that term is also sometimes used for peat). Accumulations of ''Sphagnum'' can store water, since ...

, and recycled vegetation are some of the other elements utilized in soil media engineering.

Albedo Albedo ( ; ) is the fraction of sunlight that is Diffuse reflection, diffusely reflected by a body. It is measured on a scale from 0 (corresponding to a black body that absorbs all incident radiation) to 1 (corresponding to a body that reflects ...

and heat transfer rates are key variables to consider when designing an SCV roof and do not have a significant effect on green roofs in the northern continental United States. There are three basic SCV and green roof systems available in today's market: built-up, modular, and mat. These systems vary from manufacture to manufacture and are composed of different materials such as:

foam Foams are two-phase materials science, material systems where a gas is dispersed in a second, non-gaseous material, specifically, in which gas cells are enclosed by a distinct liquid or solid material. Note, this source focuses only on liquid ...

, high density plastic, and fabrics. Many of the systems have geographic limitations and do not perform well in humid, subtropical regions based upon the intent of the system and the materials being used.

Built-up

Multi-layered systems containing the following functional layers: root barrier, protection layer, drainage layer, filter layer, growing medium and plant level.Vegetation technology

Modular systems

Self-contained units, typically square in shape, that require only the soil medium and vegetative layer for a functioning green roof. These systems are easy to install and remove. Some modular systems are pre-grown at nurseries to client specifications, forming an instant vegetative layer.Vegetation technology

Mat systems

Singled-layered systems of this type are drained by a multi-layer fabric mat called a “drainage mat” that combines soil separation, drainage, and protection functions. Current research suggests that the depth of the soil media, material, and number of layers affect the success rate of an individual green or SCV roof.Vegetation technology

Suitable plant pallets

A suitable plant species for SCV roofs consist of the following features: drought tolerant, minimal root structure, minimal height, ability to form a vegetative mat, non-rangy, heat tolerant,

frost Frost is a thin layer of ice on a solid surface, which forms from water vapor that deposits onto a freezing surface. Frost forms when the air contains more water vapor than it can normally hold at a specific temperature. The process is simila ...

tolerant, and the ability to adapt to a non-traditional soil media. Plant species that have extensive root system and tend to be rangy can puncture waterproofing elements or grow into unwanted areas causing

mold A mold () or mould () is one of the structures that certain fungus, fungi can form. The dust-like, colored appearance of molds is due to the formation of Spore#Fungi, spores containing Secondary metabolite#Fungal secondary metabolites, fungal ...

and

mildew Mildew is a form of fungus. It is distinguished from its closely related counterpart, mold, largely by its colour: molds appear in shades of black, blue, red, and green, whereas mildew is white. It appears as a thin, superficial growth consisti ...

. Water, high

nutrient A nutrient is a substance used by an organism to survive, grow and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...

, and

shade Shade, Shades or Shading may refer to: * Shade (color), a mixture of a color with black (often generalized as any variety of a color) * Shade (shadow), the blocking of sunlight * Shades or sunglasses * Shading, a process used in art and graphic ...

-dependent plants are not suitable for SCV roofs and should be avoided and can lead to expensive failures. Some of the most successful SCV roof plant species are in the families

Crassulaceae The Crassulaceae (, from Latin ''crassus'', thick), also known as the crassulas, the stonecrops or the orpine family, are a diverse Family (biology), family of dicotyledon angiosperms primarily characterized by succulent leaves and a form of phot ...

and

Aizoaceae The Aizoaceae (), or fig-marigold family, is a large family of dicotyledonous flowering plants containing 135 genera and about 1,800 species. Several genera are commonly known as 'ice plants' or 'carpet weeds'. The Aizoaceae are also referred to a ...

, which are CAM plants. A plant that uses the

crassulacean acid metabolism Crassulacean acid metabolism, also known as CAM photosynthesis, is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions that allows a plant to photosynthesize during the day, but only exchange gases at night. ...

(CAM) as an adaptation for arid conditions. CO₂ entering the stomata during the night is converted into

organic acids An organic acid is an organic compound with acidic properties. The most common organic acids are the carboxylic acids, whose acidity is associated with their carboxyl group –COOH. Sulfonic acids, containing the group –SO2OH, are r ...

, which release CO₂ for the

Calvin Cycle The Calvin cycle, light-independent reactions, bio synthetic phase, dark reactions, or photosynthetic carbon reduction (PCR) cycle of photosynthesis is a series of chemical reactions that convert carbon dioxide and hydrogen-carrier compounds into ...

during the day, when the stomata are closed.CAM plant CAM plants often show

xerophytic A xerophyte () is a species of plant that has adaptations to survive in an environment with little liquid water. Examples of xerophytes include cactus, cacti, pineapple and some gymnosperm plants. The morphology (biology), morphology and physiology ...

features, such as thick, reduced leaves with a low surface-area-to-volume ratio, thick cuticle, and

stomata In botany, a stoma (: stomata, from Greek ''στόμα'', "mouth"), also called a stomate (: stomates), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange between the internal air spa ...

sunken into pits.CAM plant Green roofs in the northern continental United States rely on sedums which are in the family Crassulaceae. Most varieties of Sedums are not appropriate for humid, subtropical climates and experience root rot and disease problems due to high temperatures and humidity levels. However, two Sedum cultivars, ‘Lemon Coral’ and’ Florida Friendly Gold’ are currently being researched at the

University of Florida The University of Florida (Florida or UF) is a public university, public land-grant university, land-grant research university in Gainesville, Florida, United States. It is a senior member of the State University System of Florida and a preem ...

and appear to be adapting to the humid, subtropical climate of

Gainesville, Florida Gainesville is the county seat of Alachua County, Florida, United States, and the most populous city in North Central Florida, with a population of 145,212 in 2022. It is the principal city of the Gainesville metropolitan area, Florida, Gainesv ...

. Example SCV roof plant palette

Challenges

SCV roofs confront a magnitude of challenges due to the adverse weather conditions of the Southeastern United States. High

humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation (meteorology), precipitation, dew, or fog t ...

levels, excessive rain amounts, prolonged heat, mold, mildew, insects, disease, weeds, soil borne disease, maintenance concerns, and sloped roofs are the major challenges faced in designing a SCV roof. High humidity levels, excessive rain amounts, prolonged heat lead to decreased plant health on CAM plants that are standard in green roof design. The decreased plant health causes diseases, insects, root rot, and plant fatality. Soil-borne diseases occur more frequently due to warm, rainy, humid environment rhythm of the humid, subtropical region. SCV roof plants are researched and tested at several different universities throughout the southeast to avoid system failure and economic loses. Mold and mildew can form on areas of the roof and building when proper ventilation is not taken into consideration and are also repercussions of high humidity levels and prolonged heat. One of the greatest challenges to SCV roofs can be

hurricanes A tropical cyclone is a rapidly rotating storm system with a low-pressure area, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its locat ...

. The strong hurricane winds can cause uplifting of the roofs. High winds can scour the growth media where the plants are established. Scouring is the blowing of the particles in the growth media from the surface of the vegetated roof, thereby reducing the volume and weight of growth media and its ability to

ballast Ballast is dense material used as a weight to provide stability to a vehicle or structure. Ballast, other than cargo, may be placed in a vehicle, often a ship or the gondola of a balloon or airship, to provide stability. A compartment within ...

the green roof.Green Roof Wind Uplift Challenges Sloped roofs that are prevalent in the southeastern United States also pose a significant challenge for SCV roofs. Soil media

erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

and poor plant establishment are the most common problems and can occur on any angle of sloped roof if not designed properly. Erosion blankets and green roof soil media stabilization products are used to mitigate the effects of sloped roofs. Flat roofs and low sloped roofs are conventional roof slopes by the building industry in the southeastern United States and allow for successful implementation of SCV roofs.

Standard roof slopes

Flat roofs – 1% to 2% slope Low slope-3:12 to 5:12 Medium Slope-6:12 to 9:12 High Slope-10:12 to 12:12 ;Subtropical regions in the US where SCV roofs could apply Here are some of the states where humid subtropical climates can be found: * Eastern half of Texas *

Louisiana Louisiana ( ; ; ) is a state in the Deep South and South Central regions of the United States. It borders Texas to the west, Arkansas to the north, and Mississippi to the east. Of the 50 U.S. states, it ranks 31st in area and 25 ...

Arkansas Arkansas ( ) is a landlocked state in the West South Central region of the Southern United States. It borders Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, Texas to the southwest, and Oklahoma ...

Alabama Alabama ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South, Deep Southern regions of the United States. It borders Tennessee to the north, Georgia (U.S. state), Georgia to the east, Florida and the Gu ...

Mississippi Mississippi ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South regions of the United States. It borders Tennessee to the north, Alabama to the east, the Gulf of Mexico to the south, Louisiana to the s ...

North Carolina North Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, South Carolina to the south, Georgia (U.S. stat ...

South Carolina South Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders North Carolina to the north and northeast, the Atlantic Ocean to the southeast, and Georgia (U.S. state), Georg ...

Tennessee Tennessee (, ), officially the State of Tennessee, is a landlocked U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders Kentucky to the north, Virginia to the northeast, North Carolina t ...

Georgia Georgia most commonly refers to: * Georgia (country), a country in the South Caucasus * Georgia (U.S. state), a state in the southeastern United States Georgia may also refer to: People and fictional characters * Georgia (name), a list of pe ...

Kentucky Kentucky (, ), officially the Commonwealth of Kentucky, is a landlocked U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders Illinois, Indiana, and Ohio to the north, West Virginia to the ...

* most of Florida *

Virginia Virginia, officially the Commonwealth of Virginia, is a U.S. state, state in the Southeastern United States, Southeastern and Mid-Atlantic (United States), Mid-Atlantic regions of the United States between the East Coast of the United States ...

* southern

West Virginia West Virginia is a mountainous U.S. state, state in the Southern United States, Southern and Mid-Atlantic (United States), Mid-Atlantic regions of the United States.The United States Census Bureau, Census Bureau and the Association of American ...

The climate in many of these states can vary and be extreme. Benefits (Performance ratings) * Reduces stormwater volume (50%–85%) * Improves stormwater quality through load reduction * Saves water by

rainwater harvesting Rainwater harvesting (RWH) is the collection and storage of rain, rather than allowing it to run off. Rainwater is collected from a roof-like surface and redirected to a Rainwater tank, tank, cistern, deep pit (well, shaft, or borehole), Aquifer s ...

* Reduces

heat island effect Urban areas usually experience the urban heat island (UHI) effect; that is, they are significantly warmer than surrounding rural areas. The temperature difference is usually larger at night than during the day, and is most apparent when winds ar ...

* Lowers surface temperatures by 40–50 degrees

Fahrenheit The Fahrenheit scale () is a scale of temperature, temperature scale based on one proposed in 1724 by the German-Polish physicist Daniel Gabriel Fahrenheit (1686–1736). It uses the degree Fahrenheit (symbol: °F) as the unit. Several accou ...

* Energy savings can reach 15%–30% * Reduces noise for building occupantsPublic Benefits * Increases the life of the roof and reduces roof maintenance * Contributes to

biodiversity Biodiversity is the variability of life, life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and Phylogenetics, phylogenetic diversity. Diversity is not distribut ...

and creates

habitats In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...

for birds and

invertebrates Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordate subphylum ...

Public Benefits * Filters air pollutant particlesPublic Benefits * Increased storm event safety * Neighborhood diversity * Aesthetic value * Reduces need for retention ponds and

ditches A ditch is a small to moderate trench created to channel water. A ditch can be used for drainage, to drain water from low-lying areas, alongside roadways or fields, or to channel water from a more distant source for plant irrigation. Ditches a ...

Costs

Initially, vegetated roofs can have a high short-term capital but the long-term energy and maintenance savings outweigh them. Even the

U.S. Green Building Council The U.S. Green Building Council (USGBC), founded in 1993, is a private 501(c)(3), membership-based non-profit organization that promotes sustainability in building design, construction, and operation. USGBC is best known for its development of t ...

and some new advances in green roofs suggest that green buildings don't necessarily have to cost more than a conventional one.

Successful examples

Project name: Shadow Wood Preserve Green Roof Demonstration * Location: Ft. Myers, FL, USA * Size: 2400 sq.ft. Project name: Charles R. Perry Construction Yard, University of Florida * Location: Gainesville, FL, USA * Size: 2600 sq.ft. Project name: Student Union Expansion at the

University of Central Florida The University of Central Florida (UCF) is a public university, public research university with its main campus in unincorporated area, unincorporated Orange County, Florida, United States. It is part of the State University System of Florida. ...

(UCF) * Location: Orlando, FL, USA * Size: 1600 sq ft

References

External links

* * * * * * https://books.google.com.lp.hscl.ufl.edu/books?hl=en&lr=&id=KNktsuZMtboC&oi=fnd&pg=PA125&dq=soil+diseases+humid+subtropical+regions&ots=RVN_l-UXUA&sig=MUA4wZo4IVPddW6FS8KcNbyqwUA#v=onepage&q=warm%2C%20rainy&f=false * *
epa.gov
* * {{DEFAULTSORT:Subtropical Climate Vegetated Roofs (SCV Roof) Roof gardens Sustainable architecture Sustainable gardening Sustainable building Types of garden Landscape architecture Hydrology and urban planning Environmental engineering Landscape ecology