A subtropical climate vegetated roof (SCV roof) is a type of green building practice that employs a planted soil media installed above a waterproof roof deck to obtain

environmental A biophysical environment is a biotic and abiotic surrounding of an organism or population, and consequently includes the factors that have an influence in their survival, development, and evolution. A biophysical environment can vary in scale f ...

benefits and address

sustainability Specific definitions of sustainability are difficult to agree on and have varied in the literature and over time. The concept of sustainability can be used to guide decisions at the global, national, and individual levels (e.g. sustainable livi ...

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 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. Central Park, Fred ...

, storm water mitigation, carbon reduction,

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 energy for continuous service) or changing one's behavior to use less service (f ...

, aesthetics, and therapeutic values depending on the geographic location 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 o ...

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 degrading the environment. It is closely related with ecological economics, but has a more politi ...

, clean energy 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 spelled 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 la ...

on the roof surface and lower the thermal loading 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 an area, 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 meteorologic ...

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 as a ...

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 pools 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 tr ...

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. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...

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

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

, ash, tire crumbs, sand,

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

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

Albedo Albedo (; ) is the measure of the diffuse reflection of sunlight, solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body ...

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, 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 A root barrier is an underground wall placed to block plant roots. This is often for the purpose of protecting structures or other plants, but root barriers are also used to preserve soil moisture. Development Root barriers were developed to stop ...

, 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 in an above-freezing atmosphere coming in contact with a solid surface whose temperature is below freezing, and resulting in a phase change from water vapor (a gas) ...

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 and mildew. 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-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 and

Aizoaceae The Aizoaceae, or fig-marigold family, is a large family of dicotyledonous flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is d ...

, which are CAM plants. A plant that uses the crassulacean acid metabolism (CAM) as an adaptation for arid conditions. CO₂ entering the stomata during the night is converted into organic acids, 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 features, such as thick, reduced leaves with a low surface-area-to-volume ratio, thick cuticle, and

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

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 land-grant research university in Gainesville, Florida. It is a senior member of the State University System of Florida, traces its origins to 1853, and has operated continuously on its ...

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

Gainesville, Florida Gainesville is the county seat of Alachua County, Florida, Alachua County, Florida, and the largest city in North Central Florida, with a population of 141,085 in 2020. It is the principal city of the Gainesville metropolitan area, Florida, Gaine ...

. 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, dew, or fog to be present. Humidity depe ...

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. 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 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 water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distin ...

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 , group=pronunciation (French: ''La Louisiane'') is a state in the Deep South and South Central regions of the United States. It is the 20th-smallest by area and the 25th most populous of the 50 U.S. states. Louisiana is borde ...

Arkansas Arkansas ( ) is a landlocked state in the South Central United States. It is bordered by Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, and Texas and Oklahoma to the west. Its name is from the Osage ...

Alabama (We dare defend our rights) , anthem = "Alabama (state song), Alabama" , image_map = Alabama in United States.svg , seat = Montgomery, Alabama, Montgomery , LargestCity = Huntsville, Alabama, Huntsville , LargestCounty = Baldwin County, Al ...

Mississippi Mississippi () is a state in the Southeastern region of the United States, bordered to the north by Tennessee; to the east by Alabama; to the south by the Gulf of Mexico; to the southwest by Louisiana; and to the northwest by Arkansas. Miss ...

North Carolina North Carolina () is a state in the Southeastern region of the United States. The state is the 28th largest and 9th-most populous of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, Georgia and So ...

South Carolina )''Animis opibusque parati'' ( for, , Latin, Prepared in mind and resources, links=no) , anthem = " Carolina";" South Carolina On My Mind" , Former = Province of South Carolina , seat = Columbia , LargestCity = Charleston , LargestMetro = ...

Tennessee Tennessee ( , ), officially the State of Tennessee, is a landlocked state in the Southeastern region of the United States. Tennessee is the 36th-largest by area and the 15th-most populous of the 50 states. It is bordered by Kentucky to th ...

* Georgia *

Kentucky Kentucky ( , ), officially the Commonwealth of Kentucky, is a state in the Southeastern region of the United States and one of the states of the Upper South. It borders Illinois, Indiana, and Ohio to the north; West Virginia and Virginia to ...

* most of Florida *

Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth ar ...

* southern

West Virginia West Virginia is a state in the Appalachian, Mid-Atlantic and Southeastern regions of the United States.The Census Bureau and the Association of American Geographers classify West Virginia as part of the Southern United States while the Bur ...

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 tank, cistern, deep pit (well, shaft, or borehole), aquifer, or a reservoir w ...

* Reduces

heat island effect An urban heat island (UHI) is an urban or metropolitan area that is significantly warmer than its surrounding rural areas due to human activities. The temperature difference is usually larger at night than during the day, and is most apparent w ...

* Lowers surface temperatures by 40–50 degrees Fahrenheit * 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 or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...

and creates

habitats In ecology, the term habitat summarises the array of resources, physical and 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 ...

for birds and

invertebrates Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

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 divot 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 ar ...

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), co-founded by Mike Italiano, David Gottfried and Rick Fedrizzi in 1993, is a private 501(c)3, membership-based non-profit organization that promotes sustainability in building design, construction, and op ...

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 research university whose main campus is in unincorporated Orange County, Florida. UCF also has nine smaller regional campuses throughout central Florida. It is part of the State University ...

(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 * * * http://www.epa.gov/region08/greenroof/pdf/green%20roof.pdf * * {{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